2024 |
Aas, W., Fagerli, H., Alastuey, A., Cavalli, F., Degorska, A., Feigenspan, S., et al. (2024). Trends In Air Pollution In Europe, 2000-2019. Aerosol And Air Quality Research, 242(4).
Abstract: This Paper Encompasses An Assessment Of Air Pollution Trends In Rural Environments In Europe Over The 2000-2019 Period, Benefiting From Extensive Long-Term Observational Data From The Emep Monitoring Network And Emep Msc-W Model Computations. The Trends In Pollutant Concentrations Align With The Decreasing Emission Patterns Observed Throughout Europe. Annual Average Concentrations Of Sulfur Dioxide, Particulate Sulfate, And Sulfur Wet Deposition Have Shown Consistent Declines Of 3-4% Annually Since 2000. Similarly, Oxidized Nitrogen Species Have Markedly Decreased Across Europe, With An Annual Reduction Of 1.5-2% In Nitrogen Dioxide Concentrations, Total Nitrate In The Air, And Oxidized Nitrogen Deposition. Notably, Emission Reductions And Model Predictions Appear To Slightly Surpass The Observed Declines In Sulfur And Oxidized Nitrogen, Indicating A Potential Overestimation Of Reported Emission Reductions. Ammonia Emissions Have Decreased Less Compared To Other Pollutants Since 2000. Significant Reductions In Particulate Ammonium Have However, Been Achieved Due To The Impact Of Reductions In Sox And Nox Emissions. For Ground Level Ozone, Both The Observed And Modelled Peak Levels In Summer Show Declining Trends, Although The Observed Decline Is Smaller Than Modelled. There Have Been Substantial Annual Reductions Of 1.8% And 2.4% In The Concentrations Of Pm10 And Pm2.5, Respectively. Elemental Carbon Has Seen A Reduction Of Approximately 4.5% Per Year Since 2000. A Similar Reduction For Organic Carbon Is Only Seen In Winter When Primary Anthropogenic Sources Dominate. The Observed Improvements In European Air Quality Emphasize The Importance Of Comprehensive Legislations To Mitigate Emissions.
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Amato, F., Van Drooge, B., Jaffrezo, J., Favez, O., Colombi, C., Cuccia, E., et al. (2024). Aerosol Source Apportionment Uncertainty Linked To The Choice Of Input Chemical Components. Environment International, 1841.
Abstract: For A Positive Matrix Factorization (Pmf) Aerosol Source Apportionment (Sa) Studies There Is No Standard Procedure To Select The Most Appropriate Chemical Components To Be Included In The Input Dataset For A Given Site Typology, Nor Specific Recommendations In This Direction. However, These Choices Are Crucial For The Final Sa Outputs Not Only In Terms Of Number Of Sources Identified But Also, And Consequently, In The Source Contributions Estimates. In Fact, Pmf Tends To Reproduce Most Of Pm Mass Measured Independently And Introduced As A Total Variable In The Input Data, Regardless Of The Percentage Of Pm Mass Which Has Been Chemically Characterized, So That The Lack Of Some Specific Source Tracers (E.G. Levoglucosan) Can Potentially Affect The Results Of The Whole Source Apportionment Study. The Present Study Elaborates Further On The Same Concept, Evaluating Quantitatively The Impact Of Lacking Specific Sources' Tracers On The Whole Source Apportionment, Both In Terms Of Identified Sources And Source Contributions. This Work Aims To Provide First Recommendations On The Most Suitable And Critical Components To Be Included In Pmf Analyses In Order To Reduce Pmf Output Uncertainty As Much As Possible, And Better Represent The Most Commons Pm Sources Observed In Many Sites In Western Countries. To This Aim, We Performed Three Sensitivity Analyses On Three Different Datasets Across Eu, Including Extended Sets Of Organic Tracers, In Order To Cover Different Types Of Urban Conditions (Mediterranean, Continental, And Alpine), Source Types, And Pm Fractions. Our Findings Reveal That The Vehicle Exhaust Source Resulted To Be Less Sensitive To The Choice Of Analytes, Although Source Contributions Estimates Can Deviate Significantly Up To 44 %. On The Other Hand, For The Detection Of The Non-Exhaust One Is Clearly Necessary To Analyze Specific Inorganic Elements. The Choice Of Not Analysing Non-Polar Organics Likely Causes The Loss Of Separation Of Exhaust And Non-Exhaust Factors, Thus Obtaining A Unique Road Traffic Source, Which Provokes A Significant Bias Of Total Contribution. Levoglucosan Was, In Most Cases, Crucial To Identify Biomass Burning Contributions In Milan And In Barcelona, In Spite Of The Presence Of Pahs In Barcelona, While For The Case Of Grenoble, Even Discarding Levoglucosan, The Presence Of Pahs Allowed Identifying The Bb Factor. Modifying The Rest Of Analytes Provoke A Systematic Underestimation Of Biomass Burning Source Contributions. Sia Factors Resulted To Be Generally Overestimated With Respect To The Base Case Analysis, Also In The Case That Ions Were Not Included In The Pmf Analysis. Trace Elements Were Crucial To Identify Shipping Emissions (V And Ni) And Industrial Sources (Pb, Ni, Br, Zn, Mn, Cd And As). When Changing The Rest Of Input Variables, The Uncertainty Was Narrow For Shipping But Large For Industrial Processes. Major And Trace Elements Were Also Crucial To Identify The Mineral/Soil Factor At All Cities. Biogenic Soa And Anthropogenic Soa Factors Were Sensitive To The Presence Of Their Molecular Tracers, Since The Availability Of Oc Alone Is Unable To Separate A Soa Factor. Arabitol And Sorbitol Were Crucial To Detecting Fungal Spores While Odd Number Of Higher Alkanes (C27 To C31) For Plant Debris.
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Amory, C., Buizert, C., Buzzard, S., Case, E., Clerx, N., Culberg, R., et al. (2024). Firn On Ice Sheets. Nature Reviews Earth & Environment, .
Abstract: Most Of The Greenland And Antarctic Ice Sheets Are Covered With Firn – The Transitional Material Between Snow And Glacial Ice. Firn Is Vital For Understanding Ice-Sheet Mass Balance And Hydrology, And Palaeoclimate. In This Review, We Synthesize Knowledge Of Firn, Including Its Formation, Observation, Modelling And Relevance To Ice Sheets. The Refreezing Of Meltwater In The Pore Space Of Firn Currently Prevents 50% Of Meltwater In Greenland From Running Off Into The Ocean And Protects Antarctic Ice Shelves From Catastrophic Collapse. Continued Atmospheric Warming Could Inhibit Future Protection Against Mass Loss. For Example, Warming In Greenland Has Already Contributed To A 5% Reduction In Firn Pore Space Since 1980. All Projections Of Future Firn Change Suggest That Surface Meltwater Will Have An Increasing Impact On Firn, With Melt Occurring Tens To Hundreds Of Kilometres Further Inland In Greenland, And More Extensively On Antarctic Ice Shelves. Although Progress In Observation And Modelling Techniques Has Led To A Well-Established Understanding Of Firn, The Large Uncertainties Associated With Meltwater Percolation Processes (Refreezing, Ice-Layer Formation And Storage) Must Be Reduced Further. A Tighter Integration Of Modelling Components (Firn, Atmosphere And Ice-Sheet Models) Will Also Be Needed To Better Simulate Ice-Sheet Responses To Anthropogenic Warming And To Quantify Future Sea-Level Rise. A Firn Layer Covers The Earth'S Ice Sheets. This Review Outlines Techniques To Observe And Model Changes In Firn Properties And Meltwater Retention To Understand How This Firn Layer Will Respond To Climate Change.
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Aroskay, A., Martin, E., Bekki, S., Le Pennec, J., Savarino, J., Temel, A., et al. (2024). Geological Evidence Of Extensive N- Fixation By Volcanic Lightning During Very Large Explosive Eruptions. Proceedings Of The National Academy Of Sciences Of The United States Of America, 1211(7).
Abstract: Most Of The Nitrogen (N) Accessible For Life Is Trapped In Dinitrogen (N2), The Most Stable Atmospheric Molecule. In Order To Be Metabolized By Living Organisms, N2 Has To Be Converted Into Biologically Assimilable Forms, So – Called Fixed N. Nowadays, Nearly All The N- Fixation Is Achieved Through Biological And Anthropogenic Processes. However, In Early Prebiotic Environments Of The Earth, N- Fixation Must Have Occurred Via Natural Abiotic Processes. One Of The Most Invoked Processes Is Electrical Discharges, Including From Thunderstorms And Lightning Associated With Volcanic Eruptions. Despite The Frequent Occurrence Of Volcanic Lightning During Explosive Eruptions And Convincing Laboratory Experimentation, No Evidence Of Substantial N- Fixation Has Been Found In Any Geological Archive. Here, We Report On The Discovery Of A Significant Amount Of Nitrate In Volcanic Deposits From Neogene Caldera- Forming Eruptions, Which Are Well Correlated With The Concentrations Of Species Directly Emitted By Volcanoes (Sulfur, Chlorine). The Multi- Isotopic Composition (Delta 18O, Delta 17O) Of The Nitrates Reveals That They Originate From The Atmospheric Oxidation Of Nitrogen Oxides Formed By Volcanic Lightning. According To These First Geological Volcanic Nitrate Archive, We Estimate That, On Average, About 60 Tg Of N Can Be Fixed During A Large Explosive Event. Our Findings Hint At A Unique Role Potentially Played By Subaerial Explosive Eruptions In Supplying Essential Ingredients For The Emergence Of Life On Earth.
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Bacer, S., Beaumet, J., Ménégoz, M., Gallée, H., Le Bouëdec, E., & Staquet, C. (2024). Impact Of Climate Change On Persistent Cold-Air Pools In An Alpine Valley During The 21St Century. Weather And Climate Dynamics, 5(1), 211–229.
Abstract: When Anticyclonic Conditions Persist Over Mountainous Regions In Winter, Cold-Air Pools (I.E. Thermal Inversions) Develop In Valleys And Persist From A Few Days To A Few Weeks. During These Persistent Cold-Air Pool (Pcap) Episodes The Atmosphere Inside The Valley Is Stable And Vertical Mixing Is Prevented, Promoting The Accumulation Of Pollutants Close To The Valley Bottom And Worsening Air Quality. The Purpose Of This Paper Is To Address The Impact Of Climate Change On Pcaps Until The End Of This Century For The Alpine Grenoble Valleys.The Long-Term Projections Produced With The General Circulation Model Mpi (From The Max Planck Institute) Downscaled Over The Alps With The Regional Climate Model Mar (Modele Atmospherique Regional) Are Used To Perform A Statistical Study Of Pcaps Over The Period 1981-2100. The Trends Of The Main Characteristics Of Pcaps, Namely Their Intensity, Duration, And Frequency, Are Investigated For Two Future Scenarios, Ssp2-4.5 And Ssp5-8.5. We Find That The Intensity Of Pcaps Displays A Statistically Significant Decreasing Trend For The Ssp5-8.5 Scenario Only. This Decay Is Explained By The Fact That Air Temperature Over The Century Increases More At 2 M Above The Valley Bottom Than In The Free Air At Mid-Altitudes In The Valley; This Might Be Due To The Increase Of Specific Humidity Near The Ground.The Vertical Structure Of Two Pcaps, One In The Past And One Around 2050, Is Next Investigated In Detail. For This Purpose, The Wrf (Weather Research And Forecasting) Model, Forced By Mar For The Worst-Case Scenario (Ssp5-8.5), Is Used At A High Resolution (111 M). The Pcap Episodes Are Carefully Selected From The Mar Data So That A Meaningful Comparison Can Be Performed. The Future Episode Is Warmer At All Altitudes Than The Past Episode (By At Least 4 Circle C) And Displays A Similar Inversion Height, Which Are Very Likely Generic Features Of Future Pcaps. The Selected Episodes Also Have Similar Along-Valley Wind But Different Stability, With The Future Episode Being More Stable Than The Past Episode.Overall, This Study Shows That The Atmosphere In The Grenoble Valleys During Pcap Episodes Tends To Be Slightly Less Stable In The Future Under The Ssp5-8.5 Scenario, And Statistically Unchanged Under The Ssp2-4.5 Scenario, But That Very Stable Pcaps Can Still Form.
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Benning, L., Wagner, D., Larose, C., Gunde-Cimerman, N., & Haeggblom, M. (2024). Editorial: Thematic Issue On Polar And Alpine Microbiology. Fems Microbiology Ecology, 1001(4).
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Bhowmick, S., Chaudhary, A., Jishad, M., Seemanth, M., Utkarsh, Agarwal, N., et al. (2024). How Useful Are Mispointing Phase Saral/Altika Geophysical Products For Ocean Applications? Advances In Space Research, 737(1), 414–425.
Abstract: Saral/Altika, The First Microwave Altimeter Operating At Ka -Band Frequency, Recently Completed Nine Years Of Operations In Orbit. During These Years, It Has Catered To Many Applications Related To Operational Oceanography, Climate Sciences, Hydrology And Cryosphere. More Specifically, In Oceanography, Saral Has Contributed Immensely To Operational Wave And Circulation Modelling, Eddy Detection/Tracking, Ocean Current Generation And Many More. However, Since Feb 2019, Saral Has Moved From The Drifting Phase (Dp) To The Mispointing Phase (Mp) Due To The Malfunctioning Of The Star Sensor Of The Spacecraft. In This Study, We Analyse The Instrument'S Performance And Its Waveforms During Its Ongoing Mp. We Find Out That During The Mp, Significant Wave Height (Swh) Measurements Are Anomalously High Between 18 And 24 M, And Wind Speed Measurements Are Between 16 And 19 M/S. In Sea Surface Height Anomaly (Ssha), There Is A Steady Rise In Negative Values During The Mp. In The Return Waveform, -15% Degradation In Brown -Type Waveforms In The Open Ocean Region Is Noticed. These Changes Significantly Impact The Saral Applications. Two Important Applications Of Wave Forecast And Eddy Detection Are Discussed Here As Examples. Following This, We Also Recommend Using Provided Quality Flags So That The Data Can Be Further Explored For Various Ocean Applications. (C) 2023 Cospar. Published By Elsevier B.V. All Rights Reserved.
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Bodart, G., Le Coz, J., Jodeau, M., & Hauet, A. (2024). Quantifying And Reducing The Operator Effect In Lspiv Discharge Measurements. Water Resources Research, 606(2).
Abstract: Operator Choices, Both In Acquiring The Video And Data And In Processing Them, Can Be A Prominent Source Of Error In Image-Based Velocimetry Methods Applied To River Discharge Measurements. The Large Scale Particle Image Velocimetry (Lspiv) Is Known To Be Sensitive To The Parameters And Computation Choices Set By The User, But No Systematic Comparisons With Discharge References Or Intercomparisons Have Been Conducted Yet To Evaluate This Operator Effect In Lspiv. In This Paper, An Analysis Of A Video Gauging Intercomparison, The Video Globe Challenge 2020, Is Proposed To Evaluate Such Operator Effect. The Analysis Is Based On The Gauging Reports Of The 15 To 23 Participants Using The Fudaa-Lspiv Software And Intents To Identify The Most Sensitive Parameters For The Eight Videos. The Analysis Highlighted The Significant Impact Of The Time Interval, The Grid Points And The Filters On The Lspiv Discharge Measurements. These Parameters Are Often Inter-Dependent And Should Be Correctly Set Together To Strongly Reduce The Discharge Errors. Based On The Results, Several Automated Tools Were Proposed To Reduce The Operator Effect. These Tools Consist Of Several Parameter Assistants To Automatically Set The Orthorectification Resolution, The Grid And The Time Interval, And Of A Sequence Of Systematic And Automatic Filters To Ensure Reliable Velocity Measurements Used For Discharge Estimation. The Application Of The Assisted Lspiv Workflow Using The Proposed Tools Leads To Significant Improvements Of The Discharge Measurements With Strong Reductions Of The Inter-Participant Variability. On The Eight Videos, The Mean Interquartile Range Of The Discharge Errors Is Reduced From 17% To 5% And The Mean Discharge Bias Is Reduced From -9% To 1% With The Assisted Lspiv Workflow. The Remaining Inter-Participant Variability Is Mainly Due To The User-Defined Surface Velocity Coefficient Alpha.
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Buri, P., Fatichi, S., Shaw, T., Fyffe, C., Miles, E., Mccarthy, M., et al. (2024). Land Surface Modeling Informed By Earth Observation Data: Toward Understanding Blue-Green-White Water Fluxes In High Mountain Asia. Geo-Spatial Information Science, .
Abstract: Mountains Are Important Suppliers Of Freshwater To Downstream Areas, Affecting Large Populations In Particular In High Mountain Asia (Hma). Yet, The Propagation Of Water From Hma Headwaters To Downstream Areas Is Not Fully Understood, As Interactions In The Mountain Water Cycle Between The Cryo-, Hydro- And Biosphere Remain Elusive. We Review The Definition Of Blue And Green Water Fluxes As Liquid Water That Contributes To Runoff At The Outlet Of The Selected Domain (Blue) And Water Lost To The Atmosphere Through Vapor Fluxes, That Is Evaporation From Water, Ground, And Interception Plus Transpiration (Green) And Propose To Add The Term White Water To Account For The (Often Neglected) Evaporation And Sublimation From Snow And Ice. We Provide An Assessment Of Models That Can Simulate The Cryo-Hydro-Biosphere Continuum And The Interactions Between Spheres In High Mountain Catchments, Going Beyond Disciplinary Separations. Land Surface Models Are Uniquely Able To Account For Such Complexity, Since They Solve The Coupled Fluxes Of Water, Energy, And Carbon Between The Land Surface And Atmosphere. Due To The Mechanistic Nature Of Such Models, Specific Variables Can Be Compared Systematically To Independent Remote Sensing Observations – Providing Vital Insights Into Model Accuracy And Enabling The Understanding Of The Complex Watersheds Of Hma. We Discuss Recent Developments In Spaceborne Earth Observation Products That Have The Potential To Support Catchment Modeling In High Mountain Regions. We Then Present A Pilot Study Application Of The Mechanistic Land Surface Model Tethys & Chloris To A Glacierized Watershed In The Nepalese Himalayas And Discuss The Use Of High-Resolution Earth Observation Data To Constrain The Meteorological Forcing Uncertainty And Validate Model Results. We Use These Insights To Highlight The Remaining Challenges And Future Opportunities That Remote Sensing Data Presents For Land Surface Modeling In Hma.
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Camman, J., Chazeau, B., Marchand, N., Durand, A., Gille, G., Lanzi, L., et al. (2024). Oxidative Potential Apportionment Of Atmospheric Pm1: A New Approach Combining High-Sensitive Online Analysers For Chemical Composition And Offline Op Measurement Technique. Atmospheric Chemistry And Physics, 242(5), 3257–3278.
Abstract: Source Apportionment Models Were Widely Used To Successfully Assign Highly Time-Resolved Aerosol Data To Specific Emissions And/Or Atmospheric Chemical Processes. These Techniques Are Necessary For Targeting The Sources Affecting Air Quality And For Designing Effective Mitigation Strategies. Moreover, Evaluation Of The Toxicity Of Airborne Particulate Matter Is Important Since The Classically Measured Particulate Matter (Pm) Concentrations Appear Insufficient For Characterizing The Impact On Human Health. Oxidative Potential (Op) Measurement Has Recently Been Developed To Quantify The Capability Of Pm To Induce An Oxidative Imbalance In The Lungs. As A Result, This Measurement Unit Could Be A Better Proxy Than Pm Mass Concentration To Represent Pm Toxicity. In The Present Study, Two Source Apportionment Analyses Were Performed Using Positive Matrix Factorization (Pmf) From Organic Aerosol (Oa) Mass Spectra Measured At A 15 Min Time Resolution Using A Time-Of-Flight Aerosol Chemical Speciation Monitor (Tof-Acsm) And From 19 Trace Elements Measured On An Hourly Basis Using An Online Metal Analyser (Xact 625I). The Field Measurements Were Carried Out In Summer 2018. While It Is Common To Perform Pmf Studies Individually On Acsms And More Recently On Xact Datasets, Here We Used A Two-Step Methodology Leading To A Complete Pm 1 Source Apportionment. The Outputs From Both Oa Pmf And Xact Pmf, The Inorganic Species Concentrations From The Acsm, And The Black Carbon (Bc) Fractions (Fossil Fuel And Wood Burning) Measured Using An Aethalometer (Ae33) Were Gathered Into A Single Dataset And Subjected To A Combined Pmf Analysis. Overall, Eight Factors Were Identified, Each Of Them Corresponding To A More Precise Source Than Performing Single Pmf Analyses. The Results Show That Besides The High Contribution Of Secondary Ammonium Sulfate (28 %) And Organic Nitrate (19 %), About 50 % Of Pm 1 Originated From Distinct Combustion Sources, Including Emissions From Traffic, Shipping, Industrial Activities, Cooking, And Biomass Burning. Simultaneously, Pm 1 Filters Were Collected During The Experimental Period On A 4 H Sampling Basis. On These Filters, Two Acellular Op Assays Were Performed (Dithiothreitol; Op Dtt And Ascorbic Acid; Op Aa ) And An Inversion Method Was Applied On Factors Issued From All Pmfs To Assess The Contribution Of The Pm Sources To The Op. This Work Highlights The Sensitivity Of Op Aa To Industrial And Dust Resuspension Sources And Those Of Op Dtt To Secondary Ammonium Sulfate, Shipping, And Biomass Burning.
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Cantera, I., Carteron, A., Guerrieri, A., Marta, S., Bonin, A., Ambrosini, R., et al. (2024). The Importance Of Species Addition 'Versus' Replacement Varies Over Succession In Plant Communities After Glacier Retreat. Nature Plants, .
Abstract: The Mechanisms Underlying Plant Succession Remain Highly Debated. Due To The Local Scope Of Most Studies, We Lack A Global Quantification Of The Relative Importance Of Species Addition 'Versus' Replacement. We Assessed The Role Of These Processes In The Variation (Beta-Diversity) Of Plant Communities Colonizing The Forelands Of 46 Retreating Glaciers Worldwide, Using Both Environmental Dna And Traditional Surveys. Our Findings Indicate That Addition And Replacement Concur In Determining Community Changes In Deglaciated Sites, But Their Relative Importance Varied Over Time. Taxa Addition Dominated Immediately After Glacier Retreat, As Expected In Harsh Environments, While Replacement Became More Important For Late-Successional Communities. These Changes Were Aligned With Total Beta-Diversity Changes, Which Were More Pronounced Between Early-Successional Communities Than Between Late-Successional Communities (>50 Yr Since Glacier Retreat). Despite The Complexity Of Community Assembly During Plant Succession, The Observed Global Pattern Suggests A Generalized Shift From The Dominance Of Facilitation And/Or Stochastic Processes In Early-Successional Communities To A Predominance Of Competition Later On.
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Chahrour, N., Bérenguer, C., & Tacnet, J. (2024). Incorporating Cascading Effects Analysis In The Maintenance Policy Assessment Of Torrent Check Dams Against Torrential Floods. Reliability Engineering & System Safety, 2432.
Abstract: In Mountainous Regions, Protection Infrastructures Designed To Mitigate The Impacts Of Torrential Floods Often Consist Of A Complex System Of Several Structural Components (Check Dams). Over Time, The Efficacy Of This System In Protecting Downstream Assets Diminishes As The Structural Components Deteriorate. The Extent Of Deterioration Is Influenced By The Interdependencies Between The Failure Modes Of Individual Components, As Well As Those Between Multiple Components Of The System. Understanding And Quantifying The Chain Of Failure Events, Known As Cascading Effects, Is A Critical Scientific Challenge That Remains Largely Unexplored. In This Study, We Propose A Novel Approach That Employs Physics-Based Models To Examine The Deterioration Of A Series Of Check Dams Over Time, While Considering Failure Dependencies And Bidirectional Interactions Between Consecutive Dams. The Results Obtained From This Approach Reveals That The Absence Of A Downstream Dam Accelerates The Deterioration Rate Of Upstream Dams, While Its Presence Serves To Stabilize Them. We Further Incorporate Stochastic Deterioration And Maintenance Processes Using Stochastic Petri Nets To Support Decision-Making Regarding Maintenance Actions For Each Dam, While Also Considering Economic Factors. Strategies Involving Minor Operations Achieved Cost-Effectiveness And Prolonged Satisfactory Performance Of The Dams, With Notable Impacts From Upstream And Downstream Dam Presence On Maintenance Costs. We Illustrate Our Approach Using A Case Study Of The Faucon Torrent In France, Where We Model The Deterioration Of Three Consecutive Check Dams Subjected To Torrential Floods Over A Period Of 100 Years.
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Chahrour, N., Piton, G., Tacnet, J., & Bérenguer, C. (2024). A Surrogate Deterioration Model Of Debris Retention Systems Towards Cost-Effective Maintenance Strategies And Increased Protection Efficacy. Engineering Structures, 3003.
Abstract: Protection Systems Are Usually Implemented In Mountains Aiming To Resist Natural Dangerous Phenomena. As Any Other Critical Infrastructure, Protection Systems Should Always Withstand And Operate Efficiently As They Guarantee The Safety Of People And Protect Socio-Economic Assets. However, The Efficacy Of These Systems Decreases With The Increase Of The Deterioration Level Of The Interdependent Components, Which Constitute Them. To Provide Desirable Operation Over Their Lifetime, The Management Of Protection Systems Is Of Paramount Importance. A Major Key Issue In Such Critical Infrastructure Management Is To Optimize The Cost Effectiveness Of Maintenance Actions While Maintaining A Sufficient Protection Efficacy. This Study Proposes A Decision-Aiding Model To Assess Different Maintenance Strategies Applied To A Protection System Against Debris Flows. The Model Is Constructed Using Physics-Based Stochastic Petri Nets. It Incorporates (1) A Stochastic Deterioration Model, Which Is A Surrogate Model Of A Physics-Based Model Developed For Building Deterioration Trajectories Of The System And (2) Maintenance Model That Permits Assessing The Cost And Efficiency Of Maintenance Strategies. This Study Addresses The Case Of A Debris Retention System, In Which The Progressive Filling Of Its Basin By Debris Materials Is Modeled. This Is Followed By Assessing Several Maintenance Strategies Concerning The Cleaning Of The Basin. A Simple Sensitivity Analysis Is Also Carried Out In Order To Check The Effect Of The Uncertainty That Invades The Model'S Inputs On Maintenance Decisions. A Numerical Analysis Is Performed Using Real Data Of The Retention System Located In The Claret Torrent In France And Subjected To Debris Flows Over A Period Of 50 Years.
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Charrondiere, C., Hopfinger, E., Brun, C., Cohard, J., & Sicart, J. (2024). Evidence Of Strong Wave Turbulence And Of Bolgiano Temperature Spectra In Katabatic Winds On Steep Slopes. Physics Of Fluids, 363(2).
Abstract: The Katabatic Winds On Steep Slopes Investigated In The Present Study Reveal A Novel Spectral Behavior, Observed In The Outer Part Of The Jet. At Low Wavenumbers, The One-Dimensional (1D) Velocity Spectra Show Evidence Of A K(X)(-1) Range For The Three Components Of The Velocity Vector: E-U(K(X)), E-V(K(X)), E-W(K(X)) Proportional To K(X)(-1) [As Well As For The 1D Temperature Spectrum E-Theta(K(X)) Proportional To K(X)(-1)]. This Suggests The Existence Of Strong Wave Turbulence. A Necessary Condition For Strong Wave Turbulence To Be Manifest Is That The Flow Direction Wavenumber, K(X), Extends To Much Lower Values Than The Slope Normal One, K(Z). This Is Satisfied In The Present Field Experiment Where Wave Energy Is Injected At Wavenumber K(X) = K(N) = (N-A Sin Alpha)/(U(J)) Over Bar, While K(Z) Similar To 1/Delta(Z), With N-A The Ambient Stratification, Alpha The Slope Angle, (U(J)) Over Bar The Maximum Wind Velocity, And Delta(Z) The Shear Layer Thickness Of The Jet. In The Inertial Range, The Velocity Spectra Exhibit A Power Law K(X)(-5/3) Over Two Decades, Whereas The Temperature-Buoyancy Spectra Show Evidence Of A – 7/5 Slope In The Buoyancy Sub-Range, Followed By A – 5/3 Slope. The Change In Spectral Slopes Occurs At The Bolgiano Scale L-B That Is Close To The Dougherty-Ozmidov Scale L-Oz. The High Reynolds Number Based On The Taylor Micro-Scale, Re-Lambda Similar To 10(3), Allows Clear Identification Of The Spectral Laws.
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Charton, J., Schimmelpfennig, I., Jomelli, V., Verfaillie, D., Delpech, G., Guillaume, D., et al. (2024). Late Pleistocene Glaciations On The Sub-Antarctic Kerguelen Archipelago: New Evidence From 36Cl Cre Dating And Comparison With Other Southern Mid-Latitude Glacier Records. Quaternary Science Reviews, 3283.
Abstract: Previous Paleo-Glacial Studies On Kerguelen Showed A Singular Pattern Of Holocene Glacier Evolution On This Archipelago In Comparison With Other Southern Mid-Latitude Glacier Records. In This Study, We Aim To Test This Singularity On A Longer Timescale, Based On 26 New In Situ-Produced 36Cl Ages From Pre-Holocene Glaciogeomorphic Features. Samples From Moraine Boulders And Glacially Polished Bedrock Were Extracted At Six Different Sites, Located Near The Port-Aux-Francais Scientific Station (Paf Site), On Longue Island, Australia Island, On The Port-Jeanne D'Arc Peninsula (Pjda Site), On The Gallieni Peninsula At Baie Larose (Blr Site) And The Mcmurdo Island. The Moraine Ages Indicate That Glacier Culminations Occurred During Marine Isotopic Stage 3 (Mis 3) At 42.2 +/- 4.9 Ka On The Paf Site, And During The Global Last Glacial Maximum (Glgm) At 21.5 +/- 3.2 Ka On The Pjda Site And At 21.4 +/- 3.7 Ka And 19.4 +/- 2.6 On Baie Larose Site. This Is The First Time That Late Pleistocene Glacier Culminations Are Evidenced On Kerguelen By Direct Moraine Dating, Thus Allowing Comparison With Other Moraine Records From The Southern Mid-Latitudes. While It Remains Speculative Whether Or Not The Mis 3 Glacial Maximum At -42.2 Ka Is In Phase With Other Glaciers At This Latitude (Due To High Age Uncertainties), The Glgm Glacial Maximum Is Synchronous With That In Other Southern Mid-Latitude Regions. 36Cl Cre Ages Of Glacially Polished Bedrock Surfaces Sampled In Different Locations Of The Archipelago Vary From -39 Ka To -19 Ka. We Interpret These Results As Reflecting Periods Of Deglaciation That Occurred In Between The Two Glacier Culminations And Right After The Glgm On Kerguelen. These Ages Also Suggest That Some Places Of The Archipelago Were Free Of Ice At Least Since – 39 Ka. The Presence Of A Mis 3 Moraine At Paf Site That Has Not Been Obliterated By A Glgm Advance Suggests That The – 42.2 Ka Glacier Extent Was At Least As Large As Glgm Glacial Maxima On The Archipelago. The Glacier Culmination During Mis 3 Being Larger Than That During The Glgm On The Kerguelen Archipelago Matches Observations In Other Southern Mid-Latitude Regions. Late Pleistocene Glacier Culminations On Kerguelen May Have Been In Phase With Cold Temperatures Recorded In Sst Records, Which Suggest A Cooling Around Kerguelen. However, Climate Drivers Responsible For The Larger Mis 3 Glacier Culmination On Kerguelen Still Remain Unclear Even If We Hypothesize That Changes In Precipitation May Have Superimposed On Temperature Changes.
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Chifflet, S., Guyomarc'H, L., Dominutti, P., Heimbürger-Boavida, L., Angeletti, B., Louvat, P., et al. (2024). Seasonal Variations Of Metals And Metalloids In Atmospheric Particulate Matter (Pm2.5) In The Urban Megacity Hanoi. Atmospheric Pollution Research, 151(1).
Abstract: Fine Particulate Matter (Pm2.5) In The Atmosphere Is Of Particular Concern Due To Its Adverse Effects On Human Health And Its Impact On Global Warming. Southeast Asia Is A Hot Spot For Fossil Fuel Combustion With Recurrent Release Of Large Plumes Spreading Over The Ocean And Neighbouring Countries. Due To The Complex Mixture Of Pm2.5, The Atmospheric Sources Contribution Related To Local And Regional Emissions In Hanoi (Northern Vietnam) Is Still Ill-Constrained. Here, We Present A Year-Round Study (November 2019 To December 2020) With Mea-Surements Of 18 Metals And Metalloids (Mm) And Lead Isotopes In The Pm2.5 Fraction To Quantify Weather-Related Atmospheric Inputs And To Assess Risk To Human Health. Anthropogenic Inputs From Fossil Fuel Combustion Accounted For About 80% In Pm2.5. We Found High Pm2.5-Bound Mm Concentrations Often Exceeding National And Global Standards With A Low Risk Of Chronic Inhalation And Carcinogenicity, Mainly Attributable To Cr. During Winter Monsoon (Northeastern Winds), Stable Weather Conditions Led To The Enrichment Of Long-Range Air Mass Transport Of Local Particulate Emissions. During The Summer Monsoon (Southeastern Winds), Warm And Moist Winds Reduced Coal Contribution In Pm2.5. Our Study Highlights The Need For A Strict Implementation Of Policies To Control Hazardous Mm Emissions By Reducing Fossil Fuel Combustion. On The One Hand, Reducing Coal-Related Activities Could Reduce Cr Emissions And Therefore Improve The Risks To Human Health. On The Other Hand, Public Policies Should Encourage Conversion To Green Transport In Order To Reduce Petrol Combustion And Thus Limit Global Warming.
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Clauzel, L., Anquetin, S., Lavaysse, C., Tremoy, G., & Raynaud, D. (2024). West African Operational Daily Solar Forecast Errors And Their Link With Meteorological Conditions. Renewable Energy, 2242.
Abstract: West Africa Is At The Forefront Of Global Environmental Challenges With Its Commitment To Reduce Greenhouse Gas Emissions And Harnessing The Potential Of Renewable Energy, Especially The Promising Solar Power. This Study Evaluates Global Horizontal Irradiance (Ghi) Operational Forecast Errors For The Zagtouli (Burkina-Faso) And Sococim (Senegal) Solar Plants, And Investigates Their Links With Local Meteorological Conditions, Particularly Clouds And Dust Aerosols. Firstly, The Evaluation Of Aerosol Products Indicates That Cams Reanalysis Is Reliable For Assessing Aerosol Optical Depth. We Then Examine The Accuracy Of Three Operational Ghi Forecast Products: The Global Forecast System (Gfs, Ncep), The Integrated Forecast System (Ifs, Ecmwf), And Steadymet (Sm, French Company Steadysun). The Analysis Reveals That Ifs And Sm Outperform Gfs, Sm Having A Slight Advantage Due To Its Probabilistic Nature. Closer Examination Reveals A Significant Relationship Between Ghi Forecast Errors And Local Meteorological Characteristics. These Errors Are More Pronounced During The Wet Season, Primarily Attributed To Cloud Occurrence. Dust Events Play A Secondary Influential Role, Especially During The Dry Season. Correlation Analyses Emphasize The Forecast Errors' Major Link With Cloudiness, While Co-Occurrences Highlight That Dust Aerosol Is A Secondary Factor In Forecast Errors For The Ghi Directly Or For Cloud Representation (Aerosolcloud Interaction).
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Coulon, V., Klose, A., Kittel, C., Edwards, T., Turner, F., Winkelmann, R., et al. (2024). Disentangling The Drivers Of Future Antarctic Ice Loss With A Historically Calibrated Ice-Sheet Model. Cryosphere, 181(2), 653–681.
Abstract: We Use An Observationally Calibrated Ice-Sheet Model To Investigate The Future Trajectory Of The Antarctic Ice Sheet Related To Uncertainties In The Future Balance Between Sub-Shelf Melting And Ice Discharge, On The One Hand, And The Surface Mass Balance, On The Other. Our Ensemble Of Simulations, Forced By A Panel Of Climate Models From The Sixth Phase Of The Coupled Model Intercomparison Project (Cmip6), Suggests That The Ocean Will Be The Primary Driver Of Short-Term Antarctic Mass Loss, Initiating Ice Loss In West Antarctica Already During This Century. The Atmosphere Initially Plays A Mitigating Role Through Increased Snowfall, Leading To An Antarctic Contribution To Global Mean Sea-Level Rise By 2100 Of 6 (-8 To 15) Cm Under A Low-Emission Scenario And 5.5 (-10 To 16) Cm Under A Very High-Emission Scenario. However, Under The Very High-Emission Pathway, The Influence Of The Atmosphere Shifts Beyond The End Of The Century, Becoming An Amplifying Driver Of Mass Loss As The Ice Sheet'S Surface Mass Balance Decreases. We Show That This Transition Occurs When Antarctic Near-Surface Warming Exceeds A Critical Threshold Of +7.5 Circle C, At Which The Increase In Surface Runoff Outweighs The Increase In Snow Accumulation, A Signal That Is Amplified By The Melt-Elevation Feedback. Therefore, Under The Very High-Emission Scenario, Oceanic And Atmospheric Drivers Are Projected To Result In A Complete Collapse Of The West Antarctic Ice Sheet Along With Significant Grounding-Line Retreat In The Marine Basins Of The East Antarctic Ice Sheet, Leading To A Median Global Mean Sea-Level Rise Of 2.75 (6.95) M By 2300 (3000). Under A More Sustainable Socio-Economic Pathway, We Find That The Antarctic Ice Sheet May Still Contribute To A Median Global Mean Sea-Level Rise Of 0.62 (1.85) M By 2300 (3000). However, The Rate Of Sea-Level Rise Is Significantly Reduced As Mass Loss Is Likely To Remain Confined To The Amundsen Sea Embayment, Where Present-Day Climate Conditions Seem Sufficient To Commit To A Continuous Retreat Of Thwaites Glacier.
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Courtial-Manent, L., Ravanel, L., Mugnier, J., Deline, P., Lhosmot, A., Rabatel, A., et al. (2024). 18-Years Of High-Alpine Rock Wall Monitoring Using Terrestrial Laser Scanning At The Tour Ronde East Face, Mont-Blanc Massif. Environmental Research Letters, 191(3).
Abstract: Since The End Of The 20Th Century, Each Decade Has Been Warmer Than The Previous One In The European Alps. As A Consequence, Alpine Rock Walls Are Generally Facing High Rockfall Activity, Likely Due To Permafrost Degradation. We Use A Unique Terrestrial Laser Scanning Derived Rockfall Catalog Over 18 Years (2005-2022) Compared With Photographs (1859-2022) To Quantify The Evolution Of The East Face Of Tour Ronde (3440-3792 M A.S.L.) In The Mont-Blanc Massif (Western European Alps) That Is Permafrost-Affected. Overall, 210 Rockfalls Were Identified, From 1 To 15 500 M(3). Forty-Five Events Were >100 M(3) While Cumulated Volume Of Events <10 M(3) Represents <1% Of The Fallen Rocks. The Rockfall Magnitude-Frequency Distribution Of The Overall Inventory Follows A Power Law, With A Mean Exponent B Of 0.44 +/- 0.03, Characterizing A High Contribution Of Large Rockfalls. The Depth Of Failure Ranges From A Few Centimeters To More Than 20 M While 95% Of The Rockfalls Depth Is <5 M, Highlighting The Role Of The Active Layer. The Mean Rock Wall Erosion Rate Is 18.3 +/- 0.2 Mm Yr(-1) For The 2005-2022 Period And Ranks In The Top Range Of Reported Values In The Alps. It Has Greatly Increased Between The Periods 2006-2014 And 2016-2022, Probably In Relation To A Series Of Summer Heat Waves. The Exceptional Erosion Rate Of 2015 Is Driven By One Large Rockfall In August. Since 2006, An Ice Apron That Covered 16 100 M(2) Has Now Almost Vanished, And The Surface Of The Glacier Du G & Eacute;Ant At The Rock Wall Foot Has Lowered By Several Tens Of Meters. The Retreat Of These Two Ice Masses Contributed To The Rock Wall Instability As More Than 35% Of The Rockfall Volume Detached From The Deglaciated Surfaces.
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Delhasse, A., Beckmann, J., Kittel, C., & Fettweis, X. (2024). Coupling Mar (Modèle Atmosphérique Régional) With Pism (Parallel Ice Sheet Model) Mitigates The Positive Melt-Elevation Feedback. Cryosphere, 181(2), 633–651.
Abstract: The Greenland Ice Sheet Is A Key Contributor To Sea Level Rise. By Melting, The Ice Sheet Thins, Inducing Higher Surface Melt Due To Lower Surface Elevations, Accelerating The Melt Coming From Global Warming. This Process Is Called The Melt-Elevation Feedback And Can Be Considered By Using Two Types Of Models: Either (1) Atmospheric Models, Which Can Represent The Surface Mass Balance (Smb), Or Smb Estimates Resulting From Simpler Models Such As Positive Degree Day Models Or (2) Ice Sheet Models Representing The Surface Elevation Evolution. The Latter Ones Do Not Represent The Surface Mass Balance Explicitly As Well As Polar-Oriented Climate Models. A New Coupling Between The Mar (Modele Atmospherique Regional) Regional Climate Model And The Pism (Parallel Ice Sheet Model) Ice Sheet Model Is Presented Here Following The Cesm2 (Community Earth System Model; Ssp5-8.5, Shared Socioeconomic Pathway) Scenario Until 2100 At The Mar Lateral Boundaries. The Coupling Is Extended To 2200 With A Stabilised Climate (+7 Circle C Compared To 1961-1990) By Randomly Sampling The Last 10 Years Of Cesm2 To Force Mar And Reaches A Sea Level Rise Contribution Of 64 Cm. The Fully Coupled Simulation Is Compared To A One-Way Experiment Where Surface Topography Remains Fixed In Mar. However, The Surface Mass Balance Is Corrected For The Melt-Elevation Feedback When Interpolated On The Pism Grid By Using Surface Mass Balance Vertical Gradients As A Function Of Local Elevation Variations (Offline Correction). This Method Is Often Used To Represent The Melt-Elevation Feedback And Prevents A Coupling Which Is Too Expensive In Computation Time. In The Fully Coupled Mar Simulation, The Ice Sheet Morphology Evolution (Changing Slope And Reducing The Orographic Barrier) Induces Changes In Local Atmospheric Patterns. More Specifically, Wind Regimes Are Modified, As Well As Temperature Lapse Rates, Influencing The Melt Rate Through Modification Of Sensible Heat Fluxes At The Ice Sheet Margins. We Highlight Mitigation Of The Melt Lapse Rate On The Margins By Modifying The Surface Morphology. The Lapse Rates Considered By The Offline Correction Are No Longer Valid At The Ice Sheet Margins. If Used (One-Way Simulation), This Correction Implies An Overestimation Of The Sea Level Rise Contribution Of 2.5 %. The Mitigation Of The Melt Lapse Rate On The Margins Can Only Be Corrected By Using A Full Coupling Between An Ice Sheet Model And An Atmospheric Model.
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Diedhiou, C., Panthou, G., Diatta, S., Sané, Y., Vischel, T., & Camara, M. (2024). Simple Scaling Of Extreme Precipitation Regime In Senegal. Scientific African, 232.
Abstract: Extreme Precipitation Exhibits High Temporal And Spatial Variability, And Understanding This Variability Is Crucial For Designing Hydraulic Infrastructures And Assessing The Impacts Of Natural Risks Such As Floods And Droughts. The Simple Scaling (Ss) Model, Which Describes The Dependence Of Extreme Rainfall Statistics On Timescales, Is Used To Estimate Intensity Duration Frequency (Idf) Curves. This Study Aims To Evaluate The Validity Of The Simple Scaling (Ss) Hypothesis For 14 Rain Gauges In Senegal And Explore The Existence Of Breaks In Temporal Scaling Regimes (Transition Regimes). For The Analysis Of Extreme Characteristics, We Considered The Annual Maximum Series (Ams) Of Precipitation In Sub-Hourly And Supra-Daily Durations Ranging From 10 Min To 7 Days. The Empirical Validation Of The Ss Models Was Confirmed For The Majority Of The Scaling Intervals. We Identified Two Scaling Breaks, Indicating The Presence Of Three Scaling Regimes: Short Durations (Sd), Intermediate Durations (Id), And Long Durations (Ld). The Spatial Variation Of Scaling Exponents Reveals The Existence Of Different Scaling Regimes Across Senegal. The Results Are Valuable For Modeling The Spatial Distribution Of Scaling Exponents, Which Can Aid In Characterizing Idf Curves At Ungauged Locations.
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Evin, G., Le Lay, M., Fouchier, C., Penot, D., Colleoni, F., Mas, A., et al. (2024). Evaluation Of Hydrological Models On Small Mountainous Catchments: Impact Of The Meteorological Forcings. Hydrology And Earth System Sciences, 282(1), 261–281.
Abstract: Hydrological Modelling Of Small Mountainous Catchments Is Particularly Challenging Because Of The High Spatio-Temporal Resolution Required For The Meteorological Forcings. In Situ Measurements Of Precipitation Are Typically Scarce In These Remote Areas, Particularly At High Elevations. Precipitation Reanalyses Propose Different Alternative Forcings For The Simulation Of Streamflow Using Hydrological Models. In This Paper, We Evaluate The Performances Of Two Hydrological Models Representing Some Of The Key Processes For Small Mountainous Catchments ( < 300 Km( 2) ), Using Different Meteorological Products With A Fine Spatial And Temporal Resolution. The Evaluation Is Performed On 55 Small Catchments Of The Northern French Alps. While The Simulated Streamflows Are Adequately Reproduced For Most Of The Configurations, These Evaluations Emphasize The Added Value Of Radar Measurements, In Particular For The Reproduction Of Flood Events. However, These Better Performances Are Only Obtained Because The Hydrological Models Correct The Underestimations Of Accumulated Amounts (E.G. Annual) From The Radar Data In High-Elevation Areas.
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Flamant, C., Chaboureau, J., Delanoë, J., Gaetani, M., Jamet, C., Lavaysse, C., et al. (2024). Cyclogenesis In The Tropical Atlantic First Scientific Highlights From The Clouds-Atmospheric Dynamics-Dust Interactions In West Africa (Caddiwa) Field Campaign. Bulletin Of The American Meteorological Society, 1051(2), E387–E417.
Abstract: During The Boreal Summer, Mesoscale Convective Systems Generated Over West Africa Propagate Westward And Interact With African Easterly Waves, And Dust Plumes Transported From The Sahel And Sahara By The African Easterly Jet. Once Off West Africa, The Vortices In The Wake Of These Mesoscale Convective Systems Evolve In A Complex Environment Sometimes Leading To The Development Of Tropical Storms And Hurricanes, Especially In September When Sea Surface Temperatures Are High. Numerical Weather Predictions Of Cyclogenesis Downstream Of West Africa Remains A Key Challenge Due To The Incomplete Understanding Of The Clouds-Atmospheric Dynamics-Dust Interactions That Limit Predictability. The Primary Objective Of The Clouds-Atmospheric Dynamics-Dust Interactions In West Africa (Caddiwa) Project Is To Improve Our Understanding Of The Relative Contributions Of The Direct, Semidirect, And Indirect Radiative Effects Of Dust On The Dynamics Of Tropical Waves As Well As The Intensification Of Vortices In The Wake Of Offshore Mesoscale Convective Systems And Their Evolution Into Tropical Storms Over The North Atlantic. Airborne Observations Relevant To The Assessment Of Such Interactions (Active Remote Sensing, In Situ Microphysics Probes, Among Others) Were Made From 8 To 21 September 2021 In The Tropical Environment Of Sal Island, Cape Verde. The Environments Of Several Tropical Cyclones, Including Tropical Storm Rose, Were Monitored And Probed. The Airborne Measurements Also Serve The Purpose Of Regional Model Evaluation And The Validation Of Spaceborne Wind, Aerosol And Cloud Products Pertaining To Satellite Missions Of The European Space Agency And Eumetsat (Including The Aeolus, Earthcare, And Iasi Missions).
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Fourteau, K., Brondex, J., Brun, F., & Dumont, M. (2024). A Novel Numerical Implementation For The Surface Energy Budget Of Melting Snowpacks And Glaciers. Geoscientific Model Development, 171(4), 1903–1929.
Abstract: The Surface Energy Budget Drives The Melt Of The Snow Cover And Glacier Ice And Its Computation Is Thus Of Crucial Importance In Numerical Models. This Surface Energy Budget Is The Result Of Various Surface Energy Fluxes, Which Depend On The Input Meteorological Variables And Surface Temperature; Of Heat Conduction Towards The Interior Of The Snow/Ice; And Potentially Of Surface Melting If The Melt Temperature Is Reached. The Surface Temperature And Melt Rate Of A Snowpack Or Ice Are Thus Driven By Coupled Processes. In Addition, These Energy Fluxes Are Non-Linear With Respect To The Surface Temperature, Making Their Numerical Treatment Challenging. To Handle This Complexity, Some Of The Current Numerical Models Tend To Rely On A Sequential Treatment Of The Involved Physical Processes, In Which Surface Fluxes, Heat Conduction, And Melting Are Treated With Some Degree Of Decoupling. Similarly, Some Models Do Not Explicitly Define A Surface Temperature And Rather Use The Temperature Of The Internal Point Closest To The Surface Instead. While These Kinds Of Approaches Simplify The Implementation And Increase The Modularity Of Models, They Can Also Introduce Several Problems, Such As Instabilities And Mesh Sensitivity. Here, We Present A Numerical Methodology To Treat The Surface And Internal Energy Budgets Of Snowpacks And Glaciers In A Tightly Coupled Manner, Including Potential Surface Melting When The Melt Temperature Is Reached. Specific Care Is Provided To Ensure That The Proposed Numerical Scheme Is As Fast And Robust As Classical Numerical Treatment Of The Surface Energy Budget. Comparisons Based On Simple Test Cases Show That The Proposed Methodology Yields Smaller Errors For Almost All Time Steps And Mesh Sizes Considered And Does Not Suffer From Numerical Instabilities, Contrary To Some Classical Treatments.
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Fugger, S., Shaw, T., Jouberton, A., Miles, E., Buri, P., Mccarthy, M., et al. (2024). Hydrological Regimes And Evaporative Flux Partitioning At The Climatic Ends Of High Mountain Asia. Environmental Research Letters, 191(4).
Abstract: High Elevation Headwater Catchments Are Complex Hydrological Systems That Seasonally Buffer Water And Release It In The Form Of Snow And Ice Melt, Modulating Downstream Runoff Regimes And Water Availability. In High Mountain Asia (Hma), Where A Wide Range Of Climates From Semi-Arid To Monsoonal Exist, The Importance Of The Cryospheric Contributions To The Water Budget Varies With The Amount And Seasonal Distribution Of Precipitation. Losses Due To Evapotranspiration And Sublimation Are To Date Largely Unquantified Components Of The Water Budget In Such Catchments, Although They Can Be Comparable In Magnitude To Glacier Melt Contributions To Streamflow. Here, We Simulate The Hydrology Of Three High Elevation Headwater Catchments In Distinct Climates In Hma Over 10 Years Using An Ecohydrological Model Geared Towards High-Mountain Areas Including Snow And Glaciers, Forced With Reanalysis Data. Our Results Show That Evapotranspiration And Sublimation Together Are Most Important At The Semi-Arid Site, Kyzylsu, On The Northernmost Slopes Of The Pamir Mountain Range. Here, The Evaporative Loss Amounts To 28% Of The Water Throughput, Which We Define As The Total Water Added To, Or Removed From The Water Balance Within A Year. In Comparison, Evaporative Losses Are 19% At The Central Himalayan Site Langtang And 13% At The Wettest Site, 24 K, On The Southeastern Tibetan Plateau. At The Three Sites, Respectively, Sublimation Removes 15%, 13% And 6% Of Snowfall, While Evapotranspiration Removes The Equivalent Of 76%, 28% And 19% Of Rainfall. In Absolute Terms, And Across A Comparable Elevation Range, The Highest Et Flux Is 413 Mm Yr-1 At 24 K, While The Highest Sublimation Flux Is 91 Mm Yr-1 At Kyzylsu. During Warm And Dry Years, Glacier Melt Was Found To Only Partially Compensate For The Annual Supply Deficit.
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Fürst, J., Farías-Barahona, D., Blindow, N., Casassa, G., Gacitúa, G., Koppes, M., et al. (2024). The Foundations Of The Patagonian Icefields. Communications Earth & Environment, 5(1).
Abstract: The Two Vast Patagonian Icefields Are A Global Hotspot For Ice-Loss. However, Not Much Is Known About The Total Ice Volume They Store – Let Alone Its Spatial Distribution. One Reason Is That The Abundant Record Of Direct Thickness Measurements Has Never Been Systematically Exploited. Here, This Record Is Combined With Remotely-Sensed Information On Past Ice Thickness Mapped From Glacier Retreat. Both Datasets Are Incorporated In A State-Of-The-Art, Mass-Conservation Approach To Produce A Well-Informed Map Of The Basal Topography Beneath The Icefields. Its Major Asset Is The Reliability Increase Of Thicknesses Values Along The Many Marine- And Lake-Terminating Glaciers. For These, Frontal Ice-Discharge Is Notably Lower Than Previously Reported. This Finding Implies That Direct Climatic Control Was More Influential For Past Ice Loss. We Redact A Total Volume For Both Icefields In 2000 Of 5351 Km3. Despite The Wealth Of Observations Used In This Assessment, Relative Volume Uncertainties Remain Elevated. The Southern Patagonian Icefield Likely Stores Around 10% More Ice Than Previously Believed, According To Ice Thickness Estimates Based On Remote Sensing And Direct Measurement-Informed Mapping Of The Sub-Glacial Topography.
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Gao, Q., Sime, L., Mclaren, A., Bracegirdle, T., Capron, E., Rhodes, R., et al. (2024). Evaporative Controls On Antarctic Precipitation: An Echam6 Model Study Using Innovative Water Tracer Diagnostics. Cryosphere, 181(2), 683–703.
Abstract: Improving Our Understanding Of The Controls On Antarctic Precipitation Is Critical For Gaining Insights Into Past And Future Polar And Global Environmental Changes. Here We Develop Innovative Water Tracing Diagnostics In The Atmospheric General Circulation Model Echam6. These Tracers Provide New Detailed Information On Moisture Source Locations And Properties Of Antarctic Precipitation. In The Preindustrial Simulation, Annual Mean Antarctic Precipitation Originating From The Open Ocean Has A Source Latitude Range Of 49-35 Circle S, A Source Sea Surface Temperature Range Of 9.8-16.3 Circle C, A Source 2 M Relative Humidity Range Of 75.6 %-83.3 %, And A Source 10 M Wind Velocity (Vel10) Range Of 10.1 To 11.3 Ms-1. These Results Are Consistent With Estimates From Existing Literature. Central Antarctic Precipitation Is Sourced From More Equatorward (Distant) Sources Via Elevated Transport Pathways Compared To Coastal Antarctic Precipitation. This Has Been Attributed To A Moist Isentropic Framework; I.E. Poleward Vapour Transport Tends To Follow Constant Equivalent Potential Temperature. However, We Find Notable Deviations From This Tendency Especially In The Lower Troposphere, Likely Due To Radiative Cooling. Heavy Precipitation Is Sourced By Longer-Range Moisture Transport: It Comes From 2.9 Circle (300 Km, Averaged Over Antarctica) More Equatorward (Distant) Sources Compared To The Rest Of Precipitation. Precipitation During Negative Phases Of The Southern Annular Mode (Sam) Also Comes From More Equatorward Moisture Sources (By 2.4 Circle, Averaged Over Antarctica) Compared To Precipitation During Positive Sam Phases, Likely Due To Amplified Planetary Waves During Negative Sam Phases. Moreover, Source Vel10 Of Annual Mean Precipitation Is On Average 2.1 Ms-1 Higher Than Annual Mean Vel10 At Moisture Source Locations From Which The Precipitation Originates. This Shows That The Evaporation Of Moisture Driving Antarctic Precipitation Occurs Under Windier Conditions Than Average. We Quantified This Dynamic Control Of Southern Ocean Surface Wind On Moisture Availability For Antarctic Precipitation. Overall, The Innovative Water Tracing Diagnostics Enhance Our Understanding Of The Controlling Factors Of Antarctic Precipitation.
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Guerrieri, A., Cantera, I., Marta, S., Bonin, A., Carteron, A., Ambrosini, R., et al. (2024). Local Climate Modulates The Development Of Soil Nematode Communities After Glacier Retreat. Global Change Biology, 303(1).
Abstract: The Worldwide Retreat Of Glaciers Is Causing A Faster Than Ever Increase In Ice-Free Areas That Are Leading To The Emergence Of New Ecosystems. Understanding The Dynamics Of These Environments Is Critical To Predicting The Consequences Of Climate Change On Mountains And At High Latitudes. Climatic Differences Between Regions Of The World Could Modulate The Emergence Of Biodiversity And Functionality After Glacier Retreat, Yet Global Tests Of This Hypothesis Are Lacking. Nematodes Are The Most Abundant Soil Animals, With Keystone Roles In Ecosystem Functioning, But The Lack Of Global-Scale Studies Limits Our Understanding Of How The Taxonomic And Functional Diversity Of Nematodes Changes During The Colonization Of Proglacial Landscapes. We Used Environmental Dna Metabarcoding To Characterize Nematode Communities Of 48 Glacier Forelands From Five Continents. We Assessed How Different Facets Of Biodiversity Change With The Age Of Deglaciated Terrains And Tested The Hypothesis That Colonization Patterns Are Different Across Forelands With Different Climatic Conditions. Nematodes Colonized Ice-Free Areas Almost Immediately. Both Taxonomic And Functional Richness Quickly Increased Over Time, But The Increase In Nematode Diversity Was Modulated By Climate, So That Colonization Started Earlier In Forelands With Mild Summer Temperatures. Colder Forelands Initially Hosted Poor Communities, But The Colonization Rate Then Accelerated, Eventually Leveling Biodiversity Differences Between Climatic Regimes In The Long Term. Immediately After Glacier Retreat, Communities Were Dominated By Colonizer Taxa With Short Generation Time And R-Ecological Strategy But Community Composition Shifted Through Time, With Increased Frequency Of More Persister Taxa With K-Ecological Strategy. These Changes Mostly Occurred Through The Addition Of New Traits Instead Of Their Replacement During Succession. The Effects Of Local Climate On Nematode Colonization Led To Heterogeneous But Predictable Patterns Around The World That Likely Affect Soil Communities And Overall Ecosystem Development.
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Guillemot, A., Bontemps, N., Larose, E., Teodor, D., Faller, S., Baillet, L., et al. (2024). Investigating Subglacial Water-Filled Cavities By Spectral Analysis Of Ambient Seismic Noise: Results On The Polythermal Tête-Rousse Glacier (Mont Blanc, France). Geophysical Research Letters, 515(4).
Abstract: Polythermal Glaciers Can Trap Considerable Volumes Of Liquid Water With The Potential To Generate Devastating Outburst Floods. This Study Aims To Identify Water-Filled Subglacial Reservoirs From Ambient Seismic Noise Collected By Moderate-Cost Surveys. The Horizontal-To-Vertical Spectral Ratio Technique Is Highly Sensitive To Impedance Contrasts At Interfaces, Thus Commonly Used To Estimate Glacier Thickness. Here, We Focus On The Inverse Ratio, That Is, The V/H Spectral Ratio (Vhsr), Whose High Values Indicate A Low Impedance Volume Beneath The Surface, Suggesting Subglacial Cavities. We Analyze Vhsr Peaks From A Seismic Array Of 60 Nodes Installed On The Tete-Rousse Glacier (Mont Blanc Massif, French Alps); Data Were Gathered Over 15 Days. Mapping The Vhsr Amplitude Over The Free Surface Reveals The Main Cavity Locations And The Basal Areas Affected By Melting Within The Glacier. Results Obtained In The Field Are Supported By A Conceptual Model Based On 3D Finite-Element Simulations. Considerable Volumes Of Liquid Water May Be Trapped Within Cavities In Polythermal Glaciers. If These Cavities Rupture, The Resulting Outburst Flood Has The Potential To Cause Devastation In Populated Mountain Areas. With The Aim Of Testing Methods To Locate Such Cavities, We Installed 60 Small 3-Component Seismic Sensors On The Tete-Rousse Glacier (Mont Blanc Massif, French Alps), Which Is Known To Contain Such Cavities. We Used These Sensors To Test A Detection Method Based On Ambient Seismic Noise. For 3 Weeks, The Sensors Recorded Vibrations Within The Glacier. On A Glacier Without Cavities, These Vibrations Ought To Be Predominantly In The Horizontal Direction. In The Presence Of A Cavity, We Expect The Ice Above The Cavity To Vibrate Mostly Vertically-Like A Bridge. In This Paper, We Highlight Areas On The Glacier Where Vertical Vibrations Were Stronger Than Horizontal Vibrations. These Areas Fit Well With The Locations Of The Main Known Cavities In This Glacier, And With Areas Affected By Basal Melting. We Supported Our Field Observations With Modeling Based On 3D Simulations, Paving The Way To A New Method To Locate Water-Filled Cavities Within Glaciers. Spectral Analysis From Ambient Seismic Noise Is Complementary To Other Geophysical Methods For Investigating Glaciers At Depth Results Suggest That The Vertical-To-Horizontal Spectral Ratio Is A Reliable Proxy To Locate Subglacial Cavities Experimental Results Were Confirmed Using A Simplified Numerical Model
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Gustin, M., Dunham-Cheatham, S., Osterwalder, S., Magand, O., & Dommergue, A. (2024). What Is The Utility Of Measuring Gaseous Hgii Dry Deposition Using Aerohead Samplers?: A Review. Science Of The Total Environment, 9079.
Abstract: The Most Efficient Way To Quantify Hgii Inputs To Ecosystems Is To Measure Wet And Dry Deposition. Wet Deposition Of Hgii Is Determined By Measuring Hg Concentrations And The Volume Of Precipitation. Dry Deposition Of Hgii Is Determined Through Direct Measurement And/Or Determined Indirectly By Measuring Air Concentrations And Using Model-Generated Deposition Velocities. Here, Data Collected Using An Aerohead Sampler Holding Cation Exchange Membranes Are Summarized, And The Utility Of This Method For Understanding Dry Deposition, And Other Measurements And Processes Is Discussed. This Analysis Includes Information From Publications, And Recent Data Collected At Guadalupe Mountains National Park, Texas, Usa, And Amsterdam Island, Southern Indian Ocean. This Method Primarily Measures Gaseous Hgii And Little Particulate-Bound Hg. The Aerohead Method Is Useful For Looking At Large-Scale Trends In Deposition, Verifying Hg Depletion Events, Calculating Dry Deposition Velocities For Compounds With Specific Chemistry, And Identification Of Sources Of Hgii. At Numerous Locations In The Western Usa, Deposition Rates Were Greater At Higher Elevations Due To Elevated Concentrations Associated With Longrange Transport Of Atmospheric Pollution. When Used In Tandem With The Reactive Mercury Active System Or A Dual-Channel System, More Accurate Deposition Velocities – That Vary As A Function Of Gom Compound Chemistry – Can Be Calculated.
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Hachgenei, N., Robinet, N., Baduel, C., Nord, G., Spadini, L., Martins, J., et al. (2024). Catchment-Scale Rapid Transfer Of Livestock Pharmaceuticals Under Mediterranean Climate. Science Of The Total Environment, 9069.
Abstract: Various Pharmaceuticals Are Essential For Livestock Farming, But Some Are Highly Toxic To Aquatic Life If They Reach Surface Water Bodies. Mediterranean Climate Is Characterized By Dry Summers Followed By Intense Autumn Storms. We Studied The Effect Of These Climatic Conditions On The Risk Of Pharmaceutical Residues Transfer To Streams At The Catchment-Scale. Pharmaceutical Products Routinely Used In The Study Area, As Well As Their Application Frequency And Season, Were Identified Through Interviews With Farmers. As A Proof A Concept, Three Veterinary Pharmaceuticals (Fenbendazole (Fbz), Mebendazole (Mbz) And Ivermectin (Ivm)) Were Chosen As Model Chemicals Based On Their Relatively High Usage, Their Specificity To Represent Different Types Of Livestock (Swine, Sheep And Cattle), And Their Ability To Be Analyzed Using The Same Analytical Method. Stream Water Was Analyzed During Low Flow Periods And At High Frequency (Up To 2 H(-1)) During Flood Events. The Selected Veterinary Pharmaceuticals Were Not Detected During Low Flow, But Fbz And Mbz Reached High Concentrations For Short Periods During Floods. Due To The Event-Driven Nature Of Their Transfer, A Significant Load Of Veterinary Pharmaceuticals Can Reach The River And Cause Temporary But Significant Degradation Of Water Quality (E.G. For Fbz, The Water Concentration Reached Up To 355 Times The Predicted No Effect Concentration (Pnec)). This Indicates That Special Care Should Be Taken To Avoid Keeping Freshly Treated Livestock On Pastures That May Become Hydrologically Connected Under Wet Conditions. In Addition, It Suggests That Low-Frequency Monitoring Is Not Sufficient To Detect Those High Concentration Levels That Exist During Very Short Periods.
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Haruna, A., Blanchet, J., & Favre, A. (2024). Estimation Of Intensity-Duration-Area-Frequency Relationships Based On The Full Range Of Non-Zero Precipitation From Radar-Reanalysis Data. Water Resources Research, 606(2).
Abstract: Intensity-Duration-Area-Frequency (Idaf) Models Provide The Mathematical Link Between Precipitation Intensities (I), Durations (D), Areas (A), And Frequency Of Occurrence (F). They Play A Critical Role In Hydrological Design, Areal Rainfall Hazard Quantification, Storm Characterization, And Early Warning System Development. Idaf Models Extend The Conventional Intensity-Duration-Frequency Models By Accounting For The Spatial Extent Of Precipitation (I.E., The Area). In This Study, We Develop Idaf Models Using The Entire Non-Zero Precipitation Intensities, Not Only The Extremes. We Use The Extended Generalized Pareto Distribution (Egpd) To Model The Precipitation Intensities. To Build The Idaf Models, We Adopt A Data-Driven Approach That Allows The Linkage Of Egpd Parameters With Duration And Area, Based On Empirically Determined Parametric Relationships. The Inference Of Model Parameters Is Done Using A Global Maximum Likelihood Estimation, And Uncertainties Are Assessed By The Bootstrap Method. The Study Area Is Switzerland, A Topographically Complex Region Of 42,000 Km2 With Regional Precipitation Variability And Clear Seasonality. The Study Utilizes 17 Years Of Data From Combiprecip, A Radar-Reanalysis Product Developed By Geostatistically Merging Radar And Rain Gauge Data In An Operational Setting. We Build The Idaf Models For The Spatiotemporal Range Of 1-72 Hr And 1 To 1,089 Km2 At Each Pixel In The Study Area. To The Best Of Our Knowledge, Our Study Is The First Attempt To Use The Egpd In Idaf Curve Modeling. It Discusses The Use And Limitations Of Combiprecip In Extreme Value Analysis And Highlights The Challenges Of Modeling Areal Precipitation In A Complex Topographical Environment. We Develop Seasonal Intensity Duration Area Frequency Models At Every Pixel Location In Switzerland We Use All The Non-Zero Precipitation Data And Model The Intensities Using The Extended Generalized Pareto Distribution We Highlight The Complexity Of Modeling Areal Precipitation In Mountainous Regions
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Jager, E., Gillet-Chaulet, F., Mouginot, J., & Millan, R. (2024). Validating Ensemble Historical Simulations Of Upernavik Isstrøm (1985-2019) Using Observations Of Surface Velocity And Elevation. Journal Of Glaciology, .
Abstract: The Future Of Tidewater Glaciers In Response To Climate Warming Is One Of The Largest Sources Of Uncertainty In The Contribution Of The Greenland Ice Sheet To Global Sea-Level Rise. In This Study, We Investigate The Ability Of An Ice-Sheet Model To Reproduce The Past Evolution Of The Velocity And Surface Elevation Of A Tidewater Glacier, Upernavik Isstrom, By Prescribing Front Positions. To Achieve This, We Run Two Ensembles Of Simulations With A Weertman And A Regularised-Coulomb Friction Law. We Show That The Ice-Flow Model Has To Include A Reduction In Friction In The First 15 Km Upstream Of The Ice Front In Fast-Flowing Regions To Capture The Trends Observed During The 1985-2019 Period. Without This Process, The Ensemble Model Overestimates The Ice Flow Before The Retreat Of The Front In 2005 And Does Not Fully Reproduce Its Acceleration During The Retreat. This Results In An Overestimation Of The Total Mass Loss Between 1985 And 2019 Of 50% (300 Vs 200 Gt). Using A Variance-Based Sensitivity Analysis, We Show That Uncertainties In The Friction Law And The Ice-Flow Law Have A Greater Impact On The Model Results Than Surface Mass Balance And Initial Surface Elevation.
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Jonville, T., Flamant, C., & Lavaysse, C. (2024). Dynamical Study Of Three African Easterly Waves In September 2021. Quarterly Journal Of The Royal Meteorological Society, .
Abstract: Three Convectively Active African Easterly Waves (Aews) That Propagated South Of The African Easterly Jet Were Observed Over The Northeast Atlantic Ocean In September 2021. Their Evolution Is Studied Using A Suite Of Theoretical Frameworks, As Well As The European Centre For Medium-Range Weather Forecast Reanalyses And Satellite-Derived Brightness Temperature Observations. The Environment Of These Aews Was Sampled During The Cloud-Atmospheric Dynamics-Dust Interactions In West Africa Campaign Near Cape Verde With The Goal To Assess Their Potential For Developing Into Tropical Cyclones. We Highlight The Processes That Inhibited The Development Of The First Aew (Which Evolved Into Tropical Disturbance Pierre-Henri) And That Played A Role In The Development Of The Later Two Into Tropical Storms Rose And Peter On September 19, 2021. The Three Aews Developed A So-Called “Marsupial Protective” Pouch. For Peter And Rose, The Pouch Was Associated With A Vertically Aligned Vortex At Low Levels And Efficiently Protected The Convective Systems Inside From Dry And Dusty Air Intrusion. The Development Of This Low-Level Vortex Is Associated With An Interaction With The Monsoon Trough For Rose And With A Vorticity Center Associated With A Wave Propagating North Of The African Easterly Jet (Aej) In The Case Of Peter. The Presence Of A Dust Flux Toward The Convective Core Near The Surface Is Highlighted For Rose And Peter In Spite Of The Presence Of The Protective Marsupial Pouch. On The Other Hand, Pierre-Henri Interacted Positively With Both The Monsoon Trough And An Aew North Of The Aej But Failed To Develop Into A Tropical Cyclone. The Wave North Of The Aej Brought Saharan Air Layer Air Masses Inside The Pouch That Led To A Drying Of The Circulation That May Explain The Decrease In Convective Activity. We Used Different Methods To Analyse The Processes That Helped Or Inhibited The Development Of Three African Easterly Waves (Aews) Into Tropical Cyclones. A Wave Pouch Structure That Protects A Convective System Moving With The Wave Is Observed In The Three Cases And Studied Within The Marsupial Paradigm Framework. The Development Of An Aligned Vortex At Low Levels, Either By Interaction With The Monsoon Trough Or Between Aews North And South Of The African Easterly Jet, Are Highlighted. In One Case, The Latter Interaction Caused The Intrusion Of Dry Air That Might Have Inhibited Cyclogenesis. Image
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Jurasz, J., Guezgouz, M., Campana, P., Kazmierezak, B., Kuriqi, A., Bloomfield, H., et al. (2024). Complementarity Of Wind And Solar Power In North Africa: Potential For Alleviating Energy Droughts And Impacts Of The North Atlantic Oscillation. Renewable & Sustainable Energy Reviews, 1911.
Abstract: With Growing Gas And Oil Prices, Electricity Generation Based On These Fossil Fuels Is Becoming Increasingly Expensive. Furthermore, The Vision Of Natural Gas As A Transition Fuel Is Subject To Many Constraints And Uncertainties Of Economic, Environmental, And Geopolitical Nature. Consequently, Renewable Energies Such As Solar And Wind Power Are Expected To Reach New Records Of Installed Capacity Over The Upcoming Years. Considering The Above, North Africa Is One Of The Regions With The Largest Renewable Resource Potential Globally. While Extensively Studied In The Literature, These Resources Remain Underutilized. Thus, To Contribute To Their Future Successful Deployment And Integration With The Power System, This Study Presents A Spatial And Temporal Analysis Of The Nature Of Solar And Wind Resources Over North Africa From The Perspective Of Energy Droughts. Both The Frequency And Maximal Duration Of Energy Droughts Are Addressed. Both Aspects Of Renewables' Variable Nature Have Been Evaluated In The North Atlantic Oscillation (Nao) Context. The Analysis Considers The Period Between 1960 And 2020 Based On Hourly Reanalysis Data (I.E., Near-Surface Shortwave Irradiation, Wind Speed, And Air Temperature) And The Hurrel Nao Index. The Findings Show An In-Phase Relationship Between Solar Power And Winter Nao Index, Particularly Over The Coastal Regions In Western North Africa And Opposite Patterns In Its Eastern Part. For Wind Energy, The Connection With Nao Has A More Zonal Pattern, With Negative Correlations In The North And Positive Correlations In The South. Solar Energy Droughts Dominate Northern Tunisia, Algeria, And Morocco, While Wind Energy Droughts Mainly Occur In The Atlas Mountains Range. On Average, Solar Energy Droughts Tend Not To Exceed 2-3 Consecutive Days, With The Longest Extending For Five Days. Wind Energy Droughts Can Be As Prolonged As 80 Days (Atlas Mountains). Hybridizing Solar And Wind Energy Reduces The Potential For Energy Droughts Significantly. At The Same Time, The Correlation Between Their Occurrence And The Nao Index Remains Low. These Findings Show The Potential For Substantial Resilience To Inter-Annual Climate Variability, Which Could Benefit The Future Stability Of Renewables-Dominated Power Systems.
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Katharina, K., Berg, P., Bozhinova, D., Crochemore, L., Du, Y., Pechlivanidis, I., et al. (2024). Robustness Of Hydrometeorological Extremes In Surrogated Seasonal Forecasts. International Journal Of Climatology, .
Abstract: Water And Disaster Risk Management Require Accurate Information About Hydrometeorological Extremes. However, Estimation Of Rare Events Using Extreme Value Analysis Is Hampered By Short Observational Records, With Large Resulting Uncertainties. Here, We Present A Surrogate World Setup That Makes Use Of Data Samples From Meteorological And Hydrological Seasonal Re-Forecasts To Explore Extremes For Long Return Periods. The Surrogate Timeseries Allow Us To Pool The Re-Forecasts Into 1000-Year-Long Timeseries. We Can Then Calculate Return Values Of Extremes And Explore How They Are Affected By The Size Of Sub-Samples As Method For Estimating The Uncertainty. The Approach Relies On The Fact That Probabilistic Seasonal Re-Forecasts, Initialized With Perturbed Initial Conditions, Have Limited Predictive Skill With Increasing Lead Time. At Long Lead Times Re-Forecasts Will Diverge Into Independent Samples. The Meteorological Seasonal Re-Forecasts Are Taken From The Seas5 System, And Hydrological Re-Forecasts Are Generated With The E-Hype Process-Based Model For The Pan-European Domain. Extreme Value Analysis Is Applied To Annual Maxima Of Precipitation And Streamflow For Return Periods Of 100 Years. The Analysis Clearly Demonstrates The Large Uncertainty In Long Return Period Estimates With Typical Available Samples Of Only Few Decades. The Uncertainty Is Somewhat Reduced For 100-Year Samples, But Several 100 Years Seem To Be Necessary To Have Robust Estimates. The Bootstrap With Replacement Approach Is Applied To Shorter Timeseries, And Is Shown To Well Reproduce The Uncertainty Range Of The Longer Samples. However, The Main Estimate Of The Return Value Can Be Significantly Offset. Although The Method Is Model Based, With The Associated Uncertainties And Bias Compared To The Real World, The Surrogate Approach Is Likely Useful To Explore Rare And Compounding Extremes. A Method To Generate 1000-Of-Years Long Surrogate Timeseries For Assessing Extreme Streamflow Using Seasonal Forecast Data Is Presented. Illustrative Cases Compare Conventional Bootstrap Method On Single Shorter Timeseries To The Surrogate Data, And Show A Rather Good Sampling Of The Uncertainty, But A Lack Of Precision For The Expected Value. Image
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Kellerer-Pirklbauer, A., Bodin, X., Delaloye, R., Lambiel, C., Gärtner-Roer, I., Bonnefoy-Demongeot, M., et al. (2024). Acceleration And Interannual Variability Of Creep Rates In Mountain Permafrost Landforms (Rock Glacier Velocities) In The European Alps In 1995-2022. Environmental Research Letters, 191(3).
Abstract: Cryospheric Long-Term Timeseries Get Increasingly Important. To Document Climate-Related Effects On Long-Term Viscous Creep Of Ice-Rich Mountain Permafrost, We Investigated Timeseries (1995-2022) Of Geodetically-Derived Rock Glacier Velocity (Rgv), I.E. Spatially Averaged Interannual Velocity Timeseries Related To A Rock Glacier (Rg) Unit Or Part Of It. We Considered 50 Rgv From 43 Rgs Spatially Covering The Entire European Alps. Eight Of These Rgs Are Destabilized. Results Show That Rgv Are Distinctly Variable Ranging From 0.04 To 6.23 M A-1. Acceleration And Deceleration At Many Rgs Are Highly Correlated With Similar Behaviour Over 2.5 Decades For 15 Timeseries. In Addition To A General Long-Term, Warming-Induced Trend Of Increasing Velocities, Three Main Phases Of Distinct Acceleration (2000-2004, 2008-2015, 2018-2020), Interrupted By Deceleration Or Steady State Conditions, Were Identified. The Evolution Is Attributed To Climate Forcing And Underlines The Significance Of Rgv As A Product Of The Essential Climate Variable (Ecv) Permafrost. We Show That Rgv Data Are Valuable As Climate Indicators, But Such Data Should Always Be Assessed Critically Considering Changing Local Factors (Geomorphic, Thermal, Hydrologic) And Monitoring Approaches. To Extract A Climate Signal, Larger Rgv Ensembles Should Be Analysed. Criteria For Selecting New Rgv-Sites Are Proposed.
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Lapere, R., Thomas, J., Favier, V., Angot, H., Asplund, J., Ekman, A., et al. (2024). Polar Aerosol Atmospheric Rivers: Detection, Characteristics, And Potential Applications. Journal Of Geophysical Research-Atmospheres, 1291(2).
Abstract: Aerosols Play A Key Role In Polar Climate, And Are Affected By Long-Range Transport From The Mid-Latitudes, Both In The Arctic And Antarctic. This Work Investigates Poleward Extreme Transport Events Of Aerosols, Referred To As Polar Aerosol Atmospheric Rivers (P-Aar), Leveraging The Concept Of Atmospheric Rivers (Ar) Which Signal Extreme Transport Of Moisture. Using Reanalysis Data, We Build A Detection Catalog Of P-Aars For Black Carbon, Dust, Sea Salt And Organic Carbon Aerosols, For The Period 1980-2022. First, We Describe The Detection Algorithm, Discuss Its Sensitivity, And Evaluate Its Validity. Then, We Present Several Extreme Transport Case Studies, In The Arctic And In The Antarctic, Illustrating The Complementarity Between Ars And P-Aars. Despite Similarities In Transport Pathways During Co-Occurring Ar/P-Aar Events, Vertical Profiles Differ Depending On The Species, And Large-Scale Transport Patterns Show That Moisture And Aerosols Do Not Necessarily Originate From The Same Areas. The Complementarity Between Ar And P-Aar Is Also Evidenced By Their Long-Term Characteristics In Terms Of Spatial Distribution, Seasonality And Trends. P-Aar Detection, As A Complement To Ar, Can Have Several Important Applications For Better Understanding Polar Climate And Its Connections To The Mid-Latitudes. The Extreme Transport Of Aerosol-Containing Air Masses, From The Mid-Latitudes To The Polar Regions, Can Be Characterized And Quantified By Leveraging Polar Aerosol Atmospheric Rivers (P-Aars). This Is Similar To The Atmospheric Rivers (Ars) Which Carry Large Amounts Of Water To The Poles And Affect The Overall Stability Of Polar Ecosystems. In This Work, We Establish A Detection Algorithm For P-Aars And Evaluate It For Different Well-Known Aerosol Intrusions Or Ar Events. The Areas Most Affected By P-Aars Are Described, Their Trends Are Investigated And We Discuss The Potential Applications Of P-Aar Detection For A Better Understanding Of Polar Climate. A Catalog Of Polar Aerosol Atmospheric Rivers (P-Aar) Is Provided For 1980-2022 By Adapting An Atmospheric River (Ar) Detection Schemeimportant P-Aar Events, Representing Rapid Poleward Transport Of Aerosol-Enriched Air Masses, Are Presentedcombining Ar And P-Aar Can Improve Our Understanding Of The Links Between Mid- And Polar-Latitudes, In The Past, Present And Future Climate
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Legrand, M., Preunkert, S., Kutuzov, S., Siour, G., Mikhalenko, V., Dolgova, E., et al. (2024). 20Th Century Changes Of Doc And Its <Sup>14</Sup>C Signature Archived In Caucasus Ice-Core: Implications For Past Sources Of Organic Carbon Aerosol In South-Eastern Europe. Journal Of Geophysical Research-Atmospheres, 1291(5).
Abstract: To Reconstruct The History Of Organic Carbon (Oc) Aerosol Over South-Eastern Europe, Dissolved Organic Carbon (Doc) And Its C-14 Signature ((Doc)-C-14) Were Investigated Along An Ice Core Drilled At The Mount Elbrus (Elb) In Caucasus. In Summer, Compared To Pre-1945 Levels, The Doc Concentrations Increased By 45% After 1960, The Mean Do C-14 Depletion In Recent Elb Ice Relative To Atmospheric (Co2)-C-14 Of 32% Being Attributed To Fossil-Fuel Sources. (Doc)-C-14 Content Of Ice Deposited During The Bomb-Peak Era (1955-1980) Closely Followed Atmospheric (Co2)-C-14 Changes Caused By Atmospheric Nuclear Tests, Suggesting The Living Biosphere As The Main Biogenic Source Of Doc In Summer In This Region. Elb Data Contrast With Those Previously Obtained In Summer Alpine (Western Europe) Ice In Which A Post-1950 Doubling Of Doc Was Observed And Attributed To Enhanced Emissions Of Organic Compounds From Vegetation In France. This Regional Difference Is Discussed With Respect To Changes Of Biogenic Organic Compound Emissions In Response To Past Change Of Use-Land And Global Warming. Elb Data Document, For The First Time, Changes Of Doc And (Doc)-C-14 In Winter Mountain Ice Showing An Increase By 44% Of Doc Levels Associated With A C-14 Signature Being 47% Lower Than That Of Atmospheric (Co2)-C-14 In Elb Ice Deposited After 1960. The C-14 Winter Elb Ice Record Followed Atmospheric (Co2)-C-14 Changes With A Delay Of Similar To 3 Years, Suggesting That Remaining Emissions From The Living Biosphere, Together With A Small Contribution From Wood Burning, Are The Main Biogenic Sources Of Doc In Winter In This Region.
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Leriche, M., Tulet, P., Deguillaume, L., Burnet, F., Colomb, A., Borbon, A., et al. (2024). Measurement Report: Bio-Physicochemistry Of Tropical Clouds At Maïdo (Réunion, Indian Ocean): Overview Of Results From The Bio-Maïdo Campaign. Atmospheric Chemistry And Physics, 242(7), 4129–4155.
Abstract: The Bio-Maido (Bio-Physicochemistry Of Tropical Clouds At Maido: Processes And Impacts On Secondary Organic Aerosols Formation) Campaign Was Conducted From 13 March To 4 April 2019 On The Tropical Island Of Reunion. The Main Objective Of The Project Was To Improve Understanding Of Cloud Impacts On The Formation Of Secondary Organic Aerosols (Soa) From Biogenic Volatile Organic Compound (Bvoc) Precursors In A Tropical Environment. Instruments Were Deployed At Five Sites: A Receptor Site, Maido Observatory (Mo) At 2165 M A.S.L. And Four Sites Along The Slope Of The Maido Mountain. Observations Include Measurements Of Volatile Organic Compounds (Vocs) And Characterization Of The Physical, Chemical And Biological (Bacterial Diversity And Culture-Based Approaches) Properties Of Aerosols And Cloud Water. Turbulent Parameters Of The Boundary Layer, Radiative Fluxes And Emissions Fluxes Of Bvocs From The Surrounding Vegetation Were Measured To Help Interpret Observed Chemical Concentrations In The Different Phases. Dynamical Analyses Showed Two Preferred Trajectory Routes For Air Masses Arriving At Mo During The Daytime. Both Trajectories Correspond To Return Branches Of The Trade Winds Associated With Upslope Thermal Breezes, Where Air Masses Likely Encountered Cloud Processing. The Highest Mixing Ratios Of Oxygenated Vocs (Ovocs) Were Measured Above The Site Located In The Endemic Forest And The Highest Contribution Of Ovocs To Total Vocs At Mo. Chemical Compositions Of Particles During Daytime Showed Higher Concentrations Of Oxalic Acid, A Tracer Of Cloud Processing And Photochemical Aging, And A More Oxidized Organic Aerosol At Mo Than At Other Sites. Approximately 20 % Of The Dissolved Organic Compounds Were Analyzed. Additional Analyses By Ultra-High-Resolution Mass Spectrometry Will Explore The Complexity Of The Missing Cloud Organic Matter.
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Liébault, F., Melun, G., Piton, G., Chapuis, M., Passy, P., & Tacon, S. (2024). Channel Change During Catastrophic Flood: Example Of Storm Alex In The Vesubie And Roya Valleys. Geomorphology, 4464.
Abstract: Documenting And Interpreting Channel Responses To Catastrophic Floods Help Understanding How Rapid Fluvial Metamorphosis Can Propagate In A Catchment Under Sediment Cascading Effects. The Recent Example Of The October 2020 Storm Alex In Se France (Similar To 500 Mm Of Rain In 24 H) Provides A Unique Opportunity To Investigate Major Geomorphic Responses Along 70 Km Of Two Confined Alpine Valleys (V & Eacute;Subie And Roya) And To Link Them To Sediment Wave Initiation And Propagation. Gis-Based Analysis Of Remote Sensing Data (High-Resolution Ortho-Imagery And Airborne Lidar Data) Acquired Before And After The Flood Allowed Combining Channel Changes With Sediment Erosion And Deposition Along A 35-Km Reach Of The V & Eacute;Subie, Including The Most Impacted Portions Of The Valley. In The Roya, The Analysis Was Restricted To 2D Morphological Changes Reconstructed With The Sequence Of Ortho-Imagery. Archives Of Aerial Imagery Were Also Used To Integrate The Storm Impact In The Historical Trajectory Of The Rivers. The Reconstruction Of Geomorphic Responses Shows A Quasi-Continuous Fluvial Metamorphosis Along The Investigated Stream Networks, With Dramatic Active Channel Widening And Aggradation, Having No Antecedent Analogs During The Last 70 Years In Both Valleys. The Different Glacial Imprints Between The Two Valleys Are Considered A Key Factor Explaining The Exacerbated Channel Response In The V & Eacute;Subie, Where A Braided Channel Emerged Along A 35-Km River Length. Many Evidences Strongly Support That The Fuelling Effect Of Alluvial Storage Is A Key Element Of The Sediment Cascade At The Origin Of The Braided Channel Formation. This Regional Case Study Allows Us To Discuss The Critical Role Of Floodplain And Terrace Erosion In The Formation Of The Post-Flood Braided Channel, And To Compare The Geomorphic Impact Of The Storm With Similar Reported Cases In The Literature.
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Manrique, M., Consonni, V., Boubenia, S., Roussel, H., Zeghouane, M., Labau, S., et al. (2024). Enhancing The Output Voltage Of Piezoelectric Nanogenerators Based On Zno Nanowires Grown By Chemical Bath Deposition Using Compensatory Cu Doping. Energy Technology, .
Abstract: The Screening Effect In Zno Nanowires (Nws) Coming From The High Density Of Free Electrons Has Emerged As One Of The Major Issues For Their Efficient Integration Into Piezoelectric Devices. Herein, The Compensatory Cu Doping Of Zno Nws Grown By Chemical Bath Deposition In The High-Ph Region Using Cu(No3)2 And Ammonia As Chemical Additives Is Developed And The Effects Of A Postdeposition Thermal Annealing Under Oxygen Atmosphere Are Investigated. It Is Shown That The Cu Dopants Are Incorporated Into Zno Nws With An Atomic [Cu]/[Zn] Ratio In The Range Of 50-65 Ppm And Undergo A Migration Process Into Their Bulk After Thermal Annealing. Importantly, The Electrical Resistivity Of Cu-Doped Zno Nws Is Found To Increase By A Factor Of 4 Compared To Unintentionally N-Doped Zno Nws. The Increase Is Even More Pronounced After Different Thermal Annealing, Reaching A Factor Exceeding 100, Which Is Explained By The Redistribution Of Hydrogen- And Nitrogen-Related Defects Along With The Thermal Activation Of Cu Dopants. Additionally, It Is Revealed That A Rigid Piezoelectric Nanogenerator Based On A Cu-Doped Zno Nw Matrix Exhibits The Highest Output Voltage And Effective Piezoelectric Coefficient D33Eff Thanks To The Reduction Of The Screening Effect, Opening Perspectives In The Field Of Piezoelectric Devices. Cu-Doped Zno Nanowires (Nws) Grown By Chemical Bath Deposition Exhibited A Free Electron Density Decrease Of 50% As Compared To Pristine Zno Nws. Additionally, Cu-Doped Zno Nw Based Piezoelectric Nanogenerators Showed The Highest Output Voltage Along With The Effective Piezoelectric Coefficient At Different Mechanical Stress Conditions.Image (C) 2024 Wiley-Vch Gmbh
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Marsal, A., Sauvain, J., Thomas, A., Lyon-Caen, S., Borlaza, L., Philippat, C., et al. (2024). Effects Of Personal Exposure To The Oxidative Potential Of Pm<Sub>2.5</Sub> On Oxidative Stress Biomarkers In Pregnant Women. Science Of The Total Environment, 9119.
Abstract: Oxidative Stress Is A Prominent Pathway For The Health Effects Associated With Fine Particulate Matter (Pm2.5) Exposure. Oxidative Potential (Op) Of Pm Has Been Associated To Several Health Endpoints, But Studies On Its Impact On Biomarkers Of Oxidative Stress Remains Insufficient. 300 Pregnant Women From The Sepages Cohort (France) Carried Personal Pm2.5 Samplers For A Week And Op Was Measured Using Ascorbic Acid (Aa) And Dithiothreitol (Dtt) Assays, And Normalized By 1) Pm2.5 Mass (Opm) And 2) Sampled Air Volume (Opv). A Pool Of Three Urine Spots Collected On The 7Th Day Of Pm Sampling Was Analyzed For Biomarkers, Namely 8-Hydroxy-2-Deoxyguanosine (8-Ohdg), Malondialdehyde (Mda) And 8-Isoprostaglandin-F2 Alpha (8-Isopgf2 Alpha). Associations Were Investigated Using Adjusted Multiple Linear Regressions. Op Effects Were Additionally Investigated By Stratifying By Median Pm2.5 Concentration (14 Mu G M(-3)). In The Main Models, No Association Was Observed With 8-Isopgf2 Alpha, Nor Mda. An Interquartile Range (Iqr) Increase In Opmaa Exposure Was Associated With Increased 8-Ohdg (Percent Change: 6.2 %; 95 % Ci: 0.2 % To 12.6 %). In The Stratified Analysis, Exposure To Opmaa Was Associated With 8-Ohdg For Participants Exposed To Low Levels Of Pm2.5 (Percent Change: 11.4 %; 95 % Ci: 3.3 % To 20.1 %), But Not For Those Exposed To High Levels (Percent Change: -1.0 %; 95 % Ci: -10.6 % To 9.6 %). Associations For Opmdtt Also Followed A Similar Pattern (P-Values For Opmaa-Pm And Opmdtt-Pm Interaction Terms Were 0.12 And 0.11, Respectively). Overall, Our Findings Suggest That Opmaa May Be Associated With Increased Dna Oxidative Damage. This Association Was Not Observed With Pm2.5 Mass Concentration Exposure. The Effects Of Opmaa In 8-Ohdg Tended To Be Stronger At Lower (Below Median) Vs. Higher Concentrations Of Pm2.5. Further Epidemiological, Toxicological And Aerosol Research Are Needed To Further Investigate The Opmaa Effects On 8-Ohdg And The Potential Modifying Effect Of Pm Mass Concentration On This Association.
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Mayer, L., Degrendele, C., Senk, P., Kohoutek, J., Pribylová, P., Kukucka, P., et al. (2024). Widespread Pesticide Distribution In The European Atmosphere Questions Their Degradability In Air. Environmental Science & Technology, 585(7), 3342–3352.
Abstract: Risk Assessment Of Pesticide Impacts On Remote Ecosystems Makes Use Of Model-Estimated Degradation In Air. Recent Studies Suggest These Degradation Rates To Be Overestimated, Questioning Current Pesticide Regulation. Here, We Investigated The Concentrations Of 76 Pesticides In Europe At 29 Rural, Coastal, Mountain, And Polar Sites During The Agricultural Application Season. Overall, 58 Pesticides Were Observed In The European Atmosphere. Low Spatial Variation Of 7 Pesticides Suggests Continental-Scale Atmospheric Dispersal. Based On Concentrations In Free Tropospheric Air And At Arctic Sites, 22 Pesticides Were Identified To Be Prone To Long-Range Atmospheric Transport, Which Included 15 Substances Approved For Agricultural Use In Europe And 7 Banned Ones. Comparison Between Concentrations At Remote Sites And Those Found At Pesticide Source Areas Suggests Long Atmospheric Lifetimes Of Atrazine, Cyprodinil, Spiroxamine, Tebuconazole, Terbuthylazine, And Thiacloprid. In General, Our Findings Suggest That Atmospheric Transport And Persistence Of Pesticides Have Been Underestimated And That Their Risk Assessment Needs To Be Improved.
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Médieu, A., Point, D., Sonke, J., Angot, H., Allain, V., Bodin, N., et al. (2024). Stable Tuna Mercury Concentrations Since 1971 Illustrate Marine Inertia And The Need For Strong Emission Reductions Under The Minamata Convention. Environmental Science & Technology Letters, 111(3), 250–258.
Abstract: Humans Are Exposed To Toxic Methylmercury Mainly By Consuming Marine Fish. While Reducing Mercury Emissions And Releases Aims To Protect Human Health, It Is Unclear How This Affects Methylmercury Concentrations In Seawater And Marine Biota. We Compiled Existing And Newly Acquired Mercury Concentrations In Tropical Tunas From The Global Ocean To Explore Multidecadal Mercury Variability Between 1971 And 2022. We Show The Strong Inter-Annual Variability Of Tuna Mercury Concentrations At The Global Scale, After Correcting For Bioaccumulation Effects. We Found Increasing Mercury Concentrations In Skipjack In The Late 1990S In The Northwestern Pacific, Likely Resulting From Concomitant Increasing Asian Mercury Emissions. Elsewhere, Stable Long-Term Trends Of Tuna Mercury Concentrations Contrast With An Overall Decline In Global Anthropogenic Mercury Emissions And Deposition Since The 1970S. Modeling Suggests That This Limited Response Observed In Tunas Likely Reflects The Inertia Of Surface Ocean Mercury With Respect To Declining Emissions, As It Is Supplied By Legacy Mercury That Accumulated In The Subsurface Ocean Over Centuries. To Achieve Measurable Declines In Mercury Concentrations In Highly Consumed Pelagic Fish In The Near Future, Aggressive Emission Reductions And Long-Term And Continuous Mercury Monitoring In Marine Biota Are Needed.
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Merlo-Reyes, A., Baduel, C., Duwig, C., & Ramirez, M. (2024). Risk Assessment Of Pesticides Used In The Eastern Avocado Belt Of Michoacan, Mexico: A Survey And Water Monitoring Approach. Science Of The Total Environment, 9169.
Abstract: Pesticides Use Raises Concerns Regarding Environmental Sustainability, As Pesticides Are Closely Linked To The Decline Of Biodiversity And Adverse Human Health Outcomes. This Study Proposed A Holistic Approach For Assessing The Potential Risks Posed By Pesticides For Human Health And The Environment In The Eastern Region Of Michoacan, Where Extensive Agricultural Lands, Especially Corn And Avocado Fields, Surround The Monarch Butterfly Biosphere Reserve. We Used A Combination Of Qualitative (Semi -Structured Interviews) And Quantitative (Chemical Analysis) Data. Fifty-Five Interviews With Smallholder Farmers Allowed Us To Identify Pesticide Types, Quantities, Frequencies, And Application Methods. A Robust And Precise Analytical Method Based On Solid -Phase Extraction And Lc-Ms/Ms Was Developed And Validated To Quantify 21 Different Pesticides In 16 Water Samples (Rivers, Wells, Runoff Areas). We Assessed Environmental And Human Health Risks Based On The Pesticides Detected In The Water Samples And Reported In The Interviews. The Interviews Revealed The Use Of 28 Active Ingredients, Including Glyphosate (29 % Of Respondents), Imidacloprid (27 %), And Benomyl (24 %). The Pesticide Analysis Showed The Presence Of 13 Different Pesticides And Degradation Products In The Water Samples. The Highest Concentrations Were Found For Imidacloprid (1195 Ngl-1) And Carbendazim (A Degradation Product Of Benomyl; 932 Ngl-1), Along With The Metabolite Of Pyrethroid Insecticides, 3-Pba (494 Ngl-1). The Risk Assessment Indicates That Among The Most Used Pesticides, The Fungicide Benomyl And Carbendazim Pose The Highest Risk To Human Health And Aquatic Ecosystems, Respectively. This Study Unveils Novel Insights On Agricultural Practices For The Avocado, A Globally Consumed Crop That Is Undergoing Rapid Production Expansion. It Calls For The Harmonisation Of Crop Protection With Environmental Responsibility, Safeguarding The Health Of The People Involved And The Surrounding Ecosystems.
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Michot, V., Corpetti, T., Ronchail, J., Espinoza, J., Arvor, D., Funatsu, B., et al. (2024). Seasonal Types In Homogeneous Rainfall Regions Of The Amazon Basin. International Journal Of Climatology, 444(4), 1224–1244.
Abstract: Due To Its Size And Geographical Features, Different Average Annual Rainfall Regimes Co-Exist In The Amazon Basin, With Distinct Year-To-Year Variability Dependent On Regions Within The Basin. In This Study, We Define And Explain The Seasonal Regional Types Of Annual Regimes, That Is, Years With Similar Seasonal Anomalies. Our Work Is Based On A 205 Rain Gauge Network Distributed Over Five Amazonian Countries, Spanning A Period Over 30 Years. Using A Spectral Clustering Method, We Identified Seven Sub-Regions Within The Basin In Which Annual Rainfall Regimes Are Spatially Homogenous. For Each Sub-Domain, We Estimated Specific Parameters That Characterize The Rainy Season (Onset And Demise Dates, Sign And Duration Of Rainfall Anomalies). Finally, Using Spectral Analysis We Identified Between Two And Four 'Seasonal Type' Of Precipitation In These Seven Sub-Domains. Most Of These Seasonal Types Are In Phase With The Large-Scale Atmospheric Circulation, Which Explains The Temporal Link With Rainfall Anomalies. The Seasonal Types Result Of The Superposition Of Inter-Annual And Intra-Seasonal Variability Whose Factors Are Then Difficult To Identify And Attribute. Part Of The Rainfall Anomalies Characterizing Seasonal Types Is Related To The Inter-Annual Variability Of The Sea Surface Temperature In The Atlantic Or The Pacific Oceans, Especially In The Northeast And Southeast Part Of The Amazon Basin, Whereas In Other Parts, Strong Intra-Seasonal And Local Factors Have A Larger Impact. The Same Sign And Duration Of Anomalies Do Not Concomitantly Affect The Various Regions Of The Amazon Basin, Confirming That One Mode Of Variability Does Not Homogeneously Affect Precipitation In Different Parts Of The Basin. Based On Rain Gauges Data And Spectral Analysis, We Identified Between Two And Four 'Seasonal Type' Of Precipitation, Compared With The Historical Mean Seasonal Regime, In Seven Homogeneous Rainfall Regions Of The Amazon Basin. Seasonal Types Result Of The Superposition Of Inter-Annual And Intra-Seasonal Variability. Part Of The Rainfall Anomalies Is Related To The Inter-Annual Variability Of The Sea Surface Temperature In The Surrounding Oceans, Especially In The Northeast And Southeast Part Of The Amazon Basin. Image
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Montoya-Coronado, V., Tedoldi, D., Castebrunet, H., Molle, P., & Kouyi, G. (2024). Data-Driven Methodological Approach For Modeling Rainfall-Induced Infiltration Effects On Combined Sewer Overflow In Urban Catchments. Journal Of Hydrology, 6326.
Abstract: Combined Sewer System Deterioration Poses Significant Challenges, Especially As It Leads To Substantial Volumes Of Permanent Infiltration Inflow (Pii) And Rain-Induced Infiltration (Rii) To Percolate Into Sewer Pipes. This Infiltration Increases The Risk Of Combined Sewer Overflow (Cso) Events And Reduces The Treatment Plant'S Efficiency By Diluting Raw Effluent. To Effectively Decrease Cso Volumes, It Is Crucial To Identify The Various Flow Components And Their Contribution To Overflow Volumes. In This Study, A Data-Driven Hydrological Model Was Developed, Conceptualizing The Surface Hydrological Processes As Well As The Interactions Between Soil Water And The Sewer System, Based On Long-Term Monitoring. Four Flow Components At The Outlet Of The Catchment Were Identified And Characterized: Wastewater, Surface Runoff, Pii, And Rii. The Model Was Applied And Evaluated Using Monitored Data From The Ecully Catchment In France. The Model Demonstrated Its Suitability In Replicating The Observed Hydrograph And Estimating Cso Volumes. Two Sewer System Scenarios Were Proposed, Investigating The Effect Of Partial And Complete Reduction Of Pii And Rii On Cso Volumes. The Results Showed A Reduction Of The Annual Cso Volume By 5 % To 7.5 %, And 12 % To 17 %, In The First And Second Scenario, Respectively. To Compare The Performance Of These Scenarios With Stormwater Management Strategies, Two Other Scenarios Were Considered Where Source Control Measures Allowed Infiltration Of The First 5 And 10 Mm Of Rainfall. The Results Demonstrated That These Measures Could, Respectively, Reduce Cso Volumes By 13 % To 48 % And Completely Eliminate Cso For Half Of The Events. This Study Highlights The Limitations Of Relying Solely On Pii And Rii Strategies To Eliminate Cso Events And Emphasizes The Necessity Of Considering Stormwater Management Strategies.
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Moreno, C., Krejci, R., Jaffrezo, J., Uzu, G., Alastuey, A., Andrade, M., et al. (2024). Tropical Tropospheric Aerosol Sources And Chemical Composition Observed At High Altitude In The Bolivian Andes. Atmospheric Chemistry And Physics, 242(5), 2837–2860.
Abstract: The Chemical Composition Of Pm 10 And Non-Overlapping Pm 2.5 Was Studied At The Summit Of Mt. Chacaltaya (5380 M A.S.L., Lat. – 16.346950 Degrees, Long. – 68.128250 Degrees) Providing A Unique Long-Term Record Spanning From December 2011 To March 2020. The Chemical Composition Of Aerosol At The Chacaltaya Global Atmosphere Watch (Gaw) Site Is Representative Of The Regional Background, Seasonally Affected By Biomass Burning Practices And By Nearby Anthropogenic Emissions From The Metropolitan Area Of La Paz-El Alto. Concentration Levels Are Clearly Influenced By Seasons With Minima Occurring During The Wet Season (December To March) And Maxima Occurring During The Dry And Transition Seasons (April To November). Ions, Total Carbon (Ec + Oc), And Saccharide Interquartile Ranges For Concentrations Are 558-1785, 384-1120, And 4.3-25.5 Ng M – 3 For Bulk Pm 10 And 917-2308, 519-1175, And 3.9-24.1 Ng M – 3 For Pm 2.5 , Respectively, With Most Of The Aerosol Seemingly Present In The Pm 2.5 Fraction. Such Concentrations Are Overall Lower Compared To Other High-Altitude Stations Around The Globe But Higher Than Amazonian Remote Sites (Except For Oc). For Pm 10 , There Is Dominance Of Insoluble Mineral Matter (33 %-56 % Of The Mass), Organic Matter (7 %-34 %), And Secondary Inorganic Aerosol (15 %-26 %). Chemical Composition Profiles Were Identified For Different Origins: Ec, No 3 – , Nh 4 + , Glucose, And C 2 O 4 2 – For The Nearby Urban And Rural Areas; Oc, Ec, No 3 – , K + , Acetate, Formate, Levoglucosan, And Some F – And Br – For Biomass Burning; Meso 3 – , Na + , Mg 2 + , K + , And Ca 2 + For Aged Marine Emissions From The Pacific Ocean; Arabitol, Mannitol, And Glucose For Biogenic Emissions; Na + , Ca 2 + , Mg 2 + , And K + For Soil Dust; And So 4 2 – , F – , And Some Cl – For Volcanism. Regional Biomass Burning Practices Influence The Soluble Fraction Of The Aerosol Between June And November. The Organic Fraction Is Present All Year Round And Has Both Anthropogenic (Biomass Burning And Other Combustion Sources) And Natural (Primary And Secondary Biogenic Emissions) Origins, With The Oc / Ec Mass Ratio Being Practically Constant All Year Round (10.5 +/- 5.7, Iqr 8.1-13.3). Peruvian Volcanism Has Dominated The So 4 2 – Concentration Since 2014, Though It Presents Strong Temporal Variability Due To The Intermittence Of The Sources And Seasonal Changes In The Transport Patterns. These Measurements Represent Some Of The First Long-Term Observations Of Aerosol Chemical Composition At A Continental High-Altitude Site In The Tropical Southern Hemisphere.
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Murfitt, J., Duguay, C., Picard, G., & Lemmetyinen, J. (2024). Forward Modelling Of Synthetic-Aperture Radar (Sar) Backscatter During Lake Ice Melt Conditions Using The Snow Microwave Radiative Transfer (Smrt) Model. Cryosphere, 181(2), 869–888.
Abstract: Monitoring Of Lake Ice Is Important To Maintain Transportation Routes, But In Recent Decades The Number Of In Situ Observations Have Declined. Remote Sensing Has Worked To Fill This Gap In Observations, With Active Microwave Sensors, Particularly Synthetic-Aperture Radar (Sar), Being A Crucial Technology. However, The Impact Of Wet Conditions On Radar And How Interactions Change Under These Conditions Have Been Largely Ignored. It Is Important To Understand These Interactions As Warming Conditions Are Likely To Lead To An Increase In The Occurrence Of Slush Layers. This Study Works To Address This Gap Using The Snow Microwave Radiative Transfer (Smrt) Model To Conduct Forward-Modelling Experiments Of Backscatter For Lake Oulujarvi In Finland. Experiments Were Conducted Under Dry Conditions, Under Moderate Wet Conditions, And Under Saturated Conditions. These Experiments Reflected Field Observations During The 2020-2021 Ice Season. Results Of The Dry-Snow Experiments Support The Dominance Of Surface Scattering From The Ice-Water Interface. However, Conditions Where Layers Of Wet Snow Are Introduced Show That The Primary Scattering Interface Changes Depending On The Location Of The Wet Layer. The Addition Of A Saturated Layer At The Ice Surface Results In The Highest Backscatter Values Due To The Larger Dielectric Contrast Created Between The Overlying Dry Snow And The Slush Layer. Improving The Representation Of These Conditions In Smrt Can Also Aid In More Accurate Retrievals Of Lake Ice Properties Such As Roughness, Which Is Key For Inversion Modelling Of Other Properties Such As Ice Thickness.
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Pant, M., Shahi, N., Remedio, A., Mall, R., Rai, S., & Bhatla, R. (2024). Representing Rainfall Extremes Over The Indo-Gangetic Plains Using Cordex-Core Simulations. Climate Dynamics, .
Abstract: The Indo-Gangetic Plain (Igp), Which Is The Site Of India'S Green Revolution, Covers Almost 15% Of The Country'S Landmass And Is Among The Most Extensively Fertile Lands Across The World. The Densely Populated Igp Region Bears Great Importance For The Socioeconomic Facets Of India And Contributes To A Major Share Of The Gdp Of The Country. The Present Study Demonstrates The Regional-Specific Assessment Of Summer Monsoon Precipitation And Associated Extremes With Dynamical And Thermodynamical Aspects Over The Igp Region Using High-Resolution Regional Climate Models (Rcms) Under The Cordex-Core Framework. The Analysis Reveals That The Eastern Parts Of The Igp Receive Low-To-Moderate Precipitation With A Higher Tail Than The Western Parts, Which Is Due To The Direction Of The Monsoon Low-Level Flow. The Observed Mean Precipitation Characteristics Are Well Represented By The Rcms. Further, The Research Identifies Extreme Precipitation Events Over The Igp And Conducts Comprehensive Analysis To Understand Their Underlying Mechanisms. It Has Been Observed That Extreme Precipitation Events Are Linked With The Moisture Transport Associated With Trough Activity And Instability, And Rcms Are Capable In Representing The Observed Precipitation Extremes And Underlying Mechanisms At Localized Scales. Overall, This Study Represents A Significant Step Forward In Understanding The Evolution Of Spatio-Temporal Variability Of Precipitation Over The Igp Region, Where Agriculture Is A Major Economic Activity And Millions Of People Depend On Rainfed Agriculture.
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Piton, G., Cohen, M., Flipo, M., Nowak, M., Chapuis, M., Melun, G., et al. (2024). Large In-Stream Wood Yield During An Extreme Flood (Storm Alex, October 2020, Roya Valley, France): Estimating The Supply, Transport, And Deposition Using Gis. Geomorphology, 4464.
Abstract: During Major Floods, Rivers Erode Their Banks And Thus Recruit Large Wood Pieces From The Riparian Zones. There Is Still A Lack Of Knowledge About The Transport Of Large Wood, The Volumes Involved And The Flux Distribution, I.E. The Large Wood Connectivity At Catchment Scale. During Storm Alex (October 2020), The French Roya Catchment (394 Km2) Experienced A Paroxysmal Morphogenic Flood Involving Massive Bank Erosion. The Riparian Vegetation Was Largely Recruited, With Large Wood Contributing To Logjams And Bridge Destruction. This Paper Presents A Methodology For Volumetric Assessment Of The Large Wood Fluxes Involved. Simple Approaches Are Used To (I) Quantify The Inputs From Stand Density Data From The National Forest Inventory And From Source Areas Based On Diachronic Analysis Of Active Channels Highlighting The Erosion Of 87 Ha Of Wooded Areas; And (Ii) Quantify The Volumes Deposited Via An Exhaustive Manual Digitisation Of 16,846 Pieces Of Large Wood Deposited On 59 Km Of Channels On The Roya And Its Tributaries. This Catchment-Scale, Large Wood Connectivity Analysis Shows That The Flood Recruited And Transported Downstream A Volume Of Around 14,000 M3 Of Large Wood (Uncertainty Range: 7000-29,500 M3). Drone Observations Of The Roya River Mouth In Italy And Satellite Images Showing A Raft Of Driftwood, Several Km Long, Drifting Off The Roya River Mouth In The Aftermath Of The Flood Corroborate Our Findings.
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Popov, M., Brankart, J., Capet, A., Cosme, E., & Brasseur, P. (2024). Ensemble Analysis And Forecast Of Ecosystem Indicators In The North Atlantic Using Ocean Colour Observations And Prior Statistics From A Stochastic Nemo-Pisces Simulator. Ocean Science, 202(1), 155–180.
Abstract: This Study Is Anchored In The H2020 Seamless Project (Https://Www.Seamlessproject.Org, Last Access: 29 January 2024), Which Aims To Develop Ensemble Assimilation Methods To Be Implemented In Copernicus Marine Service Monitoring And Forecasting Systems, In Order To Operationally Estimate A Set Of Targeted Ecosystem Indicators In Various Regions, Including Uncertainty Estimates. In This Paper, A Simplified Approach Is Introduced To Perform A 4D (Space-Time) Ensemble Analysis Describing The Evolution Of The Ocean Ecosystem. An Example Application Is Provided, Which Covers A Limited Time Period In A Limited Subregion Of The North Atlantic (Between 31 And 21 Circle W, Between 44 And 50.5 Circle N, Between 15 March And 15 June 2019, At A 1/4 Circle And A 1 D Resolution). The Ensemble Analysis Is Based On Prior Ensemble Statistics From A Stochastic Nemo (Nucleus For European Modelling Of The Ocean)-Pisces Simulator. Ocean Colour Observations Are Used As Constraints To Condition The 4D Prior Probability Distribution.As Compared To Classic Data Assimilation, The Simplification Comes From The Decoupling Between The Forward Simulation Using The Complex Modelling System And The Update Of The 4D Ensemble To Account For The Observation Constraint. The Shortcomings And Possible Advantages Of This Approach For Biogeochemical Applications Are Discussed In The Paper. The Results Show That It Is Possible To Produce A Multivariate Ensemble Analysis Continuous In Time And Consistent With The Observations. Furthermore, We Study How The Method Can Be Used To Extrapolate Analyses Calculated From Past Observations Into The Future. The Resulting 4D Ensemble Statistical Forecast Is Shown To Contain Valuable Information About The Evolution Of The Ecosystem For A Few Days After The Last Observation. However, As A Result Of The Short Decorrelation Timescale In The Prior Ensemble, The Spread Of The Ensemble Forecast Increases Quickly With Time. Throughout The Paper, A Special Emphasis Is Given To Discussing The Statistical Reliability Of The Solution.Two Different Methods Have Been Applied To Perform This 4D Statistical Analysis And Forecast: The Analysis Step Of The Ensemble Transform Kalman Filter (With Domain Localization) And A Monte Carlo Markov Chain (Mcmc) Sampler (With Covariance Localization), Both Enhanced By The Application Of Anamorphosis To The Original Variables. Despite Being Very Different, The Two Algorithms Produce Very Similar Results, Thus Providing Support To Each Other'S Estimates. As Shown In The Paper, The Decoupling Of The Statistical Analysis From The Dynamical Model Allows Us To Restrict The Analysis To A Few Selected Variables And, At The Same Time, To Produce Estimates Of Additional Ecological Indicators (In Our Example: Phenology, Trophic Efficiency, Downward Flux Of Particulate Organic Matter). This Approach Can Easily Be Appended To Existing Operational Systems To Focus On Dedicated Users' Requirements, At A Small Additional Cost, As Long As A Reliable Prior Ensemble Simulation Is Available. It Can Also Serve As A Baseline To Compare With The Dynamical Ensemble Forecast And As A Possible Substitute Whenever Useful.
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Pühl, M., Roiger, A., Fiehn, A., Negron, A., Kort, E., Schwietzke, S., et al. (2024). Aircraft-Based Mass Balance Estimate Of Methane Emissions From Offshore Gas Facilities In The Southern North Sea. Atmospheric Chemistry And Physics, 242(2), 1005–1024.
Abstract: Atmospheric Methane (Ch 4 ) Concentrations Have More Than Doubled Since The Beginning Of The Industrial Age, Making Ch 4 The Second Most Important Anthropogenic Greenhouse Gas After Carbon Dioxide (Co 2 ). The Oil And Gas Sector Represents One Of The Major Anthropogenic Ch 4 Emitters As It Is Estimated To Account For 22 % Of Global Anthropogenic Ch 4 Emissions. An Airborne Field Campaign Was Conducted In April-May 2019 To Study Ch 4 Emissions From Offshore Gas Facilities In The Southern North Sea With The Aim Of Deriving Emission Estimates Using A Top-Down (Measurement-Led) Approach. We Present Ch 4 Fluxes For Six Uk And Five Dutch Offshore Platforms Or Platform Complexes Using The Well-Established Mass Balance Flux Method. We Identify Specific Gas Production Emissions And Emission Processes (Venting And Fugitive Or Flaring And Combustion) Using Observations Of Co-Emitted Ethane (C 2 H 6 ) And Co 2 . We Compare Our Top-Down Estimated Fluxes With A Ship-Based Top-Down Study In The Dutch Sector And With Bottom-Up Estimates From A Globally Gridded Annual Inventory, Uk National Annual Point-Source Inventories, And Operator-Based Reporting For Individual Dutch Facilities. In This Study, We Find That All The Inventories, Except For The Operator-Based Facility-Level Reporting, Underestimate Measured Emissions, With The Largest Discrepancy Observed With The Globally Gridded Inventory. Individual Facility Reporting, As Available For Dutch Sites For The Specific Survey Date, Shows Better Agreement With Our Measurement-Based Estimates. For All The Sampled Dutch Installations Together, We Find That Our Estimated Flux Of (122.9 +/- 36.8) Kg H – 1 Deviates By A Factor Of 0.64 (0.33-12) From Reported Values (192.8 Kg H – 1 ). Comparisons With Aircraft Observations In Two Other Offshore Regions (The Norwegian Sea And The Gulf Of Mexico) Show That Measured, Absolute Facility-Level Emission Rates Agree With The General Distribution Found In Other Offshore Basins Despite Different Production Types (Oil, Gas) And Gas Production Rates, Which Vary By 2 Orders Of Magnitude. Therefore, Mitigation Is Warranted Equally Across Geographies.
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Richard, G. (2024). Roll Waves In A Predictive Model For Open-Channel Flows In The Smooth Turbulent Case. Journal Of Fluid Mechanics, 9839.
Abstract: A Depth-Averaged Model For Turbulent Open-Channel Flows With Breaking Roll Waves On A Sloping Smooth Bottom Is Derived Under An Assumption Of Independence Between The Wall Turbulence And The Roller Turbulence. The Model Includes Four Variables – The Water Depth, The Average Velocity, And Two Variables Called Enstrophy, The Shear Enstrophy And The Roller Enstrophy – Which Take Into Account The Deviations Of The Velocity With Respect To Its Depth-Averaged Value Due To Shear Effect And Roller Turbulence, Respectively. The Four Equations Of The Model Are The Mass, Momentum, Energy And Shear Enstrophy Balance Equations, With The Mathematical Structure Of The Euler Equations Of Compressible Fluids, With An Additional Transport Equation And With Source Terms. The System Is Hyperbolic. The Roller Enstrophy Is Created By Shocks. A Non-Zero Value Of The Roller Enstrophy Indicates A Breaking Wave And A Turbulent Roller. The Model Is Solved By A Fast And Well-Known Numerical Scheme, With An Explicit Finite-Volume Method In One Step. The Model Is Used To Simulate Periodic And Natural Roll Waves With A Good Agreement With Existing Experimental Results. There Is No Parameter To Calibrate In The Model, Which Gives It A Predictive Character.
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Rossi, F., Duchaine, C., Tignat-Perrier, R., Joly, M., Larose, C., Dommergue, A., et al. (2024). Temporal Variations Of Antimicrobial Resistance Genes In Aerosols: A One-Year Monitoring At The Puy De Dome Summit (Central France). Science Of The Total Environment, 9129.
Abstract: The Recent Characterization Of Antibiotic Resistance Genes (Args) In Clouds Evidenced That The Atmosphere Actively Partakes In The Global Spreading Of Antibiotic Resistance Worldwide. Indeed, The Outdoor Atmosphere Continuously Receives Large Quantities Of Particles Of Biological Origins, Emitted From Both Anthropogenic Or Natural Sources At The Near Earth'S Surface. Nonetheless, Our Understanding Of The Composition Of The Atmospheric Resistome, Especially At Mid-Altitude (I.E. Above 1000 M A.S.L.), Remains Largely Limited. The Atmosphere Is Vast And Highly Dynamic, So That The Diversity And Abundance Of Args Are Expected To Fluctuate Both Spatially And Temporally. In This Work, The Abundance And Diversity Of Args Were Assessed In Atmospheric Aerosol Samples Collected Weekly Between July 2016 And August 2017 At The Mountain Site Of Puy De Dome (1465 M A.S.L., Central France). Our Results Evidence The Presence Of 33 Different Subtypes Of Args In Atmospheric Aerosols, Out Of 34 Assessed, Whose Total Concentration Fluctuated Seasonally From 59 To 1.1 X 10(5) Copies M(-3) Of Air. These Were Heavily Dominated By Genes From The Quinolone Resistance Family, Notably The Qepa Gene Encoding Efflux Pump Mechanisms, Which Represented >95 % Of Total Args Concentration. Its Abundance Positively Correlated With That Of Bacteria Affiliated With The Genera Kineococcus, Neorhizobium, Devosia Or Massilia, Ubiquitous In Soils. This, Along With The High Abundance Of Sphingomonas Species, Points Toward A Large Contribution Of Natural Sources To The Airborne Args. Nonetheless, The Increased Contribution Of Macrolide Resistance (Notably The Erm35 Gene) During Winter Suggests A Sporadic Diffusion Of Args From Human Activities. Our Observations Depict The Atmosphere As An Important Vector Of Args From Terrestrial Sources. Therefore, Monitoring Args In Airborne Microorganisms Appears Necessary To Fully Understand The Dynamics Of Antimicrobial Resistances In The Environment And Mitigate The Threats They May Represent.
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Sadhvi, K., Suresh, I., Lengaigne, M., Izumo, T., Penduff, T., Molines, J., et al. (2024). Intrinsic Versus Wind-Forced Great Whirl Non-Seasonal Variability. Journal Of Geophysical Research-Oceans, 1291(2).
Abstract: The Great Whirl (Gw) Is A Quasi-Permanent Anticyclonic Eddy That Appears Every Summer Monsoon Offshore Of The Somalia Upwelling. The Annual Cycle Of The Gw Is Well Described, But Deviations From Its Mean Seasonal Cycle (Hereafter Non-Seasonal Variability) Have Been Less Explored. Satellite Observations Reveal That The Leading Mode Of Summer Non-Seasonal Sea-Level Variability In This Region Is Associated With Similar To 100-Km Northward Or Southward Gw Shifts From Its Climatological Position. Northward Shifts Are Associated With A Stronger Gw, And Two Cold, Productive Coastal Upwelling Wedges At 5 Degrees N And 10 Degrees N. Southward Shifts Are Associated With A Weaker Gw, No Wedge At 5 Degrees N And A Single Stronger-Than-Usual Cold And Productive Wedge At 10 Degrees N. An Eddy-Permitting (25-Km Resolution) 50-Member Ensemble Ocean Simulation Reproduces This Gw Variability Well. It Indicates That The Non-Seasonal Gw Variability Has A Short Similar To 20 Days Timescale Intrinsic Component, Associated With The Gw Interaction With Mesoscale Eddies, And A Lower-Frequency, Similar To 100 Days Externally Forced Component. Intrinsic Variability Dominates At Both Subseasonal (Two Thirds Of The Variance) And Interannual Timescales (57% Of The Variance). The Externally Forced Signal Results From Shifts In The Probability Distribution Of The Subseasonal Gw Position (E.G., More Likely Northward Than Southward Shifted Instantaneous Gw Positions Over A Season). The Mechanism For This External Forcing Is Not Entirely Clear, But It Appears To Be Related To The Rossby Wave Response To Offshore Wind Stress Curl Forcing, Which Evolves Into A North-South Dipole That Projects Onto The Gw Variability Pattern. The Great Whirl (Gw) Is A Similar To 500-Km Diameter Oceanic Eddy That Forms Each Summer Off The Somalia Coast. The Gw Influences The Temperature And Biological Productivity Of The Somalia Coastal Upwelling. The Gw Seasonal Cycle, Including Its Northward Movement At The End Of The Monsoon, Is Known. Here, We Study Deviations From This Mean Seasonal Cycle. The Gw Exhibits Fast (Typically 20 Days Long), Similar To 100-Km Northward Or Southward Displacements. These Displacements Result From Interactions With Smaller Neighboring Oceanic Eddies, And Are Hence The Consequence Of An Intrinsic Ocean Dynamics, Rather Than Atmospheric Forcing. The Gw Is More Pronounced When Displaced Northward, And The Somalia Coastal Upwelling Has Two Clear “Wedges” Of Cold, Plankton-Rich Water At 5 Degrees And 10 Degrees N. When Displaced Southward, The Gw Is Less Pronounced, And There Is A Single, Stronger-Than-Usual Wedge Of Cold Water At 10 Degrees N. We Also Show That Atmospheric Forcing Can Induce Seasonal Gw Displacements, By Making, For Example, Northward Events More Likely Than The Southward. Thus, The Seasonal Mean Gw Position Has Both A Predictable (Due To Atmospheric Forcing) And Slightly Larger Unpredictable (Due To Interactions With Eddies) Component. We Propose That The Atmospheric Forcing Influences The Fast Oscillations Of The Gw Through Slow Oceanic Adjustment To Wind Variations Further East. The Great Whirl (Gw) Non-Seasonal Variability Is Dominated By Similar To 100-Km Northward Or Southward Shifts Relative To Its Climatological Position Those Shifts Induce Sea Level, Surface Temperature And Chlorophyll Signals Those Gw Displacements Have A Fast (Similar To 20 Days) Intrinsic Variability Component And A Slower, Seasonal Forced Component
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Shangguan, Y., Zhuang, X., Querol, X., Li, B., Moreno, N., Trechera, P., et al. (2024). Physicochemical Characteristics And Oxidative Potential Of Size-Segregated Respirable Coal Mine Dust: Implications For Potentially Hazardous Agents And Health Risk Assessment. International Journal Of Coal Geology, 2822.
Abstract: The Health Risks Associated With Exposure To Respirable Dust In Coal Mines Have Been Attracted Much Attention By An Increasing Number Of Researchers. However, The Accurate Identification Of Potentially Hazardous Agents In Respirable Dusts And The Evaluation Of The Potential Health Risks Arising From It Still Remains Controversial To Varying Degrees. A Comprehensive Understanding Of The Physicochemical Properties Of Respirable Dust Is A Prerequisite And An Important Basis For Resolving This Controversy. Therefore, In This Study, The Particle Size Distribution And Morphology, Pore Structure, Mineralogical And Geochemical Patterns, And Oxidative Potential (Op) Of Respirable Coal Mine Dust Were Comprehensively Investigated. Stepwise Multiple Linear Regression Was Employed To Identify Dust Components Driving Op, Such As Anatase, Tobelite, Quartz, And Ankerite, In Respirable Coal Mine Dust, Along With Na, Ni, Se, W, And As. On This Basis, We Performed A Single-Factor Risk Prediction For Different Coal Mines By Considering Factors That May Impact Miners' Health, With The Analyses Yielding Somewhat Contradictory Results. Therefore, A Multifactor Integrated Prediction Model Is Proposed Using An Entropy-Based Technique For Order Preference By Similarity To The Ideal Solution To Categorize Coal Mines In The Study Area Into Three Risk Categories, High-, Medium-, And Low-Risk Dust Mines, Which Is Important For The Hierarchical Classification And Control Of Coal Mines And For Formulating Appropriate Dust Prevention And Control Measures.
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Sicaud, E., Fortier, D., Dedieu, J., & Franssen, J. (2024). Pairing Remote Sensing And Clustering In Landscape Hydrology For Large-Scale Change Identification: An Application To The Subarctic Watershed Of The George River (Nunavik, Canada). Hydrology And Earth System Sciences, 282(1), 65–86.
Abstract: For Remote And Vast Northern Watersheds, Hydrological Data Are Often Sparse And Incomplete. Landscape Hydrology Provides Useful Approaches For The Indirect Assessment Of The Hydrological Characteristics Of Watersheds Through Analysis Of Landscape Properties. In This Study, We Used Unsupervised Geographic Object-Based Image Analysis (Geobia) Paired With The Fuzzy C -Means (Fcm) Clustering Algorithm To Produce Seven High-Resolution Territorial Classifications Of Key Remotely Sensed Hydro-Geomorphic Metrics For The 1985-2019 Time Period, Each With A Frequency Of 5 Years. Our Study Site Is The George River Watershed (Grw), A 42 000 Km 2 Watershed Located In Nunavik, Northern Quebec (Canada). The Subwatersheds Within The Grw, Used As The Objects Of The Geobia, Were Classified As A Function Of Their Hydrological Similarities. Classification Results For The Period 2015-2019 Showed That The Grw Is Composed Of Two Main Types Of Subwatersheds Distributed Along A Latitudinal Gradient, Which Indicates Broad-Scale Differences In Hydrological Regimes And Water Balances Across The Grw. Six Classifications Were Computed For The Period 1985-2014 To Investigate Past Changes In Hydrological Regime. The Time Series Of Seven Classifications Showed A Homogenization Of Subwatershed Types Associated With Increases In Vegetation Productivity And In Water Contents In Soil And Vegetation, Mostly Concentrated In The Northern Half Of The Grw, Which Were The Major Changes Occurring In The Land Cover Metrics Of The Grw. An Increase In Vegetation Productivity Likely Contributed To An Augmentation In Evaporation And May Be A Primary Driver Of Fundamental Shifts In The Grw Water Balance, Potentially Explaining A Measured Decline Of About 1 % ( Similar To 0.16 Km 3 Yr – 1 ) In The George River'S Discharge Since The Mid-1970S. Permafrost Degradation Over The Study Period Also Likely Affected The Hydrological Regime And Water Balance Of The Grw. However, The Shifts In Permafrost Extent And Active Layer Thickness Remain Difficult To Detect Using Remote-Sensing-Based Approaches, Particularly In Areas Of Discontinuous And Sporadic Permafrost.
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Silué, F., Diawara, A., Koné, B., Diedhiou, A., Kouassi, A., Kouassi, B., et al. (2024). Assessment Of The Sensitivity Of The Mean Climate Simulation Over West Africa To Planetary Boundary Layer Parameterization Using Regcm5 Regional Climate Model. Atmosphere, 151(3).
Abstract: This Study Evaluates The Performance Of Two Planetary Boundary Parameterizations In Simulating The Mean Climate Of West Africa Using The Regional Climate Model Version 5 (Regcm5). These Planetary Boundary Parameterizations Are The Holtslag Scheme And The University Of Washington Scheme. Two Sets Of Three One-Year Simulations Were Carried Out At 25 Km Horizontal Resolution With Three Different Initial Conditions. The First Set Of Simulations Used The Holtslag Scheme (Hereafter Referred To As Hol), While The Second Used The University Of Washington (Uw) Scheme (Hereafter Referred To As Uw). The Results Displayed In This Study Are An Average Of The Three Simulations. During The Jjas Rainy Season, With Respect To Gpcp, Both Models Overestimated Total Rainfall In The Orographic Regions. The Uw Experiment Represented Total Rainfall Fairly Well Compared To Its Counterpart, Hol. Both Models Reproduced Convective Rainfall Well, With A Relatively Weak Dry Bias Over The Guinean Coast Subregion. Globally, Uw Performed Better Than Hol In Simulating Precipitation. The Pattern Of Near-Surface Temperature In Both Models Was Well Reproduced With A Higher Bias With Hol Than With Uw. Indeed, The Uw Scheme Led To A Cooling Effect Owing To The Reduction In Eddy Heat Diffusivity In The Lower Troposphere Contributing To Reduce The Bias. As A Consequence, The Height Of The Planetary Boundary Layer (Pbl) Was Best Simulated Using The Uw Scheme But Was Underestimated Compared To Era5, While Using The Hol Scheme Failed To Capture The Height Of The Pbl. This Is Coherent With The Distribution Of Total Cloud Cover, Which Was Better Simulated With The Uw Scheme Compared To The Hol Scheme. This Study Shows That Use Of Both Planetary Boundary Parameterizations Leads To A Good Simulation Of Most Of The Climatological Characteristics Of The West African Region. Nevertheless, Use Of The Uw Scheme Contributes To A Better Performance Than Use Of The Hol Scheme, And The Differentiation Between The Two Schemes Is Significant Along The Guinea Coast And In Orographic Regions. In These Topographically Complex Regions, Uw Appears To Be More Appropriate Than Hol. This Study Emphasizes The Importance Of Planetary Boundary Parameterizations For Accurately Simulating Climate Variables And For Improving Climate Forecasts And Projections In West Africa.
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Spolaor, A., Scoto, F., Larose, C., Barbaro, E., Burgay, F., Bjorkman, M., et al. (2024). Climate Change Is Rapidly Deteriorating The Climatic Signal In Svalbard Glaciers. Cryosphere, 181(1), 307–320.
Abstract: The Svalbard Archipelago Is Particularly Sensitive To Climate Change Due To The Relatively Low Altitude Of Its Main Ice Fields And Its Geographical Location In The Higher North Atlantic, Where The Effect Of Arctic Amplification Is More Significant. The Largest Temperature Increases Have Been Observed During Winter, But Increasing Summer Temperatures, Above The Melting Point, Have Led To Increased Glacier Melt. Here, We Evaluate The Impact Of This Increased Melt On The Preservation Of The Oxygen Isotope ( Delta 18 O) Signal In Firn Records. Delta 18 O Is Commonly Used As A Proxy For Past Atmospheric Temperature Reconstructions, And, When Preserved, It Is A Crucial Parameter To Date And Align Ice Cores. By Comparing Four Different Firn Cores Collected In 2012, 2015, 2017 And 2019 At The Top Of The Holtedahlfonna Ice Field (1100 M A.S.L.), We Show A Progressive Deterioration Of The Isotope Signal, And We Link Its Degradation To The Increased Occurrence And Intensity Of Melt Events. Our Findings Indicate That, Starting From 2015, There Has Been An Escalation In Melting And Percolation Resulting From Changes In The Overall Atmospheric Conditions. This Has Led To The Deterioration Of The Climate Signal Preserved Within The Firn Or Ice. Our Observations Correspond With The Model'S Calculations, Demonstrating An Increase In Water Percolation Since 2014, Potentially Reaching Deeper Layers Of The Firn. Although The Delta 18 O Signal Still Reflects The Interannual Temperature Trend, More Frequent Melting Events May In The Future Affect The Interpretation Of The Isotopic Signal, Compromising The Use Of Svalbard Ice Cores. Our Findings Highlight The Impact And The Speed At Which Arctic Amplification Is Affecting Svalbard'S Cryosphere.
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Stefanini, C., Macelloni, G., Leduc-Leballeur, M., Favier, V., Pohl, B., & Picard, G. (2024). Extreme Events Of Snow Grain Size Increase In East Antarctica And Their Relationship With Meteorological Conditions. Cryosphere, 181(2), 593–608.
Abstract: This Study Explores The Seasonal Variations In Snow Grain Size On The East Antarctic Plateau, Where Dry Metamorphism Occurs, By Using Microwave Radiometer Observations From 2000 To 2022. Local Meteorological Conditions And Large-Scale Atmospheric Phenomena Have Been Considered In Order To Explain Some Peculiar Changes In The Snow Grains. We Find That The Highest Ice Divide Is The Region With The Largest Grain Size In The Summer, Mainly Because The Wind Speed Is Low. Moreover, Some Extreme Grain Size Values With Respect To The Average (Over +3 Sigma) Were Identified. In These Cases, The Era5 Reanalysis Revealed A High-Pressure Blocking Close To The Onsets Of The Summer Increase In The Grain Size. It Channels Moisture Intrusions From The Mid-Latitudes, Through Atmospheric Rivers That Cause Major Snowfall Events Over The Plateau. If Conditions Of Weak Wind And Low Temperature Occur During The Following Weeks, Dry Snow Metamorphism Is Facilitated, Leading To Grain Growth. This Determines Anomalous High Maximums Of The Snow Grain Size At The End Of Summer. These Phenomena Confirm The Importance Of Moisture Intrusion Events In East Antarctica And Their Impact On The Physical Properties Of The Ice Sheet Surface, With A Co-Occurrence Of Atmospheric Rivers And Seasonal Changes In The Grain Size With A Significance Of Over 95 %.
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Stefanini, C., Macelloni, G., Leduc-Leballeur, M., & Picard, G. (2024). Influence Of Surface Snow Properties On An 89-Ghz Brightness Temperature Extreme Event At Dome Fuji, Antarctica. Ieee Geoscience And Remote Sensing Letters, 212.
Abstract: Microwave Brightness Temperatures Observed In Antarctica At 89 Ghz From The Advanced Microwave Sounding Unit B (Amsu-B) Point Out An Exceptional Decrease Of 57 K At Dome Fuji ( 77.31(Degrees)S, 39.70(Degrees)E) During The 2019-2020 Summer. The Grain Size Index (Gsi) Based On 89 And 150 Ghz From Amsu-B And Independent Observations At 89 Ghz From The Advanced Microwave Scanning Radiometer 2 (Amsr-2) Also Show Concurrent Unusual Values. To Explain Such Event, A Theoretical Analysis Was Carried Out By Means Of A Radiative Transfer Model. We Explore The Sensitivity Of Brightness Temperature To Surface Snow Properties Focusing On December, Just Before The Decrease, And April, At Its End. Results Confirm That This Variation Is Mainly Related To An Increase In Snow Grain Size. A Decrease In Snow Density Is Also Involved As Suggested By The Increase In Brightness Temperature At 1.4 Ghz From Soil Moisture And Ocean Salinity (Smos) And In The Polarization Ratio At 36 Ghz From Amsr-2. Extreme Values Observed At Multiple Frequencies, As Well As Peculiar Atmospheric Conditions Explored In A Previous Study, Confirm The Uniqueness Of This Event At Least On Decennial Scale.
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Sulca, J., Takahashi, K., Espinoza, J., Tacza, J., Zubieta, R., Mosquera, K., et al. (2024). A Multiple Linear Regression Model For The Prediction Of Summer Rainfall In The Northwestern Peruvian Amazon Using Large-Scale Indices. Climate Dynamics, .
Abstract: The Northwestern Peruvian Amazon (Nwpa) Basin (78.4-75.8 Degrees W, 7.9-5.4 Degrees S) Is An Important Region For Coffee And Rice Production In Peru. Currently, No Prediction Models Are Available For Estimating Rainfall In Advance During The Wet Season (January-February-March, Jfm). Hence, We Developed Multiple Linear Regression (Mlr) Models Using Predictors Derived From Sea Surface Temperature (Sst) Indices Of The Pacific, Atlantic, And Indian Oceans, Including Central El Nino (C), Eastern El Nino (E), Tropical South Atlantic (Tsatl), Tropical North Atlantic (Tnatl), Extratropical North Atlantic (Enatl), And Indian Ocean Basin-Wide With E And C Removed (Iobw*) Indices. Additionally, We Utilized Large-Scale Convection Indices, Namely, The Eastern Pacific Intertropical Convergence Zone (Itcze) And South American Monsoon System (Samsi) Indices, For The 1981-2018 Period. Rainfall In The Lowland Nwpa Exhibits A Bimodal Annual Cycle, Whereas Rainfall In The Highland Nwpa Exhibits A Unimodal Annual Cycle. The Mlr Model Can Be Used To Accurately Capture The Interannual Variability During The Wet Season In The Highland Nwpa By Utilizing Predictors Derived From The C And Samsi Indices. In Contrast, Regarding Rainfall In The Lowland Nwpa, The Pacific Sst Variability, Sams And Tropical North Atlantic Index Were Relevant. For Long Lead Times, The Mlr Model Provided Reliable Forecasts Of Jfm Rainfall Anomalies In The Highlands (R3, Approximately 2700 M Asl) As These Regions Are Governed By Pacific Variability. However, The Mlr Model Exhibited Limitations In Accurately Estimating The Wettest Jfm Season In The Highlands Due To The Absence Of A Predictor For The Amplified Effect Of The Madden-Julian Oscillation On Rainfall.
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Sundu, K., Freitag, J., Fourteau, K., & Löwe, H. (2024). A Microstructure-Based Parameterization Of The Effective Anisotropic Elasticity Tensor Of Snow, Firn, And Bubbly Ice. Cryosphere, 181(4), 1579–1596.
Abstract: Quantifying The Link Between Microstructure And Effective Elastic Properties Of Snow, Firn, And Bubbly Ice Is Essential For Many Applications In Cryospheric Sciences. The Microstructure Of Snow And Ice Can Be Characterized By Different Types Of Fabrics (Crystallographic And Geometrical), Which Give Rise To Macroscopically Anisotropic Elastic Behavior. While The Impact Of The Crystallographic Fabric Has Been Extensively Studied In Deep Firn, The Present Work Investigates The Influence Of The Geometrical Fabric Over The Entire Range Of Possible Volume Fractions. To This End, We Have Computed The Effective Elasticity Tensor Of Snow, Firn, And Ice By Finite-Element Simulations Based On 391 X-Ray Tomography Images Comprising Samples From The Laboratory, The Alps, Greenland, And Antarctica. We Employed A Variant Of Eshelby'S Tensor That Has Been Previously Utilized For The Parameterization Of Thermal And Dielectric Properties Of Snow And Utilized Hashin-Shtrikman Bounds To Capture The Nonlinear Interplay Between Density And Geometrical Anisotropy. From That We Derive A Closed-Form Parameterization For All Components Of The (Transverse Isotropic) Elasticity Tensor For All Volume Fractions Using Two Fit Parameters Per Tensor Component. Finally, We Used The Thomsen Parameter To Compare The Geometrical Anisotropy To The Maximal Theoretical Crystallographic Anisotropy In Bubbly Ice. While The Geometrical Anisotropy Clearly Dominates Up To Ice Volume Fractions Of Phi Approximate To 0.7 , A Thorough Understanding Of Elasticity In Bubbly Ice May Require A Coupled Elastic Theory That Includes Geometrical And Crystallographic Anisotropy.
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Tkachenko, K., & Jacobi, H. (2024). Electrical Charging Of Snow And Ice In Polar Regions And The Potential Impact On Atmospheric Chemistry. Environmental Science-Atmospheres, 4(2), 144–163.
Abstract: Charging Of The Ice-Vapor Interface Is A Well-Studied Topic In Ice Physics And Atmospheric Electrification. However, These Effects Were Not Yet Considered To Examine Chemical Processes In Snow In Polar Regions Because Electric Potentials At Ice Surfaces Have So Far Been Considered Insufficient To Initiate Chemical Reactions And Processes. In This Review, We Analyze Literature Data To Estimate Levels Of Electrification In Snow And Other Frozen Objects That Can Be Caused By Different Processes Occurring At The Earth'S Surface. This Analysis Demonstrates That Threshold Values Of Electric Field Strength Can Be Exceeded For The Appearance Of Corona Discharges And Even For The Formation Of Rayleigh Jets Due To Combined Effects Of Different Meteorological And Physical Processes. The Accumulation Of Electrical Charges Can Lead To Different Chemical Modifications Such As Electroosmotic Phenomena Or The Accumulation Of Impurities From The Atmosphere In Growing Ice Crystals. Moreover, Highly Energetic States That Occur And Dissipate In Microseconds As “Hot Spots” Have The Potential To Initiate Free Radical Processes And Even The Production Of Charged Aerosols. The Review Also Discusses In Detail Selected Field Observations To Point Out How Processes Driven By Electrical Charging May Help To Interpret These Observations, Which Are At Least Partly Inconsistent With Our Present Understanding Of Snow And Ice Chemistry. Finally, Some Approaches Are Presented How These Effects Can Be Studied In Field And Laboratory Experiments. A Further Development Of This New Field At The Intersection Of Ice Physics And Snow Chemistry Seems Very Promising For A Better Understanding Of Relevant Chemical Processes Related To The Cryosphere. Different Processes Can Lead To High Electrical Field Strengths In Snow And Ice In Polar Regions With The Potential To Initiate Free Radical Processes And A Number Of Other Chemical Modifications.
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Uchida, T., Jamet, Q., Dewar, W., Deremble, B., Poje, A., & Sun, L. (2024). Imprint Of Chaos On The Ocean Energy Cycle From An Eddying North Atlantic Ensemble. Journal Of Physical Oceanography, 545(3), 679–696.
Abstract: We Examine The Ocean Energy Cycle Where The Eddies Are Defined About The Ensemble Mean Of A Partially Air-Sea Coupled, Eddy -Rich Ensemble Simulation Of The North Atlantic. The Decomposition About The Ensemble Mean Leads To A Parameter -Free Definition Of Eddies, Which Is Interpreted As The Expression Of Oceanic Chaos. Using The Ensemble Framework, We Define The Reservoirs Of Mean And Eddy Kinetic Energy (Mke And Eke, Respectively) And Mean Total Dynamic Enthalpy (Mtde). We Opt For The Usage Of Dynamic Enthalpy (De) As A Proxy For Potential Energy Due To Its Dynamically Consistent Relation To Hydrostatic Pressure In Boussinesq Fluids And Nonreliance On Any Reference Stratification. The Curious Result That Emerges Is That The Potential Energy Reservoir Cannot Be Decomposed Into Its Mean And Eddy Components, And The Eddy Flux Of De Can Be Absorbed Into The Eke Budget As Pressure Work. We Find From The Energy Cycle That While Baroclinic Instability, Associated With A Positive Vertical Eddy Buoyancy Flux, Tends To Peak Around February, Eke Takes Its Maximum Around September In The Wind -Driven Gyre. Interestingly, The Energy Input From Mke To Eke, A Process Sometimes Associated With Barotropic Processes, Becomes Larger Than The Vertical Eddy Buoyancy Flux During The Summer And Autumn. Our Results Question The Common Notion That The Inverse Energy Cascade Of Wintertime Eke Energized By Baroclinic Instability Within The Mixed Layer Is Solely Responsible For The Summer -To -Autumn Peak In Eke And Suggest That Both The Eddy Transport Of De And Transfer Of Energy From Mke To Eke Contribute To The Seasonal Eke Maxima.
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Uroz, L., Yan, Y., Benoit, A., Rabatel, A., Giffard-Roisin, S., & Lin-Kwong-Chon, C. (2024). Using Deep Learning For Glacier Thickness Estimation At A Regional Scale. Ieee Geoscience And Remote Sensing Letters, 212.
Abstract: Mountain Glaciers Play A Critical Role For Mountain Ecosystems And Society With Major Concerns Related To Their Future Evolution And Related Water Resources. Modeling Glacier Future Evolution Allows Anticipating Climate Change Impacts And Informing Policy Decisions. It Relies On Accurate Ice Thickness Estimation At Regional Scales. This Letter Proposes A Deep Learning-Based Approach In A Supervised Learning Framework For Ice Thickness Estimation At A Regional Scale From Surface Ice Velocity Measurements And A Digital Elevation Model (Dem). A Neural Network Model Built Upon A Resnet Architecture Is Proposed Based On The Trade-Off Between The Model Complexity And The Prediction Efficiency. Promising Results Are Obtained From Data Including 1400 Glaciers In The Swiss Alps, Highlighting The Potential Of Deep Learning-Based Approach For Large-Scale Ice Thickness Estimation. The Incorporation Of Expert'S Knowledge Into The Neural Network Model Further Helps Refine The Model Prediction And Improve The Model Relevance. The Ice Volume Difference Between The Reference Issued From Ground Penetrating Radar (Gpr) Measurements And The Predictions By The Proposed Neural Network Model Varies Between 0.5% And 16% Of The Reference Volume. Larger Ice Volume Difference Is Mainly Related To Over-Deepening Of The Bedrock Resulting From Past Larger Extent Of The Glacier, Which Information Is Not Included In The Data.
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Valois, R., Rivière, A., Vouillamoz, J., & Rau, G. (2024). Technical Note: Analytical Solution For Well Water Response To Earth Tides In Leaky Aquifers With Storage And Compressibility In The Aquitard. Hydrology And Earth System Sciences, 282(4), 1041–1054.
Abstract: In Recent Years, There Has Been A Growing Interest In Utilizing The Groundwater Response To Earth Tides As A Means Of Estimating Subsurface Properties. However, Existing Analytical Models Have Been Insufficient In Accurately Capturing Realistic Physical Conditions. This Study Presents A New Analytical Solution To Calculate The Groundwater Response To Earth Tide Strains, Including Storage And Compressibility Of The Aquitard, Borehole Storage, And Skin Effects. We Investigate The Effects Of Aquifer And Aquitard Parameters On The Well Water Response To Earth Tides At Two Dominant Frequencies ( O-1 And M-2 ) And Compare Our Results With Hydraulic Parameters Obtained From A Pumping Test. Inversion Of The Six Hydro-Geomechanical Parameters From Amplitude Response And Phase Shift In Both Semi-Diurnal And Diurnal Tides Provides Relevant Information About Aquifer Transmissivity, Storativity, Well Skin Effect, Aquitard Hydraulic Conductivity, And Diffusivity. The New Model Is Able To Reproduce Previously Unexplained Observations Of The Amplitude And Frequency Responses. We Emphasize The Usefulness In Developing A Relevant Methodology To Use The Groundwater Response To Natural Drivers In Order To Characterize Hydrogeological Systems.
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Védrine, L., Hagenmuller, P., Gélébart, L., Montagnat, M., & Bernard, A. (2024). Role Of Ice Mechanics On Snow Viscoplasticity. Geophysical Research Letters, 515(7).
Abstract: The Porous Structure Of Snow Becomes Denser With Time Under Gravity, Primarily Due To The Creep Of Its Ice Matrix With Viscoplasticity. Despite Investigation Of This Behavior At The Macroscopic Scale, The Driving Microscopic Mechanisms Are Still Not Well Understood. Thanks To High-Performance Computing And Dedicated Solvers, We Modeled Snow Elasto-Viscoplasticity With 3D Images Of Its Microstructure And Different Mechanical Models Of Ice. The Comparison Of Our Numerical Experiments To Oedometric Compression Tests Measured By Tomography Showed That Ice In Snow Rather Behaves As A Heterogeneous Set Of Ice Crystals Than As Homogeneous Polycrystalline Ice. Similarly To Dense Ice, The Basal Slip System Contributed At Most, In The Simulations, To The Total Snow Deformation. However, In The Model, The Deformation Accommodation Between Crystals Was Permitted By The Pore Space And Did Not Require Any Prismatic And Pyramidal Slips, Whereas The Latter Are Pre-Requisite For The Simulation Of Dense Ice. Knowledge Of Snow Settlement Is Essential For Many Applications, Such As Paleoclimatology And Avalanche Forecasting. Snow Densification Is Mainly Driven By Time Dependent And Irreversible Deformations. Simulating This Highly Nonlinear Behavior For Intricate Microstructures Is Time-Consuming, Leading To A Scarcity Of Studies And A Limited Understanding Of The Underlying Microscale Mechanisms. In This Study, We Took Advantage Of An Advanced Numerical Solver To Calculate The Behavior Of 3D Imaged Snow Samples And Compared It With In Situ Experiments. Our Analysis Has Shown That The Crystalline Structure Must Be Taken Into Account, But The Discrepancy Between Experiments And Simulations Suggests The Existence Of Other Mechanisms, Particularly Between Snow Grains. Interestingly, Deformation Mechanisms Other Than Those Required To Simulate Dense Ice Have Been Observed. Ice In Snow Cannot Be Considered As Homogeneous, Individual Crystals Are Shown To Impact Snow Creep The Models Shows That Basal Glide Of A Few Ice Zones Supports Most Of The Snow Deformation In The Simulations, The Contribution Of The Hard Slip Systems Is Negligible, And Deformation Accommodation Is Enabled By The Pore Space
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Wang, Q., Shu, Q., Bozec, A., Chassignet, E., Fogli, P., Fox-Kemper, B., et al. (2024). Impact Of Increased Resolution On Arctic Ocean Simulations In Ocean Model Intercomparison Project Phase 2 (Omip-2). Geoscientific Model Development, 171(1), 347–379.
Abstract: This Study Evaluates The Impact Of Increasing Resolution On Arctic Ocean Simulations Using Five Pairs Of Matched Low- And High-Resolution Models Within The Omip-2 (Ocean Model Intercomparison Project Phase 2) Framework. The Primary Objective Is To Assess Whether A Higher Resolution Can Mitigate Typical Biases In Low-Resolution Models And Improve The Representation Of Key Climate-Relevant Variables. We Reveal That Increasing The Horizontal Resolution Contributes To A Reduction In Biases In Mean Temperature And Salinity And Improves The Simulation Of The Atlantic Water Layer And Its Decadal Warming Events. A Higher Resolution Also Leads To Better Agreement With Observed Surface Mixed-Layer Depth, Cold Halocline Base Depth And Arctic Gateway Transports In The Fram And Davis Straits. However, The Simulation Of The Mean State And Temporal Changes In Arctic Freshwater Content Does Not Show Improvement With Increased Resolution. Not All Models Achieve Improvements For All Analyzed Ocean Variables When Spatial Resolution Is Increased So It Is Crucial To Recognize That Model Numerics And Parameterizations Also Play An Important Role In Faithful Simulations. Overall, A Higher Resolution Shows Promise In Improving The Simulation Of Key Arctic Ocean Features And Processes, But Efforts In Model Development Are Required To Achieve More Accurate Representations Across All Climate-Relevant Variables.
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Zimmer, A., Beach, T., Luzzadder-Beach, S., Rabatel, A., Encarnación, R., Robles, J., et al. (2024). Soil Temperature And Local Initial Conditions Drive Carbon And Nitrogen Build-Up In Young Proglacial Soils In The Tropical Andes And European Alps. Catena, 2352.
Abstract: Climate Warming Has Accelerated The Retreat Of Mountain Glaciers Worldwide, Exposing New Areas To Weathering, Vegetation Colonization, And Soil Formation. In Light Of Probable Climate Changes Such As Warming And New Extremes, Understanding The Factors That Control Soil Organic Carbon (Soc) And Nitrogen Build-Up Is Crucial To Comprehend Proglacial Soils And Ecosystem Formation. To This End, We Examine The Evolution Of Soc, Nitrogen (Total N And Nh4+), And Phosphorus (Available P) Along Nine 120-Year Chronosequences Of Deglacierization Distributed Between The European Alps And Tropical Andes. Our Dataset Includes Geochemical Analyses Of 188 Soil Samples, In Situ Soil Temperature Data For The Period 2019-2022, And Hydrographic Variables. Although Time Controls Proglacial Soil Development At All Sites, Our Study Highlights Distinct Pedogenesis Dynamics Between Proglacial Landscapes Depending On The Micro And Macro Environmental Context. Differences In Soil Development Were Strongly Driven By Growing Degree Days (Gdd), Maximum Soil Temperature, And Parent Material. Notably, We Identified A Positive Effect Of Gdd On Soc And N (Total N And Nh4+), While Our Results Indicate A Negative Effect Of Maximum Soil Temperature On Soc And Nh4+, Suggesting That Overly High Temperatures Reduce Microbial Mineralization And Organic Matter Input To The Soil Matrix. We Reported The Presence Of Higher Initial Soc, Total N, And Nh4+ In The Andean Sites Than In The Alps Sites, Suggesting Enhanced Soil Development At The Andean Locations. This Comparative Study Suggests The Relative Importance Of Maximum Temperature And Initial Site Conditions (E.G., Parent Materials, Glacier Biomes) During Proglacial Pedogenesis. Our Findings Highlight That Soil Temperature Modulates Pedogenesis In A Complex Way And Suggest Avoiding Simply Associating Greater Soil Development With Higher Soil Temperature In Proglacial Landscapes.
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Zimmer, A., Beach, T., Luzzadder-Beach, S., Rabatel, A., Robles, J., Encarnaci, R., et al. (2024). Physico-Chemical Properties And Toxicity Of Young Proglacial Soils In The Tropical Andes And Alps. Catena, 2372.
Abstract: New Soils Formed After Glacier Retreat Can Provide Insights Into The Rates Of Soil Formation In The Context Of Accelerated Warming Due To Climate Change. Recently Deglacierized Terrains (Since The Little Ice Age) Are Subject To Weathering And Pedogenesis, And Freshly Exposed Sediments Are Prone To React Readily With The Environment. This Study Aims To Determine The Impact Of Parent Material And Time On Soil Physical And Chemical Properties Of Nine Proglacial Landscapes Distributed In The Tropical Andes And Alps. A Total Of 188 Soil Samples Were Collected Along Chronosequences Of Deglacierization And From Sites That Differed In Terms Of Parent Material And Classified Following Three Parent Material Groups: (1) Granodiorite-Tonalite (Gt), (2) Gneiss-Shales-Schists (Gss), And (3) Mont-Blanc Granite (Mbg). We Determined Physical And Chemical Soil Properties Such As Contents Of Clay, Silt, Sand, Organic Carbon, Bulk Density (Bd), Ph, Extractable Cation (Exca, Exmg, Exk), Elemental Composition By Xray Fluorescence (Al, Si, P, S, K, Ca, Mn, Fe, Cu, Zn, As, Mo, Hg, Pb) And Icp-Ms (Al, Ca, Cu, Fe, K, Mg, Mn, Mo, Na, P, S, Zn), And Mineral Phase (Xrd Diffraction Analysis). Parent Material-Controlled Particle-Size Distribution, Soc, Ph, Available P, Exca, And Exmg, Whereas Time Since Deglacierization Only Affected Soc And P, And Exmg Globally. Most Of The Significant Differences In Soil Properties Between Parent Material Groups Occurred Within The First 17 Years After Deglacierization, And Then We Observed A Homogenization Between Sites. While The Higher Soc And P Contents Observed Within The Gt Andean Sites Might Be Due To The Parent Material Composition Leading To Faster Initial Soil Formation, We Identified Potential As, Cu, Mo, And Mn Toxicity Within Those Soils. Our Study Highlights The Need To Investigate Further Proglacial Soil'S Buffering Capacity And Carbon Sequestration To Globally Inform The Conservation And Management Of Novel Proglacial Ecosystems.
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2023 |
Acary, V., Bourrier, F., & Viano, B. (2023). Variational Approach For Nonsmooth Elasto-Plastic Dynamics With Contact And Impacts. Computer Methods In Applied Mechanics And Engineering, .
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Agudelo, J., Espinoza, J., Junquas, C., Arias, P., Sierra, J., & Olmo, M. (2023). Future Projections Of Low-Level Atmospheric Circulation Patterns Over South Tropical South America: Impacts On Precipitation And Amazon Dry Season Length. Journal Of Geophysical Research-Atmospheres, 1281(222).
Abstract: The Last Few Decades Have Shown Evidence Of A Lengthening Dry Season In Southern Amazonia, Which Is Associated With A Delay In The Onset Of The South American Monsoon System (Sams). Using A Pattern Recognition Framework Of Atmospheric Circulation Patterns (Cps), Previous Studies Have Identified Specific Atmospheric Situations Related To The Onset Of The Sams. Here, We Analyze The Future Changes In The Cps That Largely Define The Main Hydro-Climatological States Of Tropical South America. We Evaluated The Cp Changes That Occurred Between Two Periods: Historical (1970-2000) And Future (2040-2070), Using Six General Circulation Models (Gcms) From The Coupled Model Intercomparison Project Phase 6. Future Gcm Projections Show Significant Spatio-Temporal Changes In The Cps Associated With The Dry Season In Southern Amazonia During The Mid-21St Century. These Changes Are Related To Both A Late Onset Of The Sams And An Early Demise Of The Sams. Particularly, The Cp Methodology Allowed For A Better Understanding Of The Behavior Of The Southern Amazon Dry Season Under Future Conditions, Showing An Increase In The Frequency Of The Cps Typically Observed During The Dry Season. The Occurrence Of Dry Days In The Amazon Basin During The Austral Winter Of The Mid-21St Century Increases By 19.4% On Average, With Respect To The Historical Period. This Methodology Also Identified A Future Increase In The Frequency Of Dry Cps, Both At The Beginning Of The Dry-To-Wet Transition Period (8%) And At The End Of The Wet-To-Dry Transition Season (11%).
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Ahmed, S., Thomas, J., Angot, H., Dommergue, A., Archer, S., Bariteau, L., et al. (2023). Modelling The Coupled Mercury-Halogen-Ozone Cycle In The Central Arctic During Spring. Elementa-Science Of The Anthropocene, .
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Aidara, M., Fam, P., Danso, D., Mortey, E., Mbaye, A., Ndiaye, M., et al. (2023). Contribution To The Building Of A Weather Information Service For Solar Panel Cleaning Operations At Diass Plant (Senegal, Western Sahel). Open Geosciences, 151(1).
Abstract: The Accumulation Of Dust On The Surface Of Solar Panels Reduces The Amount Of Sunlight Reaching The Solar Cells And Results In A Decrease In Panel Performance. To Avoid This Loss Of Production And Thus, To Improve The Performance Capacity, Solar Panels Must Be Cleaned Frequently. The West African Region Is Well Known For Its High Solar Energy Potential. However, This Potential Can Be Reduced By The High Occurrence Of Dust Storms During The Year. This Article Aims To Provide A Contribution To The Construction Of A Meteorological Information Service For Solar Panel Cleaning Operations At Diass Solar Plant In Senegal (Western Sahel). It Is Based On A Full Year In Situ Experiment Comparing The Power Loss Due To Dust Between Solar Panels Cleaned At Different Frequencies And Those Not Cleaned. The Model To Determine The Cleaning Frequencies Is Based On The Deposition Rate Of Airborne Particles, The Concentration Of Airborne Particles, And The Density Of The Dust That Has A Major Impact On The Power Loss. Cleaning Frequencies Are Presented At Seasonal Scale Because In The Study Area, Dust Episodes Differ According To The Seasons. A Cost-Benefit Analysis Is Also Performed To Demonstrate The Advantage Of Using Weather Information Service To Support The Dust Cleaning Operations At Diass Plant. As Results, It Is Found That Cleaning Every 3 Weeks Is Required During The Dry Seasons, December-January-February And March-April-May. During The Rainy Season, Cleaning Every 5 Weeks Is Recommended In June-July-August, While In September-October-November Cleaning Every 4 Weeks Is Sufficient To Maintain An Optimal Performance Of The Solar Panel. The Total Costs Of Cleaning Operations Based On These Results Are Reduced Compared To The Current Costs Of Cleaning And The Benefits Are Much Higher Than Without Cleaning Action.
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Al-Yaari, A., Condom, T., Junquas, C., Rabatel, A., Ramseyer, V., Sicart, J., et al. (2023). Climate Variability And Glacier Evolution At Selected Sites Across The World: Past Trends And Future Projections. Earths Future, 111(101).
Abstract: The Availability Of Freshwater From Glaciers And Snowmelt Is Of Vital Importance For People And Ecosystems In The Context Of Global Climate Change. Here, We Focus On 25 Glaciers Located In Different Climates And Latitudes And Investigate Their Recent (1958-2020) And Future Projected Trends (2020-2050 And 2070-2100) In Monthly Precipitation (Pr), Maximum And Minimum Temperatures, Ice Mass Loss, And Their Relationships With Cloud Properties. The Study Sites Are Located In Temperate Europe (France), The Inner (Ecuador, Venezuela, And Colombia) And Outer Tropics (Bolivia And Peru), Central America (Mexico), Tropical Southeast Asia (Indonesia), Equatorial Africa (Uganda), And The Southern Dry And Patagonian Andes (Chile And Argentina). The Climate Analyses Are Based On Terraclimate Data (Monthly Climate And Climatic Water Balance For Global Terrestrial Surfaces) And 28 Cordex (Coordinated Regional Climate Downscaling Experiment) Climate Simulations. Our Findings Reveal That, Extrapolating Current Glacier Volume Change Trends, Almost Half Of The Studied Glaciers Are Likely To Vanish (95%-100% Volume Loss) By 2050, With Widespread Warming And Drying Trends Since 1958. A Shift Toward Wetter Conditions At Pico Humboldt (Venezuela) And Martial Este (Argentina) Identifiable In The Cordex Simulation Will Very Likely Not Have A Limiting Impact On Glacier Mass Loss Owing To Increasing Temperatures, Which Will Raise The Elevation Of The Rain/Snow Limit. Our Results Provide Useful New Information To Better Understand Glacier-Climate Relationships And Future Scenarios Dominated By Ice Mass Loss Trends Across The Globe. These Findings Suggest Serious Consequences For Future Water Availability, Which Exacerbate The Vulnerability Of Local Populations And Ecosystems.
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Al-Yaari, A., Zhao, Y., Cheruy, F., & Thiery, W. (2023). Heatwave Characteristics In The Recent Climate And At Different Global Warming Levels: A Multimodel Analysis At The Global Scale. Earths Future, 111(9).
Abstract: The Representation Of Heatwaves (Hws) In The Coupled Model Intercomparison Project Phase 6 (Cmip6) Models Is Analyzed. This Study (A) Evaluates The Performance Of Cmip6 Simulations Against Global Reanalysis And Observations Regarding Time- And Intensity-Related Criteria And (B) Investigates How Hws Are Projected To Change At Different Global Warming Levels (Gwls). During 1979-2014, The Dispersion Of The Models Is Comparable To The Observational Uncertainty For The Time Indices (Duration, Frequency, Number Of Events). It Is Of The Order Of One Event Per Year, 1 Day For The Duration Of The Events And 2 Days For The Frequency, With Tendencies For Over- Or Underestimation, Depending On The Reference Data Set And The Region Considered. For The Hw Magnitude, The Models ' Dispersion Can Reach 15 Degrees C For A Given Region And Is Significantly Higher Than The Observational Uncertainty. The Mean Intensity Of Hws Tends To Be Overestimated, Which Is Partly Attributed To Overly Pronounced Drying Of The Soil During Hw Events. The Contribution Of The Soil Moisture Anomaly To The Temperature Anomaly During Recent Specific Hws Is Shown To Reach Up To 30% Of The Signal. For A Given Gwl, Intensification Of Hw Occurrence, Spatial Extension, And Duration Is Detected Worldwide, But It Is Modulated At The Regional Scale And Strongly Model Dependent. For Time-Related Indices, Tropical Regions And The Arabian Peninsula Will Be Most Impacted, But The Maximum Temperature Will Strongly Increase In Mid-Latitude Regions. Time-Space Analyses Of The Evolution Of Hw Properties For A Given Gwl Are Discussed. Plain Language Summary In This Study, We Evaluate The Number Of Heatwaves (Hws) Occurrences (Hwn), The Duration Of The Longest Event (Hwd), The Frequency Of Hw Days (Hwf), The Near-Surface Maximum Temperature For Hw Days (Hwm), And The Day With The Hottest Events (Hwa) Simulated By Coupled Model Intercomparison Project Phase 6 (Cmip6) Models Against Observations And Reanalysis Over 1979-2014, And Their Projections. The Cmip6 Models Overestimate Hwn And Hwf In The Mediterranean, Central Russia, Northeast Asia, And Southeast China Against Observations. All Considered Cmip6 Models Overestimate Hwd In The Mediterranean And Southeast Chinese Regions Against Hadghcnd Observations, But The Estimates Fell Within The Range Of Observations For All Other Regions. Many Models Overestimate Hwm Against Both Observations And Reanalysis. A Global Warming Of 3 Degrees C Above Preindustrial Levels Will Significantly Increase Hwn By Over Four Events Per Year In Most Regions Except Amazonia And The Arabian Peninsula. The Longest Hw Event Is Projected To Increase By 20-30 Days Under 3 Degrees C Of Global Warming Across Amazonia, The Middle East, And Parts Of Africa. Excessive Drying Is Detected In The Recent Climate Simulated Hw'S Days, Which Might Impact The Strength Of The Response Of The Simulated Hws To Global Warming, And The Characteristics Of Future Droughts.
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Alonso-Gonzalez, E., Gascoin, S., Arioli, S., & Picard, G. (2023). Exploring The Potential Of Thermal Infrared Remote Sensing To Improve Asnowpack Model Through An Observing System Simulation Experiment. Cryosphere, 171(8), 3329–3342.
Abstract: The Assimilation Of Data From Earth Observation Satellites Into Numerical Models Is Considered To Be The Path Forward To Estimate Snow Cover Distribution In Mountain Catchments, Providing Accurate Information On The Mountainous Snow Water Equivalent (Swe). The Land Surface Temperature (Lst) Can Be Observed From Space, But Its Potential To Improve Swe Simulations Remains Underexplored. This Is Likely Due To The Insufficient Temporal Or Spatial Resolution Offered By The Current Thermal Infrared (Tir) Missions. However, Three Planned Missions Will Provide Global-Scale Tir Data At Much Higher Spatiotemporal Resolution In The Coming Years.To Investigate The Value Of Tir Data To Improve Swe Estimation, We Developed A Synthetic Data Assimilation (Da) Experiment At Five Snow-Dominated Sites Covering A Latitudinal Gradient In The Northern Hemisphere. We Generated Synthetic True Lst And Swe Series By Forcing An Energy Balance Snowpack Model With The Era5-Land Reanalysis. We Used This Synthetic True Lst To Recover The Synthetic True Swe From A Degraded Version Of Era5-Land. We Defined Different Observation Scenarios To Emulate The Revisiting Times Of Landsat 8 (16 D) And The Thermal Infrared Imaging Satellite For High-Resolution Natural Resource Assessment (Trishna) (3 D) While Accounting For Cloud Cover. We Replicated The Experiments 100 Times At Each Experimental Site To Assess The Robustness Of The Assimilation Process With Respect To Cloud Cover Under Both Revisiting Scenarios. We Performed The Assimilation Using Two Different Approaches: A Sequential Scheme (Particle Filter) And A Smoother (Particle Batch Smoother).The Results Show That Lst Da Using The Smoother Reduced The Normalized Root Mean Square Error (Nrmse) Of The Swe Simulations From 61 % (Open Loop) To 17 % And 13 % For 16 D Revisit And 3 D Revisit Respectively In The Absence Of Clouds. We Found Similar But Higher Nrmse Values By Removing Observations Due To Cloud Cover But With A Substantial Increase In The Standard Deviation Of The Nrmse Of The Replicates, Highlighting The Importance Of Revisiting Times In The Stability Of The Assimilation Performance. The Smoother Largely Outperformed The Particle Filter Algorithm, Suggesting That The Capability Of A Smoother To Propagate The Information Along The Season Is Key To Exploit Lst Information For Snow Modelling. Finally, We Have Compared The Benefit Of Assimilating Lst With Synthetic Observations Of Fractional Snow Cover Area (Fsca). Lst Da Performed Better Than Fsca Da In All The Study Sites, Suggesting That The Information Provided By Lst Is Not Limited To The Duration Of The Snow Season. These Results Suggest That The Lst Data Assimilation Has An Underappreciated Potential To Improve Snowpack Simulations And Highlight The Value Of Upcoming Tir Missions To Advance Snow Hydrology.
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Ancey, C., & Recking, A. (2023). Scaling Behavior Of Bedload Transport: What If Bagnold Was Right? Earth-Science Reviews, 2462.
Abstract: There Is A Paradox In The Relationship Between Bedload Transport Rates And Flow Variables: Laboratory And Field Studies Have Reported On How Bedload Transport Rates Depend On Flow Variables Through A Power Law, But None Of The Empirical Laws Fitted To The Data Has Managed To Provide Accurate Predictions Of Bedload Transport Over A Wide Range Of Flow Conditions. Inferring Bedload Transport'S Scaling Behavior From Data Has Remained A Stubborn Problem Because The Data Are Very Noisy. It Is, Therefore, Difficult To Progress On This Problem Without Some Informed Speculation About How Bedload And Flow Interact. Ralph Bagnold Proposed An Original Theory To Resolve This Problem. This Paper Reviews And Updates Bagnold'S Model By Separating The Effects Of Flow Resistance And Efficiency (Energy Transfer From Water To Bedload) On Dimensionless Transport Rates Phi. Both Variables' Contributions To Transport Rates Can Be Parameterized Separately For The Three Transport Regimes That Bagnold Defined (No Transport, Transitional, And Sheet Flow). We Also Consider Two Possible Control Variables: The Dimensionless Shield Stress Tau* And A Dimensionless Number Related To Stream Power. In The Transitional Regime, The Dimensionless Bedload Transport Rate Scales As Phi Proportional To Tau*3, Whereas In The Sheet-Flow Regime, It Varies As Phi Proportional To Tau*5/3. We End Up With Two Bagnold Equations: One Based On Physical Principles And Involving Shields Stress Tau*, Flow Resistance F, A Density Ratio, And A Bed Slope; The Other Based On Non-Linear Regression And Stream Power. Compared To A Large Set Of Laboratory And Field Data, Predictions From Bagnold'S Model Show Reasonable Accuracy When The Bed Is Plane.
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Arik, A., Chionne, D., Renou, Y., Brochet, A., Blanchet, J., Kharbouche, M., et al. (2023). The Limits Of Scalability: Uncovering Friction Between Levels Of Flood Risk Governance In The French Alps. International Journal Of Disaster Risk Reduction, 979.
Abstract: Flood Risk Governance Can Be A Source Of Tension Between Different Government Actors And Citizens Across Spatial Scales. In This Context, We Consider The Hydro-Social Contract (Hsc) As A Framework To Understand The Formal And Informal Societal Constructs That Aid Or Impede Effectiveness In Managing Flood Risk. Specifically, We Used Q-Methodology To Understand Different Perspectives Of Flood Risk Governance And Identify Points Of Friction In Executing The Hsc. We Interviewed 62 Flood Risk Management Actors From Small Municipalities (Intra-Watershed) To Regional State Agencies (Inter-Basin) In The Isere River Basin Of France, From Which Three Perspectives Emerged. Most Participants Correlated To A Perspective Reaffirming A Commitment To Integrated And Holistic Approaches In Flood Risk Management. However, The Second And Third Perspectives Illustrate A Governance Gap Due To An Upward Transfer Of Risk Management Responsibilities To A Broader Watershed Approach. At The Same Time, Municipalities Remain Responsible For Crisis Management In The Advent Of Flooding. Our Findings Bring Into Question The Right Balance Of Scale In Flood Risk Governance, Particularly Regarding Hydrological Boundaries That Are Incongruous With Political Jurisdictions At Multiple Scales.
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Arioli, S., Picard, G., Arnaud, L., & Favier, V. (2023). Dynamics Of The Snow Grain Size In A Windy Coastal Area Of Antarctica From Continuous In Situ Spectral-Albedo Measurements. Cryosphere, , 232322–234222.
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Autin, P., Sicart, J., Rabatel, A., Hock, R., & Jomelli, V. (2023). Climate Reconstruction Of The Little Ice Age Maximum Extent Of The Tropical Zongo Glacier Using A Distributed Energy Balancemodel. Comptes Rendus Geoscience, 3553, 381–398.
Abstract: This Study Assessed The Climate Conditions That Caused The Tropical Zongo Glacier (16 Degrees S, Bolivia) To Reach Its Little Ice Age (Lia) Maximum Extent In The Late 17Th Century. We Carried Out Sensitivity Analyses Of The Annual Surface Mass Balance To Different Physically Coherent Climate Scenarios Constrained By Information Taken From Paleoclimate Proxies And Sensitivity Studies Of Past Glacier Advances. These Scenarios Were Constrained By A 1.1 K Cooling And A 20% Increase In Annual Precipitation Compared To The Current Climate. Seasonal Precipitation Changes Were Constructed Using Shuffled Input Data For The Model: Measurements Of Air Temperature And Relative Humidity, Precipitation, Wind Speed, Incoming Short And Longwave Radiation Fluxes, And Assessed Using A Distributed Energy Balance Model. They Were Considered Plausible If Conditions Close To Equilibrium Glacier-Wide Mass Balance Were Obtained. Results Suggest That On Top Of A 1.1 K Cooling And Similar To 20% Increase In Annual Precipitation, Only Two Seasonal Precipitation Patterns Allow Lia Equilibrium: Evenly Distributed Precipitation Events Across The Year And An Early Wet Season Onset.
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Bade, R., Rousis, N., Adhikari, S., Baduel, C., Bijlsma, L., Bizani, E., et al. (2023). Three Years Of Wastewater Surveillance For New Psychoactive Substances From 16 Countries. Water Research X, 191.
Abstract: The Proliferation Of New Psychoactive Substances (Nps) Over Recent Years Has Made Their Surveillance Complex. The Analysis Of Raw Municipal Influent Wastewater Can Allow A Broader Insight Into Community Consumption Patterns Of Nps. This Study Examines Data From An International Wastewater Surveillance Program That Collected And Analysed Influent Wastewater Samples From Up To 47 Sites In 16 Countries Between 2019 And 2022. Influent Wastewater Samples Were Collected Over The New Year Period And Analysed Using Validated Liquid Chromatog-Raphy – Mass Spectrometry Methods. Over The Three Years, A Total Of 18 Nps Were Found In At Least One Site. Synthetic Cathinones Were The Most Found Class Followed By Phenethylamines And Designer Benzodiazepines. Furthermore, Two Ketamine Analogues, One Plant Based Nps (Mitragynine) And Methiopropamine Were Also Quantified Across The Three Years. This Work Demonstrates That Nps Are Used Across Different Continents And Countries With The Use Of Some More Evident In Particular Regions. For Example, Mitragynine Has Highest Mass Loads In Sites In The United States, While Eutylone And 3-Methylmethcathinone Increased Considerably In New Zealand And In Several European Countries, Respectively. Moreover, 2F-Deschloroketamine, An Analogue Of Ke-Tamine, Has Emerged More Recently And Could Be Quantified In Several Sites, Including One In China, Where It Is Considered As One Of The Drugs Of Most Concern. Finally, Some Nps Were Detected In Specific Regions During The Initial Sampling Campaigns And Spread To Additional Sites By The Third Campaign. Hence, Wastewater Surveillance Can Provide An Insight Into Temporal And Spatial Trends Of Nps Use.
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Banwell, A., Wever, N., Dunmire, D., & Picard, G. (2023). Quantifying Antarctic-Wide Ice-Shelf Surface Melt Volume Using Microwave And Firn Model Data: 1980 To 2021. Geophysical Research Letters, .
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Barten, J., Ganzeveld, L., Steeneveld, G., Blomquist, B., Angot, H., Archer, S., et al. (2023). Low Ozone Dry Deposition Rates To Sea Ice During The Mosaic Field Campaign: Implications For The Arctic Boundary Layer Ozone Budget. Elementa-Science Of The Anthropocene, .
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Bayle, A., Carlson, B., Zimmer, A., Vallee, S., Rabatel, A., Cremonese, E., et al. (2023). Local Environmental Context Drives Heterogeneity Of Early Succession Dynamics In Alpine Glacier Forefields. Biogeosciences, , 164911–166911.
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Bekaert, D., Blard, P., Raoult, Y., Pik, R., Kipfer, R., Seltzer, A., et al. (2023). Last Glacial Maximum Cooling Of 9 Degrees C In Continental Europe From A 40 Kyr-Long Noble Gas Paleothermometry Record. Quaternary Science Reviews, .
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Belmajdoub, H., El Aouni, A., & Minaoui, K. (2023). Convolutional Neural Networks For Coastal Upwelling Monitoring Along The Atlantic Coast Of Morocco. Remote Sensing Letters, , 77577–78577.
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Belmajdoub, H., Minaoui, K., El Aouni, A., Hilmi, K., Saadane, R., & Chehri, A. (2023). A New Upwelling Index For The Moroccan Atlantic Coast For The Period Between 1982-2021. Remote Sensing, .
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Bendinger, A., Cravatte, S., Gourdeau, L., Brodeau, L., Albert, A., Tchilibou, M., et al. (2023). Regional Modeling Of Internal-Tide Dynamics Around New Caledonia – Part 1: Coherent Internal-Tide Characteristics And Sea Surface Height Signature. Ocean Science, 191(4), 1315–1338.
Abstract: The Southwestern Tropical Pacific Exhibits A Complex Bathymetry And Represents A Hot Spot Of Internal-Tide Generation. Based On A Tailored High-Resolution Regional Model, We Investigate For The First Time The Internal-Tide Field Around The New Caledonia Islands Through Energy Budgets That Quantify The Coherent Internal-Tide Generation, Propagation, And Dissipation. A Total Of 15.27 Gw Is Converted From The Barotropic To The Baroclinic M2 Tide With The Main Conversion Sites Associated With The Most Prominent Bathymetric Structures Such As Continental Slopes And Narrow Passages In The North (2.17 Gw) And Ridges And Seamounts South Of New Caledonia (3.92 Gw). The Bulk Of Baroclinic Energy Is Generated In Shallow Waters Around 500 M Depth And On Critical To Supercritical Slopes, Highlighting The Limitations Of Linear Semi-Analytical Models In Those Areas. Despite The Strongly Dominant Mode-1 Generation, More Than 50 % Of The Locally Generated Energy Either Dissipates In The Near Field Close To The Generation Sites Or Loses Coherence. The Remaining Baroclinic Energy Propagates Within Well-Defined Tidal Beams With Baroclinic Energy Fluxes Of Up To 30 Kw M – 1 Toward The Open Ocean. The New Caledonia Site Represents A Challenge For Swot (Surface Water And Ocean Topography) Observability Of Balanced Motion In The Presence Of Internal Tides With Sea Surface Height (Ssh) Signatures > 6 Cm At Similar Wavelengths. We Show For Our Study Region That A Correction Of Ssh For The Coherent Internal Tide Potentially Increases The Observability Of Balanced Motion From Wavelengths > 160 Km To Well Below 100 Km.
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Berthier, E., Floriciou, D., Gardner, A., Gourmelen, N., Jakob, L., Paul, F., et al. (2023). Measuring Glacier Mass Changes From Space-A Review. Reports On Progress In Physics, 868(3).
Abstract: Glaciers Distinct From The Greenland And Antarctic Ice Sheets Are Currently Losing Mass Rapidly With Direct And Severe Impacts On The Habitability Of Some Regions On Earth As Glacier Meltwater Contributes To Sea-Level Rise And Alters Regional Water Resources In Arid Regions. In This Review, We Present The Different Techniques Developed During The Last Two Decades To Measure Glacier Mass Change From Space: Digital Elevation Model (Dem) Differencing From Stereo-Imagery And Synthetic Aperture Radar Interferometry, Laser And Radar Altimetry And Space Gravimetry. We Illustrate Their Respective Strengths And Weaknesses To Survey The Mass Change Of A Large Arctic Ice Body, The Vatnajokull Ice Cap (Iceland) And For The Steep Glaciers Of The Everest Area (Himalaya). For Entire Regions, Mass Change Estimates Sometimes Disagree When A Similar Technique Is Applied By Different Research Groups. At Global Scale, These Discrepancies Result In Mass Change Estimates Varying By 20%-30%. Our Review Confirms The Need For More Thorough Inter-Comparison Studies To Understand The Origin Of These Differences And To Better Constrain Regional To Global Glacier Mass Changes And, Ultimately, Past And Future Glacier Contribution To Sea-Level Rise.
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Berthier, E., Vincent, C., & Six, D. (2023). Exceptional Thinning Through The Entire Altitudinal Range Of Mont-Blanc Glaciers During The 2021/22 Mass Balance Year. Journal Of Glaciology, .
Abstract: Widespread Glacier Losses Have Been Observed In Most Glaciated Regions On Earth During Recent Decades, With A Typical Pattern Of Strong Thinning In Their Lower Reaches And Limited Elevation Changes In Their Accumulation Areas. Here, We Use Pleiades Satellite Stereo-Images Of The Mont-Blanc Massif (Alps) To Reveal That Thinning Took Place Through The Entire Elevation Range During The Exceptional 2021/22 Mass-Balance Year. Above 3000 M A.S.L. On Argentiere Glacier And Mer De Glace, Thinning Rates Exceeded 3.5 M A-1 While Almost No Change Occurred During The Previous 9 Years. Below 3000 M A.S.L., These Anomalous Thinning Rates Are Essentially Explained By Changes In Surface Mass Balance. At Higher Altitudes, Other Processes Such As Firn Densification May Play A Role. Our Analysis Shows That High Altitude Glaciers, Mostly Stable During The Last 100 Years, Are Now Responding To The Impact Of Climate Change.
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Blanchet, J., Blanc, A., Boulard, J., & Creutin, J. (2023). Will Future Southwestern Europe Large-Scale Circulations Resemble Past Circulations? A Focus On The Circulations Driving Extreme Precipitation In The Northern French Alps. Journal Of Geophysical Research-Atmospheres, .
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Bodjrenou, R., Cohard, J., Hector, B., Lawin, E., Chagnaud, G., Danso, D., et al. (2023). Evaluation Of Reanalysis Estimates Of Precipitation, Radiation, And Temperature Over Benin (West Africa). Journal Of Applied Meteorology And Climatology, 626(8), 1005–1022.
Abstract: In West Africa, Climatic Data Issues, Especially Availability And Quality, Remain A Significant Constraint To The Development And Application Of Distributed Hydrological Modeling. As Alternatives To Ground-Based Observations, Reanaly-Sis Products Have Received Increasing Attention In Recent Years. This Study Aims To Evaluate Three Reanalysis Products, Namely, Era5, Water And Global Change (Watch) Forcing Data (Wfd) Era5 (Wfde5), And Merra-2, From 1981 To 2019 To Determine Their Ability To Represent Four Hydrological Climates Variables Over A Range Of Space And Time Scales In Benin. The Variables From The Reanalysis Products Are Compared With Point Station Databased Metrics Kling-Gupta Effi- Ciency (Kge), Mean Absolute Error (Mae), Correlation, And Relative Error In Precipitation Annual (Repa). The Results Show That Era5 Presents A Better Correlation For Annual Mean Temperature (Between 0.74 And 0.90) Than Do Wfde5 (0.63-0.78) And Merra-2 (0.25-0.65). Both Era5 And Wfde5 Are Able To Reproduce The Observed Upward Trend Of Tem-Perature (0.2 & Deg;C Decade -1) In The Region. We Noted A Systematic Cold Bias Of -1.3 & Deg;C In All Reanalyses Except Wfde5 (-0.1 & Deg;C). On The Monthly Time Scale, The Temperature Of The Region Is Better Reproduced By Era5 And Wfde5 (Kge & Ge; 0.80) Than By Merra-2 (Kge , 0.5). At All Time Scales, Wfde5 Produces The Best Mae Scores For Longwave (Lw) And Shortwave (Sw) Radiation, Followed By Era5. Wfde5 Also Provides The Best Estimates For The Annual Precipitation (Repa 2 ]-25, 25[ And Kge & Ge; 50% At Most Stations). Era5 Produces Similar Results, But Merra-2 Performs Poorly In All The Metrics. In Addition, Era5 And Wfde5 Reproduce The Bimodal Rainfall Regime In Southern Benin, Unlike Merra-2, But All Products Have Too Many Small Rainfall Events.
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Bonneau, J., Branger, F., Castebrunet, H., & Kouyi, G. (2023). The Impact Of Stormwater Management Strategies On The Flow Regime Of A Peri-Urban Catchment Facing Urbanisation And Climate Change: A Distributed Modelling Study In Lyon, France. Urban Water Journal, .
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Borbon, A., Dominutti, P., Panopoulou, A., Gros, V., Sauvage, S., Farhat, M., et al. (2023). Ubiquity Of Anthropogenic Terpenoids In Cities Worldwide: Emission Ratios, Emission Quantification And Implications For Urban Atmospheric Chemistry. Journal Of Geophysical Research-Atmospheres, 1281(7).
Abstract: Terpenoids (Isoprene And Monoterpenes) Are Highly Reactive Volatile Organic Compounds (Vocs) Known For Decades For Their Biogenic Origin. Here, We Discuss The Nature And Magnitude Of Their Anthropogenic Emissions. We Compiled And Re-Analyzed 14 Data Sets Of In Situ Voc Observations Collected Over The Last Decade In Contrasting Urban Areas From Mid-Latitudes To Subtropical Regions. We Show The Systematic Presence Of Anthropogenic Terpenoids In Urban Ambient Air With Clear Covariations With Anthropogenic Compounds (R-2 > 0.50) Even During Mid-Latitude Winters. Despite The Emerging Importance Of Monoterpene Emissions From Consumer Products In North American Cities, There Is Some Evidence Of Monoterpene Emissions From Tailpipe Exhaust In Cities Of The Developing World. The Traffic-Related Fraction Of Monoterpenes Is Estimated And Can Account For Up To 40% Of Their Ambient Levels. The Anthropogenic Emission Ratios (Er) Of Some Terpenoids (Isoprene, A-Pinene And Limonene) Are Estimated And Spatially Compared. The Anthropogenic Emissions Of Terpenoids Are Indirectly Estimated From Those Er Combined To Regional And Global Emission Inventories (Cams-Glob-Ant_V4.2) At Urban And Country Scale Focusing On France, Lebanon, And Vietnam. Those Anthropogenic Emissions Do Not Represent More Than 3% Of Other Anthropogenic Voc Emissions. However, They Dominate By One To Three Orders Of Magnitude The Reactivity Of Other Anthropogenic Vocs Regarding No3 Oxidation And Ozonolysis. This Study Raises Two Questions Which Need Further Investigations In The Future: (A) The Significance Of Terpenoid Emissions From Traffic, Especially In Urban Areas Of The Developing World And (B) The Role Of Anthropogenic Terpenoids In Nighttime And Wintertime Atmospheric Chemistry At Mid-Latitudes.
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Borbon, A., Dominutti, P., Panopoulou, A., Gros, V., Sauvage, S., Farhat, M., et al. (2023). Ubiquity Of Anthropogenic Terpenoids In Cities Worldwide: Emission Ratios, Emission Quantification And Implications For Urban Atmospheric Chemistry. Journal Of Geophysical Research-Atmospheres, .
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Borlaza, L., Thuy, V., Grange, S., Socquet, S., Moussu, E., Mary, G., et al. (2023). Impact Of Covid-19 Lockdown On Particulate Matter Oxidative Potential At Urban Background Versus Traffic Sites. Environmental Science-Atmospheres, .
Abstract: In Europe, Covid-19 Lockdown Restrictions Were First Implemented In March 2020 To Control The Spread Of The Disease From The Sars-Cov-2 Virus. Many Studies Have Focused On The Influence Of The Applied Measures On Pollution Levels During This Period, But Very Limited Information On The Oxidative Potential (Op), An Emerging Metric Of Particulate Matter (Pm) Exposure. Furthermore, Most Previous Studies Also Commonly Used Comparative Methods With Historical Datasets, Which May Not Be Estimating The Real Pollution Levels Without The Lockdown Restrictions In Place. In This Study, The Op Of Pm Collected At Urban Background (Grenoble, France) And Traffic (Bern, Switzerland) Sites Was Assessed Using Dithiothreitol (Dtt) And Ascorbic Acid (Aa) Assays. These Measurements Were Also Compared With Pm And Black Carbon (Bc) Mass Concentrations, Including The Wood Burning And Fossil Fuel Fractions Of Bc. To Obtain A More Realistic Pollution Level, Assuming There Were No Lockdown Restrictions In Place, A Machine Learning Technique Called The Random Forest (Rf) Regression Model Was Applied To Predict A Business-As-Usual (Bau) Level For Op, Pm, And Bc In Both Sites. This Model Provided A Good Estimate Of The Bau Levels, Allowing A More Realistic Assessment Of The Pollution Changes During The Lockdown Period. The Results Indicate A Clear Decrease In Op Found In The Traffic Site, While A More Modest Change In Op Was Found At The Urban Background Site, Likely Due To Sustained Contributions From Wood Burning Sources For Residential Heating. Overall, This Study Confirms The Major Roles Of Both Of These Combustion Sources In The Op Levels In Ambient Air.
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Bouchet, M., Landais, A., Grisart, A., Parrenin, F., Prié, F., Jacob, R., et al. (2023). The Antarctic Ice Core Chronology 2023 (Aicc2023) Chronological Framework And Associated Timescale For The European Project For Ice Coring In Antarctica (Epica) Dome C Ice Core. Climate Of The Past, 191(111), 2257–2286.
Abstract: The Epica (European Project For Ice Coring In Antarctica) Dome C (Edc) Ice Core Drilling In East Antarctica Reaches A Depth Of 3260 M. The Reference Edc Chronology, The Aicc2012 (Antarctic Ice Core Chronology 2012), Provides An Age Vs. Depth Relationship Covering The Last 800 Kyr (Thousands Of Years), With An Absolute Uncertainty Rising Up To 8000 Years At The Bottom Of The Ice Core. The Origins Of This Relatively Large Uncertainty Are Twofold: (1) The Delta 18 O Atm , Delta O 2 / N 2 And Total Air Content (Tac) Records Are Poorly Resolved And Show Large Gaps Over The Last 800 Kyr, And (2) Large Uncertainties Are Associated With Their Orbital Targets. Here, We Present New Highly Resolved Delta 18 O Atm , Delta O 2 / N 2 And Delta 15 N Measurements For The Edc Ice Core Covering The Last Five Glacial-Interglacial Transitions; A New Low-Resolution Tac Record Over The Period 440-800 Ka Bp (Ka: 1000 Years Before 1950); And Novel Absolute 81 Kr Ages. We Have Compiled Chronological And Glaciological Information Including Novel Orbital Age Markers From New Data On The Edc Ice Core As Well As Accurate Firn Modeling Estimates In A Bayesian Dating Tool To Construct The New Aicc2023 Chronology. For The First Time, Three Orbital Tools Are Used Simultaneously. Hence, It Is Possible To Observe That They Are Consistent With Each Other And With The Other Age Markers Over Most Of The Last 800 Kyr (70 %). This, In Turn, Gives Us Confidence In The New Aicc2023 Chronology. The Average Uncertainty In The Ice Chronology Is Reduced From 1700 To 900 Years In Aicc2023 Over The Last 800 Kyr ( 1 Sigma ). The New Timescale Diverges From Aicc2012 And Suggests Age Shifts Reaching 3800 Years Towards Older Ages Over Marine Isotope Stages (Miss) 5, 11 And 19. But The Coherency Between The New Aicc2023 Timescale And Independent Chronologies Of Other Archives (Italian Lacustrine Succession From Sulmona Basin, Dome Fuji Ice Core And Northern Alpine Speleothems) Is Improved By 1000 To 2000 Years Over These Time Intervals.
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Bouttes, N., Lhardy, F., Quiquet, A., Paillard, D., Goosse, H., & Roche, D. (2023). Deglacial Climate Changes As Forced By Different Ice Sheet Reconstructions. Climate Of The Past, , 102711–104211.
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Brun, F., King, O., Reveillet, M., Amory, C., Planchot, A., Berthier, E., et al. (2023). Everest South Col Glacier Did Not Thin During The Period 1984-2017. Cryosphere, 171(8), 3251–3268.
Abstract: The South Col Glacier Is A Small Body Of Ice And Snow (Approx. 0.2 Km(2)) Located At The Very High Elevation Of 8000Ma.S.L. (Above Sea Level) On The Southern Ridge Of Mt. Everest. A Recent Study By Potocki Et Al. (2022) Proposed That South Col Glacier Is Rapidly Losing Mass. This Is In Contradiction To Our Comparison Of Two Digital Elevation Models Derived From Aerial Photographs Taken In December 1984 And A Stereo Pleiades Satellite Acquisition From March 2017, From Which We Estimate A Mean Elevation Change Of 0.01 +/- 0.05M A(-1). To Reconcile These Results, We Investigate Some Aspects Of The Surface Energy And Mass Balance Of South Col Glacier. From Satellite Images And A Simple Model Of Snow Compaction And Erosion, We Show That Wind Erosion Has A Major Impact On The Surface Mass Balance Due To The Strong Seasonality In Precipitation And Wind And That It Cannot Be Neglected. Additionally, We Show That The Melt Amount Predicted By A Surface Energy And Mass Balance Model Is Very Sensitive To The Model Structure And Implementation. Contrary To Previous Findings, Melt Is Likely Not A Dominant Ablation Process On This Glacier, Which Remains Mostly Snow-Covered During The Monsoon.
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Burgard, C., Jourdain, N., Mathiot, P., Smith, R., Schaefer, R., Caillet, J., et al. (2023). Emulating Present And Future Simulations Of Melt Rates At The Base Of Antarctic Ice Shelves With Neural Networks. Journal Of Advances In Modeling Earth Systems, 151(121).
Abstract: Melt Rates At The Base Of Antarctic Ice Shelves Are Needed To Drive Projections Of The Antarctic Ice Sheet Mass Loss. Current Basal Melt Parameterizations Struggle To Link Open Ocean Properties To Ice-Shelf Basal Melt Rates For The Range Of Current Sub-Shelf Cavity Geometries Around Antarctica. We Present A Proof Of Concept Exploring The Potential Of Simple Deep Learning Techniques To Parameterize Basal Melt. We Train A Simple Feedforward Neural Network, Or Multilayer Perceptron, Acting On Each Grid Cell Separately, To Emulate The Behavior Of Circum-Antarctic Cavity-Resolving Ocean Simulations. We Find That This Kind Of Emulator Produces Reasonable Basal Melt Rates For Our Training Ensemble, At Least As Close As Or Closer To The Reference Than Traditional Parameterizations. On An Independent Ensemble Of Simulations That Was Produced With The Same Ocean Model But With Different Model Parameters, Cavity Geometries And Forcing, The Neural Network Yields Similar Results To Traditional Parameterizations On Present Conditions. In Much Warmer Conditions, Both Traditional Parameterizations And Neural Network Struggle, But The Neural Network Tends To Produce Basal Melt Rates Closer To The Reference Than A Majority Of Traditional Parameterizations. While This Shows That Such A Neural Network Is At Least As Suitable For Century-Scale Antarctic Ice-Sheet Projections As Traditional Parameterizations, It Also Highlights That Tuning Any Parameterization On Present-Like Conditions Can Introduce Biases And Should Be Used With Care. Nevertheless, This Proof Of Concept Is Promising And Provides A Basis For Further Development Of A Deep Learning Basal Melt Parameterization. A Warmer Ocean Around Antarctica Leads To Higher Melting Of The Floating Ice Shelves, Which Influence The Ice Loss From The Antarctic Ice Sheet And Therefore Sea-Level Rise. In Computer Simulations Of The Ocean, These Ice Shelves Are Often Not Represented. For Simulations Of The Ice Sheet, So-Called Parameterizations Are Used To Link The Oceanic Properties In Front Of The Shelf And The Melt At Their Base. We Show That This Link Can Be Emulated With A Simple Neural Network, Which Performs At Least As Well As Traditional Physical Parameterizations Both For Present And Much Warmer Conditions. This Study Also Proposes Several Potential Ways Of Further Improving The Use Of Deep Learning To Parameterize Basal Melt. We Show That Simple Neural Networks Produce Reasonable Basal Melt Rates By Emulating Circum-Antarctic Cavity-Resolving Ocean Simulationspredicted Melt Rates For Present And Warmer Conditions Are Similar Or Closer To The Reference Simulation Than Traditional Parameterizationswe Show That Neural Networks Are Suited To Be Used As Basal Melt Parameterizations For Century-Scale Ice-Sheet Projections
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Burgard, C., Jourdain, N., Mathiot, P., Smith, R., Schäfer, R., Caillet, J., et al. (2023). Emulating Present And Future Simulations Of Melt Rates At The Base Of Antarctic Ice Shelves With Neural Networks. Journal Of Advances In Modeling Earth Systems, 151(121).
Abstract: Melt Rates At The Base Of Antarctic Ice Shelves Are Needed To Drive Projections Of The Antarctic Ice Sheet Mass Loss. Current Basal Melt Parameterizations Struggle To Link Open Ocean Properties To Ice-Shelf Basal Melt Rates For The Range Of Current Sub-Shelf Cavity Geometries Around Antarctica. We Present A Proof Of Concept Exploring The Potential Of Simple Deep Learning Techniques To Parameterize Basal Melt. We Train A Simple Feedforward Neural Network, Or Multilayer Perceptron, Acting On Each Grid Cell Separately, To Emulate The Behavior Of Circum-Antarctic Cavity-Resolving Ocean Simulations. We Find That This Kind Of Emulator Produces Reasonable Basal Melt Rates For Our Training Ensemble, At Least As Close As Or Closer To The Reference Than Traditional Parameterizations. On An Independent Ensemble Of Simulations That Was Produced With The Same Ocean Model But With Different Model Parameters, Cavity Geometries And Forcing, The Neural Network Yields Similar Results To Traditional Parameterizations On Present Conditions. In Much Warmer Conditions, Both Traditional Parameterizations And Neural Network Struggle, But The Neural Network Tends To Produce Basal Melt Rates Closer To The Reference Than A Majority Of Traditional Parameterizations. While This Shows That Such A Neural Network Is At Least As Suitable For Century-Scale Antarctic Ice-Sheet Projections As Traditional Parameterizations, It Also Highlights That Tuning Any Parameterization On Present-Like Conditions Can Introduce Biases And Should Be Used With Care. Nevertheless, This Proof Of Concept Is Promising And Provides A Basis For Further Development Of A Deep Learning Basal Melt Parameterization. A Warmer Ocean Around Antarctica Leads To Higher Melting Of The Floating Ice Shelves, Which Influence The Ice Loss From The Antarctic Ice Sheet And Therefore Sea-Level Rise. In Computer Simulations Of The Ocean, These Ice Shelves Are Often Not Represented. For Simulations Of The Ice Sheet, So-Called Parameterizations Are Used To Link The Oceanic Properties In Front Of The Shelf And The Melt At Their Base. We Show That This Link Can Be Emulated With A Simple Neural Network, Which Performs At Least As Well As Traditional Physical Parameterizations Both For Present And Much Warmer Conditions. This Study Also Proposes Several Potential Ways Of Further Improving The Use Of Deep Learning To Parameterize Basal Melt. We Show That Simple Neural Networks Produce Reasonable Basal Melt Rates By Emulating Circum-Antarctic Cavity-Resolving Ocean Simulationspredicted Melt Rates For Present And Warmer Conditions Are Similar Or Closer To The Reference Simulation Than Traditional Parameterizationswe Show That Neural Networks Are Suited To Be Used As Basal Melt Parameterizations For Century-Scale Ice-Sheet Projections
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Burgos-Cuevas, A., Ruiz-Angulo, A., Ramos-Musalem, K., Palacios-Morales, C., & Garcia-Molina, C. (2023). Experimental Downslope Gravity Currents Over A Synthetic Topography. Atmosfera, 373, 383–399.
Abstract: Experimental Lock-Release Gravity Currents Are Investigated As They Propagate Downslope Over Varying Synthetic Topography. We Emulate And Investigate The Dynamics Of Thermally Driven Winds That Propagate Downslope While Interacting With The Roughness Of A Complex Topographic Surface. The Mixing Processes Between The Gravity Currents And Their Surroundings Are Studied With Particle Image Velocimetry (Piv), And Entrainment Is Quantified. The Magnitude Of The Entrainment Coefficient Is Shown To Increase As The Roughness Of The Slope Increases. Shadowgraph Visualizations Qualitatively Reproduce This Behavior. Finally, Pressure Fields Are Estimated From Velocity Fields, And Pressure Time Series Are Obtained Over Synthetic Stations Along The Topographic Surface. The Arrival Of Gravity Currents Is Shown To Be Detected In The Pressure Time Series. This Last Result May Help Detect Atmospheric Gravity Currents Using Only Surface Pressure Measurements.
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Caillet, J., Jourdain, N., Mathiot, P., Hellmer, H., & Mouginot, J. (2023). Drivers And Reversibility Of Abrupt Ocean State Transitions In The Amundsen Sea, Antarctica. Journal Of Geophysical Research-Oceans, 1281(1).
Abstract: Ocean Warming Around Antarctica Has The Potential To Trigger Marine Ice-Sheet Instabilities. It Has Been Suggested That Abrupt And Irreversible Cold-To-Warm Ocean Tipping Points May Exist, With Possible Domino Effect From Ocean To Ice-Sheet Tipping Points. A 1/4 & Deg; Ocean Model Configuration Of The Amundsen Sea Sector Is Used To Investigate The Existence Of Ocean Tipping Points, Their Drivers, And Their Potential Impact On Ice-Shelf Basal Melting. We Apply Idealized Atmospheric Perturbations Of Either Heat, Freshwater, Or Momentum Fluxes, And We Characterize The Key Physical Processes At Play In Warm-To-Cold And Cold-To-Warm Climate Transitions. Relatively Weak Perturbations Of Any Of These Fluxes Are Able To Switch The Amundsen Sea To An Intermittent Or Permanent Cold State, That Is, With Ocean Temperatures Close To The Surface Freezing Point And Very Low Ice-Shelf Melt Rate. The Transitions Are Reversible, That Is, Canceling The Atmospheric Perturbation Brings The Ocean System Back To Its Unperturbed State Within A Few Decades. All The Transitions Are Primarily Driven By Changes In Surface Buoyancy Fluxes Resulting From The Freshwater Flux Perturbation Or From Modified Net Sea-Ice Production Due To Either Heat Flux Or Sea-Ice Advection Anomalies. These Changes Affect The Vertical Ocean Stratification Over The Continental Shelf And Thereby The Eastward Undercurrent At The Shelf Break, Which Both Impact Ice-Shelf Melting. As Sea-Ice Induced Deep Convection Is Already Quite Limited In Present-Day Conditions, Surface Buoyancy Gain In A Warmer Climate Has Relatively Little Effect On Deep Ocean Properties Compared To Colder Climate Conditions.
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Camberlin, P., Togbedji, C., Pergaud, J., Berger, A., Aellig, R., Fink, A., et al. (2023). The Representation Of Dry-Season Low-Level Clouds Over Western Equatorial Africa In Reanalyses And Historical Cmip6 Simulations. Climate Dynamics, .
Abstract: Within The Equatorial Zone, Western Equatorial Africa (Wea) Has A Record Low Sunshine Duration During The June-September Dry Season Due To The Persistence Of Low Clouds. This Study Examines The Ability Of Two Reanalysis Products (Era5 And Merra-2) And Eight Cmip6 Models (Both Coupled And Atmosphere-Only Historical Simulations) To Reproduce The Climatology Of These Low Clouds, By Comparing It With Ground Observations And A Satellite Product. All Datasets Show A Reasonable Representation Of The Regional Distribution Of Low Clouds Over The Tropical Atlantic And The Neighbouring African Continent. However, Cmip6 Models Tend To Underestimate The Low Cloud Fraction, Especially Over Wea In The Coupled Simulations. This Underestimation Is Partly Due To An Insufficient Seasonal Sea-Surface Temperature (Sst) Cooling Over The Eastern Equatorial Atlantic From April To July In Most Models, Which Reduces The Lower-Tropospheric Stability (Lts). However, The Inability To Reproduce The Jjas Low Cloud Fraction Does Not Necessarily Scale With The Sst Biases Of The Cmip6 Models. Observed Interannual Variations Of Wea Low-Cloud Fraction Are Strongly Controlled By Lts, Itself Mostly Related To Atlantic Sst. The Strong Dependence Of Low Clouds On Interannual Sst Variations Is Captured By Most, But Not All The Cmip6 Models. Additional Drivers Of Interannual Variations Identified In This Study, Such As Mid-Tropospheric Temperatures Over Wea And Bight Of Bonny Surface Winds, Emerge Inconsistently In Cmip6. Further Analyses Are Needed To Disentangle The Roles Played By Sst And Independent Atmospheric Forcings On Wea Low Cloud Formation.
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Caracciolo, R., Escher, B., Lai, F., Nguyen, T., Le, T., Schlichting, R., et al. (2023). Impact Of A Megacity On The Water Quality Of A Tropical Estuary Assessed By A Combination Of Chemical Analysis And In-Vitro Bioassays. Science Of The Total Environment, 8778.
Abstract: Tropical Estuaries Are Threatened By Rapid Urbanization, Which Leads To The Spread Of Thousands Of Micropollutants And Poses An Environmental Risk To Such Sensitive Aqueous Ecosystems. In The Present Study, A Combination Of Chemical And Bioanalytical Water Characterization Was Applied To Investigate The Impact Of Ho Chi Minh Megacity (Hcmc, 9.2 Mil-Lion Inhabitants In 2021) On The Saigon River And Its Estuary And Provide A Comprehensive Water Quality Assessment. Water Samples Were Collected Along A 140-Km Stretch Integrating The River-Estuary Continuum From Upstream Hcmc Down To The Estuary Mouth In The East Sea. Additional Water Samples Were Collected At The Mouth Of The Four Main Ca-Nals Of The City Center. Chemical Analysis Was Performed Targeting Up To 217 Micropollutants (Pharmaceuticals, Plasti-Cizers, Pfass, Flame Retardants, Hormones, Pesticides). Bioanalysis Was Performed Using Six In-Vitro Bioassays For Hormone Receptor-Mediated Effects, Xenobiotic Metabolism Pathways And Oxidative Stress Response, Respectively, All Accompanied By Cytotoxicity Measurement. A Total Of 120 Micropollutants Were Detected And Displayed High Variabil-Ity Along The River Continuum With Total Concentration Ranging From 0.25 To 78 Mu G L-1. Among Them, 59 Micropollutants Were Ubiquitous (Detection Frequency >= 80 %). An Attenuation Was Observed In Concentration And Ef-Fect Proflles Towards The Estuary. The Urban Canals Were Identifled As Major Sources Of Micropollutants And Bioactivity To The River, And One Canal (Blatin Small Letter E With Circumflex And Acuten Nghe) Exceeded The Effect-Based Trigger Values Derived For Estrogenicity And Xenobiotic Metabolism. Iceberg Modelling Apportioned The Contribution Of The Quantifled And The Unknown Chemicals To The Mea-Sured Effects. Diuron, Metolachlor, Chlorpyrifos, Daidzein, Genistein, Climbazole, Mebendazole And Telmisartan Were Identified As Main Risk Drivers Of The Oxidative Stress Response And Xenobiotic Metabolism Pathway Activation. Our Study Reinforced The Need For Improved Wastewater Management And Deeper Evaluations Of The Occurrence And Fate Of Micropollutants In Urbanized Tropical Estuarine Environments.
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Cassel, M., Navratil, O., Liebault, F., Recking, A., Vazquez-Tarrio, D., Bakker, M., et al. (2023). Assessment Of Pebble Virtual Velocities By Combining Active Rfid Fixed Stations With Geophones. Earth Surface Processes And Landforms, .
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Cebrián-Piqueras, M., Palomo, I., Lo, V., López-Rodríguez, M., Filyushkina, A., Fischborn, M., et al. (2023). Leverage Points And Levers Of Inclusive Conservation In Protected Areas. Ecology And Society, 282(4).
Abstract: Inclusive Conservation Approaches That Effectively Conserve Biodiversity While Improving Human Well-Being Are Gaining Traction In The Face Of The Sixth Mass Extinction Of Biodiversity. Despite Much Theorization On The Governance Of Inclusive Conservation, Empirical Research On Its Practical Implementation Is Urgently Needed. Here, Using A Correlation Network Analysis And Drawing On Empirical Results From 263 Sites Described On The Web Platform Of The Panorama Initiative (Iucn), We Inductively Identified Global Clusters Of Conservation Outcomes In Protected And Conserved Areas. These Clusters Represent Five Conservation Foci Or Archetypes, Namely (I) Community-Based Conservation, (Ii) Sustainable Management, (Iii) Conflict Resolution, (Iv) Multi-Level And Co-Governance, And (V) Environmental Protection And Nature'S Contribution To People. Our Empirical Approach Further Revealed That Some Dimensions Of Inclusive Conservation Are Crucial As Leverage Points To Manage Protected Areas Related To These Clusters Successfully, Namely Improvements In The Socio-Cultural Context And Social Cohesion, Enhancing The Status And Participation Of Youth, Women, And Minorities, Improved Human Health, Empowerment Of Local Communities, Or Reestablishment Of Dialogue And Trust. We Highlight Inclusive Interventions Such As Education And Capacity Building, Development Of Alliances And Partnerships, And Enabling Sustainable Livelihoods, Or Governance Arrangements Led By Indigenous Peoples And Local Communities Or Private Actors, As Levers To Promote Positive Transformations In The Social-Ecological Systems Of Protected Areas. We Argue That Although Some Of The Leverage Points We Identified Are Less Targeted In Current Protected Area Management, They Can Represent Powerful Areas Of Intervention To Enhance Social And Ecological Outcomes In Protected Areas.
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Celli, G., Cairns, W., Scarchilli, C., Cuevas, C., Saiz-Lopez, A., Savarino, J., et al. (2023). Bromine, Iodine And Sodium Along The Eaiist Traverse: Bulk And Surface Snow Latitudinal Variability. Environmental Research, 2392.
Abstract: During The East Antarctic International Ice Sheet Traverse (Eaiist, December 2019), In An Unexplored Part Of The East Antarctic Plateau, Snow Samples Were Collected To Expand Our Knowledge Of The Latitudinal Variability Of Iodine, Bromine And Sodium As Well As Their Relation In Connection With Emission Processes And Photochemical Activation In This Unexplored Area. A Total Of 32 Surface (0-5 Cm) And 32 Bulk (Average Of 1 M Depth) Samples Were Taken And Analysed By Inductively Coupled Plasma Mass Spectrometry (Icp-Ms). Our Results Show That There Is No Relevant Latitudinal Trend For Bromine And Sodium. For Bromine They Also Show That It Has No Sig-Nificant Post-Depositional Mechanisms While Its Inland Surface Snow Concentration Is Influenced By Spring Coastal Bromine Explosions. Iodine Concentrations Are Several Orders Of Magnitude Lower Than Bromine And Sodium And They Show A Decreasing Trend In The Surface Samples Concentration Moving Southward. This Suggests That Other Processes Affect Its Accumulation In Surface Snow, Probably Related To The Radial Reduction In The Ozone Layer Moving Towards Central Antarctica. Even Though All Iodine, Bromine And Sodium Present Similar Long-Range Transport From The Dominant Coastal Antarctic Sources, The Annual Seasonal Cycle Of The Ozone Hole Over Antarctica Increases The Amount Of Uv Radiation (In The 280-320 Nm Range) Reaching The Surface, Thereby Affecting The Surface Snow Photoactivation Of Iodine. A Comparison Between The Bulk And Surface Samples Supports The Conclusion That Iodine Undergoes Spring And Summer Snow Recycling That Increases Its Atmospheric Lifetime, While It Tends To Accumulate During The Winter Months When Photochemistry Ceases.
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Chabi, B., Alassane, A., Kpegli, K., Lawson, F., Zakari, A., Koukpohounsi, B., et al. (2023). Characterising Groundwater And Surface-Water Interconnections Using Hydrogeology, Hydrochemistry And Stable Isotopes In The Oueme Delta, Southern Benin. Hydrogeology Journal, .
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Chahinian, N., Alcoba, M., Dembele, N., Cazenave, F., & Bouvier, C. (2023). Evaluation Of An Early Flood Warning System In Bamako (Mali): Lessons Learned From The Flood Of May 2019. Journal Of Flood Risk Management, .
Abstract: Devastating Floods Have Plagued Many West African Cities In The Past Decades. In An Attempt To Reduce Flood Damage In Bamako (Mali), An Early Warning System (Ews) Demonstrator (Raincell App) Was Developed For Flash Floods. On 16 May 2019, While The Demonstrator Was Partially Operational, An Intense Rainfall Event Led To Devastating Floods. We Carried Out An Experience Feedback On This Flood Event By Comparing Ews Simulations To The Results Of A Field Survey. Given The Synoptic Situation And The Rapid Development Pattern Of The Storm, None Of The Global Forecasting Systems Were Able To Foresee Its Occurrence And Magnitude. The Hydrological Model Developed As Part Of The Demonstrator Correctly Identified Most Of The Locations Where Overbank Flow Occurred. In The Absence Of Data, The Predicted Discharge And Volume Values Could Not Be Validated. However, They Are Realistic Based On The Water Levels Reported In The Post-Disaster Needs Assessment Report. It Would Be Advisable To Couple It To A Two-Dimensional Hydraulic Model And Add Discharge And Water Level Monitoring To The Already Existing Rainfall Surveillance Scheme To Further Improve The System'S Performance. Increasing The Local Population'S Awareness Of The Dangers Of Clogged Waterways Is Also Mandatory.
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Chaillot, J., Dasari, S., Fleurbaey, H., Daeron, M., Savarino, J., & Kassi, S. (2023). High-Precision Laser Spectroscopy Of H<Sub>2</Sub>S For Simultaneous Probing Of Multiple-Sulfur Isotopes. Environmental Science-Advances, 2(1), 78–86.
Abstract: The Simultaneous Monitoring Of The Triple Stable S-Isotopes (S-32, S-33 And S-34) Of Hydrogen Sulfide Has Been Conducted With A Vcof-Crds Set-Up (A V-Shaped Cavity For Optical Feedback Coupled To A Cavity Ring Down Spectrometer). The Spectroscopic Investigation Of H2S Was Performed For The First Time In The Near-Infrared Region (Approximate To 1.6 Mu M) With A Stabilized Laser Of Linewidth < 1 Khz And An Optical Pathlength Of 90 Km, Providing Unparalleled Sensitivity And Precision. Pressure Dependencies Of The System Were Explored To As Low As 0.1 Mbar Revealing The Lamb Dip Feature Of The Isotopologue Transitions. A Model Was Developed To Fit Experimental Spectra With Accuracy Better By One Order Of Magnitude Than What The Literature Provides. The S-Isotope Composition Delta S-34 And S-Isotope Anomaly Delta S-33 Are Determined With An Uncertainty Of 5 X 10(-6) Within 10 Seconds, Limited By H2S Reactivity Inside The Measurement Cell. Such High Precision Represents A New Benchmark For Laser Spectroscopy Of H2S And Optical Determination Of Isotopic Measurements And Makes Vcof-Crds A Promising Tool For A Plethora Of Future Applications.
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Champagne, O., Aellig, R., Fink, A., Philippon, N., Camberlin, P., Moron, V., et al. (2023). Climatology Of Low-Level Clouds Over Western Equatorial Africa Based On Ground Observations And Satellites. Journal Of Climate, , 428944–430644.
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Champagne, O., Arain, A., Wang, S., & Leduc, M. (2023). Future Change In Amplitude And Timing Of High-Flow Events In A Canadian Subarctic Watershed. Cold Regions Science And Technology, 2092.
Abstract: The Hudson Bay Basin Is A Large Contributor Of Freshwater Input In The Arctic Ocean And Is Also An Area Affected By Destructive Spring Floods. In This Study, The Hydrological Model Mesh (Modelisation Environmentale Com-Munautaire -Surface And Hydrology) Was Set Up For The Groundhog River Watershed Situated In The Hudson Bay Basin, To Simulate The Future Evolution Of Streamflow And Annual Maximum Streamflow. Mesh Was Forced By Meteorological Data From Era5 Reanalyses In The Historical Period (1979-2018) And 12 Models Of The Coupled Model Intercomparison Project Phase 5 (Cmip5) Downscaled With The Canadian Regional Climate Model Version 5 (Crcm5) In Historical (1979-2005) And Scenario Period (2006-2098). The Projections Consistently Indicate An Earlier Spring Flow And A Reduction In The Amount Of Annual Maximum Streamflow By The End Of The 21St Century. Under The Rcp8.5 Scenario, The Annual Maximum Streamflow Occurring In The Spring Is Expected To Be Advanced By 2 Weeks And Reduced On Average From 852 M3/S (+/- 265) In The Historical Period (1979-2018) To 717M3/S (+/- 250) By The End Of The 21St Century (2059-2098). Because The Seasonal Projection Of Streamflow Was Not Investigated In Previous Studies, This Work Is An Important First Step To Assess The Seasonal Change Of Streamflow In The Hudson Bay Region Under Climate Change.
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Chung, A., Parrenin, F., Steinhage, D., Mulvaney, R., Martín, C., Cavitte, M., et al. (2023). Stagnant Ice And Age Modelling In The Dome C Region, Antarctica. Cryosphere, 171(8), 3461–3483.
Abstract: The European Beyond Epica Project Aims To Extract A Continuous Ice Core Of Up To 1.5 Ma, With A Maximum Age Density Of 20 Kyr M(-1) At Little Dome C (Ldc). We Present A 1D Numerical Model Which Calculates The Age Of The Ice Around Dome C. The Model Inverts For Basal Conditions And Accounts Either For Melting Or For A Layer Of Stagnant Ice Above The Bedrock. It Is Constrained By Internal Reflecting Horizons Traced In Radargrams And Dated Using The Epica Dome C (Edc) Ice Core Age Profile. We Used Three Different Radar Datasets Ranging From A 10 000 Km(2) Airborne Survey Down To 5 Km Long Ground-Based Radar Transects Over Ldc. We Find That Stagnant Ice Exists In Many Places, Including Above The Ldc Relief Where The New Beyond Epica Drill Site (Beldc) Is Located. The Modelled Thickness Of This Layer Of Stagnant Ice Roughly Corresponds To The Thickness Of The Basal Unit Observed In One Of The Radar Surveys And In The Autonomous Phase-Sensitive Radio-Echo Sounder (Apres) Dataset. At Beldc, The Modelled Stagnant Ice Thickness Is 198 +/- 44 M And The Modelled Oldest Age Of Ice Is 1.45 +/- 0.16 Ma At A Depth Of 2494 +/- 30 M. This Is Very Similar To All Sites Situated On The Ldc Relief, Including That Of The Million Year Ice Core Project Being Conducted By The Australian Antarctic Division. The Model Was Also Applied To Radar Data In The Area 10-15 Km North Of Edc (North Patch), Where We Find Either A Thin Layer Of Stagnant Ice (Generally <60 M) Or A Negligible Melt Rate (<0.1 Mm Yr(-1)). The Modelled Maximum Age At North Patch Is Over 2 Ma In Most Places, With Ice At 1.5 Ma Having A Resolution Of 9-12 Kyr M(-1), Making It An Exciting Prospect For A Future Oldest Ice Drill Site.
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Clauzel, L., Menegoz, M., Gilbert, A., Gagliardini, O., Six, D., Gastineau, G., et al. (2023). Sensitivity Of Glaciers In The European Alps To Anthropogenic Atmospheric Forcings: Case Study Of The Argentiere Glacier. Geophysical Research Letters, .
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Cook, S., Gillet-Chaulet, F., & Fuerst, J. (2023). Robust Reconstruction Of Glacier Beds Using Transient 2D Assimilation With Stokes. Journal Of Glaciology, .
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Cook, S., Jouvet, G., Millan, R., Rabatel, A., Zekollari, H., & Dussaillant, I. (2023). Committed Ice Loss In The European Alps Until 2050 Using A Deep-Learning-Aided 3D Ice-Flow Model With Data Assimilation. Geophysical Research Letters, 505(232).
Abstract: Modeling The Short-Term (<50 Years) Evolution Of Glaciers Is Difficult Because Of Issues Related To Model Initialization And Data Assimilation. However, This Timescale Is Critical, Particularly For Water Resources, Natural Hazards, And Ecology. Using A Unique Record Of Satellite Remote-Sensing Data, Combined With A Novel Optimisation And Surface-Forcing-Calculation Method Within The Framework Of The Deep-Learning Based Instructed Glacier Model, We Are Able To Ameliorate Initialization Issues. We Thus Model The Committed Evolution Of All Glaciers In The European Alps Up To 2050 Using Present-Day Climate Conditions, Assuming No Future Climate Change. We Find That The Resulting Committed Ice Loss Exceeds A Third Of The Present-Day Ice Volume By 2050, With Multi-Kilometer Frontal Retreats For Even The Largest Glaciers. Our Results Show The Importance Of Modeling Ice Dynamics To Accurately Retrieve The Ice-Thickness Distribution And To Predict Future Mass Changes. Thanks To High-Performance Gpu Processing, We Also Demonstrate Our Method'S Global Potential.
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Cuesta-Valero, F., Beltrami, H., Garcia-Garcia, A., Krinner, G., Langer, M., Macdougall, A., et al. (2023). Continental Heat Storage: Contributions From The Ground, Inland Waters, And Permafrost Thawing. Earth System Dynamics, , 60966–62766.
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Cusicanqui, D., Bodin, X., Duvillard, P., Schoeneich, P., Revil, A., Assier, A., et al. (2023). Glacier, Permafrost And Thermokarst Interactions In Alpine Terrain: Insights From Seven Decades Of Reconstructed Dynamics Of The Chauvet Glacial And Periglacial System (Southern French Alps). Earth Surface Processes And Landforms, .
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Da Silva, E., Woolliams, E., Picot, N., Poisson, J., Skourup, H., Moholdt, G., et al. (2023). Towards Operational Fiducial Reference Measurement (Frm) Data For The Calibration And Validation Of The Sentinel-3 Surface Topography Mission Over Inland Waters, Sea Ice, And Land Ice. Remote Sensing, 151(191).
Abstract: The Copernicus Sentinel-3 Surface Topography Mission (Stm) Land Altimetry Provides Valuable Surface Elevation Information Over Inland Waters, Sea Ice, And Land Ice, Thanks To Its Synthetic Aperture Radar (Sar) Altimeter And Its Orbit That Covers High-Latitude Polar Regions. To Ensure That These Measurements Are Reliable And To Maximise The Return On Investment, Adequate Validation Of The Geophysical Retrieval Methods, Processing Algorithms, And Corrections Must Be Performed Using Independent Observations. The Eu-Esa Project St3Tart (Started July 2021) Aims To Generalise The Concept Of Fiducial Reference Measurements (Frms) For The Copernicus Sentinel-3 Stm. This Work Has Gathered Existing Data, Made New Observations During Field Campaigns, And Ensured That These Observations Meet The Criteria Of Frm Standards So That They Can Be Used To Validate Sentinel-3 Stm Land Altimetry Products Operationally. A Roadmap For The Operational Provision Of The Frm, Including The Definition, Consolidation, And Identification Of The Most Relevant And Cost-Effective Methods And Protocols To Be Maintained, Supported, Or Implemented, Has Been Developed. The Roadmap Includes Guidelines For Si Traceability, Definitions Of Frm Measurement Procedures, Processing Methods, And Uncertainty Budget Estimations.
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Dang, D., Ha, Q., Némery, J., & Strady, E. (2023). The Seasonal Variations In The Interactions Between Rare Earth Elements And Organic Matter In Tropical Rivers. Chemical Geology, 6386.
Abstract: The Escalation Of Global Demands For Critical Minerals To Facilitate The Green Energy Transition Creates Emerging Needs To Better Understand Their Environmental Behaviours. Several Nations Recognize Rare Earth Elements (Rees) As Priority Critical Minerals And Emphasize The Necessity To Evaluate Their Environmental Mobility And Potential Effects On Natural Ecosystems And Human Health. Here, We Investigated The Seasonal Variations In Dissolved Concentrations Of Rees And Their Leachable Fractions From Suspended Particles In Samples Collected Bi-Weekly From The Sai Gon And Dong Nai Rivers In Southern Vietnam. The Investigation Period Extended Over Sixteen Months, Including A Transition From Wet To Dry Seasons. We Reported Significant Mobility Of Rees In The River Waters During The Wet Season Due To Watershed Runoff, Especially In Sai Gon River With The Occurrence Of Acid Sulphate Soils. Dissolved Ree Concentrations In The Dry Season Were Significantly Lower Because Of The Interactions With Organic-Rich Particles (Up To 13% Of Particulate Organic Carbon, Poc) Mainly Derived From Phytoplankton Materials. The Conditional Distribution Coefficients (Logkd From 5 To 7 For Pr) Were Proportional To Poc Content. The Scavenging Capacity Of Particulate Organic Matter Also Led To Affect The Fractionation Between Light Rees And Heavy Rees In Solution, And The Characteristic Middle Ree-Enrichment Patterns For The Leachable Rees Fraction. We Also Reported Significant Eu Anomalies (Eu/Eu* Up To 7) In The Dong Nai River During The Dry Season And Associated This Observation With The Decomposition Of Organic Matter That Previously Accumulated Eu. However, Further Studies Are Required To Confirm This Hypothesis Because Of Small Reservoir Effects; Elevated Eu Anomalies Were Observed In Water Samples With Low Dissolved Eu Concentrations.
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Dasari, S., Paris, G., Pei, Q., Cong, Z., & Widory, D. (2023). Tracing The Origin Of Elevated Springtime Atmospheric Sulfate On The Southern Himalayan-Tibetan Plateau. Environmental Science-Advances, 2(8), 1110–1118.
Abstract: The Himalayan Tibetan Plateau (Htp) Is One Of The World'S Most Climate-Sensitive Regions Outside The Polar Regions. Here, The Climate-Air Quality-Hydrological Cycle Affecting Sulfate Aerosols Remains Sparsely Investigated, With Their Source Origin(S) Requiring Further Investigation. We Tracked The Evolution Of Sulfur Mass-Independent Isotope Fractionation [S-Mif I.E., Delta S-33 Not Equal 0]-As A Potential Source Tracer-In Springtime Aerosol Sulfate Over The Southern Htp. In A First, At The Southern Htp High-Altitude Receptor Site Qomolangma-Mt. Everest Station, Qoms, Similar To 4300 M A.S.L., Elevated Sulfate Concentrations And S-Mif Were Both Found To Be Associated With Biomass Burning Aerosols (So42- And Delta S-33 Vs. K+: R-2 = 0.92 [P < 0.001] And 0.61[P < 0.005], Respectively). This Is In Stark Contrast To Delta S-33 Aerosol Records From The Central Htp And A Downwind Mountainous Site Wherein Anomalous Sulfur Has Been Linked To Stratospheric Intrusions In The Past, And Geological Lake Records From The Region Which Link The Origin Of Modern Sulfate On The Htp To The Influx Of Mineral Dust, Respectively. The Findings Suggest That There Are Yet Unknown Biomass Combustion-Related Processes (E.G., Crop-Residue And Waste Burning, Wildfires) Plausibly Generating Positive Mif In Sulfur, Which Could Have Implications For Historical S-Isotope Records. Comparing The Triple-S-Isotope Imprint In Aerosol Sulfate On The Htp And Its Surrounding Regions Reveals The Existence Of Spatial Heterogeneity In The Dominance Of Competing Sulfate Transport And Formation Processes With Implications For The Regional Tropospheric Chemical And Radiation Budgets.
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Deen, T., Arain, M., Champagne, O., Chow-Fraser, P., & Martin-Hill, D. (2023). Impacts Of Climate Change On Streamflow In The Mckenzie Creek Watershed In The Great Lakes Region. Frontiers In Environmental Science, .
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Deléage, É. (2023). Well-Posedness Of Reynolds Averaged Equations For Compressible Fluids With A Vanishing Pressure. Mathematical Methods In The Applied Sciences, .
Abstract: We Show That The Reynolds Averaged Equations For Compressible Fluids (Neglecting Third Order Correlations) Are Well-Posed In Hs$$ {H} Circumflex S $$ When The Pressure Vanishes In Dimensions D=2$$ D Equal To 2 $$ And 3. In Order To Do This, We Show That The System Is Friedrichs-Symmetrizable. This Model Belongs To The Class Of Non-Conservative Hyperbolic Systems. Hence The Usual Symmetrisation Method For Conservation Laws Can Not Be Used Here.
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Deng, J., Camenen, B., Legout, C., & Nord, G. (2023). Estimation Of Fine Sediment Stocks In Gravel Bed Rivers Including The Sand Fraction. Sedimentology, .
Abstract: Fine Sediment Stored In The Gravel Bed Is An Important Component Of River Systems. Current Field Protocols Usually Allow Evaluation Of The Silt-Clay Fraction Of Fine Sediment Stocks Only And Neglect The Sand Fraction. This Study Proposes A New Protocol To Quantify Fine Sediment Stocks, Including The Sand Fraction Inside The Gravel Bed Matrix. Fine Sediment Stocks Were Sampled Within Patches Of 0.30 M X 0.30 M On The Dry Gravel Bed Surface, Separating The Surface Layer And The Subsurface Layer. The Grain-Size Distribution Of The Samples Was Obtained By Field Sieving (10 Mm, 2 Mm, 500 Mu M And 100 Mu M) Over A Bucket, Using A Known Volume Of Water. The Mass Of The Fraction Below 100 Mu M Was Measured Based On The Concentration Within The Bucket. The Local Stocks Were Then Integrated Over The Whole River Reach By Assigning Local Stocks To Facies, In Which Fine Sediment Stocks Were Assumed To Be Homogeneously Distributed. The Methodology Was Applied To A 1 Km Long Reach Of The River Galabre (Southern French Alps), Characterized By Significant Fine Sediment Stocks And Upstream Sediment Input. Results From Local Measurements Show A Large Amount Of Sand In Both Surface And Subsurface Layers. The Quantity Of Sand Can Reach Up To Three Times The Quantity Of Silt-Clay. An Estimation Of Porosity Showed That Fine Material May Play An Important Role In Structuring The Bed, Since Porosity Increases With Increasing Fine Sediment Content. The Potential Fine Sediment Stock That Can Be Resuspended Due To Channel Migration Is Found To Be Of The Same Order Of Magnitude As The Sediment Budget Estimated From The Measured Flux In The Upstream Hydrometric Station Of The Studied Reach.
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Denisenko, D., Richard, G., & Chambon, G. (2023). A Consistent Three-Equation Shallow-Flow Model For Bingham Fluids. Journal Of Non-Newtonian Fluid Mechanics, 3213.
Abstract: We Derive A Model For Bingham Fluid Flows Down An Inclined Plane With A Consistent Asymptotic Method In The Shallow-Flow Approximation. The Variables Are Expanded Up To The First Order Of Accuracy Both In The Sheared And Pseudo-Plug Layers. The Divergence Of The Strain Rate, Which Is Obtained In Classical Approaches, Is Here Avoided By A Specific Regularization Of The Rheology Allowing To Implement A Regular Perturbation Method In The Whole Fluid Domain. Unlike Classical Regularization Methods, The Material Is Here Characterized By A True Yield Stress. Below The Yield Point, The Behavior Is Perfectly Rigid. An Alternative Tensor Expression Of The Constitutive Law Is Proposed. In Particular, The Assumption Of An Alignment Between The Yield-Stress Tensor And The Strain-Rate Tensor Is Removed. The Model Is Derived By Averaging The Mass, Momentum And Energy Balance Equations Over The Depth. This Yields A Hyperbolic Model Of Three Equations For The Fluid Depth, The Average Velocity And A Third Variable, Called Enstrophy, Related To The Variance Of The Velocity. The Model Features New Relaxation Source Terms And Admits An Exact Balance Energy Equation. The Velocity Field In The Depth Is Consistently Reconstructed Using Only The Variables Of The Depth-Averaged Model Without Any Derivative. The Physical Relevance Of The Enstrophy Is Related To The Shape Of The Velocity Profile. The Linear Stability Of A Uniform Solution Is Investigated For This Model, Showing A Stabilizing Effect Of The Plasticity. Roll Waves Are Simulated Numerically Using A Classical Godunov'S Scheme. The Model For A Newtonian Fluid Is Presented As A Particular Case.
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Deremble, B., Uchida, T., Dewar, W., & Samelson, R. (2023). Eddy-Mean Flow Interaction With A Multiple Scale Quasi Geostrophic Model. Journal Of Advances In Modeling Earth Systems, 151(101).
Abstract: Parameterization Of Mesoscale Eddies In Coarse Resolution Ocean Models Is Necessary To Include The Effect Of Eddies On The Large-Scale Oceanic Circulation. We Propose To Use A Multiple-Scale Quasi-Geostrophic (Msqg) Model To Capture The Eddy Dynamics That Develop In Response To A Prescribed Large-Scale Flow. The Msqg Model Consists In Extending The Traditional Quasi Geostrophic (Qg) Dynamics To Include The Effects Of A Variable Coriolis Parameter And Variable Background Stratification. Solutions To This Msqg Equation Are Computed Numerically And Compared To A Full Primitive Equation Model. The Large-Scale Flow Field Permits Baroclinically Unstable Qg Waves To Grow. These Instabilities Saturate Due To Non-Linearities And A Filtering Method Is Applied To Remove Large-Scale Structures That Develop Due To The Upscale Cascade. The Resulting Eddy Field Represents A Dynamically Consistent Response To The Prescribed Background Flow, And Can Be Used To Rectify The Large-Scale Dynamics. Comparisons Between Gent-Mcwilliams Eddy Parameterization And The Present Solutions Show Large Regions Of Agreement, While Also Indicating Areas Where The Eddies Feed Back Onto The Large Scale In A Manner That The Gent-Mcwilliams Parameterization Cannot Capture. Also Of Interest Is The Time Variability Of The Eddy Feedback Which Can Be Used To Build Stochastic Eddy Parameterizations.
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Deremble, B., Uchida, T., Dewar, W., & Samelson, R. (2023). Eddy-Mean Flow Interaction With A Multiple Scale Quasi Geostrophic Model. Journal Of Advances In Modeling Earth Systems, 151(101).
Abstract: Parameterization Of Mesoscale Eddies In Coarse Resolution Ocean Models Is Necessary To Include The Effect Of Eddies On The Large-Scale Oceanic Circulation. We Propose To Use A Multiple-Scale Quasi-Geostrophic (Msqg) Model To Capture The Eddy Dynamics That Develop In Response To A Prescribed Large-Scale Flow. The Msqg Model Consists In Extending The Traditional Quasi Geostrophic (Qg) Dynamics To Include The Effects Of A Variable Coriolis Parameter And Variable Background Stratification. Solutions To This Msqg Equation Are Computed Numerically And Compared To A Full Primitive Equation Model. The Large-Scale Flow Field Permits Baroclinically Unstable Qg Waves To Grow. These Instabilities Saturate Due To Non-Linearities And A Filtering Method Is Applied To Remove Large-Scale Structures That Develop Due To The Upscale Cascade. The Resulting Eddy Field Represents A Dynamically Consistent Response To The Prescribed Background Flow, And Can Be Used To Rectify The Large-Scale Dynamics. Comparisons Between Gent-Mcwilliams Eddy Parameterization And The Present Solutions Show Large Regions Of Agreement, While Also Indicating Areas Where The Eddies Feed Back Onto The Large Scale In A Manner That The Gent-Mcwilliams Parameterization Cannot Capture. Also Of Interest Is The Time Variability Of The Eddy Feedback Which Can Be Used To Build Stochastic Eddy Parameterizations.
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Dethinne, T., Glaude, Q., Picard, G., Kittel, C., Alexander, P., Orban, A., et al. (2023). Sensitivity Of The Mar Regional Climate Model Snowpack To The Parameterization Of The Assimilation Of Satellite-Derived Wet-Snow Masks On The Antarctic Peninsula. Cryosphere, 171(101), 4267–4288.
Abstract: Both Regional Climate Models (Rcms) And Remote Sensing (Rs) Data Are Essential Tools In Understanding The Response Of Polar Regions To Climate Change. Rcms Can Simulate How Certain Climate Variables, Such As Surface Melt, Runoff And Snowfall, Are Likely To Change In Response To Different Climate Scenarios But Are Subject To Biases And Errors. Rs Data Can Assist In Reducing And Quantifying Model Uncertainties By Providing Indirect Observations Of The Modeled Variables On The Present Climate. In This Work, We Improve On An Existing Scheme To Assimilate Rs Wet Snow Occurrence Data With The “Modele Atmospherique Regional” (Mar) Rcm And Investigate The Sensitivity Of The Rcm To The Parameters Of The Scheme. The Assimilation Is Performed By Nudging The Mar Snowpack Temperature To Match The Presence Of Liquid Water Observed By Satellites. The Sensitivity Of The Assimilation Method Is Tested By Modifying Parameters Such As The Depth To Which The Mar Snowpack Is Warmed Or Cooled, The Quantity Of Water Required To Qualify A Mar Pixel As “Wet” (0.1 % Or 0.2 % Of The Snowpack Mass Being Water), And Assimilating Different Rs Datasets. Data Assimilation Is Carried Out On The Antarctic Peninsula For The 2019-2021 Period. The Results Show An Increase In Meltwater Production (+66.7 % On Average, Or +95 Gt), Along With A Small Decrease In Surface Mass Balance (Smb) (-4.5 % On Average, Or -20 Gt) For The 2019-2020 Melt Season After Assimilation. The Model Is Sensitive To The Tested Parameters, Albeit With Varying Orders Of Magnitude. The Prescribed Warming Depth Has A Larger Impact On The Resulting Surface Melt Production Than The Liquid Water Content (Lwc) Threshold Due To Strong Refreezing Occurring Within The Top Layers Of The Snowpack. The Values Tested For The Lwc Threshold Are Lower Than The Lwc For Typical Melt Days (Approximately 1.2 %) And Impact Results Mainly At The Beginning And End Of The Melting Period. The Assimilation Method Will Allow For The Estimation Of Uncertainty In Mar Meltwater Production And Will Enable The Identification Of Potential Issues In Modeling Near-Surface Snowpack Processes, Paving The Way For More Accurate Simulations Of Snow Processes In Model Projections.
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Diaz, E., Varando, G., Johnson, J., & Camps-Valls, G. (2023). Learning Latent Functions For Causal Discovery. Machine Learning-Science And Technology, .
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Didi, S., Diakhate, M., & Diedhiou, A. (2023). Changes In The West Africa Monsoon Precipitation Extremes During Enso Developing Phases. Atmosphere-Ocean, .
Abstract: A 37-Year Record Of Rainfall Gridded Data Covering West Africa And A Global Sea Surface Temperature (Sst) Dataset Are Used To Investigate The Remote Influence Of Sst Anomalies In The Equatorial Pacific On The Interannual Variability Of West Africa'S Extreme Rainfall Indices Over The Period 1981-2018. The Top Five (5) Years With The Strongest And Weakest Peak Of Nino3.4 Sst Monthly Anomalies Are Selected, And May-To-September (Mjjas) Composite Anomalies Of The Total And Extreme Rainfall Indices Are Performed. Results Reveal That Equatorial Pacific Sst'S Impacts On Daily Rainfall Intensity Are Generally More Robust Than That On Their Frequency. The Significant Changes In The Mean Zonal Atmospheric Circulation Associated With The Sst Lead To Significant Dynamic And Thermodynamic Changes That Affect The West African Monsoon System Locally. During El Nino (La Nina) Years, (I) A Weakening (Strengthening) Of The Tropical Easterly Jet (Tej), (Ii) A Strengthening (Weakening), And Southward (Northward) Shift Position Of The African Easterly Jet (Aej), And (Iii) A Decrease (Increase) Of The Monsoon Flow Are Noted. These Changes In The Atmospheric Circulation Prevent (Encourage) A Supply Of Moisture, Resulting In A Reduction (Increase) In Extreme Precipitation Observed Across West Africa. Equatorial Eastern Pacific Warming (Cooling) Is Also Shown To Lead To Stable (Unstable) Atmospheric Conditions Over West Africa That Block (Generate) The Development Of Convective Systems.
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Dillon, K., Tignat-Perrier, R., Joly, M., Grogan, S., Larose, C., Amato, P., et al. (2023). Comparison Of Airborne Bacterial Populations Determined By Passive And Active Air Sampling At Puy De Dome, France. Aerosol And Air Quality Research, .
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Do Amaral, F., Trung, T., Pellarin, T., & Gratiot, N. (2023). Datasets Of High-Resolution Water Level And Discharge From The Saigon-Dong Nai Estuary System Impacted By A Developing Megacity, Ho Chi Minh City-ViETNAm. Data In Brief, .
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Dominutti, P., Borlaza, L., Sauvain, J., Thuy, V., Houdier, S., Suarez, G., et al. (2023). Source Apportionment Of Oxidative Potential Depends On The Choice Of The Assay: Insights Into 5 Protocols Comparison And Implications For Mitigation Measures. Environmental Science-Atmospheres, 3(101), 1497–1512.
Abstract: The Oxidative Potential (Op) Of Particulate Matter (Pm) Has Recently Been Considered As A Viable Health-Based Metric Of Pm Exposure. Several Acellular Assays Have Been Developed To Assess Op, But There Is No Clear Consensus In The Methodology Or Protocols Used That Allows Inter-Comparison Between Studies. This Research Investigates Five Different Acellular Op Assays And Their Sensitivities With The Chemical Composition Of Atmospheric Particulate Matter (Pm10) And Its Emission Sources. We Revisited And Evaluated Pm10 Samples Collected Over One Year In The Urban Alpine City Of Grenoble, France. The Op Of Pm10 Was Assessed By Integrating Assays Commonly Found In The Literature, Such As Ascorbic Acid (Aa), Dithiothreitol (Dtt) And 2,7-Dichlorofluorescein (Dcfh) But Also Adding Novel And Less Explored Assays Such As Ferric-Xylenol Orange (Fox), And A Direct Ros-Quantification Through Oh. Detailed Source Apportionment Of Pm Using Positive Matrix Factorisation (Pmf) Previously Performed Was Coupled With Multiple Linear Regression (Mlr) Models To Determine The Op Contribution Of Pm10 Sources. The Results Highlight The Importance Of Seasonality In The Mass Contributions Of Each Source And Its Corresponding Influence On Op. These Seasonal Differences Helped To Identify The Specific Reactivity For Each Studied Op Assay. In Winter, A Good Agreement Was Found Between All The Op Assays With Anthropogenic Sources. However, During Warmer Months, With A Reduction In The Share Of Anthropogenic Emissions, A Higher Impact From Biogenic And Secondary Organic-Related Aerosols Has Been Found. Our Results Also Show A Dissimilar Sensitivity Of Each Op To The Pm10 Sources, Likely Associated With The Chemical Composition And Chemical Processes Involved. Thus, Our Findings Show The Importance Of Combining Various Op Assays To Capture Different Sensitivities To Redox-Active Species To Get A Clearer Picture Of The Intrinsic Capacity Of Pm Sources To Cause Damaging Oxidative Reactions In The Lung. Providing The Heterogeneity Of Sources Obtained With The Different Op Assays For A Given Ambient Pm Exposure, The Choice Of A Single Or A Combination Of Op Method(S) Must Be Rationally Evaluated As Part Of The Assessment Strategy. Such A Choice Would Offer Valuable Source-Related Information As A Powerful Tool To Better Understand The Nature And The Intensity Of Air Pollution And Envisage The Targeted Sources For Future Mitigation Policies.
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Dominutti, P., Hopkins, J., Shaw, M., Mills, G., Le, H., Huy, D., et al. (2023). Evaluating Major Anthropogenic Voc Emission Sources In Densely Populated ViETNAmese Cities. Environmental Pollution, .
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Dubo, T., Palomo, I., Camacho, L., Locatelli, B., Cugniet, A., Racinais, N., et al. (2023). Nature-Based Solutions For Climate Change Adaptation Are Not Located Where They Are Most Needed Across The Alps. Regional Environmental Change, 232(1).
Abstract: Climate Change Impacts Social-Ecological Systems In Mountainous Areas By Increasing Certain Natural Disasters And Changing Nature'S Contributions To People (Ncp). Nature-Based Solutions (Nbs) Are Increasingly Implemented To Help Local Communities Adapt To Climatic Hazards. However, The Relevance Of Their Location In Relation To Those Hazards And Local Ncp Has Hardly Been Addressed. In The Portal (Pathways Of Transformation In The Alps) Project, We Identified And Mapped A Portfolio Of 97 Nbs For Climate Change Adaptation In The European Alps. Most Nbs Addressed Drought Or Soil Instability And Aimed To Provide Multiple Ncp Simultaneously Such As Wood Production And Protective Function Against Landslides. We Analysed Whether Nbs Are Located Where They Are The Most Needed, According To Both Current And Future Intensity Of The Hazards They Aim To Address And To Supply-Flow-Demand Indicators Of The Ncp They Aim To Provide. We Found That The Location Of Nbs Is Not Overall Related To Current Supply-Flow-Demand Indicators Of Most Ncp, Nor To The Intensity Of Hazards. Nevertheless, Nbs Addressing Droughts And Floods Are Located In Areas Where These Hazards Are More Intense, But Do Not Match Higher Values For Ncp Indicators. Conversely, Nbs Aiming To Produce Wood And To Provide Protective Function Against Landslides Are Located In Areas With Greater Levels Of These Ncp, Regardless Of The Intensity Of Hazards. These Results Suggest That Hazards And Ncp Indicators Are Not The Main Drivers Of Nbs Implementation. We Argue That Integrating Local Climate Conditions And Current Ncp Flows Is Needed To Underpin A Macro-Regional Strategy For Planning Nbs Implementation.
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Dumont, M., Gascoin, S., Reeveillet, M., Voisin, D., Tuzet, F., Arnaud, L., et al. (2023). Spatial Variability Of Saharan Dust Deposition Revealed Through A Citizen Science Campaign. Earth System Science Data, 151(7), 3075–3094.
Abstract: Saharan Dust Outbreaks Have Profound Effects On Ecosystems, Climate, Human Health, And The Cryosphere In Europe. However, The Spatial Deposition Pattern Of Saharan Dust Is Poorly Known Due To A Sparse Network Of Ground Measurements. Following The Extreme Dust Deposition Event Of February 2021 Across Europe, A Citizen Science Campaign Was Launched To Sample Dust On Snow Over The Pyrenees And The European Alps. This Somewhat Improvised Campaign Triggered Wide Interest Since 152 Samples Were Collected From The Snow In The Pyrenees, The French Alps, And The Swiss Alps In Less Than 4 Weeks. Among The 152 Samples, 113 In Total Could Be Analysed, Corresponding To 70 Different Locations. The Analysis Of The Samples Showed A Large Variability In The Dust Properties And Amount. We Found A Decrease In The Deposited Mass And Particle Sizes With Distance From The Source Along The Transport Path. This Spatial Trend Was Also Evident In The Elemental Composition Of The Dust As The Iron Mass Fraction Decreased From 11% In The Pyrenees To 2% In The Swiss Alps. At The Local Scale, We Found A Higher Dust Mass On South-Facing Slopes, In Agreement With Estimates From High-Resolution Remote Sensing Data. This Unique Dataset, Which Resulted From The Collaboration Of Several Research Laboratories And Citizens, Is Provided As An Open Dataset To Benefit A Large Community And To Enable Further Scientific Investigations. Data Presented In This Study Are Available At Https://Doi.Org/10.5281/Zenodo.7969515 (Dumont Et Al., 2022A).
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Duvillier, C., Eckert, N., Evin, G., & Deschatres, M. (2023). Development And Evaluation Of A Method To Identify Potential Release Areas Of Snow Avalanches Based On Watershed Delineation. Natural Hazards And Earth System Sciences, 232(4), 1383–1408.
Abstract: Snow Avalanches Are A Prevalent Threat In Mountain Territories. Large-Scale Mapping Of Avalanche-Prone Terrain Is A Prerequisite For Land-Use Planning Where Historical Information About Past Events Is Insufficient. To This Aim, The Most Common Approach Is The Identification Of Potential Release Areas (Pras) Followed By Numerical Avalanche Simulations. Existing Methods For Identifying Pras Rely On Terrain Analysis. Despite Their Efficiency, They Suffer From (I) A Lack Of Systematic Evaluation On The Basis Of Adapted Metrics And Past Observations Over Large Areas And (Ii) A Limited Ability To Distinguish Pras Corresponding To Individual Avalanche Paths. The Latter May Preclude Performing Numerical Simulations Corresponding To Individual Avalanche Events, Questioning The Realism Of Resulting Hazard Assessments. In This Paper, A Method That Accurately Identifies Individual Snow Avalanche Pras Based On Terrain Parameters And Watershed Delineation Is Developed, And Confusion Matrices And Different Scores Are Proposed To Evaluate It. Comparison To An Extensive Cadastre Of Past Avalanche Limits From Different Massifs Of The French Alps Used As Ground Truth Leads To True Positive Rates (Recall) Between 80 % And 87 % In Pra Numbers And Between 92.4 % And 94 % In Pra Areas, Which Shows The Applicability Of The Method To The French Alps Context. A Parametric Study Is Performed, Highlighting The Overall Robustness Of The Approach And The Most Important Steps/Choices To Maximize Pra Detection, Among Which The Important Role Of Watershed Delineation To Identify The Right Number Of Individual Pras Is Highlighted. These Results May Contribute To Better Understanding Avalanche Hazard In The French Alps. Wider Outcomes Include An In-Depth Investigation Of The Issue Of Evaluating Automated Pra Detection Methods And A Large Data Set That Could Be Used For Additional Developments, And To Benchmark Existing And/Or New Pra Detection Methods.
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Eichler, A., Legrand, M., Jenk, T., Preunkert, S., Andersson, C., Eckhardt, S., et al. (2023). Consistent Histories Of Anthropogenic Western European Air Pollution Preserved In Different Alpine Ice Cores. Cryosphere, , 211922–213722.
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Erhardt, T., Jensen, C., Adolphi, F., Kjær, H., Dallmayr, R., Twarloh, B., et al. (2023). High-Resolution Aerosol Data From The Top 3.8 Kyr Of The East Greenland Ice Coring Project (Egrip) Ice Core. Earth System Science Data, 151(111), 5079–5091.
Abstract: Here We Present The High-Resolution Continuous Flow Analysis (Cfa) Data From The Top 479 M Of The East Greenland Ice Coring Project (Egrip) Ice Core Covering The Past 3.8 Kyr. The Data Consist Of 1 Mm Depth-Resolution Profiles Of Calcium, Sodium, Ammonium, Nitrate, And Electrolytic Conductivity As Well As Decadal Averages Of These Profiles. The Nominally 1 Mm Data Represent An Oversampling Of The Record As The True Resolution Is Limited By The Analytical Setup To Approximately 1 Cm. Alongside The Data We Provide A Description Of The Measurement Setup, Procedures, The Relevant References For The Specific Methods As Well As An Assessment Of The Precision Of The Measurements, The Sample-To-Depth Assignment, And The Depth And Temporal Resolution Of The Data Set. The Error In Absolute Depth Assignment Of The Data May Be On The Order Of 2 Cm; However, Relative Depth Offsets Between The Records Of The Individual Species Are Only On The Order Of 1 Mm. The Presented Data Have Sub-Annual Resolution Over The Entire Depth Range And Have Already Formed Part Of The Data For An Annually Layer-Counted Timescale For The Egrip Ice Core Used To Improve And Revise The Multi-Core Greenland Ice-Core Chronology (Gicc05) To A New Version, Gicc21 (Sinnl Et Al., 2022). The Data Are Available In Full 1 Mm Resolution And Decadal Averages On Pangaea (Https://Doi.Org/10.1594/Pangaea.945293, Erhardt Et Al., 2022B).
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Escobar, A., Guillard, F., Einav, I., & Faug, T. (2023). A Scaling Law For The Length Of Granular Jumps Down Smooth Inclines. Journal Of Fluid Mechanics, 9739.
Abstract: Granular Jumps Commonly Develop During Granular Flows Over Complex Topographies Or When Hitting Retaining Structures. While This Process Has Been Well-Studied For Hydraulic Flows, In Granular Flows Such Jumps Remain To Be Fully Explored, Given The Role Of Interparticle Friction. Predicting The Length Of Granular Jumps Is A Challenging Question, Relevant To The Design Of Protection Dams Against Avalanches. In This Study, We Investigate The Canonical Case Of Standing Jumps Formed In Granular Flows Down Smooth Inclines Using Extensive Numerical Simulations Based On The Discrete Element Method. We Consider Both Two- And Three-Dimensional Configurations And Vary The Chute Bottom Friction To Account For The Crucial Interplay Between The Sliding Along The Smooth Bottom And The Shearing Across The Granular Bulk Above. By Doing So, We Derived A Robust Scaling Law For The Jump Length That Is Valid Over A Wide Range Of Froude Numbers And Takes Into Account The Influence Of The Packing Density. The Findings Have Potential Implications On A Number Of Situations Encountered In Industry As Well As Problems Associated With Natural Hazards.
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Faïn, X., Etheridge, D., Fourteau, K., Martinerie, P., Trudinger, C., Rhodes, R., et al. (2023). Southern Hemisphere Atmospheric History Of Carbon Monoxide Over The Late Holocene Reconstructed From Multiple Antarctic Ice Archives. Climate Of The Past, 191(111), 2287–2311.
Abstract: Carbon Monoxide (Co) Is A Naturally Occurring Atmospheric Trace Gas, A Regulated Pollutant, And One Of The Main Components Determining The Oxidative Capacity Of The Atmosphere. Evaluating Climate-Chemistry Models Under Different Conditions Than Today And Constraining Past Co Sources Requires A Reliable Record Of Atmospheric Co Mixing Ratios ([Co]) That Includes Data Since Preindustrial Times. Here, We Report The First Continuous Record Of Atmospheric [Co] For Southern Hemisphere (Sh) High Latitudes Over The Past 3 Millennia. Our Continuous Record Is A Composite Of Three High-Resolution Antarctic Ice Core Gas Records And Firn Air Measurements From Seven Antarctic Locations. The Ice Core Gas [Co] Records Were Measured By Continuous Flow Analysis (Cfa), Using An Optical Feedback Cavity-Enhanced Absorption Spectrometer (Of-Ceas), Achieving Excellent External Precision (2.8-8.8 Ppb; 2 Sigma ) And Consistently Low Blanks (Ranging From 4.1 +/- 1.2 To 7.4 +/- 1.4 Ppb), Thus Enabling Paleo-Atmospheric Interpretations. Six New Firn Air [Co] Antarctic Datasets Collected Between 1993 And 2016 Ce At The De08-2, Dssw19K, Dssw20K, South Pole, Aurora Basin North (Abn), And Lock-In Sites (And One Previously Published Firn Co Dataset At Berkner) Were Used To Reconstruct The Atmospheric History Of Co From Similar To 1897 Ce, Using Inverse Modeling That Incorporates The Influence Of Gas Transport In Firn. Excellent Consistency Was Observed Between The Youngest Ice Core Gas [Co] And The [Co] From The Base Of The Firn And Between The Recent Firn [Co] And Atmospheric [Co] Measurements At Mawson Station (Eastern Antarctica), Yielding A Consistent And Contiguous Record Of Co Across These Different Archives. Our Antarctic [Co] Record Is Relatively Stable From – 835 To 1500 Ce, With Mixing Ratios Within A 30-45 Ppb Range (2 Sigma ). There Is A Similar To 5 Ppb Decrease In [Co] To A Minimum At Around 1700 Ce During The Little Ice Age. Co Mixing Ratios Then Increase Over Time To Reach A Maximum Of Similar To 54 Ppb By Similar To 1985 Ce. Most Of The Industrial Period [Co] Growth Occurred Between About 1940 To 1985 Ce, After Which There Was An Overall [Co] Decrease, As Observed In Greenland Firn Air And Later At Atmospheric Monitoring Sites And Attributed Partly To Reduced Co Emissions From Combustion Sources. Our Antarctic Ice Core Gas Co Observations Differ From Previously Published Records In Two Key Aspects. First, Our Mixing Ratios Are Significantly Lower Than Reported Previously, Suggesting That Previous Studies Underestimated Blank Contributions. Second, Our New Co Record Does Not Show A Maximum In The Late 1800S. The Absence Of A [Co] Peak Around The Turn Of The Century Argues Against There Being A Peak In Southern Hemisphere Biomass Burning At This Time, Which Is In Agreement With (I) Other Paleofire Proxies Such As Ethane Or Acetylene And (Ii) Conclusions Reached By Paleofire Modeling. The Combined Ice Core And Firn Air [Co] History, Spanning – 835 To 1992 Ce, Extended To The Present By The Mawson Atmospheric Record, Provides A Useful Benchmark For Future Atmospheric Chemistry Modeling Studies.
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Farvacque, M., Eckert, N., Candia, G., Bourrier, F., Corona, C., & Toe, D. (2023). Holistic Rockfall Risk Assessment In High Mountain Areas Affected By Seismic Activity: Application To The Uspallata Valley, Central Andes, Chile. Risk Analysis, .
Abstract: Over Large Regions Exposed To Natural Disasters, Cascading Effects Resulting From Complex Or Concatenated Natural Processes May Represent A Large Portion Of Total Risk. Populated High-Mountain Environments Are A Major Concern, And Methods For Large-Scale Quantitative Risk Analyses Are Urgently Required To Improve Risk Mitigation. This Article Presents A Comprehensive Quantitative Rockfall Risk Assessment Over A Large Archetypal Valley Of The Andean Mountains, In Central Chile, Which Integrates A Wide Spectrum Of Elements At Risk. Risk Is Expressed As An Expected Damage Both In Monetary Terms And Casualties, At Different Scales Relevant For Decision Making. Notably, Total Rockfall Risk Is Divided Into Its Main Drivers, Which Allows Quantifying Seismically Induced Rockfall Risk. For This Purpose, The Local Seismic Hazard Is Quantified And The Yield Acceleration, That Is, Acceleration Required To Initiate Rockfall, Is Determined At The Regional Scale. The Probability Of Failure Is Thereafter Derived In Terms Of Annual Frequency Of Rockfall Initiation And Integrated In The Quantitative Risk Assessment (Qra) Process. Our Results Show The Significant Role Of Seismic Activity As The Triggering Mechanism Of Rockfalls, And Highlight Elements At Risk That Have A Major Contribution To The Total Risk. Eventually A Sensitivity Analysis Is Conducted To (I) Assess The Robustness Of Obtained Risk Estimates To The Data And Modeling Choices And (Ii) Identify The Most Influential Assumptions. Our Approach Evidences The Feasibility Of Large-Scale Qras In Sensitive Environments And Opens Perspectives For Refining Qras In Similar Territories Significantly Affected By Cascading Effects And Multihazards.
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Favillier, A., Guillet, S., Lopez-Saez, J., Giacona, F., Eckert, N., Zenhausern, G., et al. (2023). Identifying And Interpreting Regional Signals In Tree-Ring Based Reconstructions Of Snow Avalanche Activity In The Goms Valley (Swiss Alps). Quaternary Science Reviews, .
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Fleischmann, A., Papa, F., Hamilton, S., Fassoni-Andrade, A., Wongchuig, S., Espinoza, J., et al. (2023). Increased Floodplain Inundation In The Amazon Since 1980. Environmental Research Letters, 181(3).
Abstract: Extensive Floodplains Throughout The Amazon Basin Support Important Ecosystem Services And Influence Global Water And Carbon Cycles. A Recent Change In The Hydroclimatic Regime Of The Region, With Increased Rainfall In The Northern Portions Of The Basin, Has Produced Record-Breaking High Water Levels On The Amazon River Mainstem. Yet, The Implications For The Magnitude And Duration Of Floodplain Inundation Across The Basin Remain Unknown. Here We Leverage State-Of-The-Art Hydrological Models, Supported By In-Situ And Remote Sensing Observations, To Show That The Maximum Annual Inundation Extent Along The Central Amazon Increased By 26% Since 1980. We Further Reveal Increased Flood Duration And Greater Connectivity Among Open Water Areas In Multiple Amazon Floodplain Regions. These Changes In The Hydrological Regime Of The World'S Largest River System Have Major Implications For Ecology And Biogeochemistry, And Require Rapid Adaptation By Vulnerable Populations Living Along Amazonian Rivers.
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Fotso-Nguemo, T., Weber, T., Diedhiou, A., Chouto, S., Vondou, D., Rechid, D., et al. (2023). Projected Impact Of Increased Global Warming On Heat Stress And Exposed Population Over Africa. Earths Future, .
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Fremand, A., Fretwell, P., Bodart, J., Pritchard, H., Aitken, A., Bamber, J., et al. (2023). Antarctic Bedmap Data: Findable, Accessible, Interoperable, And Reusable (Fair) Sharing Of 60 Years Of Ice Bed, Surface, And Thickness Data. Earth System Science Data, 151(7), 2695–2710.
Abstract: One Of The Key Components Of This Research Has Been The Mapping Of Antarctic Bed Topography And Ice Thickness Parameters That Are Crucial For Modelling Ice Flow And Hence For Predicting Future Ice Loss And The Ensuing Sea Level Rise. Supported By The Scientific Committee On Antarctic Research (Scar), The Bedmap3 Action Group Aims Not Only To Produce New Gridded Maps Of Ice Thickness And Bed Topography For The International Scientific Community, But Also To Standardize And Make Available All The Geophysical Survey Data Points Used In Producing The Bedmap Gridded Products. Here, We Document The Survey Data Used In The Latest Iteration, Bedmap3, Incorporating And Adding To All Of The Datasets Previously Used For Bedmap1 And Bedmap2, Including Ice Bed, Surface And Thickness Point Data From All Antarctic Geophysical Campaigns Since The 1950S. More Specifically, We Describe The Processes Used To Standardize And Make These And Future Surveys And Gridded Datasets Accessible Under The Findable, Accessible, Interoperable, And Reusable (Fair) Data Principles. With The Goals Of Making The Gridding Process Reproducible And Allowing Scientists To Re-Use The Data Freely For Their Own Analysis, We Introduce The New Scar Bedmap Data Portal (Https://Bedmap.Scar.Org, Last Access: 1 March 2023) Created To Provide Unprecedented Open Access To These Important Datasets Through A Web-Map Interface. We Believe That This Data Release Will Be A Valuable Asset To Antarctic Research And Will Greatly Extend The Life Cycle Of The Data Held Within It. Data Are Available From The Uk Polar Data Centre: Https://Data.Bas.Ac.Uk (Last Access: 5 May 2023 ). See The Data Availability Section For The Complete List Of Datasets.
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Gaetani, M., Ceglar, A., Diedhiou, A., Jerez, S., Rodriguez-Fonseca, B., & Sultan, B. (2023). Editorial: (10 Years) Water-Energy-Food Nexus: Impact Of Climate Variability And Change On The Water-Energy-Food Nexus. Frontiers In Climate, .
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Ghasemi, M., Charrahy, Z., & Gonzalez-Garcia, A. (2023). Mapping Cultural Ecosystem Services Provision: An Integrated Model Of Recreation And Ecotourism Opportunities. Land Use Policy, .
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Gilbert, A., Gimbert, F., Gagliardini, O., & Vincent, C. (2023). Inferring The Basal Friction Law From Long Term Changes Of Glacier Length, Thickness And Velocity On An Alpine Glacier. Geophysical Research Letters, 505(161).
Abstract: Basal Sliding Of Glaciers And Ice Sheets Remains A Source Of Uncertainty In Simulating The Long-Term Evolution Of Ice Masses. In Particular, The Response Of Ice Flow To Changes In Driving Stress Depends Strongly On The Value Of The Exponent M In Nonlinear Friction Laws (E.G., Weertman'S Law), Which Is Poorly Constrained By Observations. Here We Constrain The Friction Law At A Natural Scale On Argentiere Glacier (French Alps, Hard-Bed), Taking Advantage Of Well-Resolved Observations Of Glacier Mass Balance, Geometry And Basal Sliding Over Time Spans That Include Large Changes In Driving Stress. By Combining Three Different Independent Methods Based On (A) Surface Velocity Inversion, (B) Transient Length Change Modeling, And (C) Direct Local Sliding Measurements, We Consistently Find A Value Of M = 3.1 +/- 0.3. We Suggest That Weertman'S Law Is Suitable For Modeling The Long-Term Evolution Of Hard-Bedded Glaciers And Ice Sheets.
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Gilbert, A., Gimbert, F., Gagliardini, O., & Vincent, C. (2023). Inferring The Basal Friction Law From Long Term Changes Of Glacier Length, Thickness And Velocity On An Alpine Glacier. Geophysical Research Letters, 505(161).
Abstract: Basal Sliding Of Glaciers And Ice Sheets Remains A Source Of Uncertainty In Simulating The Long-Term Evolution Of Ice Masses. In Particular, The Response Of Ice Flow To Changes In Driving Stress Depends Strongly On The Value Of The Exponent M In Nonlinear Friction Laws (E.G., Weertman'S Law), Which Is Poorly Constrained By Observations. Here We Constrain The Friction Law At A Natural Scale On Argentiere Glacier (French Alps, Hard-Bed), Taking Advantage Of Well-Resolved Observations Of Glacier Mass Balance, Geometry And Basal Sliding Over Time Spans That Include Large Changes In Driving Stress. By Combining Three Different Independent Methods Based On (A) Surface Velocity Inversion, (B) Transient Length Change Modeling, And (C) Direct Local Sliding Measurements, We Consistently Find A Value Of M = 3.1 +/- 0.3. We Suggest That Weertman'S Law Is Suitable For Modeling The Long-Term Evolution Of Hard-Bedded Glaciers And Ice Sheets.
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Gonzalez, A., Fontaine, F., Barruol, G., Recking, A., Burtin, A., Join, J., et al. (2023). Seismic Signature Of A River Flooding In La R & Prime;Eunion Island During The Tropical Cyclone Dumazile (March 2018). Journal Of Applied Geophysics, 2152.
Abstract: Monitoring Of Sediment Transport During Extreme Flood Events Is Difficult And Often Impossible. Fluvial Seismology Can Provide Constraints On The Mechanisms Of This Transport And On The Seismic Sources But Few Cases Of Application In Context Of Extreme Events Such As Tropical Cyclones Were Realized. Recordings From Three Seismic Stations Temporarily Installed Along A River (The Rivie`Re Du Ma<Sic>T) Located In La Re & Prime;Union Island (Indian Ocean) Are Analysed To Characterize High-Frequency (> 1 Hz) Seismic Noise Induced By The Extreme Flood Generated By The Tropical Cyclone Dumazile (March 2018). We Evidence A Good Correlation (R2 = 0.94) Between The Amplitude Of The Seismic Signal And The Water Level At Lower Frequencies (2-7 Hz), Particularly During The Rising Limb Of The River Flood. The Relationship Between Seismic Amplitude And Water Level Measurements Tested At Multiple Frequency Ranges Are Consistent With A Signal Dominated By Water Flow At Lower Frequencies And By Sediment Transport At Higher Frequencies (15-45 Hz). We Show That The Use Of Seismic Measurement, Particularly At Stations Located Very Close To The Riverbed Can Provide Comprehensive Information On The Mechanisms Involved During Sediment Transport Associated With Extreme Flood Events When Direct Measurements Are Not Possible.
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Gonzalez-Garcia, A., Aguado, M., Solascasas, P., Palomo, I., Gonzalez, J., Garcia-Llorente, M., et al. (2023). Co-Producing An Ecosystem Services-Based Plan For Sustainable University Campuses. Landscape And Urban Planning, 2302.
Abstract: In The Context Of Global Change, Social-Ecological Perspectives For Organisations And Territorial Planning Schemes Are Key To Facilitate A Transition Towards Sustainability. Consequently, Ecosystem Services (Es) Assessment And Mapping Are Being Increasingly Used To Enhance Knowledge Co-Production For More Sustainable Territorial Management. Higher Education Organizations Have The Potential To Catalyse The Sustainability Transition Of So-Ciety, But There Is A Lack Of Studies Integrating Novel And Current Sustainable Development Approaches In Spatial Planning At University Campuses. Here, We Proposed An Integrated Approach For Developing An Ecosystem Services-Based Plan To Manage The Campus Of The Autonomous University Of Madrid (Spain). We Developed A Participatory Process Integrating All The Various Actors And The Decision Making-Bodies Of The University. This Participatory Process Involved Meetings With Different Groups And 2,126 Surveys Administrated To Students, Professors, Researchers And Administration/Services Staff. We Also Developed A Technical Process For Assessing Es Including Eight Es Maps (Four Regulating, One Provisioning And Three Cultural), Consulted With The Experts And Stakeholders Involved, And Built The Final Version Of The Planning Guide Integrating All Perspectives To Promote Es-Based Strategic Lines. Our Results Showed That Es Maps Are Useful For Creating Management Units And For Multi -Scale Analysis. Es Maps Highlighted Important Values Of The Campus, Allowing The Integration Of More Social Actors That Allow A Stronger Participative Process And The Creation Of A Long-Term Planning Scheme. However, We Identified Certain Aspects Of The Es Approach That Hinder Real-World Application, Including Inherent Problems Associated With Shifting Politics.
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Gonzalez-Garcia, A., Aguado, M., Solascasas, P., Palomo, I., Gonzalez, J., Garcia-Llorente, M., et al. (2023). Co-Producing An Ecosystem Services-Based Plan For Sustainable University Campuses. Landscape And Urban Planning, 2302.
Abstract: In The Context Of Global Change, Social-Ecological Perspectives For Organisations And Territorial Planning Schemes Are Key To Facilitate A Transition Towards Sustainability. Consequently, Ecosystem Services (Es) Assessment And Mapping Are Being Increasingly Used To Enhance Knowledge Co-Production For More Sustainable Territorial Management. Higher Education Organizations Have The Potential To Catalyse The Sustainability Transition Of So-Ciety, But There Is A Lack Of Studies Integrating Novel And Current Sustainable Development Approaches In Spatial Planning At University Campuses. Here, We Proposed An Integrated Approach For Developing An Ecosystem Services-Based Plan To Manage The Campus Of The Autonomous University Of Madrid (Spain). We Developed A Participatory Process Integrating All The Various Actors And The Decision Making-Bodies Of The University. This Participatory Process Involved Meetings With Different Groups And 2,126 Surveys Administrated To Students, Professors, Researchers And Administration/Services Staff. We Also Developed A Technical Process For Assessing Es Including Eight Es Maps (Four Regulating, One Provisioning And Three Cultural), Consulted With The Experts And Stakeholders Involved, And Built The Final Version Of The Planning Guide Integrating All Perspectives To Promote Es-Based Strategic Lines. Our Results Showed That Es Maps Are Useful For Creating Management Units And For Multi -Scale Analysis. Es Maps Highlighted Important Values Of The Campus, Allowing The Integration Of More Social Actors That Allow A Stronger Participative Process And The Creation Of A Long-Term Planning Scheme. However, We Identified Certain Aspects Of The Es Approach That Hinder Real-World Application, Including Inherent Problems Associated With Shifting Politics.
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Gonzalez-Garcia, A., Aguado, M., Solascasas, P., Palomo, I., Gonzalez, J., Garcia-Llorente, M., et al. (2023). Co-Producing An Ecosystem Services-Based Plan For Sustainable University Campuses. Landscape And Urban Planning, .
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Goodwin, S., Lapillonne, S., Piton, G., & Chambon, G. (2023). An Sph Study On Viscoplastic Surges Overriding Mobile Beds: The Many Regimes Of Entrainment. Computers & Geosciences, 1811.
Abstract: Flow-Type Landslides Entrain Mobile Bed Material, But The Processes Involved Are Diverse And Require Systematic Study. We Perform Direct Numerical Simulations Using The Open-Source Sph Package Dualsphysics With A Regularized Herschel-Bulkley Rheology. We Then Compare Model Output With Physical Test Data, And Hence Investigate The Effects Of Varying The Bed Yield Stress Tau(Gamma,B) And Bed Depth H(B), Interpreting The Results Using A Newly-Identified Set Of Dimensionless Numbers. Results Reveal Diverse Interaction Regimes Between Surges And Mobile Beds, Including ''Rigid Bed'', ''Lubrication'', ''Shallow Ploughing'', ''Surfing'', ''Plunging'', And ''Deep Ploughing''. Shallow, Borderline-Stable Beds ''Lubricate'' The Surge: Once Destabilized, These Beds Cause Strong Acceleration Of The Combined Flow Front. Deeper Borderline-Stable Beds Allow The Surge Material To ''Plunge'' Downward, Massively Displacing Bed Material Upward And Downstream. For Stabler Beds, ''Ploughing'' And ''Surfing'' Are Associated With Intermediate And High Values Of Tau(Gamma,B), Respectively. In Both Cases, Beds Retard The Surge, With Mobile Dams Forming For ''Ploughing'' Regimes. Across All Regimes Identified, The Influence Of Tau(Gamma,B) Is Non-Monotonic, With Intermediate Values Decelerating The Combined Flow Fronts The Most. Furthermore, The Different Interaction Regimes Exhibit Unique Velocity Profiles. We Develop Phase Diagrams Based On Three Dimensionless Numbers, Demarcating These Regimes.
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Grilli, R., Delsontro, T., Garnier, J., Jacob, F., & Nemery, J. (2023). A Novel High-Resolution In Situ Tool For Studying Carbon Biogeochemical Processes In Aquatic Systems: The Lake Aiguebelette Case Study. Journal Of Geophysical Research-Biogeosciences, 1281(121).
Abstract: Lakes And Reservoirs Are A Significant Source Of Atmospheric Methane (Ch4), With Emissions Comparable To The Largest Global Ch4 Emitters. Understanding The Processes Leading To Such Significant Emissions From Aquatic Systems Is Therefore Of Primary Importance For Producing Accurate Projections Of Emissions In A Changing Climate. In This Work, We Present The First Deployment Of A Novel Membrane Inlet Laser Spectrometer (Mils) For Fast Simultaneous Detection Of Dissolved Ch4, Ethane (C2H6) And The Stable Carbon Isotope Of Methane (Delta 13Ch4). During A 1-Day Field Campaign, We Performed 2D Mapping Of Surface Water Of Lake Aiguebelette (France). Average Dissolved Ch4 Concentrations And Delta 13Ch4 Were 391.9 +/- 156.3 Nmol L-1 And -67.3 +/- 3.4 Parts Per Thousand In The Littoral Area And 169.8 +/- 26.6 Nmol L-1 And -61.5 +/- 3.6 Parts Per Thousand In The Pelagic Area. The Dissolved Ch4 Concentration In The Pelagic Zone Was 50 Times Larger Than The Concentration Expected At Equilibrium With The Atmosphere, Confirming An Oversaturation Of Dissolved Ch4 In Surface Waters Over Shallow And Deep Areas. The Results Suggest The Presence Of Ch4 Sources Less Enriched In 13C In The Littoral Zone (Presumably The Littoral Sediments). The Ch4 Pool Became More Enriched In 13C With Distance From Shore, Suggesting That Oxidation Prevailed Over Epilimnetic Ch4 Production And It Was Further Confirmed By An Isotopic Mass Balance Technique With The High-Resolution Data. This New In Situ Fast Response Sensor Allows One To Obtain Unique High-Resolution And High-Spatial Coverage Data Sets Within A Limited Amount Of Survey Time. This Tool Will Be Useful In The Future For Studying Processes Governing Ch4 Dynamics In Aquatic Systems. High-Resolution Mapping Of Surface Methane And Its Isotopic Signature Enables Accurate Characterization Of Aquatic Systems And Discrimination Of Biochemical Processes At Work. At Lake Aiguebelette, This New In Situ Tool Allowed Us To Conclude That Methane Present At The Surface Comes Mainly From Shallow Littoral Areas, Where Sediments, Which Are A Source Of Methane, Are Closer To The Surface. During Lateral Transport Of Water Masses From The Littoral Zone, The Change In Isotopic Signature Reveals That Methane Oxidation Prevails Over Local In Situ Production. Comparison With Previous Studies Validates The Importance Of High-Resolution Measurements (Particularly To Capture The High Variability In The Littoral Zone) And Showed That Smaller Lakes Experience Stronger Methane Isotopic Signature Changes For A Given Methane Concentration Variation. This Can Be Explained By The Fact That The Smaller Lake Has A Larger Littoral-To-Total Surface Area. This New Tool Will Be Useful In The Nearby Future To Study The Processes Governing Ch4 Dynamics In Aquatic Systems. Fast In Situ Measurements Of Dissolved Methane And Its Stable Carbon Isotopehigh-Spatial Resolution Mapping Of Dissolved Methane And Its Stable Carbon Isotopeimproved Production/Oxidation Process Identification Over Discrete Sampling
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Guilbert, A., Bernard, J., Peyre, H., Costet, N., Hough, I., Seyve, E., et al. (2023). Prenatal And Childhood Exposure To Ambient Air Pollution And Cognitive Function In School-Age Children: Examining Sensitive Windows And Sex-Specific Associations. Environmental Research, 2352.
Abstract: Background: Combined Effect Of Both Prenatal And Early Postnatal Exposure To Ambient Air Pollution On Child Cognition Has Rarely Been Investigated And Periods Of Sensitivity Are Unknown. This Study Explores The Temporal Relationship Between Pre- And Postnatal Exposure To Pm10, Pm2.5, No2 And Child Cognitive Function. Methods: Using Validated Spatiotemporally Resolved Exposure Models, Pre- And Postnatal Daily Pm2.5, Pm10 (Satellite Based, 1 Km Resolution) And No2 (Chemistry-Transport Model, 4 Km Resolution) Concentrations At The Mother'S Residence Were Estimated For 1271 Mother-Child Pairs From The French Eden And Pelagie Cohorts. Scores Representative Of Children'S General, Verbal And Non-Verbal Abilities At 5-6 Years Were Constructed Based On Subscale Scores From The Wppsi-Iii, Wisc-Iv Or Nepsy-Ii Batteries, Using Confirmatory Factor Analysis (Cfa). Associations Of Both Prenatal (First 35 Gestational Weeks) And Postnatal (60 Months After Birth) Exposure To Air Pollutants With Child Cognition Were Explored Using Distributed Lag Non-Linear Models Adjusted For Confounders. Results: Increased Maternal Exposure To Pm10, Pm2.5 And No2, During Sensitive Windows Comprised Between The 15Th And The 33Rd Gestational Weeks, Was Associated With Lower Males' General And Non-Verbal Abilities. Higher Postnatal Exposure To Pm2.5 Between The 35Th And 52Nd Month Of Life Was Associated With Lower Males' General, Verbal And Non-Verbal Abilities. Some Protective Associations Were Punctually Observed For The Very First Gestational Weeks Or Months Of Life For Both Males And Females And The Different Pollutants And Cognitive Scores. Discussion: These Results Suggest Poorer Cognitive Function At 5-6 Years Among Males Following Increased Maternal Exposure To Pm10, Pm2.5 And No2 During Mid-Pregnancy And Child Exposure To Pm2.5 Around 3-4 Years. Apparent Protective Associations Observed Are Unlikely To Be Causal And Might Be Due To Live Birth Selection Bias, Chance Finding Or Residual Confounding.
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Guilbert, A., Hough, I., Seyve, E., Rolland, M., Quentin, J., Slama, R., et al. (2023). Association Of Prenatal And Postnatal Exposures To Warm Or Cold Air Temperatures With Lung Function In Young Infants. Jama Network Open, 6(3).
Abstract: Importance Little Is Known About Long-Term Associations Of Early-Life Exposure To Extreme Temperatures With Child Health And Lung Function. Objectives To Investigate The Association Of Prenatal And Postnatal Heat Or Cold Exposure With Newborn Lung Function And Identify Windows Of Susceptibility. Design, Setting, And Participants This Population-Based Cohort Study (Sepages) Recruited Pregnant Women In France Between July 8, 2014, And July 24, 2017. Data On Temperature Exposure, Lung Function, And Covariates Were Available From 343 Mother-Child Dyads. Data Analysis Was Performed From January 1, 2021, To December 31, 2021. Exposures Mean, Sd, Minimum, And Maximum Temperatures At The Mother-Child'S Residence, Estimated Using A State-Of-The-Art Spatiotemporally Resolved Model. Main Outcomes And Measures Outcome Measures Were Tidal Breathing Analysis And Nitrogen Multiple-Breath Washout Test Measured At 2 Months Of Age. Adjusted Associations Between Both Long-Term (35 Gestational Weeks And First 4 Weeks After Delivery) And Short-Term (7 Days Before Lung Function Test) Exposure To Ambient Temperature And Newborn Lung Function Were Analyzed Using Distributed Lag Nonlinear Models. Results A Total Of 343 Mother-Child Pairs Were Included In The Analyses (Median [Iqr] Maternal Age At Conception, 32 [30.0-35.2] Years; 183 [53%] Male Newborns). A Total Of 246 Mothers And/Or Fathers (72%) Held At Least A Master'S Degree. Among The 160 Female Newborns (47%), Long-Term Heat Exposure (95Th Vs 50Th Percentile Of Mean Temperature) Was Associated With Decreased Functional Residual Capacity (-39.7 Ml; 95% Ci, -68.6 To -10.7Ml For 24 Degrees C Vs 12 Degrees C At Gestational Weeks 20-35 And Weeks 0-4 After Delivery) And Increased Respiratory Rate (28.0/Min; 95% Ci, 4.2-51.9/Min For 24 Degrees C Vs 12 Degrees C At Gestational Weeks 14-35 And Weeks 0-1 After Delivery). Long-Term Cold Exposure (5Th Vs 50Th Percentile Of Mean Temperature) Was Associated With Lower Functional Residual Capacity (-21.9 Ml; 95% Ci, -42.4 To -1.3 Ml For 1 Degrees C Vs 12 Degrees C At Gestational Weeks 15-29), Lower Tidal Volume (-23.8 Ml; 95% Ci, -43.1 To -4.4 Ml For 1 Degrees C Vs 12 Degrees C At Gestationalweeks 14-35 And Weeks 0-4 After Delivery), And Increased Respiratory Rate (45.5/Min; 95% Ci, 10.1-81.0/Min For 1 Degrees C Vs 12 Degrees C At Gestational Weeks 6-35 And Weeks 0-1 After Delivery) In Female Newborns As Well. No Consistent Association Was Observed For Male Newborns Or Short-Term Exposure To Cold Or Heat. Conclusions And Relevance In This Cohort Study, Long-Term Heat And Cold Exposure From The Second Trimester Until 4 Weeks After Birth Was Associated With Newborn Lung Volumes, Especially Among Female Newborns.
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Guillevic, F., Rossi, M., Develle, A., Spadini, L., Martins, J., Arnaud, F., et al. (2023). Pb Dispersion Pathways In Mountain Soils Contaminated By Ancient Mining And Smelting Activities. Applied Geochemistry, 1501.
Abstract: Over The Last Millennia, Mining And Smelting Activities Have Produced Large Amounts Of Mine And Metallurgical Wastes That Remain Enriched In Potentially Toxic Trace Elements (Pte). A Spatial Distribution Of Pb Content Was Coupled To Mineralogical Observations And Single Extraction Tests To Characterise The Pb Contamination Legacy And Pb Dispersion Trajectories In An Ancient Mining And Smelting Site That Has Been Abandoned For Approximatively 200 Years. In The Peisey-Nancroix Pb-Ag Mine (Savoy, France), Extreme Anthropogenic Pb Contamination Is Located Close To The Slag Heaps And Along Ore And Slag Transport Paths. The Contamination Gradient Is Restricted To A Few Hundred Metres Downhill, Down To Background Pb Values. The Pb-Bearing Phases Change Along The Contamination Gradient. The Most Contaminated Soils Contain Significant Amounts Of Galena And Slags That Are More Or Less Weathered Into Pyromorphite And Cerussite. Pb-Bearing Mn (Hydr-)Oxides Are The Most Stable And Ubiquitous Forms Of Pb, Which Proportions Increase Downgradient. Despite The Presence Of Some Stable Pbbearing Phases (Pyromorphite, Pb-Bearing Mn (Hydr-)Oxides), Extraction Tests Indicate That A Small Proportion Of Pb May Still Be Mobile Over Time.
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Guo, L., Li, J., Dehecq, A., Li, Z., Li, X., & Zhu, J. (2023). A New Inventory Of High Mountain Asia Surging Glaciers Derived From Multiple Elevation Datasets Since The 1970S. Earth System Science Data, , 284122–286122.
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Gupta, A., Reverdy, A., Cohard, J., Hector, B., Descloitres, M., Vandervaere, J., et al. (2023). Impact Of Distributed Meteorological Forcing On Simulated Snow Cover And Hydrological Fluxes Over A Mid-Elevation Alpine Micro-Scale Catchment. Hydrology And Earth System Sciences, 272(1), 191–212.
Abstract: From The Micro- To The Mesoscale, Water And Energy Budgets Of Mountainous Catchments Are Largely Driven By Topographic Features Such As Terrain Orientation, Slope, Steepness, And Elevation, Together With Associated Meteorological Forcings Such As Precipitation, Solar Radiation, And Wind Speed. Those Topographic Features Govern The Snow Deposition, Melting, And Transport, Which Further Impacts The Overall Water Cycle. However, This Microscale Variability Is Not Well Represented In Earth System Models Due To Coarse Resolutions. This Study Explores The Impact Of Precipitation, Shortwave Radiation, And Wind Speed On The Water Budget Distribution Over A 15.28 Ha Small, Mid-Elevation (2000-2200 M) Alpine Catchment At Col Du Lautaret (France). The Grass-Dominated Catchment Remains Covered With Snow For 5 To 6 Months Per Year. The Surface-Subsurface Coupled Distributed Hydrological Model Parflow-Clm Is Used At A Very High Resolution (10 M) To Simulate The Impacts On The Water Cycle Of Meteorological Variability At Very Small Spatial And Temporal Scales. These Include 3D Simulations Of Hydrological Fluxes With Spatially Distributed Forcing Of Precipitation, Shortwave Radiation, And Wind Speed Compared To 3D Simulations Of Hydrological Fluxes With Non-Distributed Forcing. Our Precipitation Distribution Method Encapsulates The Spatial Snow Distribution Along With Snow Transport. The Model Simulates The Dynamics And Spatial Variability Of Snow Cover Using The Common Land Model (Clm) Energy Balance Module And Under Different Combinations Of Distributed Forcing. The Resulting Subsurface And Surface Water Transfers Are Computed By The Parflow Module. Distributed Forcing Leads To Spatially Heterogeneous Snow Cover Simulation, Which Becomes Patchy At The End Of The Melt Season And Shows A Good Agreement With The Remote Sensing Images (Mean Bias Error (Mbe) = 0.22). This Asynchronous Melting Results In A Longer Melting Period Compared To The Non-Distributed Forcing, Which Does Not Generate Any Patchiness. Among The Distributed Meteorological Forcings Tested, Precipitation Distribution, Including Snow Transport, Has The Greatest Impact On Spatial Snow Cover (Mbe = 0.06) And Runoff. Shortwave Radiation Distribution Has An Important Impact, Reducing Evapotranspiration As A Function Of The Slope Orientation (Decreasing The Slope Between Observed And Simulated Evapotranspiration From 1.55 To 1.18). For The Primarily East-Facing Catchment Studied Here, Distributing Shortwave Radiation Helps Generate Realistic Timing And Spatial Heterogeneity In The Snowmelt At The Expense Of An Increase In The Mean Bias Error (From 0.06 To 0.22) For All Distributed Forcing Simulations Compared To The Simulation With Only Distributed Precipitation. Distributing Wind Speed In The Energy Balance Calculation Has A More Complex Impact On Our Catchment, As It Accelerates Snowmelt When Meteorological Conditions Are Favorable But Does Not Generate Snow Patches At The End Of Our Test Case. This Shows That Slope- And Aspect-Based Meteorological Distribution Can Improve The Spatio-Temporal Representation Of Snow Cover And Evapotranspiration In Complex Mountain Terrain.
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Gupta, R., Bourrier, F., Acary, V., & Lambert, S. (2023). Bayesian Interface Based Calibration Of A Novel Rockfall Protection Structure Modelled In The Non-Smooth Contact Dynamics Framework. Engineering Structures, 2972.
Abstract: This Article Presents The Development And Calibration Of A Numerical Model Simulating The Response Of A Novel Rockfall Protection Structure Subjected To Localized Dynamic Loading. This Structure Is Made Of Piled-Up Concrete Blocks Interconnected Via Metallic Components Whose Dynamics Response Under Projectile Impact Is Examined Via Real-Scale Experiments. The Corresponding Numerical Model Is Developed In A Python Based Open Source Software Siconos Which Implements The Non-Smooth Contact Dynamics (Nscd) Method. The Geometrical Features And Mechanical Properties Are Incorporated In The Model Via Specific Developments Pertinent To The Modelling Requirements In Siconos. Some Parameters Peculiar To The Numerical Model Are Calibrated Against The Spatial-Temporal Measurements From Two Full-Scale Impact Experiments. The Bayesian Interface Statistical Learning Method Aided By The Polynomial Chaos Expansion Based Meta-Model Of The Nscd Model Is Deployed For The Calibration. The Additional Understanding Of The Model Dynamics Through The Byproducts Of The Meta-Model Is Highlighted. In The End, The Nscd Model Is Successfully Calibrated Against The Spatial-Temporal Response Of The Experimental Structure With More Than 90% Accuracy For Impact Energies Up To 1 Mj.
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Gustin, M., Dunham-Cheatham, S., Allen, N., Choma, N., Johnson, W., Lopez, S., et al. (2023). Observations Of The Chemistry And Concentrations Of Reactive Hg At Locations With Different Ambient Air Chemistry. Science Of The Total Environment, 9049.
Abstract: The Hg Research Community Needs Methods To More Accurately Measure Atmospheric Hg Concentrations And Chemistry. The Reactive Mercury Active System (Rmas) Uses Cation Exchange, Nylon, And Ptfe Membranes To Determine Reactive Mercury (Rm), Gaseous Oxidized Mercury, And Particulate-Bound Mercury (Pbm) Concentrations And Chemistry. New Data For Atlanta, Georgia (Nrgt) Demonstrated That Particulate-Bound Hg Was Dominant And The Chemistry Was Primarily N And S Hg-Ii Compounds. At Great Salt Lake, Utah (Gsl), Rm Was Predominately Pbm, With N=S > Organics > Halogen > O Hg-Ii Compounds. At Guadalupe Mountains National Park, Texas (Gumo), Halogenated Compound Concentrations Were Lowest When Air Interacting With The Site Was Primarily Derived From The Midwest, And Highest When The Air Was Sourced From Mexico. At Amsterdam Island, Southern Indian Ocean, Compounds Were Primarily Halogenated With Some N, S, And Organic Hg-Ii Compounds Potentially Associated With Biological Activity. The Geos-Chem Model Was Applied To See If It Predicted Measurements At Five Field Sites. Model Values Were Higher Than Observations At Gsl, Slightly Lower At Nrgt, And Observations Were An Order Of Magnitude Higher Than Modeled Values For Gumo And Reno, Nevada. In General, Data Collected From 13 Locations Indicated That N, S, And Organic Rm Compounds Were Associated With City And Forest Locations, Halogenated Compounds Were Sourced From The Marine Boundary Layer, And O Compounds Were Associated With Long-Range Transport. Data Being Developed Currently, And In The Past, Suggest There Are Multiple Forms Of Rm That Modelers Must Consider, And Pbm Is An Important Component Of Rm.
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Halas, P., Mouginot, J., De Fleurian, B., & Langebroek, P. (2023). Impact Of Seasonal Fluctuations Of Ice Velocity On Decadal Trends Observed In Southwest Greenland. Remote Sensing Of Environment, 2852.
Abstract: By Tracking The Feature Displacement Between Satellite Images Spaced Approximately One Year Apart, Surface Runoff Has Been Shown To Have A Long-Term Impact On The Average Ice Flow Of A Land-Terminating Sector Of Greenland. In This Study, We Revisit The Multi-Year Trends In Ice Flow By Assessing More Carefully The Impact Of Seasonal Fluctuation In Velocity On The Annual Mean Ice Velocity. We Find That, Depending On The Length And Period Used To Measure Displacement, Seasonal Fluctuations Do Have An Impact On Observed Velocities On Up To 15%, And Can Affect Decadal Trends. Nevertheless, The Magnitude Of This Fluctuation Is Small Enough To Confirm The General Slowdown Observed During The 2000-2012 Period. Between 2012 And 2019, We Find Significant Re-Acceleration Of Low-Lying Glaciers Tongue But Velocity Trends Elsewhere Are Generally Insignificant And Not Spatially Consistent. Finally, We Propose A More Selective Approach To Recovering Velocity Trends Using Satellite Imagery That Involves Using Only Measurements Where The Image Pair Starting Date Is Before Summer, In Order To Have Comparable Measurements For Every Year, Sampling A Melt Season And The Following Winter.
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Haruna, A., Blanchet, J., & Favre, A. (2023). Modeling Intensity-Duration-Frequency Curves For The Whole Range Of Non-Zero Precipitation: A Comparison Of Models. Water Resources Research, .
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Heintzenberg, J., Legrand, M., Gao, Y., Hara, K., Huang, S., Humphries, R., et al. (2023). Spatio-Temporal Distributions Of The Natural Non-Sea-Salt Aerosol Over The Southern Ocean And Coastal Antarctica And Its Potential Source Regions. Tellus Series B-Chemical And Physical Meteorology, 757(1).
Abstract: More Than 40 Years Of Aerosol Data Including Concentrations Of Particle Number And Of Nine Major Ions Collected Over The Southern Ocean And Coastal Stations Have Been Aggregated And Filtered With Back Trajectories To Reduce The Risk Of Influence From Adjacent Continents. That Provided A Rich Dataset Including Latitudinal Distribution And Seasonality Of Physical And Chemical Aerosol Parameters That Allow Insights Into Aerosol Sources Over The Southern Ocean. These Data Together With Statistics Of Back Trajectory Paths Of High (75% Percentile) And Low (25% Percentile) Concentrations Of The Studied Aerosol Parameters Were Used To Identify Potential Source Regions Of The Respective Compounds. For Particle Number Concentrations, Msa, And The Non-Sea-Salt Fractions Of Ca And Potassium The Most Prominent Source Regions Were Found In High Dms-Areas Close To Antarctica, Whereas The Potential Source Regions Of Nh4 And The Non-Sea-Salt Fraction Of Mg Were Located In Part Further North Over The Southern Ocean. These Geographical Differences Would Reflect Differences In The Marine Biota.
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Hellal, J., Lise, B., Annette, B., Aurélie, C., Giulia, C., Simon, C., et al. (2023). Unlocking Secrets Of Microbial Ecotoxicology: Recent Achievements And Future Challenges. Fems Microbiology Ecology, 999(101).
Abstract: Environmental Pollution Is One Of The Main Challenges Faced By Humanity. By Their Ubiquity And Vast Range Of Metabolic Capabilities, Microorganisms Are Affected By Pollution With Consequences On Their Host Organisms And On The Functioning Of Their Environment. They Also Play Key Roles In The Fate Of Pollutants Through The Degradation, Transformation, And Transfer Of Organic Or Inorganic Compounds. Thus, They Are Crucial For The Development Of Nature-Based Solutions To Reduce Pollution And Of Bio-Based Solutions For Environmental Risk Assessment Of Chemicals. At The Intersection Between Microbial Ecology, Toxicology, And Biogeochemistry, Microbial Ecotoxicology Is A Fast-Expanding Research Area Aiming To Decipher The Interactions Between Pollutants And Microorganisms. This Perspective Paper Gives An Overview Of The Main Research Challenges Identified By The Ecotoxicomic Network Within The Emerging One Health Framework And In The Light Of Ongoing Interest In Biological Approaches To Environmental Remediation And Of The Current State Of The Art In Microbial Ecology. We Highlight Prevailing Knowledge Gaps And Pitfalls In Exploring Complex Interactions Among Microorganisms And Their Environment In The Context Of Chemical Pollution And Pinpoint Areas Of Research Where Future Efforts Are Needed. Overview Of The Main Research Challenges At Different Scales For Microbial Ecotoxicology As Identified By The Ecotoxicomic Network In The Light Of The Current State Of The Art.
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Heutte, B., Bergner, N., Beck, I., Angot, H., Dada, L., Quéléver, L., et al. (2023). Measurements Of Aerosol Microphysical And Chemical Properties In The Central Arctic Atmosphere During Mosaic. Scientific Data, 101(1).
Abstract: The Arctic Environment Is Transforming Rapidly Due To Climate Change. Aerosols' Abundance And Physicochemical Characteristics Play A Crucial, Yet Uncertain, Role In These Changes Due To Their Influence On The Surface Energy Budget Through Direct Interaction With Solar Radiation And Indirectly Via Cloud Formation. Importantly, Arctic Aerosol Properties Are Also Changing In Response To Climate Change. Despite Their Importance, Year-Round Measurements Of Their Characteristics Are Sparse In The Arctic And Often Confined To Lower Latitudes At Arctic Land-Based Stations And/Or Short High-Latitude Summertime Campaigns. Here, We Present Unique Aerosol Microphysics And Chemical Composition Datasets Collected During The Year-Long Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition, In The Central Arctic. These Datasets, Which Include Aerosol Particle Number Concentrations, Size Distributions, Cloud Condensation Nuclei Concentrations, Fluorescent Aerosol Concentrations And Properties, And Aerosol Bulk Chemical Composition (Black Carbon, Sulfate, Nitrate, Ammonium, Chloride, And Organics) Will Serve To Improve Our Understanding Of High-Arctic Aerosol Processes, With Relevance Towards Improved Modelling Of The Future Arctic (And Global) Climate.
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Hill, E., Urruty, B., Reese, R., Garbe, J., Gagliardini, O., Durand, G., et al. (2023). The Stability Of Present-Day Antarctic Grounding Lines – Part 1: No Indication Of Marine Ice Sheet Instability In The Current Geometry. Cryosphere, 171(9), 3739–3759.
Abstract: Theoretical And Numerical Work Has Shown That Under Certain Circumstances Grounding Lines Of Marine-Type Ice Sheets Can Enter Phases Of Irreversible Advance And Retreat Driven By The Marine Ice Sheet Instability (Misi). Instances Of Such Irreversible Retreat Have Been Found In Several Simulations Of The Antarctic Ice Sheet. However, It Has Not Been Assessed Whether The Antarctic Grounding Lines Are Already Undergoing Misi In Their Current Position. Here, We Conduct A Systematic Numerical Stability Analysis Using Three State-Of-The-Art Ice Sheet Models: Ua, Elmer/Ice, And The Parallel Ice Sheet Model (Pism). For The First Two Models, We Construct Steady-State Initial Configurations Whereby The Simulated Grounding Lines Remain At The Observed Present-Day Positions Through Time. The Third Model, Pism, Uses A Spin-Up Procedure And Historical Forcing Such That Its Transient State Is Close To The Observed One. To Assess The Stability Of These Simulated States, We Apply Short-Term Perturbations To Submarine Melting. Our Results Show That The Grounding Lines Around Antarctica Migrate Slightly Away From Their Initial Position While The Perturbation Is Applied, And They Revert Once The Perturbation Is Removed. This Indicates That Present-Day Retreat Of Antarctic Grounding Lines Is Not Yet Irreversible Or Self-Sustained. However, Our Accompanying Paper (Part 2, ) Shows That If The Grounding Lines Retreated Further Inland, Under Present-Day Climate Forcing, It May Lead To The Eventual Irreversible Collapse Of Some Marine Regions Of West Antarctica.
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Hollender, F., Theodoulidis, N., Mariscal, A., Chaudat, T., Steidl, J., & Roumelioti, Z. (2023). The ?Glass Beads? Coupling Solution For Borehole And Posthole Accelerometers: Shaking Table Tests And Field Retrievability. Seismological Research Letters, 949(2), 925–934.
Abstract: Borehole Accelerometers Are Designed To Record Strong Ground Movements At Depth. They Have Become An Important Complement To Surface Accelerometers For Seismic And Earthquake Engineering Applications. Borehole Accelerometers Present Several Imple-Mentation Challenges, Including Their Coupling With The Geological Environment. One Possible Coupling Solution Is The Use Of Small Glass Beads, Which Are Placed Inside The Borehole Casing With The Purpose Of Filling In Any Empty Space Between The Sensor And The Casing Walls. We Carried Out A Test On A Shaking Table, Over A Wide Range Of Peak Ground Accelerations (Pga From 0.17 To 1.64G), Allowing The Comparison Of The Sig-Nals Between A Surface Accelerometer And A Borehole Accelerometer Coupled Through The Glass Beads. These Tests Show That There Is Almost No Difference Between The Surface And Borehole Accelerometer Signals Between 0.5 And 25 Hz, And Only Very Small Differences Outside This Band (0.2-0.5 Hz And 25-80 Hz). Furthermore, Experience From Multiple Ver-Tical Accelerometric Arrays Show That An Installation Using Glass Beads Is “Reversible”, That Is, 30 Yr After The Initial Installation It Can Still Be Possible To Easily Extract The Acceler-Ometers For Repair Or Replacement, Without Any Problems Or Damage To The Sensors.
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Houngnibo, M., Ali, A., Agali, A., Waongo, M., Lawin, A., & Cohard, J. (2023). Stochastic Disaggregation Of Seasonal Precipitation Forecasts Of The West African Regional Climate Outlook Forum. International Journal Of Climatology, .
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Houphlet, S., Dusseux, P., Adiko, A., Konan-Waidhet, A., Munoz, F., Bigot, S., et al. (2023). Object-Based Characterization Of Vegetation Heterogeneity With Sentinel Images Proves Efficient In A Highly Human-Influenced National Park Of Cote D'Ivoire. Environmental Monitoring And Assessment, 1951(1).
Abstract: Forest Monitoring Requires More Automated Systems To Analyze High Ecosystem Heterogeneity. The Traditional Pixel-Based Detection Method Has Proven To Be Less And Less Effective. A Novel Change Detection Method Is Therefore Proposed To Detect Changes In Forest Cover Using Satellite Images At Very High Spatial Resolution. This Is Object-Oriented Classification, Which Groups Pixels Into Interpreted Objects, Based On Their Spectral Values, Spatial, And Textural Properties. Using Sentinel And Lansat Images, We Tested For The First Time In The West African Rainforest Zone The Effectiveness Of This Method For Better Detection, Delineation, And Analysis Of Land Use And Occupation Types. The Mean Shift Algorithm Was Used In Both The Segmentation And Classification Processes. Next, We Compared The Proposed Object-Oriented Method With A Pixel-Based Image Classification Detection Method By Implementing Both Methods Under The Same Conditions. High Detection Accuracy (> 90%) And An Overall Kappa Greater Than 0.90 Were Obtained By The Object-Oriented Method, Which Is About 20% Higher Than The Pixel-Based Method. The Object-Based Method Was Free Of Salt And Pepper Effects And Was Less Prone To Image Misregistration In Terms Of Change Detection Accuracy And Mapping Results. This Study Demonstrates That The Object-Based Classifier Is A Much Better Approach Than The Classical Pixel-Based Classifier. In Addition, It Shows The Problems Of Detecting Heterogeneous Landscapes And Explains The Observed Confusions Between The Types Of Vegetation Formations Specific To Tropical Wetlands. The Results Obtained Are Encouraging And The Contribution Of High-Resolution Images And The Object-Based Method To Better Discrimination Of Tropical Wetland Vegetation Is Discussed.
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Hutchinson, K., Deshayes, J., Ethe, C., Rousset, C., De Lavergne, C., Vancoppenolle, M., et al. (2023). Improving Antarctic Bottom Water Precursors In Nemo For Climate Applications. Geoscientific Model Development, , 362933–365033.
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Jacobs, S., Kelemen, E., O'Farrell, P., Martin, A., Schaafsma, M., Dendoncker, N., et al. (2023). The Pitfalls Of Plural Valuation. Current Opinion In Environmental Sustainability, 646.
Abstract: This Paper Critically Examines The Current Political Context In Which Valuation Studies Of Nature Are Undertaken. It Challenges The Belief That Somehow, More And Technically Better Valuation Will Drive The Societal Change Toward More Just And Sustainable Futures. Instead, We Argue That Current And Proposed Valuation Practices Risk To Continue To Overrepresent The Values Of Those Who Hold Power And Dominate The Valuation Space, And To Perpetuate The Discrimination Of The Views And Values Of Nondominant Stakeholders. In Tackling This Politically Sensitive Issue, We Define A Political Typology Of Valuations, Making Explicit The Roles Of Power And Discrimination. This Is Done To Provide Valuation Professionals And Other Actors With A Simple Framework To Determine If Valuation Actions And Activities Are Constructive, Inclusive, Resolve Injustices And Enable Systemic Change, Or Rather Entrench The Status Quo Or Aggravate Existing Injustices. The Objective Is To Buttress Actors In Their Decisions To Support, Accept, Improve, Oppose, Or Reject Such Valuations.
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Jenkins, J., Paiement, A., Ourmieres, Y., Le Sommer, J., Verron, J., Ubelmann, C., et al. (2023). A Dnn Framework For Learning Lagrangian Drift With Uncertainty. Applied Intelligence, .
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Jomelli, V., Wagnon, P., Swingedouw, D., Charton, J., Braucher, R., Hue, A., et al. (2023). Unraveling The Climate Control On Debris-Free Glacier Evolution In The Everest Region (Nepal, Central Himalaya) During The Holocene. Quaternary Science Reviews, .
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Jones, N., Strozzi, T., Rabatel, A., Ducasse, E., & Mouginot, J. (2023). Surface Instability Mapping In Alpine Paraglacial Environments Using Sentinel-1 Dinsar Techniques. Ieee Journal Of Selected Topics In Applied Earth Observations And Remote Sensing, 161, 45.
Abstract: Current Climate Warming Leads To Widespread Glacier Shrinkage In High Alpine Terrains And Associated Changes In Surface Dynamics Of Deglacierized Environments. In Consequence, Slope Instabilities Increasingly Develop Along Retreating Glaciers Through Debuttressing Effects Or Degrading Permafrost Conditions. In The Context Of Associated Hazards To The Local Environment And Infrastructure, A Thorough Analysis Of Slope Instabilities Is Highly Relevant. Affected Regions Are Mostly Inaccessible And Cover Large Areas, Therefore Remote Sensing Techniques Such As Differential Interferometric Synthetic Aperture Radar (Dinsar) Are Valuable Tools To Monitor Surface Movements And Assess Their Evolution. We Apply Standard And Advanced Dinsar Methods Using Sentinel-1 Sar Data From 2015 Until Late 2021 To Map And Classify Slope Instabilities In Three Glacierized Regions In The European Alps. The Final Products Include An Inventory Per Region, With A Total Of 815 Mapped Slope Instabilities, Of Which 38% Move <3, 9% Move 3-10, 42% Move 10-30, And 11% Move >30 Cm/Yr. An Additional Assessment Of Four Landslides Occurring Along Shrinking Glaciers Shows Time Series With Recent Accelerations In 2018/19. Validation Of Sentinel-1 Derived Slope Movement Products Is Performed By Comparison With Shorter Wavelength Terrasar-X And Optical Sentinel-2 Derived Data Using Offset Tracking. Results Clearly Show The Suitability Of Sentinel-1 Dinsar Methods To Detect A Range Of Slope Movements In High Alpine Terrain, Yet Also Highlight The Limitations. We Therefore Recommend A Combination Of Advanced Sentinel-1 Dinsar And Sentinel-2 Offset Tracking Methods To Develop A Comprehensive Inventory Of Alpine Slope Motion.
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Jourdain, B., Vincent, C., Réveillet, M., Rabatel, A., Brun, F., Six, D., et al. (2023). A Method To Estimate Surface Mass-Balance In Glacier Accumulation Areas Based On Digital Elevation Models And Submergence Velocities. Journal Of Glaciology, 696(2772), 1403–1418.
Abstract: Measuring Surface Mass-Balance In The Accumulation Areas Of Glaciers Is Challenging Because Of The High Spatial Variability Of Snow Accumulation And The Difficulty Of Conducting Annual Field Glaciological Measurements. Here, We Propose A Method That Can Solve Both These Problems For Many Locations. Ground-Penetrating Radar Measurements And Firn Cores Extracted From A Site In The French Alps Were First Used To Reconstruct The Topography Of A Buried End-Of-Summer Snow Horizon From A Past Year. Using These Data And Surface Elevation Observations From Lidar And Global Navigation Satellite System Instruments, We Calculated The Submergence Velocities Over The Period Between The Buried Horizon And More Recent Surface Elevation Observations. The Differences Between The Changes In Surface Elevation And The Submergence Velocities Were Then Used To Calculate The Annual Surface Mass-Balances With An Accuracy Of +/- 0.34 M W.E. Assuming That The Submergence Velocities Remain Stable Over Several Years, The Surface Mass-Balance Can Be Reconstructed For Subsequent Years From The Differences In Surface Elevation Alone. As Opposed To The Glaciological Method That Requires Substantial Fieldwork Year After Year To Provide Only Point Observations, This Method, Once Submergence Velocities Have Been Calculated, Requires Only Remote-Sensing Data To Provide Spatially Distributed Annual Mass-Balances In Accumulation Areas.
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Kern, H., Jomelli, V., Eckert, N., Grancher, D., Deschatres, M., & Arnaud-Fassetta, G. (2023). Influence Of Snow And Meteorological Conditions On Snow-Avalanche Deposit Volumes And Consequences For Road-Network Vulnerability. Land Degradation & Development, .
Abstract: Snow Avalanches Are A Major Component Of The Mountain Cryosphere That Frequently Create Road Obstructions. Deposit Characteristics Determine The Extent Of Damage To The Road Infrastructures And The Period Of Disruption Of The Road Network, But The Factors Controlling Snow-Deposit Volumes Remain Largely Unknown. This Study Investigates The Influence Of Meteorological And Snowpack Conditions On Snow-Avalanche Deposits And Road-Network Vulnerability Based On 1986 Deposit Volumes From 182 Paths Located In Two Regions Of The French Alps Between 2003 And 2017: The Guil And Haute-Maurienne Valleys. During The Period, 195 Avalanches Impacted The Road Network In These Areas, Leading To Major Disruptions. In The Haute-Maurienne, Correlations Between Deposit Volumes And Meteorological And Snowpack Conditions Are High In Winter. However, The Relationships Differ With Path Elevation And Orientation. Results Do Not Show Any Significant Relationship Between Volumes And Meteorological Or Snowpack Conditions For The Spring Season. Focusing On Deposits That Disturbed The Road Network In Winter And Spring Reveals A Distinct Influence Of Meteorological And Snow Variables Compared To The Overall Dataset, With Snowfall Intensity As The Predominant Control Variable Of Deposit Volumes Leading To Road Cuts. When The Same Analysis Is Conducted By Considering Guil Valley Separately Or By Aggregating The Haute-Maurienne With Guil Valley Area Data, Results Do Not Show Any Significant Relationship, Highlighting The Specific Local Nature Of Relations Between Deposit Volumes And Meteorological And Snowpack Conditions.
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Klein, C., Hanchen, L., Potter, E., Junquas, C., Harris, B., & Maussion, F. (2023). Untangling The Importance Of Dynamic And Thermodynamic Drivers For Wet And Dry Spells Across The Tropical Andes. Environmental Research Letters, 181(3).
Abstract: Andean Vegetation And Agriculture Depend On The Patterns Of Rainfall During The South American Monsoon. However, Our Understanding On The Importance Of Dynamic (Upper-Level Wind Circulation) As Compared To Thermodynamic (Amazon Basin Moisture) Drivers For Andes Rainfall Remains Limited. This Study Examines The Effect Of These Drivers On 3-7 Day Wet And Dry Spells Across The Tropical Andes And Assesses Resulting Impacts On Vegetation. Using Reanalysis And Remote Sensing Data From 1985-2018, We Find That Both Dynamic And Thermodynamic Drivers Play A Role In Determining The Rainfall Patterns. Notably, We Show That The Upper-Level Wind Is An Important Driver Of Rainfall Across The Entire Tropical Andes Mountain Range, But Not In The Amazon Lowlands, Suggesting A Crucial Role Of Topography In This Relationship. From Thermodynamic Perspective, We Find Wet Spell Conditions To Be Associated With Increased Moisture Along The Andes' Eastern Foothills Accompanied By A Strengthened South American Low-Level Jet, With Moisture Lifted Into The Andes Via Topography And Convection For All Considered Regions. Our Results Suggest That While Changes In Amazon Basin Moisture Dominate Rainfall Changes On Daily Time Scales Associated With Three Day Spells, Upper-Level Dynamics Play A More Important Role On The Synoptic Time Scale Of 5-7 Day Spells. Considering Impacts On The Ground, We Find That Only 5-7 Day Spells In The Semi-Arid Andes Have A Prolonged Effect On Vegetation. Our Study Emphasizes The Need To Consider Both Dynamic And Thermodynamic Drivers When Estimating Rainfall Changes In The Tropical Andes, Including In The Context Of Future Climate Projections.
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Kleindienst, A., Zivkovic, I., Tessier, E., Koenig, A., Heimbürger-Boavida, L., Horvat, M., et al. (2023). Assessing Comparability And Uncertainty Of Analytical Methods For Methylated Mercury Species In Seawater. Analytica Chimica Acta, 12781.
Abstract: Background: The Relative Distribution And Importance Of Monomethylmercury (Mmhg) And Dimethylmercury (Dmhg) In Seawater Is Still Under Debate. A Lack Of Comparability Between Measurements At Sub-Picomolar Levels Hampered The Further Understanding Of The Biogeochemical Hg Cycle. To Overcome This, We Assessed The Relative Standard Measurement Uncertainties (U-Ex,U-R) For Direct Measurements Of Mmhg And Dmhg By Species-Specific Isotope Dilution Icp-Ms And Cryo-Focusing Gc-Icp-Ms At Femtomolar Concentrations. Furthermore, U-Ex,U-R Was Determined For The Indirect Determination Of Dmhg (Dmhgcalc = Mehg – Mmhg) And Mehg (Mehgcalc = Mmhg + Dmhg) To Compare The Two Methodologies.Results: Expanded U-Ex,U-R (Confidence Interval Of 95%) For Cryo-Focusing Gc-Icp-Ms Was 14.4 (<50 Fm) And 14.2% (>50 Fm) And For Ss-Id Gc-Icp-Ms 5.6 (<50 Fm) And 3.7% (>50 Fm). For Concentrations Above 50 Fm, U-Ex,U-R For Dmhgcalc Was Always Lower Than For Direct Measurements (14.2%). For Mehgcalc, On The Other Hand, U-Ex,U-R Was Always Higher For Concentrations Above 115 Fm (Range: 3.7-13.9%) Than For Direct Measurements (3.7%). We Evaluated The Comparability Of Directly Measured And Calculated Dmhg And Mehg Concentrations Based On Hg Speciation Measurements For Two Vertical Profiles In The Mediterranean Sea. We Show That Directly Measured And Indirectly Determined Dmhg And Mehg Concentrations Yield Comparable Results.Significance: Our Results Validate The Application Of The Indirect Method For The Determination Of Dmhg If A Direct Measurement Method With A Low U-Ex,U-R Such As Isotope Dilution Is Used For Mmhg And Mehg Measurements. The Validation Of The Indirect Measurement Approach Opens New Possibilities To Generate More Precise And Accurate Dmhg Data In The Global Ocean.
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Klotz, S., Le Bouteiller, C., Mathys, N., Fontaine, F., Ravanat, X., Olivier, J., et al. (2023). A High-Frequency, Long-Term Data Set Of Hydrology And Sediment Yield: Thealpine Badland Catchments Of Draix-Bléone Observatory. Earth System Science Data, 151(101), 4371–4388.
Abstract: Draix-Bleone Critical Zone Observatory Was Created In 1983 To Study Erosion Processes In A Mountainous Badland Region Of The French Southern Alps. Six Catchments Of Varying Size (0.001 To 22 Km(2)) And Vegetation Cover Are Equipped To Measure Water And Sediment Fluxes, Both As Bedload And Suspended Load. This Paper Presents The Core Dataset Of The Observatory, Including Rainfall And Meteorology, High-Frequency Discharge And Suspended-Sediment Concentration, And Event-Scale Bedload Volumes. The Longest Records Span Almost 40 Years. Measurement And Data-Processing Methods Are Presented, As Well As Data Quality Assessment Procedures And Examples Of Results. All The Data Presented In This Paper Are Available On The Open Repository 10.17180/Obs.Draix (Draix-Bleone Observatory, 2015), And A 5-Year Snapshot Is Available For Review At 10.57745/Beyqfq (Klotz Et Al., 2023).
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Knuth, F., Shean, D., Bhushan, S., Schwat, E., Alexandrov, O., Mcneil, C., et al. (2023). Historical Structure From Motion (Hsfm): Automated Processing Of Historical Aerial Photographs For Long-Term Topographic Change Analysis. Remote Sensing Of Environment, 2852.
Abstract: Precisely Measuring The Earth'S Changing Surface On Decadal To Centennial Time Scales Is Critical For Many Science And Engineering Applications, Yet Long-Term Records Of Quantitative Landscape Change Are Often Temporally And Geographically Sparse. Archives Of Scanned Historical Aerial Photographs Provide An Opportunity To Augment These Records With Accurate Elevation Measurements That Capture The Historical State Of The Earth Surface. Structure From Motion (Sfm) Photogrammetry Workflows Produce High-Quality Digital Elevation Models (Dems) And Orthoimage Mosaics From These Historical Images, But Time-Intensive Tasks Like Manual Image Preprocessing (E.G., Fiducial Marker Identification) And Ground Control Point (Gcp) Selection Impede Processing At Scale. We Developed An Automated Method To Process Historical Images And Generate Self-Consistent Time Series Of High-Resolution (0.5-2 M) Dems And Orthomosaics, Without Manual Gcp Selection. The Method Relies On Sfm To Correct Camera Interior And Exterior Orientation And A Robust Multi-Stage Co-Registration Approach Using Modern Reference Terrain Datasets For Geolocation Refinement. We Demonstrate The Method Using Scanned Images From The North American Glacier Aerial Photography (Nagap) Archive Collected Between 1967 And 1997. We Present Results For Two Sites With Variable Photo Acquisition Geometry And Overlap – Mount Baker And South Cascade Glacier In Washington State, Usa. The Automated Method Corrects Initial Camera Position Errors Of Several Kilometers And Produces Accurately Georeferenced, High-Resolution Dems And Orthoimages, Regardless Of Camera Configuration, Acquisition Geometry, Terrain Characteristics, And Reference Dem Properties. The Average Rms Reprojection Error Following Bundle Adjustment Optimization Was 0.67 Px (0.15 M) For The 261 Images Contributing To 10 Final Dem Mosaics Between 1970 And 1992 At Mount Baker, And 0.65 Px (0.13 M) For The 243 Images Contributing To 18 Individual Dems Between 1967 And 1997 At South Cascade Glacier. The Relative Accuracy Of Elevation Values In The Historical Time Series Stacks Was 0.68 M At Mount Baker And 0.37 M At South Cascade Glacier. Our Products Have Reduced Systematic Error And Improved Accuracy Compared To Dem Products Generated Using Sfm With Manual Gcp Selection. Final Elevation Change Measurement Precision Was Similar To 0.7-1.0 M Over A 30-Year Period, Enabling The Study Of Processes With Rates As Low As Similar To 1-3 Cm/Yr. Our Results Demonstrate The Potential Of This Scalable Method To Rapidly Process Archives Of Historical Imagery And Deliver New Quantitative Insights On Long-Term Geodetic Change And Earth Surface Processes.
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Kochtitzky, W., Copland, L., King, M., Hugonnet, R., Jiskoot, H., Morlighem, M., et al. (2023). Closing Greenland'S Mass Balance: Frontal Ablation Of Every Greenlandic Glacier From 2000 To 2020. Geophysical Research Letters, 505(171).
Abstract: In Greenland, 87% Of The Glacierized Area Terminates In The Ocean, But Mass Lost At The Ice-Ocean Interface, Or Frontal Ablation, Has Not Yet Been Fully Quantified. Using Measurements And Models We Calculate Frontal Ablation Of Greenland'S 213 Outlet And 537 Peripheral Glaciers And Find A Total Frontal Ablation Of 481.8 +/- 24.0 For 2000-2010 And 510.2 +/- 18.6 Gt A(-1) For 2010-2020. Ice Discharge Accounted For Similar To 90% Of Frontal Ablation During Both Periods, While Mass Loss Due To Terminus Retreat Comprised The Remainder. Only 16 Glaciers Were Responsible For The Majority (>50%) Of Frontal Ablation From 2010 To 2020. These Estimates, Along With The Climatic-Basal Balance, Allow For A More Complete Accounting Of Greenland Ice Sheet And Peripheral Glacier Mass Balance. In Total, Greenland Accounted For Similar To 90% Of Northern Hemisphere Frontal Ablation For 2000-2010 And 2010-2020.
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Koenig, A., Magand, O., Rose, C., Di Muro, A., Miyazaki, Y., Colomb, A., et al. (2023). Observed In-Plume Gaseous Elemental Mercury Depletion Suggests Significant Mercury Scavenging By Volcanic Aerosols. Environmental Science-Atmospheres, .
Abstract: Terrestrial Volcanism Is Known To Emit Mercury (Hg) Into The Atmosphere. However, Despite Many Years Of Investigation, Its Net Impact On The Atmospheric Hg Budget Remains Insufficiently Constrained, In Part Because The Transformations Of Hg In Volcanic Plumes As They Age And Mix With Background Air Are Poorly Understood. Here We Report The Observation Of Complete Gaseous Elemental Mercury (Gem) Depletion Events In Dilute And Moderately Aged (& Sim;3-7 Hours) Volcanic Plumes From Piton De La Fournaise On Reunion Island. While It Has Been Suggested That Co-Emitted Bromine Could, Once Photochemically Activated, Deplete Gem In A Volcanic Plume, We Measured Low Bromine Concentrations In Both The Gas- And Particle-Phase And Observed Complete Gem Depletion Even Before Sunrise, Ruling Out A Leading Role Of Bromine Chemistry Here. Instead, We Hypothesize That The Gem Depletions Were Mainly Caused By Gas-Particle Interactions With Sulfate-Rich Volcanic Particles (Mostly Of Submicron Size), Abundantly Present In The Dilute Plume. We Consider Heterogeneous Gem Oxidation And Gem Uptake By Particles As Plausible Manifestations Of Such A Process And Derive Empirical Rate Constants. By Extrapolation, We Estimate That Volcanic Aerosols May Scavenge 210 Mg Y(-1) (67-480 Mg Y(-1)) Of Hg From The Atmosphere Globally, Acting Effectively As Atmospheric Mercury Sink. While This Estimate Is Subject To Large Uncertainties, It Highlights That Hg Transformations In Aging Volcanic Plumes Must Be Better Understood To Determine The Net Impact Of Volcanism On The Atmospheric Hg Budget And Hg Deposition Pathways.
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Koenig, A., Magand, O., Verreyken, B., Brioude, J., Amelynck, C., Schoon, N., et al. (2023). Mercury In The Free Troposphere And Bidirectional Atmosphere-Vegetation Exchanges – Insights From Maido Mountain Observatory In The Southern Hemisphere Tropics. Atmospheric Chemistry And Physics, 232(2), 1309–1328.
Abstract: Atmospheric Mercury (Hg) Observations In The Lower Free Troposphere (Lft) Can Give Important Insights Into Hg Redox Chemistry And Can Help Constrain Hg Background Concentrations On A Regional Level. Relatively Continuous Sampling Of Lft Air, Inaccessible To Most Ground-Based Stations, Can Be Achieved At Highaltitude Observatories. However, Such High-Altitude Observatories Are Rare, Especially In The Southern Hemisphere (Sh), And Atmospheric Hg In The Sh Lft Is Unconstrained. To Fill This Gap, We Continuously Measured Gaseous Elemental Mercury (Gem; Hourly) And Reactive Mercury (Rm; Integrated Over Similar To 6-14 D) For 9 Months At Maido Mountain Observatory (2160Ma.S.L.) On Remote Reunion Island (21.1 Degrees S, 55.5 Degrees E) In The Tropical Indian Ocean. Gem Exhibits A Marked Diurnal Variation Characterized By A Midday Peak (Mean: 0.95 Ngm(-3); Sd: 0.08 Ngm(-3)) And A Nighttime Low (Mean: 0.78 Ngm(-3); Sd: 0.11 Ngm(-3)). We Find That This Diurnal Variation Is Likely Driven By The Interplay Of Important Gem Photo-Reemission From The Islands' Vegetated Surfaces (I.E. Vegetation C Soil) During Daylight Hours (8-22 Ngm(-2) H(-1)), Boundary Layer Influences During The Day, And Predominant Lft Influences At Night. We Estimate Gem In The Lft Based On Nighttime Observations In Particularly Dry Air Masses And Find A Notable Seasonal Variation, With Lft Gem Being Lowest From December To March (Mean 0.66 Ngm 3; Sd: 0.07 Ngm 3) And Highest From September To November (Mean: 0.79 Ng M(-3); Sd: 0.09 Ng M(-3)). Such A Clear Gem Seasonality Contrasts With The Weak Seasonal Variation Reported For The Sh Marine Boundary Layer But Is In Line With Modeling Results, Highlighting The Added Value Of Continuous Hg Observations In The Lft. Maido Rm Is 10.6 Pg M(-3) (Sd: 5.9 Pg M(-3)) On Average, But Rm In The Cloud-Free Lft Might Be About Twice As High, As Weekly-Biweekly Sampled Rm Observations Are Likely Diluted By Low-Rm Contributions From The Boundary Layer And Clouds.
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Kokhanovsky, A., Brell, M., Segl, K., Bianchini, G., Lanconelli, C., Lupi, A., et al. (2023). First Retrievals Of Surface And Atmospheric Properties Using Enmap Measurements Over Antarctica. Remote Sensing, .
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Konate, D., Didi, S., Dje, K., Diedhiou, A., Kouassi, K., Kamagate, B., et al. (2023). Observed Changes In Rainfall And Characteristics Of Extreme Events In Cote D'Ivoire (West Africa). Hydrology, .
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Kondi-Akara, G., Hingray, B., Francois, B., & Diedhiou, A. (2023). Recent Trends In Urban Electricity Consumption For Cooling In West And Central African Countries. Energy, .
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Kopp, R., Oppenheimer, M., O'Reilly, J., Drijfhout, S., Edwards, T., Fox-Kemper, B., et al. (2023). Communicating Future Sea-Level Rise Uncertainty And Ambiguity To Assessment Users. Nature Climate Change, .
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Lalande, M., Ménégoz, M., Krinner, G., Ottlé, C., & Cheruy, F. (2023). Improving Climate Model Skill Over High Mountain Asia By Adapting Snow Cover Parameterization To Complex-Topography Areas. Cryosphere, 171(121), 5095–5130.
Abstract: This Study Investigates The Impact Of Topography On Five Snow Cover Fraction (Scf) Parameterizations Developed For Global Climate Models (Gcms), Including Two Novel Ones. The Parameterization Skill Is First Assessed With The High Mountain Asia Snow Reanalysis (Hmasr), And Three Of Them Are Implemented In The Orchidee Land Surface Model (Lsm) And Tested In Global Land-Atmosphere Coupled Simulations. Hmasr Includes Snow Depth (Sd) Uncertainties, Which May Be Due To The Elevation Differences Between In Situ Stations And Hmasr Grid Cells. Nevertheless, The Scf-Sd Relationship Varies Greatly Between Mountainous And Flat Areas In Hmasr, Especially During The Snow-Melting Period. The New Parameterizations That Include A Dependency On The Subgrid Topography Allow A Significant Scf Bias Reduction, Reaching 5 % To 10 % On Average In The Global Simulations Over Mountainous Areas, Which In Turn Leads To A Reduction Of The Surface Cold Bias From – 1.8 Circle C To About – 1 Circle C In High Mountain Asia (Hma). Furthermore, The Seasonal Hysteresis Between Scf And Sd Found In Hmasr Is Better Captured In The Parameterizations That Split The Accumulation And The Depletion Curves Or That Include A Dependency On The Snow Density. The Deep-Learning Scf Parameterization Is Promising But Exhibits More Resolution-Dependent And Region-Dependent Features. Persistent Snow Cover Biases Remain In Global Land-Atmosphere Experiments. This Suggests That Other Model Biases May Be Intertwined With The Snow Biases And Points Out The Need To Continue Improving Snow Models And Their Calibration. Increasing The Model Resolution Does Not Consistently Reduce The Simulated Scf Biases, Although Biases Get Narrower Around Mountain Areas. This Study Highlights The Complexity Of Calibrating Scf Parameterizations Since They Affect Various Land-Atmosphere Feedbacks. In Summary, This Research Spots The Importance Of Considering Topography In Scf Parameterizations And The Challenges In Accurately Representing Snow Cover In Mountainous Regions. It Calls For Further Efforts To Improve The Representation Of Subgrid-Scale Processes Affecting Snowpack In Climate Models.
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Lamare, M., Domine, F., Revuelto, J., Pelletier, M., Arnaud, L., & Picard, G. (2023). Investigating The Role Of Shrub Height And Topography In Snow Accumulation On Low-Arctic Tundra Using Uav-Borne Lidar. Journal Of Hydrometeorology, , 83588–85388.
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Lambert, S., Bourrier, F., Ceron-Mayo, A., Dugelas, L., Dubois, F., & Piton, G. (2023). Small-Scale Modeling Of Flexible Barriers. I: Mechanical Similitude Of The Structure. Journal Of Hydraulic Engineering, 1491(3).
Abstract: Flexible Barriers Can Be Used To Trap Woody Debris Or Debris Flows. However, Their Small Scale Modelling Is Challenging Because Of Their Possible Deformation. This Article Addresses How To Meet The Partial Mechanical Similitude Of Manufactured Flexible Barriers. Relevant Dimensionless Parameters Are Defined From Flow Velocity, Barrier Geometry, And Component Mechanical Properties. These Similitude Criteria Are Validated Using Numerical Simulations Of Barriers Exposed To A Hydrodynamic Loading At Various Scales. The Simulations Also Confirm The Importance Of Accounting For The Mechanical Characteristics Of The Barrier Components When Designing Model Barriers In View Of Achieving Realistic Deformations. Next, A Real Barrier With Complex Features Is Scaled To Conduct Flume Experiments. This Scaled Barrier Is 3D-Printed With Material Selected To Achieve The Mechanical Similitude Criterion. Another Validation Of This Approach Is Performed Considering Hydrostatic Loading And Checking That Simulated And Measured Deformations Are Similar. As An Application Case, The Deformations Measured During The Experiments Performed With Woody Debris Are Also Compared To The Hydrostatic Loading.
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Lambert, S., Fontaine, F., & Piton, G. (2023). Flexible Barrier And Flow-Driven Woody Debris: An Experimental Investigation Of Their Interaction. European Journal Of Environmental And Civil Engineering, .
Abstract: Flexible Barriers Have Been Recently Proposed As A Promising Alternative For Trapping Woody Debris Driven By The Flow In Torrents And Rivers Before They Reach Elements At Risks. Small-Scale Experiments In Similitude With The Real-Scale Have Been Conducted In View Of Addressing The Interaction Between The Flow And The Barrier. A Particular Attention Was Paid To The Identification Of The Parameters With Influence On The Loading Experienced By The Barrier, Varying The Woody Debris Mixtures Characteristics, Water Discharge, Flume Inclination And Woody Debris Supply Mode. This Investigation Emphasised The Intricacy Of The Relation Between The Barrier Loading And The Characteristics Of The Trapped Logs And Of The Logs Accumulation. The Barrier Loading Revealed Inversely Proportional To The Woody Debris Accumulation Permittivity, Which Quantifies Its Capacity To Let The Water Seep Through. Permittivity Depended On The Way The Accumulation Built Up And On The Evolution Of Its Characteristics With Increasing Discharge And Trapped Logs Volume. Finally, The Loading Exerted By The Flow On The Barrier Was Derived From The Barrier Elongation, Revealing That It Could Be Modelled As A Hydrostatic Load With A Reduction Factor Of 0.5.
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Lamothe, A., Savarino, J., Ginot, P., Soussaintjean, L., Gautier, E., Akers, P., et al. (2023). An Extraction Method For Nitrogen Isotope Measurement Of Ammonium In Alow-Concentration Environment. Atmospheric Measurement Techniques, 161(171), 4015–4030.
Abstract: Ammonia (Nh3) Participates In The Nucleation And Growth Of Aerosols And Thus Plays A Major Role In Atmospheric Transparency, Pollution, Health, And Climate-Related Issues. Understanding Its Emission Sources Through Nitrogen Stable Isotopes Is Therefore A Major Focus Of Current Work To Mitigate The Adverse Effects Of Aerosol Formation. Since Ice Cores Can Preserve The Past Chemical Composition Of The Atmosphere For Centuries, They Are A Top Tool Of Choice For Understanding Past Nh3 Emissions Through Ammonium (Nh4+), The Form Of Nh3 Archived In Ice. However, The Remote Or High-Altitude Sites Where Glaciers And Ice Sheets Are Typically Localized Have Relatively Low Fluxes Of Atmospheric Nh4+ Deposition, Which Makes Ice Core Samples Very Sensitive To Laboratory Nh3 Contamination. As A Result, Accurate Techniques For Identifying And Tracking Nh3 Emissions Through Concentration And Isotopic Measurements Are Highly Sought To Constrain Uncertainties In Nh3 Emission Inventories And Atmospheric Reactivity Unknowns. Here, We Describe A Solid-Phase Extraction Method For Nh4+ Samples Of Low Concentration That Limits External Contamination And Produces Precise Isotopic Results. By Limiting Nh3Atm Exposure With A Scavenging Fume Hood And Concentrating The Targeted Nh4+ Through Ion Exchange Resin, We Successfully Achieve Isotopic Analysis Of 50 Nmol Nh4+ Samples With A 0.6 Parts Per Thousand Standard Deviation. This Extraction Method Is Applied To An Alpine Glacier Ice Core From Col Du Dome, Mont Blanc, Where We Successfully Demonstrate The Analytical Approach Through The Analysis Of Two Replicate 8 M Water Equivalent Ice Cores Representing 4 Years Of Accumulation With A Reproducibility Of +/- 2.1 Parts Per Thousand. Applying This Methodology To Other Ice Cores In Alpine And Polar Environments Will Open New Opportunities For Understanding Past Changes In Nh3 Emissions And Atmospheric Chemistry.
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Langue, C., Lavaysse, C., Vrac, M., & Flamant, C. (2023). Heat Wave Monitoring Over West African Cities: Uncertainties, Characterization And Recent Trends. Natural Hazards And Earth System Sciences, 232(4), 1313–1333.
Abstract: Heat Waves Can Be One Of The Most Dangerous Climatic Hazards Affecting The Planet, Having Dramatic Impacts On The Health Of Humans And Natural Ecosystems As Well As On Anthropogenic Activities, Infrastructures And Economy. Based On Climatic Conditions In West Africa, The Urban Centres Of The Region Appear To Be Vulnerable To Heat Waves. The Goals Of This Work Are Firstly To Assess The Potential Uncertainties Encountered In Heat Wave Detection And Secondly To Analyse Their Recent Trend In West Africa Cities During The Period 1993-2020. This Is Done Using Two State-Of-The-Art Reanalysis Products, Namely The Fifth-Generation European Centre For Medium-Range Weather Forecasts (Ecmwf) Reanalysis (Era5) And Modern-Era Retrospective Analysis For Research And Applications (Merra), As Well As Two Local Station Datasets, Namely Dakar-Yoff In Senegal And Aeroport Felix Houphouet-Boigny, Abidjan, In Cote D'Ivoire. An Estimate Of Station Data From Reanalyses Is Processed Using An Interpolation Technique: The Nearest Neighbour To The Station With A Land Sea Mask = 0.5. The Interpolated Temperatures From Local Stations In Dakar And Abidjan Show Slightly Better Correlation With Era5 Than With Merra. Three Types Of Uncertainty Are Discussed: The First Type Of Uncertainty Is Related To The Reanalyses Themselves, The Second Is Related To The Sensitivity Of Heat Wave Frequency And Duration To The Threshold Values Used To Monitor Them, And The Last One Is Linked To The Choice Of Indicators And The Methodology Used To Define Heat Waves. Three Sorts Of Heat Wave Have Been Analysed, Namely Those Occurring During Daytime, Nighttime, And Both Daytime And Nighttime Concomitantly. Four Indicators Have Been Used To Analyse Heat Waves Based On 2 M Temperature, Humidity, 10 M Wind Or A Combination Of These. We Found That Humidity Plays An Important Role In Nighttime Events; Concomitant Events Detected With Wet-Bulb Temperature Are More Frequent And Located Over The Northern Sahel. Strong And More Persistent Heat Waves Are Found In The Continental (Cont) Region. For All Indicators, We Identified 6 Years With A Significantly Higher Frequency Of Events (1998, 2005, 2010, 2016, 2019 And 2020), Possibly Due To Higher Sea Surface Temperatures In The Equatorial Atlantic Ocean Corresponding To El Nino Events For Some Years. A Significant Increase In The Frequency, Duration And Intensity Of Heat Waves In The Cities Has Been Observed During The Last Decade (2012-2020); This Is Thought To Be A Consequence Of Climate Change Acting On Extreme Events.
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Lapere, R., Thomas, J., Marelle, L., Ekman, A., Frey, M., Lund, M., et al. (2023). The Representation Of Sea Salt Aerosols And Their Role In Polar Climate Within Cmip6. Journal Of Geophysical Research-Atmospheres, 1281(6).
Abstract: Natural Aerosols And Their Interactions With Clouds Remain An Important Uncertainty Within Climate Models, Especially At The Poles. Here, We Study The Behavior Of Sea Salt Aerosols (Ssaer) In The Arctic And Antarctic Within 12 Climate Models From Cmip6. We Investigate The Driving Factors That Control Ssaer Abundances And Show Large Differences Based On The Choice Of The Source Function, And The Representation Of Aerosol Processes In The Atmosphere. Close To The Poles, The Cmip6 Models Do Not Match Observed Seasonal Cycles Of Surface Concentrations, Likely Due To The Absence Of Wintertime Ssaer Sources Such As Blowing Snow. Further Away From The Poles, Simulated Concentrations Have The Correct Seasonality, But Have A Positive Mean Bias Of Up To One Order Of Magnitude. Ssaer Optical Depth Is Derived From The Modis Data And Compared To Modeled Values, Revealing Good Agreement, Except For Winter Months. Better Agreement For Aerosol Optical Depth Than Surface Concentration May Indicate A Need For Improving The Vertical Distribution, The Size Distribution And/Or Hygroscopicity Of Modeled Polar Ssaer. Source Functions Used In Cmip6 Emit Very Different Numbers Of Small Ssaer, Potentially Exacerbating Cloud-Aerosol Interaction Uncertainties In These Remote Regions. For Future Climate Scenarios Ssp126 And Ssp585, We Show That Ssaer Concentrations Increase At Both Poles At The End Of The 21St Century, With More Than Two Times Mid-20Th Century Values In The Arctic. The Pre-Industrial Climate Cmip6 Experiments Suggest There Is A Large Uncertainty In The Polar Radiative Budget Due To Ssaer.Plain Language Summary Aerosols Emitted From The Ocean, Such As Sea Salt Particles (Aerosols), Are Critical For The Climate Of Polar Regions. However, There Is Still Uncertainty In Their Representation In Climate Models. The Purpose Of This Work Is To Evaluate The Representation Of Sea Salt Aerosols (Ssaer) In The Arctic And Antarctic In A Recent Model Inter-Comparison Initiative, And To Assess The Consequences For Our Understanding Of Present-Day And Future Polar Climate. We Find That The Models Disagree Between Them And With Observations From Ground Stations And From Space. This Suggests That The Formulation Of Sea Salt Emissions In Global Models Is Not Adapted For Polar Regions. With Sea Ice Retreat, Ssaer Will Most Likely Increase In The Future, Which Makes Addressing The Current Uncertainty An Important Next Step For The Scientific Community.
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Lapillonne, S., Fontaine, F., Liebault, F., Richefeu, V., & Piton, G. (2023). Debris-Flow Surges Of A Very Active Alpine Torrent: A Field Database. Natural Hazards And Earth System Sciences, 232(4), 1241–1256.
Abstract: This Paper Presents A Methodology To Analyse Debris Flows Focusing At The Surge Scale Rather Than The Full Scale Of The Debris-Flow Event, As Well As Its Application To A French Site. Providing Bulk Surge Features Like Volume, Peak Discharge, Front Height, Front Velocity And Froude Numbers Allows For Numerical And Experimental Debris-Flow Investigations To Be Designed With Narrower Physical Ranges And Thus For Deeper Scientific Questions To Be Explored. We Suggest A Method To Access Such Features At The Surge Scale That Can Be Applied To A Wide Variety Of Monitoring Stations. Requirements For Monitoring Stations For The Methodology To Be Applicable Include (I) Flow Height Measurements, (Ii) A Cross-Section Assumption And (Iii) A Velocity Estimation. Raw Data From Three Monitoring Stations On The Real Torrent (Drainage Area: 2 Km(2), Southeastern France) Are Used To Illustrate An Application To 34 Surges Measured From 2011 To 2020 At Three Monitoring Stations. Volumes Of Debris-Flow Surges On The Real Torrent Are Typically Sized At A Few Thousand Cubic Metres. The Peak Flow Height Of Surges Ranges From 1 To 2 M. The Peak Discharge Range Is Around A Few Dozen Cubic Metres Per Second. Finally, We Show That Froude Numbers Of Such Surges Are Near Critical.
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Lavorel, S., Anquetin, S., & Buclet, N. (2023). Trajectories Of Socio-Ecological Change In Mountains. Regional Environmental Change, .
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Law, R., Christoffersen, P., Mackie, E., Cook, S., Haseloff, M., & Gagliardini, O. (2023). Complex Motion Of Greenland Ice Sheet Outlet Glaciers With Basal Temperate Ice. Science Advances, 9(6).
Abstract: Uncertainty Associated With Ice Sheet Motion Plagues Sea Level Rise Predictions. Much Of This Uncertainty Arises From Imperfect Representations Of Physical Processes Including Basal Slip And Internal Ice Deformation, With Ice Sheet Models Largely Incapable Of Reproducing Borehole-Based Observations. Here, We Model Isolated Three-Dimensional Domains From Fast-Moving (Sermeq Kujalleq/Store Glacier) And Slow-Moving (Isunnguata Sermia) Ice Sheet Settings In Greenland. By Incorporating Realistic Geostatistically Simulated Topography, We Show That A Spatially Highly Variable Layer Of Temperate Ice (Much Softer Ice At The Pressure-Melting Point) Forms Naturally In Both Settings, Alongside Ice Motion Patterns Which Diverge Substantially From Those Obtained Using Smoothly Varying Bedmachine Topography. Temperate Ice Is Vertically Extensive (>100 Meters) In Deep Troughs But Thins Notably (<5 Meters) Over Bedrock Highs, With Basal Slip Rates Reaching >90 Or <5% Of Surface Velocity Dependent On Topography And Temperate Layer Thickness. Developing Parameterizations Of The Net Effect Of This Complex Motion Can Improve The Realism Of Predictive Ice Sheet Models.
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Le Cozannet, G., Nicholls, R., Durand, G., Slangen, A., Lincke, D., & Chapuis, A. (2023). Adaptation To Multi-Meter Sea-Level Rise Should Start Now. Environmental Research Letters, 181(9).
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Le Guillou, F., Gaultier, L., Ballarotta, M., Metref, S., Ubelmann, C., Cosme, E., et al. (2023). Regional Mapping Of Energetic Short Mesoscale Ocean Dynamics From Altimetry: Performances From Real Observations. Ocean Science, 191(5), 1517–1527.
Abstract: For Over 25 Years, Satellite Altimetry Has Provided Invaluable Information About The Ocean Dynamics At Many Scales. In Particular, Gridded Sea Surface Height (Ssh) Maps Allow Us To Estimate The Mesoscale Geostrophic Circulation In The Ocean. However, Conventional Interpolation Techniques Rely On Static Optimal Interpolation Schemes, Hence Limiting The Estimation Of Non-Linear Dynamics At Scales Not Well Sampled By Altimetry (I.E., Below 150-200Km At Mid-Latitudes). To Overcome This Limitation In The Resolution Of Small-Scale Ssh Structures (And Thus Small-Scale Geostrophic Currents), A Back-And-Forth Nudging Algorithm Combined With A Quasi-Geostrophic Model, A Technique Called Bfn-Qg, Has Been Successfully Applied On Simulated Ssh Data In Observing System Simulation Experiments (Osses). The Result Is A Significant Reduction In Interpolation Error And An Improvement In The Space-Time Resolutions Of The Experimental Gridded Product Compared To Those Of Operational Products. In This Study, We Propose That The Bfn-Qg Be Applied To Real Altimetric Ssh Data In A Highly Turbulent Region Spanning A Part Of The Agulhas Current. The Performances Are Evaluated Within Observing System Experiments (Oses) That Use Independent Data (Such As Independent Ssh, Sea Surface Temperature And Drifter Data) As Ground Truth. By Comparing The Mapping Performances To The Ones Obtained With Operational Products, We Show That The Bfn-Qg Improves The Mapping Of Short, Energetic Mesoscale Structures And Associated Geostrophic Currents Both In Space And Time. In Particular, The Bfn-Qg Improves (I) The Spatial Effective Resolution Of The Ssh Maps By A Factor Of 20%, (Ii) The Zonal And (Especially) The Meridional Geostrophic Currents, And (Iii) The Prediction Of Lagrangian Transport For Lead Times Up To 10D. Unlike The Results Obtained In The Osses, The Oses Reveal More Contrasting Performances In Low-Variability Regions, Which Are Discussed In The Paper.
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Le Roux, E., Evin, G., Samacoïts, R., Eckert, N., Blanchet, J., & Morin, S. (2023). Projection Of Snowfall Extremes In The French Alps As A Function Of Elevation And Global Warming Level. Cryosphere, 171(111), 4691–4704.
Abstract: Following The Projected Increase In Extreme Precipitation, An Increase In Extreme Snowfall May Be Expected In Cold Regions, E.G., For High Latitudes Or At High Elevations. By Contrast, In Low- To Medium-Elevation Areas, The Probability Of Experiencing Rainfall Instead Of Snowfall Is Generally Projected To Increase Due To Warming Conditions. Yet, In Mountainous Areas, Despite The Likely Existence Of These Contrasted Trends According To Elevation, Changes In Extreme Snowfall With Warming Remain Poorly Quantified. This Paper Assesses Projected Changes In Heavy And Extreme Snowfall, I.E., In Mean Annual Maxima And 100-Year Return Levels, In The French Alps As A Function Of Elevation And Global Warming Level. We Apply A Recent Methodology, Based On The Analysis Of Annual Maxima With Non-Stationary Extreme Value Models, To An Ensemble Of 20 Adjusted General Circulation Model-Regional Climate Model (Gcm-Rcm) Pairs From The Euro-Cordex Experiment Under The Representative Concentration Pathway 8.5 (Rcp8.5) Scenario. For Each Of The 23 Massifs Of The French Alps, Maxima In The Hydrological Sense (1 August To 31 July) Are Provided From 1951 To 2100 And Every 300 M Of Elevations Between 900 And 3600 M. Results Rely On Relative Or Absolute Changes Computed With Respect To Current Climate Conditions (Corresponding Here To + 1 Circle C Global Warming Level) At The Massif Scale And Averaged Over All Massifs. Overall, Daily Mean Annual Maxima Of Snowfall Are Projected To Decrease Below 3000 M And Increase Above 3600 M, While 100-Year Return Levels Are Projected To Decrease Below 2400 M And Increase Above 3300 M. At Elevations In Between, Values Are On Average Projected To Increase Until + 3 Circle C Of Global Warming And Then Decrease. At + 4 Circle C, Average Relative Changes In Mean Annual Maxima And 100-Year Return Levels, Respectively, Vary From – 26 % And – 15 % At 900 M To + 3 % And + 8 % At 3600 M. Finally, For Each Global Warming Level Between + 1.5 And + 4 Circle C, We Compute The Elevation Threshold That Separates Contrasted Trends, I.E., Where The Average Relative Change Equals Zero. This Elevation Threshold Is Shown To Be Lower For Higher Return Periods, And It Is Projected To Rise From 3000 M At + 1.5 Circle C To 3350 M At + 4 Circle C For Mean Annual Maxima And From 2600 To 3000 M For 100-Year Return Levels. These Results Have Implications For The Management Of Risks Related To Extreme Snowfall.
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Le, H., Nguyen, T., Gratiot, N., Deleersnijder, E., & Soares-Frazao, S. (2023). The Multi-Channel System Of The Vietnamese Mekong Delta: Impacts On The Flow Dynamics Under Relative Sea-Level Rise Scenarios. Water, 151(202).
Abstract: The Mekong Delta Has The World'S Third-Largest Surface Area. It Plays An Indisputable Role In The Economy And Livelihoods Of Vietnam And Cambodia, With Repercussions At Regional And Global Scales. During Recent Decades, The Vietnamese Part Of The Mekong Delta Underwent Profound Human Interventions (Construction Of Dykes And Multi-Channel Networks), Which Modified The Hydrodynamic Regime, Especially Cycles Of Field Submersion. In This Study, We First Applied A Full 2D Numerical Hydraulic Model, Telemac-2D, To Examine The Effects Of The Complex Channel And River Networks On The Spatial And Temporal Distribution Of The Flow In The 40,000 Km2 Of The Vietnamese Mekong Delta. Then, Two Scenarios Of Relative Sea-Level Rise In 2050 And 2100 Were Implemented To Simulate The Future Patterns Of Water Fluxes In The Delta. The Results Show That Dykes And Multi-Channel Networks Would Reduce The Inundation Area By 36% And Lessen The Peak Water Level By 15% And The Discharge Over The Floodplains By 24%. Despite This Protection, Under A Relative Sea-Level Rise Of 30 Cm And 100 Cm, The Maximum Flooded Area Could Occupy About 69% And 85% Of The Whole Delta In 2050 And 2100, Respectively.
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Lebon, Y., Francois, C., Navel, S., Vallier, F., Guillard, L., Pinasseau, L., et al. (2023). Aquifer Recharge By Stormwater Infiltration Basins: Hydrological And Vadose Zone Characteristics Control The Impacts Of Basins On Groundwater Chemistry And Microbiology. Science Of The Total Environment, 8658.
Abstract: Stormwater Infiltration Systems (Sis) Are Designed To Collect And Infiltrate Urban Stormwater Runoff Into The Ground For Flood Risk Mitigation And Artificial Aquifer Recharge. Many Studies Have Demonstrated That Infiltration Practices Can Im-Pact Groundwater Chemistry And Microbiology. However, Quantitative Assessments Of The Hydrogeological Factors Re-Sponsible Of These Changes Remain Scarce. Thus, The Present Study Aimed To Quantitatively Test Whether Changes Of Groundwater Chemistry And Microbiology Induced By Sis Were Linked To Two Factors Associated With Vadose Zone Prop-Erties (Vadose Zone Thickness, Water Transit Time From Surface To Groundwater) And One Factor Associated With Ground-Water Recharge Rate (Assessed By Groundwater Table Elevation During Rain Events). To Evaluate Changes In Chemistry (No3-, Po43- And Dissolved Organic Carbon Concentrations), Groundwater Samples Were Collected In Wells Located In Sis-Impacted And Non-Sis-Impacted Zones During Experimental Periods Of 10 Days. During The Same Periods, Clay Beads Were Incubated In The Same Wells To Measure Changes Of Groundwater Microbial Biofilms (Microbial Biomass, Dehydrogenase And Hydrolytic Activities) Induced By Sis. Results Showed That Changes In Po43- Supplied To Groundwa-Ter During Stormwater Infiltration Was Negatively Correlated With Vadose Zone Thickness. A Short Water Transit Time From Surface To Groundwater Increased Dissolved Organic Carbon Concentrations In The Aquifer Which, In Turn, Increased Biofilm Biomasses In Groundwater. The Groundwater Recharge Rate During Rain Events (Assessed By Groundwater Table Elevation) Diluted No3- Concentrations In The Aquifer But Also Influenced The Changes Of Biofilm Activities Induced By Sis. Groundwater Recharge Rate During Rain Events Probably Increased The Fluxes Of Water And Dissolved Organic Carbon In Groundwater, Stimulating The Activity Of Microbial Biofilms. Overall, The Present Study Is The First To Quantify Con-Jointly Several Factors And Processes (Water Transfer, Dilution, Solute Fluxes) That Could Explain The Impact Of Stormwater Infiltration On Chemistry And/Or Microbiology In Groundwater.
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Lecavalier, B., Tarasov, L., Balco, G., Spector, P., Hillenbrand, C., Buizert, C., et al. (2023). Antarctic Ice Sheet Paleo-Constraint Database. Earth System Science Data, 151(8), 3573–3596.
Abstract: We Present A Database Of Observational Constraints On Past Antarctic Ice Sheet Changes During The Last Glacial Cycle Intended To Consolidate The Observations That Represent Our Understanding Of Past Antarctic Changes And For State-Space Estimation And Paleo-Model Calibrations. The Database Is A Major Expansion Of The Initial Work Of Briggs And Tarasov (2013). It Includes New Data Types And Multi-Tier Data Quality Assessment. The Updated Constraint Database, Antice2 (Https://Theghub.Org/Resources/4884, Lecavalier Et Al., 2022), Consists Of Observations Of Past Grounded- And Floating-Ice-Sheet Extent, Past Ice Thickness, Past Relative Sea Level, Borehole Temperature Profiles, And Present-Day Bedrock Displacement Rates. In Addition To Paleo-Observations, The Present-Day Ice Sheet Geometry And Surface Ice Velocities Are Incorporated To Constrain The Present-Day Ice Sheet Configuration. The Method By Which The Data Are Curated Using Explicitly Defined Criteria Is Detailed. Moreover, The Observational Uncertainties Are Specified. The Methodology By Which The Constraint Database Can Be Applied To Evaluate A Given Ice Sheet Reconstruction Is Discussed. The Implementation Of The Antice2 Database For Antarctic Ice Sheet Model Calibrations Will Improve Antarctic Ice Sheet Predictions During Past Warm And Cold Periods And Yield More Robust Paleo-Model Spin Ups For Forecasting Future Ice Sheet Changes.
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Legrain, E., Blard, P., Kageyama, M., Charreau, J., Leduc, G., Bourdin, S., et al. (2023). Moisture Amplification Of The High-Altitude Deglacial Warming. Quaternary Science Reviews, 3183.
Abstract: In Response To Anthropogenic Warming, Glaciers Are Shrinking Almost Everywhere, Endangering Water Accessibility In Areas Located Downstream. Glacier Fluctuations Are At First Order Controlled By Local Precipitation And Temperature, But Large Uncertainties Persist On The Potential Role Of Local Moisture In Amplifying Or Dampening Temperature Changes At High-Elevation. Here, We Combine Glacier Extents And Sea Surface Temperature (Sst) During The Last Glacial Maximum (Lgm) To Quantify Altitudinal Thermal Gradients (Lapse Rate) From 40N To 40S Along The American Cordillera. We Also Constrain Modern Lapse Rates Based On Present Day Temperature And Sst Database To Explore How The Lapse Rate Has Changed Since The Lgm Along This North South Transect. Based On Proxy-Based Quantitative Paleo-Precipitation Estimations Above 2000 M, We Investigate How These Lapse Rate Changes Compare With Moisture Modifications Around The Cordillera And Discuss The Mechanisms That Potentially Controlled Lapse Rate Changes During The Post-Lgm Deglacial Warming. We Find That Lapse Rate Changes Are Linearly Related To Changes In Precipitation And Derive A Quantitative Relationship Between These Two Parameters. To Further Explore The Processes Involved In Controlling Lapse Rate Variations, We Use The Ipsl Global Climate Model Outputs, For The Lgm And Pre-Industrial States In This Region. The Ipsl Model Also Yields A Shallower Modern Lapse Rate In The Wetter Tropical Region, Confirming The Observed Correlation Between Precipitation Changes And Lapse Rate Variations. The Ipsl Model Also Supports A Close Coupling Of Continental Relative Moisture And Mean Annual Precipitation In The Studied Area, Indicating That Moisture Is Involved In The Precipitation – Lapse Rate Relationship. Our Results Suggest That Future Warming May Be Enhanced In High Altitude Regions Where Precipitation Is Expected To Increase. Using Our Most Reliable Relationship Linking Precipitation And Lapse Rate Changes, We Conclude That, Assuming A 1 C-Degrees Warming At Sea Level, A Mean Annual Precipitation Increases Of 500 Mm.A(-1) Could Lead To A Warming Amplification Of 4.1 +/- 0.8 C At 4000 M Asl (Mean Elevation Of Modern Glaciers). In This Case, A 2 C-Degrees Warming At Sea Level Would Yield >6 C Degrees Warming At 4000 M Asl. This Study Therefore Confirms That Special Attention Should Be Given To The Climate Projections Of Glacier Melting In Tropical And Mid Latitude Regions.
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Legrain, E., Parrenin, F., & Capron, E. (2023). A Gradual Change Is More Likely To Have Caused The Mid-Pleistocene Transition Than An Abrupt Event. Communications Earth & Environment, .
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Legrand, M., Mcconnell, J., Bergametti, G., Plach, A., Desboeufs, K., Chellman, N., et al. (2023). A Two-Fold Increase Of Phosphorus In Alpine Ice Over The Twentieth Century: Contributions From Dust, Primary Biogenic Emissions, Coal Burning, And Pig Iron Production. Journal Of Geophysical Research-Atmospheres, 1281(191).
Abstract: Phosphorus (P) Is A Key Nutrient For Many Organisms But Its Global Atmospheric Budget Is Largely Unconstrained. Estimates Of Major Emissions Sources Such As Fossil-Fuel Combustion Range From Similar To 0.02 To 1.1 Tg Yr-1, And Primary Biogenic Emissions Range From 0.16 To 1.0 Tg Yr-1. Here We Used Detailed Measurements Of Phosphorus In Alpine Ice Cores Extracted From The Col Du Dome (Cdd) Glacier Located Near The Mont Blanc Summit And Atmospheric Model Simulations To Evaluate Changes In Western European Emissions From Pre-Industrial (Pi) To Modern Times. The Ice-Core Records Show That P Concentrations During The Pi Were About 0.9 Ng G-1, Of Which One Third Was Of Crustal Origin And Two Thirds The Result Of Primary Biogenic Emissions. Concentrations Were Higher Throughout The 20Th Century, Reaching 2.5 Ng G-1 In The 1980S. Analysis Of Source Tracers Measured In The Same Ice, Commodity Productions Statistics, And Other Information Suggest That The Increase In P Throughout The 20Th Century Was Caused By Enhanced Emissions From Natural And Anthropogenic Sources. Coal Burning And Steel Industry Represented The Main Anthropogenic Sources During The First And Second Half Of The Century, Respectively. After 1950, The Increase In P Was Also Caused By Enhanced Dust Emissions, With Increased Biogenic Emissions Caused By Recent Changes Of Use-Land Also Contributing. These Findings Provide Important Constraints On The Atmospheric P Budget At The Scale Of Western Europe During The Recent Centuries. Phosphorus Is An Important Nutrient For Terrestrial And Aquatic Flora And Fauna. Whereas Dust Aerosol Emissions Are The Dominant Atmospheric Source Of Phosphorus On A Global Scale, Other Sources Such As Biogenic Particles Emitted By Vegetation, As Well As Fossil-Fuel Combustion, May Represent Important Sources In Less-Dusty Industrialized Regions. Estimates Of These Non-Crustal Sources Are Uncertain, However, With Values Often Varying By An Order Of Magnitude Or More. Comparison With Long-Term Pollution Records Extracted From Well-Dated Ice Cores Provides A Means Of Evaluating These Estimates. Here, We Analyzed Phosphorus In Ice Cores Extracted Near The Mont Blanc Summit In The French Alps To Develop An 1850 To 2000 Record. Phosphorus Deposition Doubled During This Period, With Increases Attributed To Enhancement Of Both Natural (Dust And Biogenic Particles Emitted By Vegetation) And Anthropogenic (Mainly Coal Burning And The Steel Industry) Emissions. A Doubling Of Phosphorus In Alpine Ice Deposited Between 1850 And 2000 From Increasing Natural And Anthropogenic Emissionsphosphorus Deposition Trends From 1900 To 1975 Mainly Attributed To Coal Burning And Pig Iron Industry Emissionsnatural European Phosphorus Sources Dominated By Primary Emissions Of Biogenic (70%) And Dust (30%) Particles That Were Enhanced After 1975
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Legrand, M., Mcconnell, J., Bergametti, G., Plach, A., Desboeufs, K., Chellman, N., et al. (2023). A Two-Fold Increase Of Phosphorus In Alpine Ice Over The Twentieth Century: Contributions From Dust, Primary Biogenic Emissions, Coal Burning, And Pig Iron Production. Journal Of Geophysical Research-Atmospheres, 1281(191).
Abstract: Phosphorus (P) Is A Key Nutrient For Many Organisms But Its Global Atmospheric Budget Is Largely Unconstrained. Estimates Of Major Emissions Sources Such As Fossil-Fuel Combustion Range From Similar To 0.02 To 1.1 Tg Yr(-1), And Primary Biogenic Emissions Range From 0.16 To 1.0 Tg Yr(-1). Here We Used Detailed Measurements Of Phosphorus In Alpine Ice Cores Extracted From The Col Du D & Ocirc;Me (Cdd) Glacier Located Near The Mont Blanc Summit And Atmospheric Model Simulations To Evaluate Changes In Western European Emissions From Pre-Industrial (Pi) To Modern Times. The Ice-Core Records Show That P Concentrations During The Pi Were About 0.9 Ng G(-1), Of Which One Third Was Of Crustal Origin And Two Thirds The Result Of Primary Biogenic Emissions. Concentrations Were Higher Throughout The 20Th Century, Reaching 2.5 Ng G(-1) In The 1980S. Analysis Of Source Tracers Measured In The Same Ice, Commodity Productions Statistics, And Other Information Suggest That The Increase In P Throughout The 20Th Century Was Caused By Enhanced Emissions From Natural And Anthropogenic Sources. Coal Burning And Steel Industry Represented The Main Anthropogenic Sources During The First And Second Half Of The Century, Respectively. After 1950, The Increase In P Was Also Caused By Enhanced Dust Emissions, With Increased Biogenic Emissions Caused By Recent Changes Of Use-Land Also Contributing. These Findings Provide Important Constraints On The Atmospheric P Budget At The Scale Of Western Europe During The Recent Centuries.
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Legrand, M., Mcconnell, J., Bergametti, G., Plach, A., Desboeufs, K., Chellman, N., et al. (2023). A Two-Fold Increase Of Phosphorus In Alpine Ice Over The Twentieth Century: Contributions From Dust, Primary Biogenic Emissions, Coal Burning, And Pig Iron Production. Journal Of Geophysical Research-Atmospheres, 1281(191).
Abstract: Phosphorus (P) Is A Key Nutrient For Many Organisms But Its Global Atmospheric Budget Is Largely Unconstrained. Estimates Of Major Emissions Sources Such As Fossil-Fuel Combustion Range From Similar To 0.02 To 1.1 Tg Yr(-1), And Primary Biogenic Emissions Range From 0.16 To 1.0 Tg Yr(-1). Here We Used Detailed Measurements Of Phosphorus In Alpine Ice Cores Extracted From The Col Du D & Ocirc;Me (Cdd) Glacier Located Near The Mont Blanc Summit And Atmospheric Model Simulations To Evaluate Changes In Western European Emissions From Pre-Industrial (Pi) To Modern Times. The Ice-Core Records Show That P Concentrations During The Pi Were About 0.9 Ng G(-1), Of Which One Third Was Of Crustal Origin And Two Thirds The Result Of Primary Biogenic Emissions. Concentrations Were Higher Throughout The 20Th Century, Reaching 2.5 Ng G(-1) In The 1980S. Analysis Of Source Tracers Measured In The Same Ice, Commodity Productions Statistics, And Other Information Suggest That The Increase In P Throughout The 20Th Century Was Caused By Enhanced Emissions From Natural And Anthropogenic Sources. Coal Burning And Steel Industry Represented The Main Anthropogenic Sources During The First And Second Half Of The Century, Respectively. After 1950, The Increase In P Was Also Caused By Enhanced Dust Emissions, With Increased Biogenic Emissions Caused By Recent Changes Of Use-Land Also Contributing. These Findings Provide Important Constraints On The Atmospheric P Budget At The Scale Of Western Europe During The Recent Centuries.
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Legrand, M., Mcconnell, J., Bergametti, G., Preunkert, S., Chellman, N., Desboeufs, K., et al. (2023). Alpine-Ice Record Of Bismuth Pollution Implies A Major Role Of Military Use During World War Ii. Scientific Reports, .
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Li, C., Enrico, M., Magand, O., Araujo, B., Le Roux, G., Osterwalder, S., et al. (2023). A Peat Core Hg Stable Isotope Reconstruction Of Holocene Atmospheric Hg Deposition At Amsterdam Island (37.8(O)S). Geochimica Et Cosmochimica Acta, 3413, 62–74.
Abstract: Mercury (Hg) Stable Isotopes Have Been Broadly Used To Investigate The Sources, Transformation And Deposition Of Atmospheric Hg During The Industrial Era Thanks To The Multiple Isotope Signatures Deriving From Mass-Dependent (Represented By Delta Hg-202) And Mass-Independent Fractionation (Represented By Axxxhg) In The Environment. Less Is Known About The Impact Of Past Climate Change On Atmospheric Hg Deposition And Cycling, And Whether Hg Isotopes Covary With Past Climate. Here, We Investigate Hg Concentration And Hg Isotope Signatures In A 6600-Year-Old Ombrotrophic Peat Record From Amsterdam Island (Ams, 37.8(O)S), And In Modern Ams Rainfall And Gaseous Elemental Hg (Hg-0) Samples. Results Show That Holocene Atmospheric Hg Deposition And Plant Hg Uptake Covary With Dust Deposition, And Are Both Lower Under A High Humidity Regime Associated With Enhanced Southern Westerly Winds. Modern Ams Gaseous Hg-0 And Rainfall Hgii Isotope Signatures Are Similar To Those In The Northern Hemisphere (Nh). Holocene Peat Delta Hg-199 And A200Hg Are Significantly Correlated (R2 = 0.67, P < 0.001, N = 58), Consistently Oscillating Between The Modern Hg-0 And Rainfall Hg-Ii End-Members. Peat A200Hg And Delta Hg-199 Provide Evidence Of Plant Uptake Of Hg-0 As The Dominant Pathway Of Hg Deposition To Ams Peatland, With Some Exceptions During Humid Periods. In Contrast To Nh Archives Generally Documenting A Modern Increase In Delta Hg-199, Recent Peat Layers (Post-1900Ce) From Ams Show The Lowest Delta Hg-199 In The Peat Profile (-0.42 +/- 0.27 Parts Per Thousand, 1Cs, N = 8). This Likely Reflects A Significant Change In The Post-Depositional Process On Deposited Anthropogenic Hg In 20Th Century (I.E. Dark Abiotic Reduction), Enabling More Negative Delta Hg-199 To Be Observed In Ams Peat. We Further Find That The Oscillations Of Hg Isotopes Are Consistent With Established Holocene Climate Variability From Dust Proxies. We Suggest Peat Hg Isotope Records Might Be A Valid Rainfall Indicator. (C) 2022 The Authors. Published By Elsevier Ltd.
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Li, L., Deremble, B., Lahaye, N., & Memin, E. (2023). Stochastic Data-Driven Parameterization Of Unresolved Eddy Effects In A Baroclinic Quasi-Geostrophic Model. Journal Of Advances In Modeling Earth Systems, 151(2).
Abstract: In This Work, A Stochastic Representation Based On A Physical Transport Principle Is Proposed To Account For Mesoscale Eddy Effects On The Large-Scale Oceanic Circulation. This Stochastic Framework Arises From A Decomposition Of The Lagrangian Velocity Into A Smooth-In-Time Component And A Highly Oscillating Noise Term. One Important Characteristic Of This Random Model, Without Any External Forcing And Damping, Is That It Conserves The Total Energy Of The Resolved Flow For Any Realization. The Proposed Stochastic Formulation Is Successfully Implemented In A Well Established Multi-Layered Quasi-Geostrophic Dynamical Core. The Empirical Spatial Correlation Of The Unresolved Noise Is Calibrated From The Eddy-Resolving Simulation Data. In Particular, A Stationary Correction Drift Can Be Introduced In The Noise Through Girsanov Transformation. This Non-Intuitive Term Appears To Be Important In Reproducing On A Coarse Mesh The Eastward Jet Of The Wind-Driven Double-Gyre Circulation. In Addition, A Projection Method Has Been Proposed To Constrain The Noise To Act Along The Iso-Surfaces Of The Vertical Stratification. The Resulting Noise Enables Us To Improve The Intrinsic Low-Frequency Variability Of The Large-Scale Current.
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Liebault, F., Piegay, H., Cassel, M., & Arnaud, F. (2023). Bedload Tracing With Rfid Tags In Gravel-Bed Rivers: Review And Meta-Analysis After 20?Years Of Field And Laboratory Experiments. Earth Surface Processes And Landforms, .
Abstract: Soon After Their First Deployment In Rivers In The Early 2000S, Rfid Tags Rapidly Became The Reference Technology For Bedload Tracing In Rivers. We Can Estimate From The Literature That During The Last 20 Years, More Than 30,000 Rfid Tracers Have Been Injected In Gravel-Bed Rivers All Around The World To Study Bedload Transport. Many Field Experiments Have Been Reported In A Great Diversity Of Fluvial Environments, Complemented By Many Laboratory Experiments And Methodological Developments. This Paper Proposes A Review Of These Works, Notably Based On The Compilation Of More Than 350 Rfid Surveys, Complemented By 97 Magnetic Surveys, For A Total Of 125 Study Sites. The Meta-Analysis Of This Database Shows That Rfid Tracers Have Improved Our Understanding Of Sediment Transport In Fluvial Environments With Rapid Bedload Dispersion. It Is Also Shown That Central Positions Of Tracer Plumes Are Moving Faster Over Time Than Tracer Leading Fronts, As Attested By A General Relation Between Maximum And Mean Distances Of Transport. The Most Recent Methodological Developments Based On The Use Of Active Uhf Rfid Tags Show That It Is Now Possible To Conduct Efficient Bedload Tracing Experiments Not Only In Small Streams, But Also In Large Gravel-Bed Rivers Or Very Active Braided Channels. Other Addressed Topics Include Rfid Deployment And Survey In River Channels, Controlling Factors Of Tracer Mobility (Flow Conditions, Grain-Size And Shape, Channel Morphology), Bedload Monitoring Approaches Using Rfid Tracers, And Applications Of Rfid Tracers For Evaluating Human Effects On Bedload Transport. Key Challenges Of Bedload Tracing With Rfid Tags Are Also Proposed. A Review Of Field And Laboratory Radio Frequency Identification (Rfid) Bedload Tracing Experiments Is Proposed, Including A Meta-Analysis Of Data Coming From 459 Tracer Surveys For A Total Of 125 Study Sites. Rfid Tracers Open New Avenues For Exploring Fluvial Environments Prone To Rapid Bedload Dispersion. The Most Recent Methodological Developments Based On Active Ultra-High Frequency Rfid Tags Show That It Is Now Possible To Conduct Efficient Bedload Tracing Experiments Not Only In Small Streams But Also In Large Gravel-Bed Rivers Or Active Braided Channels.Image
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Loffler, P., Escher, B., Baduel, C., Virta, M., & Lai, F. (2023). Antimicrobial Transformation Products In The Aquatic Environment: Global Occurrence, Ecotoxicological Risks, And Potential Of Antibiotic Resistance. Environmental Science & Technology, .
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Lott, F., Beljaars, A., Pauget, L., & Deremble, B. (2023). Neutral And Stratified Turbulent Boundary-Layer Flow Over Low Mountains. Quarterly Journal Of The Royal Meteorological Society, .
Abstract: A Theory For Flow Over Gentle Hills Using A Mixing-Length Turbulence Closure Is Developed To Describe The Transition From Turbulent Orographic Form Drag To Gravity Wave Drag. It Confirms That The First Is Associated With Downstream Sheltering, And The Second With Upstream Blocking And Strong Downslope Winds. It Shows That The Altitude At Which The Incident Flow Needs To Be Taken To Calculate The Drag Is The Inner Layer Scale At Which Dissipation Equilibrates Disturbance Advection. It Also Shows That The Parameter That Controls The Transition, Here A Richardson Number, Compares The Mountain Length With The Altitude Of The Turning Points Above Which The Upward-Propagating Gravity Waves Become Evanescent. Our Solutions Are Also Used To Show That The Downslope Winds Penetrate Well Into The Inner Layer And That A Good Fraction Of The Drag Is Deposited In The Inner Layer: All Of It In The Neutral Case, A Large Fraction In The Intermediate Cases When There Are Trapped Lee Waves, And Even In Stable Situations Without Trapping Part Of The Gravity Wave Drag Is Eroded In The Inner Layer. Some Discussion On How To Combine Neutral And Stratified Effects In The Parametrization Of Subgrid Scale Orography In Large-Scale Models Is Given. A Theory For The Interaction Between A Boundary Layer And A Low Mountain Is Derived. The Incident Wind Considered (U0$$ {U}_0 $$, Left Panel) Presents A Logarithmic Profile Near The Surface. The Theory Describes The Transition From Neutral To Stratified Flows, And The Systems Of Mountain Waves (Upward Propagating And Trapped, See Right Panel) That Develop During The Transition. The Theory Also Reproduces The Transition From Downstream Sheltering To Downslope Winds (Zoom) As Stratification Increases. The Mountain Drag And Reynolds Stress Profiles Are Also Discussed.Image
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Maclennan, M., Lenaerts, J., Shields, C., Hoffman, A., Wever, N., Thompson-Munson, M., et al. (2023). Climatology And Surface Impacts Of Atmospheric Rivers On West Antarctica. Cryosphere, 171(2), 865–881.
Abstract: Atmospheric Rivers (Ars) Transport Large Amounts Of Moisture From The Mid- To High-Latitudes And They Are A Primary Driver Of The Most Extreme Snowfall Events, Along With Surface Melting, In Antarctica. In This Study, We Characterize The Climatology And Surface Impacts Of Ars On West Antarctica, Focusing On The Amundsen Sea Embayment And Marie Byrd Land. First, We Develop A Climatology Of Ars In This Region, Using An Antarctic-Specific Ar Detection Tool Combined With The Modern-Era Retrospective Analysis For Research And Applications, Version 2 (Merra-2) And The European Centre For Medium-Range Weather Forecasts (Ecmwf) Reanalysis V5 (Era5) Atmospheric Reanalyses. We Find That While Ars Are Infrequent (Occurring 3 % Of The Time), They Cause Intense Precipitation In Short Periods Of Time And Account For 11 % Of The Annual Surface Accumulation. They Are Driven By The Coupling Of A Blocking High Over The Antarctic Peninsula With A Low-Pressure System Known As The Amundsen Sea Low. Next, We Use Observations From Automatic Weather Stations On Thwaites Eastern Ice Shelf With The Firn Model Snowpack And Interferometric Reflectometry (Ir) To Examine A Case Study Of Three Ars That Made Landfall In Rapid Succession From 2 To 8 February 2020, Known As An Ar Family Event. While Accumulation Dominates The Surface Impacts Of The Event On Thwaites Eastern Ice Shelf (> 100 Kgm(-2) Or Millimeters Water Equivalent), We Find Small Amounts Of Surface Melt As Well (< 5 Kgm(-2)). The Results Presented Here Enable Us To Quantify The Past Impacts Of Ars On West Antarctica'S Surface Mass Balance (Smb) And Characterize Their Interannual Variability And Trends, Enabling A Better Assessment Of Future Ar-Driven Changes In The Smb.
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Magand, O., Angot, H., Bertrand, Y., Sonke, J., Laffont, L., Duperray, S., et al. (2023). Over A Decade Of Atmospheric Mercury Monitoring At Amsterdam Island In The French Southern And Antarctic Lands. Scientific Data, 101(1).
Abstract: The Minamata Convention, A Global And Legally Binding Treaty That Entered Into Force In 2017, Aims To Protect Human Health And The Environment From Harmful Mercury (Hg) Effects By Reducing Anthropogenic Hg Emissions And Environmental Levels. The Conference Of The Parties Is To Periodically Evaluate The Convention'S Effectiveness, Starting In 2023, Using Existing Monitoring Data And Observed Trends. Monitoring Atmospheric Hg Levels Has Been Proposed As A Key Indicator. However, Data Gaps Exist, Especially In The Southern Hemisphere. Here, We Present Over A Decade Of Atmospheric Hg Monitoring Data At Amsterdam Island (37.80 Degrees S, 77.55 Degrees E), In The Remote Southern Indian Ocean. Datasets Include Gaseous Elemental And Oxidised Hg Species Ambient Air Concentrations From Either Active/Continuous Or Passive/Discrete Acquisition Methods, And Annual Total Hg Wet Deposition Fluxes. These Datasets Are Made Available To The Community To Support Policy-Making And Further Scientific Advancements.
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Mahaman, R., Nazoumou, Y., Favreau, G., Ousmane, B., Boucher, M., Babaye, M., et al. (2023). Paleochannel Groundwater Discharge To The River Niger In The Iullemmeden Basin Estimated By Near- Surface Geophysics And Piezometry. Environmental Earth Sciences, .
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Maier, N., Andersen, J., Mouginot, J., Gimbert, F., & Gagliardini, O. (2023). Wintertime Supraglacial Lake Drainage Cascade Triggers Large-Scale Ice Flow Response In Greenland. Geophysical Research Letters, 505(4).
Abstract: Surface Melt Forces Summertime Ice-Flow Accelerations On Glaciers And Ice Sheets. Here, We Show That Large Meltwater-Forced Accelerations Also Occur During Wintertime In Greenland. We Document Supraglacial Lakes (Sgls) Draining In Cascades At Unusually High Elevation, Causing An Expansive Flow Acceleration Over A Similar To 5,200 Km(2) Region During Winter. The Three-Component Interferometric Surface Velocity Field And Decomposition Modeling Reveal The Underlying Flood Propagation With Unprecedented Detail As It Traveled Over 160 Km From The Drainage Site To The Margin, Providing Novel Constraints On Subglacial Water Pathways, Drainage Morphology, And Links With Basal Sliding. The Triggering Sgls Continuously Grew Over 40 Years And Suddenly Released Decades Of Stored Meltwater, Demonstrating Surface Melting Can Impact Dynamics Well Beyond Melt Production. We Show These Events Are Likely Common And Thus Their Cumulative Impact On Dynamics Should Be Further Evaluated.
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Mallet, M., Humphries, R., Fiddes, S., Alexander, S., Altieri, K., Angot, H., et al. (2023). Untangling The Influence Of Antarctic And Southern Ocean Life On Clouds. Elementa-Science Of The Anthropocene, 111(1).
Abstract: Polar Environments Are Among The Fastest Changing Regions On The Planet. It Is A Crucial Time To Make Significant Improvements In Our Understanding Of How Ocean And Ice Biogeochemical Processes Are Linked With The Atmosphere. This Is Especially True Over Antarctica And The Southern Ocean Where Observations Are Severely Limited And The Environment Is Far From Anthropogenic Influences. In This Commentary, We Outline Major Gaps In Our Knowledge, Emerging Research Priorities, And Upcoming Opportunities And Needs. We Then Give An Overview Of The Large-Scale Measurement Campaigns Planned Across Antarctica And The Southern Ocean In The Next 5 Years That Will Address The Key Issues. Until We Do This, Climate Models Will Likely Continue To Exhibit Biases In The Simulated Energy Balance Over This Delicate Region. Addressing These Issues Will Require An International And Interdisciplinary Approach Which We Hope To Foster And Facilitate With Ongoing Community Activities And Collaborations.
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Maloku, K., Hingray, B., & Evin, G. (2023). Accounting For Precipitation Asymmetry In A Multiplicative Random Cascade Disaggregation Model. Hydrology And Earth System Sciences, 272(202), 3643–3661.
Abstract: Analytical Multiplicative Random Cascades (Mrcs) Are Widely Used For The Temporal Disaggregation Of Coarse-Resolution Precipitation Time Series. This Class Of Models Applies Scaling Models To Represent The Dependence Of The Cascade Generator On The Temporal Scale And The Precipitation Intensity. Although Determinant, The Dependence On The External Precipitation Pattern Is Usually Disregarded In The Analytical Scaling Models. Our Work Presents A Unified Mrc Modelling Framework That Allows The Cascade Generator To Depend In A Continuous Way On The Temporal Scale, Precipitation Intensity And A So-Called Precipitation Asymmetry Index.Different Mrc Configurations Are Compared For 81 Locations In Switzerland With Contrasted Climates. The Added Value Of The Dependence Of The Mrc On The Temporal Scale Appears To Be Unclear, Unlike What Was Suggested In Previous Works. Introducing The Precipitation Asymmetry Dependence Into The Model Leads To A Drastic Improvement In Model Performance For All Statistics Related To Precipitation Temporal Persistence (Wet-Dry Transition Probabilities, Lag-N Autocorrelation Coefficients, Lengths Of Dry-Wet Spells). Accounting For Precipitation Asymmetry Seems To Solve This Important Limitation Of Previous Mrcs.The Model Configuration That Only Accounts For The Dependence On Precipitation Intensity And Asymmetry Is Highly Parsimonious, With Only Five Parameters, And Provides Adequate Performances For All Locations, Seasons And Temporal Resolutions. The Spatial Coherency Of The Parameter Estimates Indicates A Real Potential For Regionalisation And For Further Application To Any Location In Switzerland.
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Mardoñez, V., Pandolfi, M., Borlaza, L., Jaffrezo, J., Alastuey, A., Besombes, J., et al. (2023). Source Apportionment Study On Particulate Air Pollution In Two High-Altitude Bolivian Cities: La Paz And El Alto. Atmospheric Chemistry And Physics, 232(181), 10325–10347.
Abstract: La Paz And El Alto Are Two Fast-Growing, High-Altitude Bolivian Cities Forming The Second-Largest Metropolitan Area In The Country. Located Between 3200 And 4050 M A.S.L. (Above Sea Level), These Cities Are Home To A Burgeoning Population Of Approximately 1.8 Million Residents. The Air Quality In This Conurbation Is Heavily Influenced By Urbanization; However, There Are No Comprehensive Studies Evaluating The Sources Of Air Pollution And Their Health Impacts. Despite Their Proximity, The Substantial Variation In Altitude, Topography, And Socioeconomic Activities Between La Paz And El Alto Result In Distinct Sources, Dynamics, And Transport Of Particulate Matter (Pm). In This Investigation, Pm10 Samples Were Collected At Two Urban Background Stations Located In La Paz And El Alto Between April 2016 And June 2017. The Samples Were Later Analyzed For A Wide Range Of Chemical Species Including Numerous Source Tracers (Oc, Ec, Water-Soluble Ions, Sugar Anhydrides, Sugar Alcohols, Trace Metals, And Molecular Organic Species). The United States Environmental Protection Agency (U.S. Epa) Positive Matrix Factorization (Pmf V.5.0) Receptor Model Was Employed For The Source Apportionment Of Pm10. This Is One Of The First Source Apportionment Studies In South America That Incorporates An Extensive Suite Of Organic Markers, Including Levoglucosan, Polycyclic Aromatic Hydrocarbons (Pahs), Hopanes, And Alkanes, Alongside Inorganic Species. The Multisite Pmf Resolved 11 Main Sources Of Pm. The Largest Annual Contribution To Pm10 Came From The Following Two Major Sources: The Ensemble Of The Four Vehicular Emissions Sources (Exhaust And Non-Exhaust), Accountable For 35 % And 25 % Of The Measured Pm In La Paz And El Alto, Respectively; And Dust, Which Contributed 20 % And 32 % To The Total Pm Mass. Secondary Aerosols Accounted For 22 % (24 %) In La Paz (El Alto). Agricultural Smoke Resulting From Biomass Burning In The Bolivian Lowlands And Neighboring Countries Contributed To 9 % (8 %) Of The Total Pm10 Mass Annually, Increasing To 17 % (13 %) Between August-October. Primary Biogenic Emissions Were Responsible For 13 % (7 %) Of The Measured Pm10 Mass. Additionally, A Profile Associated With Open Waste Burning Occurring From May To August Was Identified. Although This Source Contributed Only To 2 % (5 %) Of The Total Pm10 Mass, It Constitutes The Second Largest Source Of Pahs, Which Are Compounds Potentially Hazardous To Human Health. Our Analysis Additionally Resolved Two Different Traffic-Related Factors, A Lubricant Source (Not Frequently Identified), And A Non-Exhaust Emissions Source. Overall, This Study Demonstrates That Pm10 Concentrations In La Paz And El Alto Region Are Predominantly Influenced By A Limited Number Of Local Sources. In Conclusion, To Improve Air Quality In Both Cities, Efforts Should Primarily Focus On Addressing Dust, Traffic Emissions, Open Waste Burning, And Biomass Burning.
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Marengo, J., Espinoza, J., Bettolli, L., Cunha, A., Molina-Carpio, J., Skansi, M., et al. (2023). A Cold Wave Of Winter 2021 In Central South America: Characteristics And Impacts. Climate Dynamics, .
Abstract: During The Austral Winter (June-August) Of 2021, The Meteorological Services Of Brazil, Argentina, Peru, Paraguay, Bolivia, And Chile All Issued Forecasts For Unusually Cold Conditions. Record-Low Minimum Temperatures And Cold Spells Were Documented, Including One Strong Cold Wave Episode That Affected 5 Countries. In This Study, We Define A Cold Wave As A Period In Which Daily Maximum And Minimum Air Temperatures Are Below The Corresponding Climatological 10Th Percentile For Three Or More Consecutive Days. The Intense Cold Wave Event In The Last Week Of June, 2021, Resulted In Record-Breaking Minimum Daily Temperatures In Several Places In Central South America And Chile. Several Locations Had Temperatures About 10 Degrees C Below Average, Central South America Had Freezing Conditions, And Southern Brazil Even Saw Snow. The Cold Air Surge Was Characterized By An Intense Upper-Air Trough Located Close To 35 Degrees S And 70 Degrees W. The Southerly Flow To The West Of This Trough Brought Very Cold Air Northward Into Subtropical And Tropical South America. A Northward Flow Between The Lower-Level Cyclonic And Anticyclonic Perturbations Caused The Intense Southerly Flow Between The Upper-Level Ridge And Trough. This Condition Facilitated The Inflow Of Near-Surface Cold Air From Southern Argentina Into Southeastern Brazil And Tropical South America East Of The Andes. In The City Of Sao Paulo, The Cold Wave Caused The Death Of 13 Homeless People From Hypothermia. Frost And Snow Across Southern And Southeastern Brazil Caused Significant Damage To Coffee, Sugarcane, Oranges, Grapes, And Other Fruit And Vegetable Crops. Wine And Coffee Production Fell, The Latter By 30%, And Prices Of Food And Commodities In The Region Rose.
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Marsal, A., Slama, R., Lyon-Caen, S., Borlaza, L., Jaffrezo, J., Boudier, A., et al. (2023). Prenatal Exposure To Pm2.5 Oxidative Potential And Lung Function In Infants And Preschool- Age Children: A Prospective Study. Environmental Health Perspectives, 1311(1).
Abstract: Background: Fine Particulate Matter (Pm2.5) Has Been Found To Be Detrimental To Respiratory Health Of Children, But Few Studies Have Examined The Effects Of Prenatal Pm2.5 Oxidative Potential (Op) On Lung Function In Infants And Preschool Children.Objectives: We Estimated The Associations Of Personal Exposure To Pm2.5 And Op During Pregnancy On Offspring Objective Lung Function Parameters And Compared The Strengths Of Associations Between Both Exposure Metrics.Methods: We Used Data From 356 Mother-Child Pairs From The Sepages Cohort. Pm Filters Collected Twice During A Week Were Analyzed For Op, Using The Dithiothreitol (Dtt) And The Ascorbic Acid (Aa) Assays, Quantifying The Exposure Of Each Pregnant Woman. Lung Function Was Assessed With Tidal Breathing Analysis (Tbfvl) And Nitrogen Multiple-Breath Washout (N2Mbw) Test, Performed At 6 Wk, And Airwave Oscillometry (Aos) Performed At 3 Y. Associations Of Prenatal Pm2.5 Mass And Op With Lung Function Parameters Were Estimated Using Multiple Linear Regressions.Results: In Neonates, An Interquartile (Iqr) Increase In Opdttv (0.89 Nmol/Min/M3) Was Associated With A Decrease In Functional Residual Capacity (Frc) Measured Byn2Mbw [Beta = – 2.26 Ml; 95% Confidence Interval (Ci): -4.68, 0.15]. Associations With Pm2.5 Showed Similar Patterns In Comparison With Opdtt V But Of Smaller Magnitude. Lung Clearance Index (Lci) And Tbfvl Parameters Did Not Show Any Clear Association With The Exposures Considered. At 3 Y, Increased Frequency-Dependent Resistance Of The Lungs (Rrs7-19) From Aos Tended To Be Associated With Higher Opdtt V (Beta = 0.09 Hpa X S/L; 95% Ci: -0.06, 0.24) And Opaav (Iqr =1.14 Nmol/Min/M3; Beta = 0.12 Hpa X S/L; 95% Ci: -0.04, 0.27) But Not With Pm2.5 (Iqr = 6.9 Mu G/M3; Beta = 0.02 Hpa X S/L; 95% Ci: -0.13, 0.16). Results For Frc And Rrs7-19 Remained Similar In Op Models Adjusted On Pm2.5.Discussion: Prenatal Exposure To Opdtt V Was Associated With Several Offspring Lung Function Parameters Over Time, All Related To Lung Volumes. Https://Doi.Org/10.1289/Ehp11155
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Martin, L., Westermann, S., Magni, M., Brun, F., Fiddes, J., Lei, Y., et al. (2023). Recent Ground Thermo-Hydrological Changes In A Southern Tibetan Endorheic Catchment And Implications For Lake Level Changes. Hydrology And Earth System Sciences, 272(242), 4409–4436.
Abstract: Climate Change Modifies The Water And Energy Fluxes Between The Atmosphere And The Surface In Mountainous Regions Such As The Qinghai-Tibet Plateau (Qtp), Which Has Shown Substantial Hydrological Changes Over The Last Decades, Including Rapid Lake Level Variations. The Ground Across The Qtp Hosts Either Permafrost Or Is Seasonally Frozen, And, In This Environment, The Ground Thermal Regime Influences Liquid Water Availability, Evaporation And Runoff. Consequently, Climate-Induced Changes In The Ground Thermal Regime May Contribute To Variations In Lake Levels, But The Validity Of This Hypothesis Has Yet To Be Established.This Study Focuses On The Cryo-Hydrology Of The Catchment Of Lake Paiku (Southern Tibet) For The 1980-2019 Period. We Process Era5 Data With Downscaling And Clustering Tools (Toposcale, Toposub) To Account For The Spatial Variability Of The Climate In Our Forcing Data (Fiddes And Gruber, 2012, 2014). We Use A Distributed Setup Of The Cryogrid Community Model (Version 1.0) To Quantify Thermo-Hydrological Changes In The Ground During This Period. Forcing Data And Simulation Outputs Are Validated With Data From A Weather Station, Surface Temperature Loggers And Observations Of Lake Level Variations. Our Lake Budget Reconstruction Shows That The Main Water Input To The Lake Is Direct Precipitation (310 Mm Yr – 1 ), Followed By Glacier Runoff (280 Mm Yr – 1 ) And Land Runoff (180 Mm Yr – 1 ). However, Altogether These Components Do Not Offset Evaporation (860 Mm Yr – 1 ).Our Results Show That Both Seasonal Frozen Ground And Permafrost Have Warmed (0.17 Circle C Per Decade 2 M Deep), Increasing The Availability Of Liquid Water In The Ground And The Duration Of Seasonal Thaw. Correlations With Annual Values Suggest That Both Phenomena Promote Evaporation And Runoff. Yet, Ground Warming Drives A Strong Increase In Subsurface Runoff So That The Runoff / (Evaporation + Runoff) Ratio Increases Over Time. This Increase Likely Contributed To Stabilizing The Lake Level Decrease After 2010.Summer Evaporation Is An Important Energy Sink, And We Find Active-Layer Deepening Only Where Evaporation Is Limited. The Presence Of Permafrost Is Found To Promote Evaporation At The Expense Of Runoff, Consistently With Recent Studies Suggesting That A Shallow Active Layer Maintains Higher Water Contents Close To The Surface. However, This Relationship Seems To Be Climate Dependent, And We Show That A Colder And Wetter Climate Produces The Opposite Effect. Although The Present Study Was Performed At The Catchment Scale, We Suggest That This Ambivalent Influence Of Permafrost May Help To Understand The Contrasting Lake Level Variations Observed Between The South And North Of The Qtp, Opening New Perspectives For Future Investigations.
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Mathiot, P., & Jourdain, N. (2023). Southern Ocean Warming And Antarctic Ice Shelf Melting In Conditions Plausible By Late 23Rd Century In A High-End Scenario. Ocean Science, 191(6), 1595–1615.
Abstract: How Much Antarctic Ice Shelf Basal Melt Rates Can Increase In Response To Global Warming Remains An Open Question. Here We Describe The Response Of The Southern Ocean And Ice Shelf Cavities To An Abrupt Change To High-End Atmospheric Conditions Plausible By The Late 23Rd Century Under The Ssp5-8.5 Scenario. To Achieve This Objective, We First Present And Evaluate A New 0.25 Circle Global Configuration Of The Nemo Nucleus For European Modelling Of The Ocean Ocean And Sea Ice Model. Our Present-Day Simulations Demonstrate Good Agreement With Observational Data For Key Variables Such As Temperature, Salinity, And Ice Shelf Melt Rates, Despite The Remaining Difficulties To Simulate The Interannual Variability In The Amundsen Sea. The Ocean Response To The High-End Atmospheric Perturbation Includes A Strengthening And Extension Of The Ross And Weddell Gyres And A Quasi-Disappearance Of Sea Ice, With A Subsequent Decrease In Production Of High Salinity Shelf Water And Increased Intrusion Of Warmer Water Onto The Continental Shelves Favoured By Changes In Baroclinic Currents At The Shelf Break. We Propose To Classify The Perturbed Continental Shelf As A “Warm-Fresh Shelf”. This Induces A Substantial Increase In Ice Shelf Basal Melt Rates, Particularly In The Coldest Seas, With A Total Basal Mass Loss Rising From 1180 To 15 700 Gt Yr – 1 And An Antarctica Averaged Melt Rate Increasing From 0.8 To 10.6 M Yr – 1 . In The Perturbed Simulation, Most Ice Shelves Around Antarctica Experience Conditions That Are Currently Found In The Amundsen Sea, While The Amundsen Sea Warms By 2 Circle C. These Idealised Projections Can Be Used As A Base To Calibrate Basal Melt Parameterisations Used In Long-Term Ice Sheet Projections.
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Maure, D., Kittel, C., Lambin, C., Delhasse, A., & Fettweis, X. (2023). Spatially Heterogeneous Effect Of Climate Warming On The Arctic Land Ice. Cryosphere, 171(111), 4645–4659.
Abstract: Global Warming Has Already Substantially Altered The Arctic Cryosphere. Due To The Arctic Warming Amplification, The Temperature Is Increasing More Strongly, Leading To Pervasive Changes In This Area. Recent Years Were Notably Marked By Melt Records Over The Greenland Ice Sheet, While Other Regions Such As Svalbard Seem To Remain Less Influenced. This Raises The Question Of The Current State Of The Greenland Ice Sheet And The Various Ice Caps In The Arctic For Which Few Studies Are Available. Here, We Run The Regional Climate Model (Rcm) Modele Atmospherique Regional (Mar) At A Resolution Of 6 Km Over Four Different Domains Covering All Arctic Land Ice To Produce A Unified Surface Mass Balance Product From 1950 To The Present Day. We Also Compare Our Results To Large-Scale Indices To Better Understand The Heterogeneity Of The Evolutions Across The Arctic And Their Links To Recent Climate Change. We Find A Sharp Decrease Of Surface Mass Balance (Smb) Over The Western Arctic (Canada And Greenland) In Relationship With The Atmospheric Blocking Situations That Have Become More Frequent In Summer, Resulting In A 41 % Increase Of The Melt Rate Since 1950. This Increase Is Not Seen Over The Russian Arctic Permanent Ice Areas, Where Melt Rates Have Increased By Only 3 % On Average, Illustrating A Heterogeneity In The Arctic Smb Response To Global Warming.
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Mentani, A., Govoni, L., Bourrier, F., & Zabatta, R. (2023). Metamodelling Of The Load-Displacement Response Of Offshore Piles In Sand. Computers And Geotechnics, .
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Menut, L., Cholakian, A., Siour, G., Lapere, R., Pennel, R., Mailler, S., et al. (2023). Impact Of Landes Forest Fires On Air Quality In France During The 2022 Summer. Atmospheric Chemistry And Physics, , 728177–729677.
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Metref, S., Cosme, E., Le Lay, M., & Gailhard, J. (2023). Snow Data Assimilation For Seasonal Streamflow Supply Prediction In Mountainous Basins. Hydrology And Earth System Sciences, , 228322–229922.
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Milojevic, T., Blanchet, J., & Lehning, M. (2023). Determining Return Levels Of Extreme Daily Precipitation, Reservoir Inflow, And Dry Spells. Frontiers In Water, 5.
Abstract: Return Level Calculations Are Widely Used To Determine The Risks That Extreme Events May Pose To Infrastructure, Including Hydropower Site Operations. Extreme Events (E.G., Extreme Precipitation And Droughts) Are Expected To Increase In Frequency And Intensity In The Future, But Not Necessarily In A Homogenous Way Across Regions. This Makes Localized Assessment Important For Understanding Risk Changes To Specific Sites. However, For Sites With Relatively Small Datasets, Selecting An Applicable Method For Return Level Calculations Is Not Straightforward. This Study Focuses On The Application Of Traditional Univariate Extreme Value Approaches (Generalized Extreme Value And Generalized Pareto) As Well As Two More Recent Approaches (Extended Generalized Pareto And Metastatistical Extreme Value Distributions), That Are Specifically Suited For Application To Small Datasets. These Methods Are Used To Calculate Return Levels Of Extreme Precipitation At Six Alpine Stations And High Reservoir Inflow Events For A Hydropower Reservoir. In Addition, Return Levels Of Meteorological Drought And Low Inflow Periods (Dry Spells) Are Determined Using A Non-Parametric Approach. Return Levels For Return Periods Of 10- And 20- Years Were Calculated Using 10-, 20-, And 40- Years Of Data For Each Method. The Results Show That Even Shorter Timeseries Can Give Similar Return Levels As Longer Timeseries For Most Methods. However, The Gev Has Greater Sensitivity To Sparse Data And Tended To Give Lower Estimates For Precipitation Return Levels. The Mev Is Only To Be Preferred Over Gpd If The Underlying Distribution Fits The Data Well. The Result Is Used To Assemble A Profile Of 10- And 20-Year Return Levels Estimated With Various Statistical Approaches, For Extreme High Precipitation/Inflow And Low Precipitation/Inflow Events. The Findings Of The Study May Be Helpful To Researchers And Practitioners Alike In Deciding Which Statistical Approach To Use To Assess Local Extreme Precipitation And Inflow Risks To Individual Reservoirs.
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Molina-Carpio, J., Rivera, I., Espinoza-Romero, D., Ceron, W., Espinoza, J., & Ronchail, J. (2023). Regionalization Of Rainfall In The Upper Madeira Basin Based On Interannual And Decadal Variability: A Multi-Seasonal Approach. International Journal Of Climatology, .
Abstract: Identifying Rainfall Regions Associated With Specific Modes Of Variability Is Of Practical Interest For Water Resources Management, Seasonal Forecasting, And Mitigation Of Weather-Related Risks. This Study Aims To Identify Homogeneous Rainfall Regions Within The Similar To 1 Million Km(2) Upper Madeira River Basin-Southwestern Amazon-By Their Interannual And Decadal Variability And Relates This Variability To Ocean Indices. An Observed Dataset Of 146 Ground-Based Rainfall Stations, Distributed Throughout The Andes And The Amazon, And Homogenized At The Monthly Time-Step For The Period 1980-2016, Was Used For The Analysis. With No Spatial Constraints, Hierarchical Cluster Analysis And Principal Component Analysis (Pca) Optimally Grouped Stations Into 10 Rainfall Homogenous Regions. The Value Of The Regionalization For Interpreting The Rainfall Variability Was Evaluated By Relating The Seasonal Rainfall Time Series Of The Regions With Ocean Indices. Then, By Applying Pca To Seasonal Rainfall Series And Linking The Principal Components To Sea Surface Temperature And Ocean Indices, An Insight Into The Main Large-Scale Drivers Of The Rainfall Spatio-Temporal Variability In This Basin At Interannual And Decadal Scales Is Provided. This Analysis Identified Differences In The Year-Round Influences Of The Tropical Pacific And/Or Atlantic Oceans On The 10 Homogenous Regions.
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Molina-Carpio, J., Rivera, I., Espinoza-Romero, D., Cerón, W., Espinoza, J., & Ronchail, J. (2023). Regionalization Of Rainfall In The Upper Madeira Basin Based On Interannual And Decadal Variability: A Multi-Seasonal Approach. International Journal Of Climatology, 434(141), 6402–6419.
Abstract: Identifying Rainfall Regions Associated With Specific Modes Of Variability Is Of Practical Interest For Water Resources Management, Seasonal Forecasting, And Mitigation Of Weather-Related Risks. This Study Aims To Identify Homogeneous Rainfall Regions Within The Similar To 1 Million Km(2) Upper Madeira River Basin-Southwestern Amazon-By Their Interannual And Decadal Variability And Relates This Variability To Ocean Indices. An Observed Dataset Of 146 Groundbased Rainfall Stations, Distributed Throughout The Andes And The Amazon, And Homogenized At The Monthly Time-Step For The Period 1980-2016, Was Used For The Analysis. With No Spatial Constraints, Hierarchical Cluster Analysis And Principal Component Analysis (Pca) Optimally Grouped Stations Into 10 Rainfall Homogenous Regions. The Value Of The Regionalization For Interpreting The Rain-Fall Variability Was Evaluated By Relating The Seasonal Rainfall Time Series Of The Regions With Ocean Indices. Then, By Applying Pca To Seasonal Rainfall Series And Linking The Principal Components To Sea Surface Temperature And Ocean Indices, An Insight Into The Main Large-Scale Drivers Of The Rainfall Spatio-Temporal Variability In This Basin At Interannual And Decadal Scales Is Provided. This Analysis Identified Differences In The Year-Round Influences Of The Tropical Pacific And/Or Atlantic Oceans On The 10 Homogenous Regions.
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Morel, M., Piton, G., Kuss, D., Evin, G., & Le Bouteiller, C. (2023). Statistical Modeling Of Sediment Supply In Torrent Catchments Of The Northern French Alps. Natural Hazards And Earth System Sciences, , 176911–178711.
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Moron, V., Camberlin, P., Aellig, R., Champagne, O., Fink, A., Knippertz, P., et al. (2023). Diurnal To Interannual Variability Of Low-Level Cloud Cover Over Western Equatorial Africa In May-October. International Journal Of Climatology, .
Abstract: This Study Examines The Diurnal To Interannual Variations Of The Stratiform Cloud Cover In May-October (1971-2019) From A 3-Hourly Station Database And From Era5 Reanalyses Over Western Equatorial Africa (Wea). The Main Diurnal Variations Of The Local-Scale Fraction And Genus Of Stratiform Clouds Are Synthesized Into Three Canonical Diurnal Types (I.E., “Clear,” “Clear Afternoon,” “Cloudy” Days). The Interannual Variations Of Frequencies Of The Three Diurnal Types During The Cloudiest Months (Jjas) Are Mostly Associated With Two Main Mechanisms: A Meridional Shallow Overturning Cell Associating More “Cloudy” And Less “Clear” And “Clear Afternoon” Days To Anomalous Southerlies Below 900 Hpa Over And Around Wea, Anomalous Ascent Around 5 Degrees-7 Degrees N, Anomalous Northerlies Between 875 And 700 Hpa, And Anomalous Subsidence Over The Equatorial Atlantic. This Circulation Is Strongly Related To Interannual Variations Of The Equatorial Atlantic Upwelling (I.E., More Clouds When The Upwelling Is Strong) Associated With A Meridional Shift Of The Intertropical Convergence Zone Over The Tropical Atlantic And Adjacent Continents. The Second Mechanism Operates Mostly In The Zonal Direction And Involves Again The Coupled Ocean-Atmosphere System Over The Equatorial Atlantic, But Also The Remote El Nino-Southern Oscillation (Enso). An Anomalously Cold Equatorial Atlantic Drives Increased Low-Level Westerlies Toward The Congo Basin. Warm Enso Events Promote Broad Warm And Easterly Anomalies In The Middle And Upper Troposphere, Which Increase The Local Static Stability, And Thus The Local Stratiform Cloud Cover Over Wea. The Present Study Suggests New Mechanisms Responsible For Interannual Variations Of Stratiform Clouds In Wea, Thus Providing Avenues Of Future Research Regarding The Stability Of The Stratiform Cloud Deck Under The Ongoing Differential Warming Of Tropical Ocean And Land Masses.
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Mosbeux, C., Padman, L., Klein, E., Bromirski, P., & Fricker, H. (2023). Seasonal Variability In Antarctic Ice Shelf Velocities Forced By Sea Surfaceheight Variations. Cryosphere, , 258522–260622.
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Mouginot, J., Rabatel, A., Ducasse, E., & Millan, R. (2023). Optimization Of Cross Correlation Algorithm For Annual Mapping Of Alpine Glacier Flow Velocities; Application To Sentinel-2. Ieee Transactions On Geoscience And Remote Sensing, 616.
Abstract: Nowadays, Satellite Observations Cover Most Of The Earth'S Surface In A Repetitive Manner. This Information Is Crucial For Documenting Variability And Environmental Changes Such As Glacier Surface Velocity. With This In Mind, Digital Image Processing Has Been Developed And Improved Over The Past Decades. The Processing Challenges Are Now Related To Optimizing Parameters That Account For The High Variability Of Natural Processes, As Well As Filtering And Aggregating The Results To Provide Useful Products To End-Users. Based On The Normalized Cross Correlation (Ncc) Method Applied To Sentinel-2 Optical Satellite Observations Up To 400 Days Apart, We Present A Series Of Tests To Derive Optimal Parameter Values For The Quantification Of Alpine Glacier Ice Velocity That We Have Applied To The Mont-Blanc Massif Where In Situ Measurements Are Available. We Found That A Search Distance Adapted To The Temporal Baseline, A 16X16 Pixel Window Size, And A 5X5 Pixels Sampling Provide An Appropriate Combination Of Parameters To Process Sentinel-2 With The Ncc Method When Applied To Small Alpine Glaciers. Combining Several Spatial And Temporal Filters Applied To A Large Set Of More Than 18 000 Displacement Maps Obtained Between 2015 And 2021, Then Aggregating These Filtered Maps Using Statistical Or Linear Regressions Into Annual Maps, Yields Near-Complete Maps Of The Test Region With A Root Mean Square Error (Rmse) Reduced To About 10 M.Yr(-1) Compared To In Situ Measurements.
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Mulvaney, R., Wolff, E., Grieman, M., Hoffmann, H., Humby, J., Nehrbass-Ahles, C., et al. (2023). The St22 Chronology For The Skytrain Ice Rise Ice Core – Part 2: An Age Model To The Last Interglacial And Disturbed Deep Stratigraphy. Climate Of The Past, , 85188–86488.
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Murfitt, J., Duguay, C., Picard, G., & Gunn, G. (2023). Forward Modelling Of Synthetic Aperture Radar Backscatter From Lake Ice Over Canadian Subarctic Lakes. Remote Sensing Of Environment, 2862.
Abstract: Lake Ice Provides Important Social And Economic Services To Local Communities, In Addition To Being A Sensitive Indicator Of Climate Change. The Reduction Of Ground Observations Of Freshwater Ice Has Led To An Increased Reliance On The Use Of Satellite Remote Sensing Data. There Is Currently Interest In The Retrieval Of Lake Ice Properties (E.G., Ice Thickness, Bubble Radius, Roughness) Using Synthetic Aperture Radar (Sar). Roughness At The Ice-Water Interface Is Particularly Important As It Has Been Identified As The Dominant Mechanism For Increasing Sar Backscatter Throughout The Ice Season And Must Be Considered In Numerical Radiative Transfer Models. Therefore, This Study Determines Optimal Ice-Water Interface Roughness Height For Two Subarctic Lakes In Northern Canada And Models Backscatter Throughout Two Ice Seasons Using The Snow Microwave Radiative Transfer (Smrt) Model. The Two Lakes For This Study Are Noell Lake And Malcolm Ramsay Lake. Field Observations Of Ice Thickness, Snow Depth, Snow Density, And The Canadian Lake Ice Model (Climo) Are Used To Parameterize Smrt. Modelled L, C, And X-Band Backscatter At Different Incidence Angles Is Assessed Using Sar Imagery From Multiple Satellite Missions. Root Mean Square Errors Ranged From 0.38 To 1.45 Db For Noell Lake And 0.70 To 2.33 Db For Malcolm Ramsay Lake. Discrepancies Between Modelled And Observed Backscatter Were Found To Be Connected To The Representation Of Roughness At Different Interfaces Within The Ice Column And Changes That Occurred During Freeze-Melt Events. These Results Provide Insight Into How Changes In Ice Properties Impact Backscatter Throughout The Ice Season. Smrt Is Valuable For Modelling Backscatter From Lake Ice During The Cold Season And Could Be Used To Develop Retrieval Algorithms For Estimating Ice-Water Interface Roughness. This Would Allow For The Development Of Other Inversion Models For Retrieval Of Surface Ice Conditions And Ice Thickness.
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Nanni, U., Scherler, D., Ayoub, F., Millan, R., Herman, F., & Avouac, J. (2023). Climatic Control On Seasonal Variations In Mountain Glacier Surface Velocity. Cryosphere, 171(4), 1567–1583.
Abstract: Accurate Measurements Of Ice Flow Are Essential To Predict Future Changes In Glaciers And Ice Caps. Glacier Displacement Can In Principle Be Measured On The Large Scale By Cross-Correlation Of Satellite Images. At Weekly To Monthly Scales, The Expected Displacement Is Often Of The Same Order As The Noise For The Commonly Used Satellite Images, Complicating The Retrieval Of Accurate Glacier Velocity. Assessments Of Velocity Changes On Short Timescales And Over Complex Areas Such As Mountain Ranges Are Therefore Still Lacking But Are Essential To Better Understand How Glacier Dynamics Are Driven By Internal And External Factors. In This Study, We Take Advantage Of The Wide Availability And Redundancy Of Satellite Imagery Over The Western Pamirs To Retrieve Glacier Velocity Changes Over 10 D Intervals For 7 Years And For A Wide Range Of Glacier Geometry And Dynamics. Our Results Reveal Strong Seasonal Trends. In Spring/Summer, We Observe Velocity Increases Of Up To 300 % Compared To A Slow Winter Period. These Accelerations Clearly Migrate Upglacier Throughout The Melt Season, Which We Link To Changes In Subglacial Hydrology Efficiency. In Autumn, We Observe Glacier Accelerations That Have Rarely Been Observed Before. These Episodes Are Primarily Confined To The Upper Ablation Zone With A Clear Downglacier Migration. We Suggest That They Result From Glacier Instabilities Caused By Sudden Subglacial Pressurization In Response To (1) Supraglacial Pond Drainage And/Or (2) Gradual Closure Of The Hydrological System. Our 10 D Resolved Measurements Allow Us To Characterize The Short-Term Response Of Glaciers To Changing Meteorological And Climatic Conditions.
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Neubauer, C., Kantnerova, K., Lamothe, A., Savarino, J., Hilkert, A., Juchelka, D., et al. (2023). Discovering Nature?S Fingerprints: Isotope Ratio Analysis On Bioanalytical Mass Spectrometers. Journal Of The American Society For Mass Spectrometry, 343(4), 525–537.
Abstract: For A Generation Or More, The Mass Spectrometry That Developed At The Frontier Of Molecular Biology Was Worlds Apart From Isotope Ratio Mass Spectrometry, A Label-Free Approach Done On Optimized Gas-Source Magnetic Sector Instruments. Recent Studies Show That Electrospray-Ionization Orbitraps And Other Mass Spectrom-Eters Widely Used In The Life Sciences Can Be Fine-Tuned For High-Precision Isotope Ratio Analysis. Since Isotope Patterns Form Everywhere In Nature Based On Well-Understood Principles, Intramolecula R Isotope Measure-Ments Allow Unique Insights Into A Fascinating Range Of Research Topics. This Perspective Introduces A Wider Readership To Current Topics In Stable Isotope Research With The Aim Of Discussing How Soft-Ionization Mass Spectrometry Coupled With Ultrahigh Mass Resolution Can Enable Long-Envisioned Progress. We Highlight Novel Prospects Of Observing Isotopes In Intact Polar Compounds And Speculate On Future Directions Of This Adventure Into The Overlapping Realms Of Biology, Chemistry, And Geology.
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Nguyen, T., & Baduel, C. (2023). Optimization And Validation Of An Extraction Method For The Analysis Of Multi-Class Emerging Contaminants In Soil And Sediment. Journal Of Chromatography A, 17101.
Abstract: Analytical Methods For The Determination Of Multi-Class Emerging Contaminants Are Limited For Soil And Sediment While They Are Essential To Provide A More Complete Picture Of Their Distribution In The Environment And To Understand Their Fate In Different Environmental Compartments. In This Paper, We Present The Development And Optimization Of An Analytical Strategy That Combines Reliable Extraction, Purification And The Analysis Using Ultrapressure Liquid Chromatography Triple Quadrupole Mass Spectrometry (Uplc-Ms/Ms) Of 90 Emerging Organic Contaminants Including Pesticides, Pharmaceuticals And Personal Care Products, Flame Retardants, Per- And Polyfluoroalkyl Substances (Pfass) And Plasticizers In Soil And Sediment. To Extract A Wide Range Of Chemicals, The Extraction Strategy Is Based On The Quechers (Quick, Easy, Cheap, Effective, Rugged And Safe) Approach. A Number Of Different Options Were Investigated (Buffer, Acidification, Addition Of Edta, Different Types And Combinations Of Dispersive Spe Etc.) And The Effectiveness Of The Chemical Extraction Procedure And The Clean-Up Was Assessed For Two Matrices: Soil (Organic Matter Content Of 9%) And Sediment (Organic Matter Content Of 1.9%). The Method Was Fully Validated For Both Matrices, In Terms Of Accuracy, Linearity, Repeatability (Intraday), Reproducibility (Inter-Day), Method Limits Of Detection And Quantification (Lods And Mloqs, Respectively). The Final Performance Showed Good Accuracy And Precision (Mean Recoveries Were Between 70 And 120% With Relative Standard Deviations (Rsd) Less Than 20% In Most Cases), Low Matrix Effects, Good Linearity For The Matrixmatched Calibration Curve (R2 >= 0.991) And Mloqs Ranged From 0.25 And 10 Mu G/Kg. To Demonstrate The Applicability And Suitability Of The Validated Method, Soil And Sediment Samples From Vietnam, France, Sweden And Mexico Were Analyzed. The Results Showed That Of The 90 Target Compounds, A Total Of 33 Were Quantified In The Sediment And Soil Samples Analyzed. In Addition To Multi-Target Analysis, This Strategy Could Be Suitable For Nontarget Screening, To Provide A More Comprehensive View Of The Contaminants Present In The Samples.
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Nitzbon, J., Krinner, G., Von Deimling, T., Werner, M., & Langer, M. (2023). First Quantification Of The Permafrost Heat Sink In The Earth'S Climate System. Geophysical Research Letters, .
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Obahoundje, S., Nguessan-Bi, V., Diedhiou, A., Kravitz, B., & Moore, J. (2023). Implication Of Stratospheric Aerosol Geoengineering On Compound Precipitation And Temperature Extremes In Africa. Science Of The Total Environment, 8638.
Abstract: Three Coupled Model Intercomparison Project 5 (Cmip5) Models That Simulated The G4 Experiment Of The Geoengineering Model Intercomparison Project (Geomip) Were Used To Investigate The Impact Of Stratospheric Aerosol Injection (Sai) On Combined Temperature And Precipitation Extremes In Africa That Can Have Greater Negative Impacts On Human And The Environment Than Individual Rainfall Or Temperature Extremes. The Examined Compound Extremes Included The Dry (R-Warm Vertical Bar Dry And R-Cold Vertical Bar Dry) And Wet (R-Warm Vertical Bar Wet And R-Cold Vertical Bar Wet) Modes Assessed During The Injection (Sai, 2050-2069) And Post-Injection (Postsai, 2070-2089) Periods Compared With The Historical Period (1986-2005). We Found A Significant Projected Change In The Occurrence Of Both Wet And Dry Modes During Sai And Postsai Related To The Historical Period. The Magnitude And Sign Of This Change Depend On The Season And The Geographical Location. During The Sai And Postsai, The Wet (R-Warm Vertical Bar Wet And R-Cold Vertical Bar Wet) Modes Are Projected To Be Significantly Lower While The Dry Modes Are Noted To Increase In A Large Part Of African Continent Depending On The Season And The Geographical Location And May Consequently Leads To An Increase Of The Droughts Prone Areas. The Termination Effect Is Noted To Reduce The Occurrence Of Dry Modes, Which May Reduce The Potential Negative Effects Of The Injection After Halting. As The Effect May Vary From One Region To Another And According To The Season, It Suggested Assessing The Key Sector Impacts Of Sai. Thus, This Change In Dry Modes Due To Sai Could Affect All Activities Which Depend On Water Resources Such As Water Supply, Agriculture And Food Production, Energy Demand, And Production With Adverse Effects On Health, Security, And Sustainable Development, But This Needs To Be Assessed And Quantified At Regional Scales.
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Otosaka, I., Shepherd, A., Ivins, E., Schlegel, N., Amory, C., Van Den Broeke, M., et al. (2023). Mass Balance Of The Greenland And Antarctic Ice Sheets From 1992 To 2020. Earth System Science Data, , 159711–161611.
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Ouhechou, A., Philippon, N., Morel, B., Trentmann, J., Graillet, A., Mariscal, A., et al. (2023). Inter-Comparison And Validation Against In-Situ Measurements Of Satellite Estimates Of Incoming Solar Radiation For Central Africa: From The Annual Means To The Diurnal Cycles. Atmospheric Research, 2872.
Abstract: This Study Pictures For The First Time Incoming Solar Radiation Mean Evolution In Central Africa, Intercomparing 8 Gridded Products (Namely Ceres-Ebaf, Ceres-Syn1Deg, Tpdc, Cmsaf Sarah-2, Cmsaf Clara-A2, Cams -Jade Satellite Products, As Well As Era5 Reanalysis And Worldclim 2 Interpolated Measurements) And Station -Based Estimations (Faoclim 2) Or Measurements. At The Mean Annual Scale, All Products Picture Low Levels Of Global Horizontal Irradiance (Ghi) To The West (Sw Cameroon To Sw Republic Of Congo) And Higher Levels To-Wards The North And South Margins Of The Region. However, Ghi Levels In The Cmsaf Products Are Much Higher Than In Ceres And Tpdc. The Mean Annual Cycles Of Ghi Extracted For 6 Sub-Regions Are Bimodal, With Two Maxima During The Two Rainy Seasons (March-May And September-November) And Two Minima During The Two Dry Seasons (December-February And June-August). These Seasonal Cycles Are Well Reproduced By Most Products Except Their Amplitude Which Is Dampened In Tpdc. At The Daily And Sub-Daily Time-Scales, Products Were Compared With In-Situ Measurements From Ten Meteorological Stations Located In The Western Part Of Central Africa. The Products' Performance Is Assessed Through Scores As Bias And Rmse But Also By Considering The Diurnal Cycles' Shape, Amplitude And Frequency Of Occurrence Along The Annual Cycle. The Products Properly Reproduce The Shape Of The Four Types Of Diurnal Cycles With Nonetheless Noticeable Differences In The Cycle'S Frequencies Of Occurrence.
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Ousmane, B., Nazoumou, Y., Favreau, G., Babaye, M., Mahaman, R., Boucher, M., et al. (2023). Groundwater Quality And Its Implications For Domestic And Agricultural Water Supplies In A Semi-Arid River Basin Of Niger. Environmental Earth Sciences, .
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Ousset, I., Evin, G., Raynaud, D., & Faug, T. (2023). Back Analysis Of A Building Collapse Under Snow And Rain Loads In A Mediterranean Area. Natural Hazards And Earth System Sciences, 232(111), 3509–3523.
Abstract: At The End Of February 2018 The Mediterranean Area Of Montpellier In France Was Struck By A Significant Snowfall That Turned Into An Intense Rain Event Caused By An Exceptional Atmospheric Situation. This Rain-On-Snow Event Produced Pronounced Damage To Many Buildings Of Different Types. In This Study, We Report A Detailed Back Analysis Of The Roof Collapse Of A Large Building, Namely Irstea Cevennes. Attention Is Paid To The Dynamics Of The Climatic Event, On The One Hand, And The Mechanical Response Of The Metal Roof Structure To Different Snow And Rain Loads, On The Other Hand. The Former Aspect Relies On Multiple Sources Of Information That Provide Reliable Estimates Of Snow Heights In The Area Before The Rain Came Into Play And Substantially Modified The Load On The Roof. The Latter Aspect Relies On Detailed Finite-Element Simulations Of The Mechanical Behavior Of The Roof Structure In Order To Assess The Pressure Due To Snow And Rain Loading, Which Could Theoretically Lead To Failure. By Combining The Two Approaches, It Is Possible To Reconstruct The Most Probable Scenario For The Roof Failure Before Its Full Collapse. As An Example Of Building Behavior And Vulnerability To An Atypical Rain-On-Snow Event In The Mediterranean Area Of France, This Detailed Case Study Provides Useful Key Points To Be Considered In The Future For A Better Mitigation Of Such Events In Non-Mountainous Areas.
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Oyabu, I., Kawamura, K., Fujita, S., Inoue, R., Motoyama, H., Fukui, K., et al. (2023). Temporal Variations Of Surface Mass Balance Over The Last 5000 Years Around Dome Fuji, Dronning Maud Land, East Antarctica. Climate Of The Past, 191(2), 293–321.
Abstract: We Reconstructed Surface Mass Balance (Smb) Around Dome Fuji, Antarctica, Over The Last 5000 Years Using The Data From 15 Shallow Ice Cores And Seven Snow Pits. The Depth-Age Relationships For The Ice Cores Were Determined By Synchronizing Them With A Layer-Counted Ice Core From West Antarctica (Wais Divide Ice Core) Using Volcanic Signals. The Reconstructed Smb Records For The Last 4000 Years Show Spatial Patterns That May Be Affected By Their Locations Relative To The Ice Divides Around Dome Fuji, Proximity To The Ocean, And Wind Direction. The Smb Records From The Individual Ice Cores And Snow Pits Were Stacked To Reconstruct The Smb History In The Dome Fuji Area. The Stacked Record Exhibits A Long-Term Decreasing Trend At -0.037 +/- 0.005 Kg M(-2) Per Century Over The Last 5000 Years In The Preindustrial Period. The Decreasing Trend May Be The Result Of Long-Term Surface Cooling Over East Antarctica And The Southern Ocean And Sea Ice Expansion In The Water Vapor Source Areas. The Multidecadal To Centennial Variations Of The Dome Fuji Smb After Detrending The Record Shows Four Distinct Periods During The Last Millennium: A Mostly Negative Period Before 1300 Ce, A Slightly Positive Period From 1300 To 1450 Ce, A Slightly Negative Period From 1450 To 1850 Ce With A Weak Maximum Around 1600 Ce, And A Strong Increase After 1850 Ce. These Variations Are Consistent With Those Of Previously Reconstructed Smb Records In The East Antarctic Plateau. The Low Accumulation Rate Periods Tend To Coincide With The Combination Of Strong Volcanic Forcings And Solar Minima For The Last 1000 Years, But The Correspondence Is Not Clear For The Older Periods, Possibly Because Of The Lack Of Coincidence Of Volcanic And Solar Forcings Or The Deterioration Of The Smb Record Due To A Smaller Number Of Stacked Cores.
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Pachoud, C., Bruley, E., Grosinger, J., Crepeau, A., Salim, E., Savre, C., et al. (2023). Joint Problem Framing: A Transdisciplinary Methodology For A Sustainable Future In Mountain Areas. Sustainability Science, .
Abstract: Investigating The Sustainability Of Social-Ecological Systems In The Context Of Climatic, Economic And Social Changes Requires Novel Science Practises. Transdisciplinary Research (Tdr) Presents An Interesting Approach On How Science Can Interact With Society In Finding Meaningful Answers To Wicked Problems. Social-Ecological Systems In Mountain Areas Are Particularly Relevant Not Only Because Of Their Serious Vulnerability To Global Changes But Also Because Of Their Efforts To Move Towards Sustainability. The Researchers' Collective Perce-Neige Strives To Tackle These Challenges And Applies Novel Transdisciplinary Approaches. The Collective Is Composed Of Early Career Researchers Coming From Various Disciplines, Working On Sustainable Transitions In Mountains. For A Week, 12 Early Career Researchers Conducted Tdr For Joint Problem Framing With Inhabitants And Local Institutions Of The Municipality Of Gresse-En-Vercors In The French Alps. The Objective Was To Facilitate The Development Of A Common Vision And Initiate Collective Thinking For A Sustainable Future Of The Territoire. Participants (Researchers And Inhabitants) Became Acquainted With Each Other Through Different Interfaces Facilitating Exchanges, Reflections And Co-Constructions (Collective Walk, Individual Interviews, Participatory Workshops, Informal Daily Exchanges). The Research Allowed Us To Capture Different Perspectives On Local Issues That Cause Conflicts, And Then To Discuss And Identify Needs And Solutions. We Aim To Present And Assess The Methodology For Joint Problem Framing Developed By The Collective. This Paper Presents The Benefits Of Such A Methodology For Acculturating Early Career Researchers To Tdr, And For Framing Societal Problems And Reflecting On Actions.
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Paolini, G., Escorihuela, M., Merlin, O., Laluet, P., Bellvert, J., & Pellarin, T. (2023). Estimating Multi-Scale Irrigation Amounts Using Multi-Resolution Soil Moisture Data: A Data-Driven Approach Using Prism. Agricultural Water Management, 2902.
Abstract: Irrigated Agriculture Is The Primary Driver Of Freshwater Use And Is Continuously Expanding. Precise Knowledge Of Irrigation Amounts Is Critical For Optimizing Water Management, Especially In Semi-Arid Regions Where Water Is A Limited Resource. This Study Proposed To Adapt The Prism (Precipitation Inferred From Soil Moisture) Method-Ology To Detect And Estimate Irrigation Events From Soil Moisture Remotely Sensed Data. Prism Was Originally Conceived To Correct Precipitation Products, Assimilating Soil Moisture (Sm) Observations Into An Antecedent Precipitation Index (Api) Formula, Using A Particle Filter Scheme. This Novel Application Of Prism Uses Initial Precipitation And Sm Observations To Detect Instances Of Water Excess In The Soil (Not Caused By Precipitation) And Estimates The Amount Of Irrigation, Along With Its Uncertainty. This Newly Proposed Approach Does Not Require Extensive Calibration And Is Adaptable To Different Spatial And Temporal Scales. The Objective Of This Study Was To Analyze The Performance Of Prism For Irrigation Amount Estimation And Compare It With Current State-Of-The-Art Approaches. To Develop And Test This Methodology, A Synthetic Study Was Conducted Using Sm Observations With Various Noise Levels To Simulate Uncertainties And Different Spatial And Temporal Resolutions. The Results Indicated That A High Temporal Resolution (Less Than 3 Days) Is Crucial To Avoid Underestimating Irrigation Amounts Due To Missing Events. However, Including A Constraint On The Frequency Of Irrigation Events, Deduced From The System Of Irrigation Used At The Field Level, Could Overcome The Limitation Of Low Temporal Resolution And Significantly Reduce Underestimation Of Irrigation Amounts. Subsequently, The Developed Methodology Was Applied To Actual Satellite Sm Products At Different Spatial Scales (1 Km And 100 M) Over The Same Area. Validation Was Performed Using In Situ Data At The District Level Of Algerri-Balaguer In Catalunya, Spain, Where In Situ Irrigation Amounts Were Available For Various Years. The Validation Resulted In A Total Pearson'S Correlation Coefficient (R) Of 0.80 And A Total Root Mean Square Error (Rmse) Of 7.19 Mm/Week For The Years From 2017 To 2021. Additional Vali-Dation Was Conducted At The Field Level In The Segarra-Garrigues Irrigation District Using In Situ Data From A Field Where Sm Profiles And Irrigation Amounts Were Continuously Monitored. This Validation Yielded A Total Bi-Weekly R Of 0.81 And A Total Rmse Of-9.34 Mm/14-Days For The Years From 2017 To 2021. Overall, The Results Suggested That Prism Can Effectively Estimate Irrigation From Sm Remote Sensing Data, And The Methodology Has The Po-Tential To Be Applied On A Large Scale Without Requiring Extensive Calibration Or Site-Specific Knowledge.
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Piantini, M., Gimbert, F., Korkolis, E., Rousseau, R., Bellot, H., & Recking, A. (2023). Solid Concentration As A Main Proxy For Basal Force Fluctuations Generated By Highly Concentrated Sediment Flows. Geophysical Research Letters, 505(1).
Abstract: Sediment Flows Generate Ground Vibrations By Exerting Force Fluctuations On The Riverbed. Linking Force Fluctuations To Properties Of Highly Concentrated Sediment Flows, However, Remains Particularly Challenging Due To Complexities Arising From Grain-To-Grain Interactions. Here, We Conduct Downscaled Flume Experiments In Which We Specifically Measure Force Fluctuations And Local Seismic Vibrations Together With Flow Properties Of Highly Concentrated Sediment Flows At High Spatial And Temporal Resolution. We Observe Hysteresis Behaviors Between Force Fluctuations Amplitude And Flow Surface Elevation And Mass That Occur During Complex Changes In Internal Flow Dynamics. By Contrast, Force Fluctuations Amplitude Exhibits A Unique Negative Relationship With Solid Concentration. We Suggest This Is Due To The Rheology Of Dense Granular Flows, Where Solid Concentration Is A Proxy For Particle Agitation. We Therefore Advance That Solid Concentration Should Be Incorporated In Seismic Models Of Such Sediment Flows As A Key Parameter Describing Inter-Particle Collisions And Impacts To The Bed.
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Piantini, M., Gimbert, F., Korkolis, E., Rousseau, R., Bellot, H., & Recking, A. (2023). Solid Concentration As A Main Proxy For Basal Force Fluctuations Generated By Highly Concentrated Sediment Flows. Geophysical Research Letters, .
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Pimentel, R., Arheimer, B., Crochemore, L., Andersson, J., Pechlivanidis, I., & Gustafsson, D. (2023). Which Potential Evapotranspiration Formula To Use In Hydrological Modeling World-Wide? Water Resources Research, .
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Pimentel, R., Crochemore, L., Andersson, J., & Arheimer, B. (2023). Assessing Robustness In Global Hydrological Predictions By Comparing Modelling And Earth Observations. Hydrological Sciences Journal, .
Abstract: Hydrological Modelling To Support Hypotheses On Earth System Boundaries Or The Accelerating Water Crisis Is Nowadays Done At The Global Scale, With Difficulties Associated To Model Uncertainties. Here We Bring A Robustness Analysis Of Internal Model Variables As An Additional Tool For Model Evaluation Using Data From Six Earth Observation Products And The Global Catchment Model World-Wide Hype In A Comparative Study. The Assessment Shows That: (I) Variables Have High Agreement In Mid-Latitude Temperate Regions; (Ii) The Variables With Higher Agreement, And Associated With Good Model Performance In Streamflow, Were Actual Evapotranspiration, Fractional Snow Cover And Snow Water Equivalent; And (Iii) Changes In Total Water Storage Showed Very Poor Agreement, Probably Due To An Insufficient Number Of Aquifers In The Model Set-Up. We Propose This Procedure As A Standard Complementary Method In Global Hydrological Modelling, Highlighting The Importance Of Justifying Models Before Using Them For Scenario Analysis Or Water Accounting.
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Piton, G., Mayo, A., & Lambert, S. (2023). Small-Scale Modeling Of Flexible Barriers. Ii: Interactions With Large Wood. Journal Of Hydraulic Engineering, 1491(3).
Abstract: During Strong Floods, Rivers Often Carry Significant Amounts Of Sediment And Pieces Of Large Wood (Lw). When Bridges And Hydraulic Structures Are Unable To Allow Lw To Pass Through, It Becomes Necessary To Trap Lw Through Specific Wood Retention Structures (E.G., Flexible Barriers). This Paper Presents A Comprehensive Analysis Of The Interactions Between Lw And Flexible Barriers Using Small Scale Models. A Dimensionless Criterion Is First Proposed To Compute Blockage Probability Of Single Logs. It Is Based On Experiments Varying Log Size And Shape, Channel Slope (2%, 4%, And 6%), Water Discharge, And Barrier Bottom Clearance. Based On Runs Using Six Mixtures Of Hundreds Of Logs, An Equation Is Secondly Provided To Compute Flow Depth At A Barrier Accounting For The Head Losses Related To Large Numbers Of Logs. Conditions Leading To The Release Of Lw When The Barrier Is Severely Overwhelmed Are Also Studied. The Deformation Measured On The Barrier Proves To Be Lower With Lw-Laden Flows Than Under Full Hydrostatic Loading Of A Barrier Obstructed By A Plastic Sheet. Overall, We Demonstrate That Flexible Barriers Are Very Relevant Structures To Trap Lw. A Companion Paper Shows How To Design And Manufacture A Small Scale Flexible Barrier In Mechanical Similitude With The Prototype Scale.
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Pohl, B., Prince, H., Wille, J., Kingston, D., Cullen, N., & Fauchereau, N. (2023). Atmospheric Rivers And Weather Types In Aotearoa New Zealand: A Two-Way Story. Journal Of Geophysical Research-Atmospheres, 1281(151).
Abstract: Here, We Analyze The Inter-Relationships Between Weather Types (Wts) And Atmospheric Rivers (Ars) Around Aotearoa New Zealand (Anz), Their Respective Properties, As Well As Their Combined And Separate Influence On Daily Precipitation Amounts And Extremes. Results Show That Ars Are Often Associated With 3-4 Wts, But These Wts Change Depending On The Regions Where Ars Landfall. The Wts Most Frequently Associated With Ars Generally Correspond To Those Favoring Anomalously Strong Westerly Wind In The Mid-Latitudes, Especially For Southern Regions Of Anz, Or Northwesterly Anomalies Favoring Moisture Export From The Lower Latitudes, Especially For The Northern Regions. Wts And Ars Show Strong Within-Type And Inter-Event Diversity. The Synoptic Patterns Of The Wts Significantly Differ When They Are Associated With Ar Occurrences, With Atmospheric Centers Of Actions Being Shifted So That Moisture Fluxes Toward Anz Are Enhanced. The Location, Angle, And Persistence Of Ars Appear Strongly Driven By The Synoptic Configurations Of The Wts. Although Total Moisture Transport Shows Weaker Wt-Dependency, It Appears Strongly Related To Zonal Wind Speed To The South Of Anz, Or The Moisture Content Of The Air Mass To The North. Finally, Wt Influence On Daily Precipitation May Completely Change Depending On Their Association, Or Lack Thereof, With Ar Events. Wts Traditionally Considered As Favorable To Wet Conditions May Conceal Daily Precipitation Extremes Occurring During Ar Days, And Anomalously Dry Days Or Near-Climatological Conditions During Non-Ar Days.
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Polton, J., Harle, J., Holt, J., Katavouta, A., Partridge, D., Jardine, J., et al. (2023). Reproducible And Relocatable Regional Ocean Modelling: Fundamentals And Practices. Geoscientific Model Development, 161(5), 1481–1510.
Abstract: In Response To An Increasing Demand For Bespoke Or Tailored Regional Ocean Modelling Configurations, We Outline Fundamental Principles And Practices That Can Expedite The Process To Generate New Configurations. The Paper Develops The Principle Of Reproducibility And Advocates Adherence By Presenting Benefits To The Community And User. The Elements Of This Principle Are Reproducible Workflows And Standardised Assessment, With Additional Effort Over Existing Working Practices Being Balanced Against The Added Value Generated. The Paper Then Decomposes The Complex Build Process, For A New Regional Ocean Configuration, Into Stages And Presents Guidance, Advice And Insight For Each Component. This Advice Is Compiled From Across The Nemo (Nucleus For European Modelling Of The Ocean) User Community And Sets Out Principles And Practises That Encompass Regional Ocean Modelling With Any Model. With Detailed And Region-Specific Worked Examples In Sects. 3 And 4, The Linked Companion Repositories And Dois All Target Nemov4. The Aim Of This Review And Perspective Paper Is To Broaden The User Community Skill Base And To Accelerate Development Of New Configurations In Order To Increase The Time Available For Exploiting The Configurations.
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Rabatel, A., Ducasse, E., Millan, R., & Mouginot, J. (2023). Satellite-Derived Annual Glacier Surface Flow Velocity Products For The European Alps, 2015-2021. Data, .
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Rabatel, A., Ducasse, E., Ramseyer, V., & Millan, R. (2023). State And Fate Of Glaciers In The Val Veny (Mont- Blanc Range, Italy): Contribution Of Optical Satellite Products. Revue De Geographie Alpine-Journal Of Alpine Research, 1111(2).
Abstract: The Glaciers Of The Val Veny (Italian Side Of The Mont-Blanc Massif) Have Been The Site Of Numerous Field Observations During The Last Decades, In Particular For The Study Of Glacial Fluctuations Or Surface Processes Related To The Debris Cover. Here, We Propose To Examine How Satellite Observations Can Complement Field Measurements On The State And Fate Of The Val Veny Glaciers. Indeed, Satellite Products Obtained In A Quasi-Systematic Way Allow To Account Not Only For The Loss Of Surface And Volume, But Also For The Changes In Their Flow Velocities. The Overall Pattern We Document Is A Glacier Thinning And Slowdown Of The Ice Flow, With An Estimated Shrinkage Of 25% By 2050 And A Volume Loss Ranging Between 30 And 43% Depending On The Data Source Used For The Estimation Of The Initial Volume. In Such A Context, A Portion Of The Upper Reaches Of Brenva Glacier Shows An Unexpected Pattern Of Thickening And Increase In Ice Flow That Rises Questions On Its Origin. Finally, The Uncertainties In The Estimation Of Ice Thicknesses Remain Important And Have Repercussions On The Future Evolution Of The Glaciers And Their Contribution From A Hydrological Point Of View. By 2050, We Estimate That The Water Contribution Due To The Volume Loss Of Val Veny Glaciers Could Decrease By 40%.
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Ravanel, L., Duvillard, P., Astrade, L., Faug, T., Deline, P., Berthet, J., et al. (2023). The Taconnaz Rockfall (Mont-Blanc Massif, European Alps) Of November 2018: A Complex And At-Risk Rockwall-Glacier-Torrent Morphodynamic Continuum. Applied Sciences-Basel, 131(171).
Abstract: The Glacial And Torrential Basin Of Taconnaz (Mont-Blanc Massif, France) Dominates The Chamonix Valley. It Is One Of The Major Paths For Snow Avalanches In The Alps, Often Triggered By Serac Falls From The Taconnaz Glacier. On 24 November 2018, The Basin'S Multi-Risk Nature Was Further Accentuated By A New Type Of Hazard With A Rockfall Triggered At C. 2700 M A.S.L. It Travelled Down Over A Distance Of 1.85 Km And Stopped 165 M Away From The Construction Site Of A Micro-Hydroelectric Power Station. We Studied The Triggering Conditions At The Permafrost Lower Limit, The Effects Of The Supra-Glacial Path On The Flow Patterns, And The Fate Of The Scar And The Deposit On Torrential Activity. By Comparing A Pre-Event Structure From Motion Model With A Post-Event Lidar Model, We Estimated The Volume Of The Scar To Be 42,900 M3 (& Plusmn;5%). A Numerical Model Was Employed To Simulate The Rapid Runout. It Revealed The Complexity Of The Flow, Attributed To The Sequestration Of A Part Of The Deposit In Crevasses, The Incorporation Of A Significant Volume Of Ice Resulting In A Transition From A Dry Granular Flow To A Mud-Like Flow, And The Presence Of Numerous Deposit Zones. Subsequent Monitoring Of The Area After The Event Allowed For The Documentation Of The Scar'S Evolution, Including A Landslide, As Well As The Progressive Degradation And Evacuation Of The Deposit By The Torrent Without Producing Debris Flow. The Study Of The Triggering Factors Indicated Glacial Retreat As The Probable Main Cause, Assisted By The Melting Of Ice Lenses Left By The Permafrost Disappearance. Finally, We Present Replicable Methods For Managing Risks At The Site Following The Event. This Event Improves The Understanding Of Cascading Processes That Increasingly Impact Alpine Areas In The Context Of Climate Change.
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Ravanel, L., Guillet, G., Kaushik, S., Preunkert, S., Malet, E., Magnin, F., et al. (2023). Ice Aprons On Steep High-Alpine Slopes: Insights From The Mont-Blanc Massif, Western Alps. Journal Of Glaciology, .
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Recking, A., Tarrio, D., & Piton, G. (2023). The Contribution Of Grain Sorting To The Dynamics Of The Bedload Active Layer. Earth Surface Processes And Landforms, .
Abstract: During The Last 20 Years, Flume And Field Experiments Have Shown That Grain Sorting Contributes To Bed-Level Fluctuations And Bedload Pulses. In This Work, We Propose A New Analysis Of These Experimental Data. From The Flume Data, We Derive A Model For Gravel-Bed Rivers Where Both Local (Bedform-Scale) Slope And Bedload Are Known To Fluctuate Through Space And Time, In The So-Called 'Bedload Active Layer'. The Model Uses Standard Concepts And Empirical Tools With Reach-Averaged Data For The Hydraulics And Sediment Transport. It Considers A Maximum Slope For Local Armouring Equal To The Mean Bed Slope (Reach Scale) Affected By A Coefficient Which Expresses The Difference In Mobility Of The Coarse Fraction Considered Alone Or In A Mixture. The Minimum Local Slope For Bed Erosion Is The Mean Bed Slope Corrected By A Coefficient That Depends On The Armour Ratio A(R) (Ratio Of The Surface To The Subsurface Grain Diameter) And The Reach-Averaged Transport Rate. The Model Is Compared With A Compilation Of Scour-Fill Depths Measured In The Field. Results Suggests That The Slope Fluctuations In 1D Flume Experiments Are Consistent With In-Channel Bed-Level Fluctuations Associated With Scour-Fill Processes In The Active Layer. The Model Also Suggests That Although The Length Scale Of The Maximum Scour Depth Delta Is On The Order Of The Bed Surface D-90, It Is Well Explained By The Product Between The Mean Bed Slope S And The Active Channel Width W, With Delta Approximate To 1.4Sw. For The Pulse Intensity, We Provide A Justification For The Simplified Squared Slope Equation For Solid Concentration C = Q(S)/Q Proportional To S-2 (With Q(S) The Solid Discharge, Q The Water Discharge And S The Slope), Which Has Often Been Used In Place Of Standard Bedload Equations For Modelling Highly Concentrated Bedload Transport Events In Mountain Streams.
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Reese, R., Garbe, J., Hill, E., Urruty, B., Naughten, K., Gagliardini, O., et al. (2023). The Stability Of Present-Day Antarctic Grounding Lines – Part 2: Onset Of Irreversible Retreat Of Amundsen Sea Glaciers Under Current Climate On Centennial Timescales Cannot Be Excluded. Cryosphere, 171(9), 3761–3783.
Abstract: Observations Of Ocean-Driven Grounding-Line Retreat In The Amundsen Sea Embayment In Antarctica Raise The Question Of An Imminent Collapse Of The West Antarctic Ice Sheet. Here We Analyse The Committed Evolution Of Antarctic Grounding Lines Under The Present-Day Climate. To This Aim, We First Calibrate A Sub-Shelf Melt Parameterization, Which Is Derived From An Ocean Box Model, With Observed And Modelled Melt Sensitivities To Ocean Temperature Changes, Making It Suitable For Present-Day Simulations And Future Sea Level Projections. Using The New Calibration, We Run An Ensemble Of Historical Simulations From 1850 To 2015 With A State-Of-The-Art Ice Sheet Model To Create Model Instances Of Possible Present-Day Ice Sheet Configurations. Then, We Extend The Simulations For Another 10 000 Years To Investigate Their Evolution Under Constant Present-Day Climate Forcing And Bathymetry. We Test For Reversibility Of Grounding-Line Movement In The Case That Large-Scale Retreat Occurs. In The Amundsen Sea Embayment We Find Irreversible Retreat Of The Thwaites Glacier For All Our Parameter Combinations And Irreversible Retreat Of The Pine Island Glacier For Some Admissible Parameter Combinations. Importantly, An Irreversible Collapse In The Amundsen Sea Embayment Sector Is Initiated At The Earliest Between 300 And 500 Years In Our Simulations And Is Not Inevitable Yet – As Also Shown In Our Companion Paper Part 1,. In Other Words, The Region Has Not Tipped Yet. With The Assumption Of Constant Present-Day Climate, The Collapse Evolves On Millennial Timescales, With A Maximum Rate Of 0.9 Mma-1 Sea-Level-Equivalent Ice Volume Loss. The Contribution To Sea Level By 2300 Is Limited To 8 Cm With A Maximum Rate Of 0.4 Mma-1 Sea-Level-Equivalent Ice Volume Loss. Furthermore, When Allowing Ice Shelves To Regrow To Their Present Geometry, We Find That Large-Scale Grounding-Line Retreat Into Marine Basins Upstream Of The Filchner-Ronne Ice Shelf And The Western Siple Coast Is Reversible. Other Grounding Lines Remain Close To Their Current Positions In All Configurations Under Present-Day Climate.
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Reuter, B., Hagenmuller, P., & Eckert, N. (2023). Snow And Avalanche Climates In The French Alps Using Avalanche Problem Frequencies. Journal Of Glaciology, .
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Robledano, A., Picard, G., Dumont, M., Flin, F., Arnaud, L., & Libois, Q. (2023). Unraveling The Optical Shape Of Snow. Nature Communications, 141(1).
Abstract: The Reflection Of Sunlight Off The Snow Is A Major Driver Of The Earth'S Climate. This Reflection Is Governed By The Shape And Arrangement Of Ice Crystals At The Micrometer Scale, Called Snow Microstructure. However, Snow Optical Models Overlook The Complexity Of This Microstructure By Using Simple Shapes, And Mainly Spheres. The Use Of These Various Shapes Leads To Large Uncertainties In Climate Modeling, Which Could Reach 1.2 K In Global Air Temperature. Here, We Accurately Simulate Light Propagation In Three-Dimensional Images Of Natural Snow At The Micrometer Scale, Revealing The Optical Shape Of Snow. This Optical Shape Is Neither Spherical Nor Close To The Other Idealized Shapes Commonly Used In Models. Instead, It More Closely Approximates A Collection Of Convex Particles Without Symmetry. Besides Providing A More Realistic Representation Of Snow In The Visible And Near-Infrared Spectral Region (400 To 1400 Nm), This Breakthrough Can Be Directly Used In Climate Models, Reducing By 3 The Uncertainties In Global Air Temperature Related To The Optical Shape Of Snow. Micrometre Scale Simulation Of The Trajectory Of Sunlight As It Reaches The Snowpack Shows What Snow Looks Like From The Photon'S Perspective, Providing A More Universal Representation Of Snow In Optical Models.
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Ruiz-Villanueva, V., Piégay, H., Scorpio, V., Bachmann, A., Brousse, G., Cavalli, M., et al. (2023). River Widening In Mountain And Foothill Areas During Floods: Insights From A Meta-Analysis Of 51 European Rivers. Science Of The Total Environment, 9039.
Abstract: River Widening, Defined As A Lateral Expansion Of The Channel, Is A Critical Process That Maintains Fluvial Ecosystems And Is Part Of The Regular Functioning Of Rivers. However, In Areas With High Population Density, Channel Widening Can Cause Damage During Floods. Therefore, For Effective Flood Risk Management It Is Essential To Identify River Reaches Where Abrupt Channel Widening May Occur. Despite Numerous Efforts To Predict Channel Widening, Most Studies Have Been Limited To Single Rivers And Single Flood Events, Which May Not Be Representative Of Other Conditions. Moreover, A Multi-Catchment Scale Approach That Covers Various Settings And Flood Magnitudes Has Been Lacking. In This Study, We Fill This Gap By Compiling A Large Database Comprising 1564 River Reaches In Several Mountain Regions In Europe Affected By Floods Of Varying Magnitudes In The Last Six Decades. By Applying A Meta-Analysis, We Aimed To Identify The Types Of Floods Responsible For More Extensive Widening, The River Reach Types Where Intense Widening Is More Likely To Occur, And The Hydraulic And Morphological Variables That Explain Widening And Can Aid In Predicting Widening. Our Analysis Revealed Seven Groups Of Reaches With Significantly Different Responses To Floods Regarding Width Ratios (I.E., The Ratio Between Channel Width After And Before A Flood). Among These Groups, The River Reaches Located In The Mediterranean Region And Affected By Extreme Floods Triggered By Short And Intense Precipitation Events Showed Significantly Larger Widening Than Other River Reaches In Other Regions. Additionally, The Meta-Analysis Confirmed Valley Confinement As A Critical Morphological Variable That Controls Channel Widening But Showed That It Is Not The Only Controlling Factor. We Proposed New Statistical Models To Identify River Reaches Prone To Widening, Estimate Potential Channel Width After A Flood, And Compute Upper Bound Width Ratios. These Findings Can Inform Flood Hazard Evaluations And The Design Of Mitigation Measures.
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Ruyer-Quil, C., Bresch, D., Gisclon, M., Richard, G., Kessar, M., & Cellier, N. (2023). Sliding And Merging Of Strongly Sheared Droplets. Journal Of Fluid Mechanics, 9729.
Abstract: A Mathematical And Numerical Framework Is Proposed To Compute The Displacement And Merging Dynamics Of Sliding Droplets Under The Action Of A Constant Shear Exerted By A Gas Flow. An Augmented Formulation Is Implemented To Model Surface Tension Including The Full Curvature Of The Free Surface. A Set Of Shallow-Water Evolution Equations Is Obtained For The Film Thickness, The Averaged Velocity, An Additional Quantity (With Dimension Of A Velocity) Taking Into Account The Capillary Effects And A Tensor Called Enstrophy. The Enstrophy Accounts For The Deviation Of The Velocity Profile From A Constant Velocity Distribution. The Formulation Is Consistent With The Long-Wave Expansion Of The Basic Equations With A Conservative Part And Source Terms Including The Effect Of Viscosity, In The Form Of A Viscous Friction And The Effect Of The Shear Stress. The Model Is Hyperbolic With Generalised Diffusion Terms Due To Capillarity. Finally, Our Model Is Completed With A Disjoining Pressure Formulation That Is Able To Account For The Hysteresis Of The Static Contact Angle. In This Formulation, The Advancing Or Receding Nature Of The Contact Line Is Assessed By The Accumulation Or Reduction Of Mass Of The Droplet At The Contact Line. Simulations Of Sliding Water Droplets Are Performed With Periodic Boundary Conditions In A Domain Of Limited Size. Hysteresis Of The Static Contact Angle Causes A Slowdown Of The Drops And A Delay In The Sequence Of Coalescence Of The Drops.
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Schaafsma, M., Ahn, S., Castro, A., Dendoncker, N., Filyushkina, A., González-Jiménez, D., et al. (2023). Whose Values Count? A Review Of The Nature Valuation Studies With A Focus On Justice. Current Opinion In Environmental Sustainability, 646.
Abstract: The Values Assessment Of The Intergovernmental Science -Policy Platform On Biodiversity And Ecosystem Services Shows That Multiple Valuation Methods And Approaches Exist To Assess Diverse Value Types. The Evidence Is Based On The Largest Review Of Academic Valuation Studies On Nature To Date, Developed For The Values Assessment Of The Intergovernmental Science-Policy Platform On Biodiversity And Ecosystem Services (Ipbes). We Evaluate Studies According To Environmental Justice Criteria. The Results Suggest That Although Diverse Value Types And Indicators Are Assessed Across Studies, Few Individual Studies Are Plural, And Studies Fail To Provide Evidence On Distributive Justice And Score Low On Procedural Justice Indicators. We Provide A Set Of Recommendations For Incorporating Issues Of Justice In The Design Of Valuation Studies.
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Sedakov, R., Osadchiev, A., Barnier, B., Molines, J., & Colombo, P. (2023). Large Chocked Lagoon As A Barrier For River-Sea Flux Of Dissolved Pollutants: Case Study Of The Azov Sea And The Black Sea. Marine Pollution Bulletin, 1871.
Abstract: The Don River Is Among The Largest Rivers In The Eastern Europe And Is Heavily Polluted. This River Inflows Into Small And Semi-Isolated Sea Of Azov, Which Is Connected With The Black Sea By A Narrow Strait. Generally, The Sea Of Azov Is A Large Choked Lagoon, Which Serves As A Barrier For River-Borne Constituents. Using Numerical Modeling, We Reveal That Presence Of The Choked Lagoon Significantly Slows Down The Estuary-Seawater Flux Of Dissolved Pollutants And Slackens Its Discharge-Induced Seasonal Variability. In Particular, The Sea Of Azov Delays The 5 % And 95 % Of The Total Flux Of Riverine Pollution To The Black Sea By 9 And 36 Months, Respectively. The Obtained Results Are Important For Assessment The Influence Of Background And Emergency Pollution Accidents At The Don River On Water Quality In The Study Region. Moreover, These Results Could Be Applied To Many Other Chocked Lagoons In The World Ocean.
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Seroussi, H., Verjans, V., Nowicki, S., Payne, A., Goelzer, H., Lipscomb, W., et al. (2023). Insights Into The Vulnerability Of Antarctic Glaciers From The Ismip6 Ice Sheet Model Ensemble And Associated Uncertainty. Cryosphere, 171(121), 5197–5217.
Abstract: The Antarctic Ice Sheet Represents The Largest Source Of Uncertainty In Future Sea Level Rise Projections, With A Contribution To Sea Level By 2100 Ranging From – 5 To 43 Cm Of Sea Level Equivalent Under High Carbon Emission Scenarios Estimated By The Recent Ice Sheet Model Intercomparison For Cmip6 (Ismip6). Ismip6 Highlighted The Different Behaviors Of The East And West Antarctic Ice Sheets, As Well As The Possible Role Of Increased Surface Mass Balance In Offsetting The Dynamic Ice Loss In Response To Changing Oceanic Conditions In Ice Shelf Cavities. However, The Detailed Contribution Of Individual Glaciers, As Well As The Partitioning Of Uncertainty Associated With This Ensemble, Have Not Yet Been Investigated. Here, We Analyze The Ismip6 Results For High Carbon Emission Scenarios, Focusing On Key Glaciers Around The Antarctic Ice Sheet, And We Quantify Their Projected Dynamic Mass Loss, Defined Here As Mass Loss Through Increased Ice Discharge Into The Ocean In Response To Changing Oceanic Conditions. We Highlight Glaciers Contributing The Most To Sea Level Rise, As Well As Their Vulnerability To Changes In Oceanic Conditions. We Then Investigate The Different Sources Of Uncertainty And Their Relative Role In Projections, For The Entire Continent And For Key Individual Glaciers. We Show That, In Addition To Thwaites And Pine Island Glaciers In West Antarctica, Totten And Moscow University Glaciers In East Antarctica Present Comparable Future Dynamic Mass Loss And High Sensitivity To Ice Shelf Basal Melt. The Overall Uncertainty In Additional Dynamic Mass Loss In Response To Changing Oceanic Conditions, Compared To A Scenario With Constant Oceanic Conditions, Is Dominated By The Choice Of Ice Sheet Model, Accounting For 52 % Of The Total Uncertainty Of The Antarctic Dynamic Mass Loss In 2100. Its Relative Role For The Most Dynamic Glaciers Varies Between 14 % For Macayeal And Whillans Ice Streams And 56 % For Pine Island Glacier At The End Of The Century. The Uncertainty Associated With The Choice Of Climate Model Increases Over Time And Reaches 13 % Of The Uncertainty By 2100 For The Antarctic Ice Sheet But Varies Between 4 % For Thwaites Glacier And 53 % For Whillans Ice Stream. The Uncertainty Associated With The Ice-Climate Interaction, Which Captures Different Treatments Of Oceanic Forcings Such As The Choice Of Melt Parameterization, Its Calibration, And Simulated Ice Shelf Geometries, Accounts For 22 % Of The Uncertainty At The Ice Sheet Scale But Reaches 36 % And 39 % For Institute Ice Stream And Thwaites Glacier, Respectively, By 2100. Overall, This Study Helps Inform Future Research By Highlighting The Sectors Of The Ice Sheet Most Vulnerable To Oceanic Warming Over The 21St Century And By Quantifying The Main Sources Of Uncertainty.
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Servettaz, A., Agosta, C., Kittel, C., & Orsi, A. (2023). Control Of The Temperature Signal In Antarctic Proxies By Snowfall Dynamics. Cryosphere, 171(121), 5373–5389.
Abstract: Antarctica, The Coldest And Driest Continent, Is Home To The Largest Ice Sheet, Whose Mass Is Predominantly Recharged By Snowfall. A Common Feature Of Polar Regions Is The Warming Associated With Snowfall, As Moist Oceanic Air And Cloud Cover Increase The Surface Temperature. Consequently, Snow That Accumulates On The Ice Sheet Is Deposited Under Unusually Warm Conditions. Here We Use A Polar-Oriented Regional Atmospheric Model To Study The Statistical Difference Between Average And Snowfall-Weighted Temperatures. During Snowfall, The Warm Anomaly Scales With Snowfall Amount, With The Strongest Sensitivity Occurring At Low-Accumulation Sites. Heavier Snowfall In Winter Helps To Decrease The Annual Snowfall-Weighted Temperature, But This Effect Is Overwritten By The Event-Scale Warming Associated With Precipitating Atmospheric Systems, Which Particularly Contrast With The Extremely Cold Conditions That Occur In Winter. Consequently, The Seasonal Range Of Snowfall-Weighted Temperature Is Reduced By 20 %. On The Other Hand, The Annual Snowfall-Weighted Temperature Shows 80 % More Interannual Variability Than The Annual Temperature Due To The Irregularity Of Snowfall Occurrence And Its Associated Temperature Anomaly. Disturbances Of The Apparent Annual Temperature Cycle And Interannual Variability Have Important Consequences For The Interpretation Of Water Isotopes In Precipitation, Which Are Deposited With Snowfall And Commonly Used For Paleotemperature Reconstructions From Ice Cores.
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Servettaz, A., Orsi, A., Curran, M., Moy, A., Landais, A., Mcconnell, J., et al. (2023). A 2000-Year Temperature Reconstruction On The East Antarctic Plateau From Argon-Nitrogen And Water Stable Isotopes In The Aurora Basin North Ice Core. Climate Of The Past, , 112511–115211.
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Sherpa, T., Matthews, T., Perry, L., Thapa, A., Singh, P., Khadka, A., et al. (2023). Insights From The First Winter Weather Observations Near Mount Everest'S Summit. Weather, .
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Sherpa, T., Matthews, T., Perry, L., Thapa, A., Singh, P., Khadka, A., et al. (2023). Insights From The First Winter Weather Observations Near Mount Everest'S Summit. Weather, 787(121), 344–348.
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Sicart, J., Ramseyer, V., Picard, G., Arnaud, L., Coulaud, C., Freche, G., et al. (2023). Snow Accumulation And Ablation Measurements In A Midlatitude Mountain Coniferous Forest (Col De Porte, France, 1325 M Altitude): The Snow Under Forest (Snouf) Field Campaign Data Set. Earth System Science Data, 151(111), 5121–5133.
Abstract: Forests Strongly Modify The Accumulation, Metamorphism And Melting Of Snow In Midlatitude And High-Latitude Regions. Recently, Snow Routines In Hydrological And Land Surface Models Were Improved To Incorporate More Accurate Representations Of Forest Snow Processes, But Model Intercomparison Projects Have Identified Deficiencies, Partly Due To Incomplete Knowledge Of The Processes Controlling Snow Cover In Forests. The Snow Under Forest (Snouf) Project Was Initiated To Enhance Knowledge Of The Complex Interactions Between Snow And Vegetation. Two Field Campaigns, During The Winters 2016-2017 And 2017-2018, Were Conducted In A Coniferous Forest Bordering The Snow Study At Col De Porte (1325 M A.S.L., French Alps) To Document The Snow Accumulation And Ablation Processes. This Paper Presents The Field Site, The Instrumentation And The Collection And Postprocessing Methods. The Observations Include Distributed Forest Characteristics (Tree Inventory, Lidar Measurements Of Forest Structure, Subcanopy Hemispherical Photographs), Meteorology (Automatic Weather Station And An Array Of Radiometers), Snow Cover And Depth (Snow Pole Transect And Laser Scan) And Snow Interception By The Canopy During Precipitation Events. The Weather Station Installed Under Dense Canopy During The First Campaign Has Been Maintained Since Then And Has Provided Continuous Measurements Throughout The Year Since 2018. Data Are Publicly Available From The Repository Of The Observatoire Des Sciences De L'Univers De Grenoble (Osug) Data Center At 10.17178/Snouf.2022 (Sicart Et Al., 2022).
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Sierra, J., Espinoza, J., Junquas, C., Wongchuig, S., Polcher, J., Moron, V., et al. (2023). Impacts Of Land-Surface Heterogeneities And Amazonian Deforestation On The Wet Season Onset In Southern Amazon. Climate Dynamics, .
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Smith, M., Angot, H., Chamberlain, E., Droste, E., Karam, S., Muilwijk, M., et al. (2023). Thin And Transient Meltwater Layers And False Bottoms In The Arctic Sea Ice Pack-Recent Insights On These Historically Overlooked Features. Elementa-Science Of The Anthropocene, 111(1).
Abstract: The Rapid Melt Of Snow And Sea Ice During The Arctic Summer Provides A Significant Source Of Low-Salinity Meltwater To The Surface Ocean On The Local Scale. The Accumulation Of This Meltwater On, Under, And Around Sea Ice Floes Can Result In Relatively Thin Meltwater Layers In The Upper Ocean. Due To The Small-Scale Nature Of These Upper-Ocean Features, Typically On The Order Of 1 M Thick Or Less, They Are Rarely Detected By Standard Methods, But Are Nevertheless Pervasive And Critically Important In Arctic Summer. Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition In Summer 2020 Focused On The Evolution Of Such Layers And Made Significant Advancements In Understanding Their Role In The Coupled Arctic System. Here We Provide A Review Of Thin Meltwater Layers In The Arctic, With Emphasis On The New Findings From Mosaic. Both Prior And Recent Observational Datasets Indicate An Intermittent Yet Long-Lasting (Weeks To Months) Meltwater Layer In The Upper Ocean On The Order Of 0.1 M To 1.0 M In Thickness, With A Large Spatial Range. The Presence Of Meltwater Layers Impacts The Physical System By Reducing Bottom Ice Melt And Allowing New Ice Formation Via False Bottom Growth. Collectively, The Meltwater Layer And False Bottoms Reduce Atmosphere-Ocean Exchanges Of Momentum, Energy, And Material. The Impacts On The Coupled Arctic System Are Far-Reaching, Including Acting As A Barrier For Nutrient And Gas Exchange And Impacting Ecosystem Diversity And Productivity.
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Sonke, J., Angot, H., Zhang, Y., Poulain, A., Bjorn, E., & Schartup, A. (2023). Global Change Effects On Biogeochemical Mercury Cycling. Ambio, .
Abstract: Past And Present Anthropogenic Mercury (Hg) Release To Ecosystems Causes Neurotoxicity And Cardiovascular Disease In Humans With An Estimated Economic Cost Of $117 Billion Usd Annually. Humans Are Primarily Exposed To Hg Via The Consumption Of Contaminated Freshwater And Marine Fish. The Unep Minamata Convention On Hg Aims To Curb Hg Release To The Environment And Is Accompanied By Global Hg Monitoring Efforts To Track Its Success. The Biogeochemical Hg Cycle Is A Complex Cascade Of Release, Dispersal, Transformation And Bio-Uptake Processes That Link Hg Sources To Hg Exposure. Global Change Interacts With The Hg Cycle By Impacting The Physical, Biogeochemical And Ecological Factors That Control These Processes. In This Review We Examine How Global Change Such As Biome Shifts, Deforestation, Permafrost Thaw Or Ocean Stratification Will Alter Hg Cycling And Exposure. Based On Past Declines In Hg Release And Environmental Levels, We Expect That Future Policy Impacts Should Be Distinguishable From Global Change Effects At The Regional And Global Scales.
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Spiric, J., Salinas-Melgoza, M., Merlo-Reyes, A., & Ramirez, M. (2023). Estimating The Causal Effect Of Forestry Programs On Forest Recovery In A Redd Plus Priority Area In Michoac?An, Mexico. Forest Policy And Economics, 1461.
Abstract: We Evaluated The Causal Effect Of The Forestry Programs Implemented From 2007 To 2018 On The Forest Recovery In The Municipality Of Zit ' Acuaro In Central Mexico, Part Of The Cutzamala Region, A Redd+ Priority Implementation Area. We Produced Detailed Land Use/Land Cover (Lulc) Maps To Measure Forest Loss And Recovery In The Study Period At The Municipal Level. To Evaluate The Effect Of Active Forest Recovery We Used A Quasi-Experimental Design To Compare Forest Cover Change Between Agrarian Nuclei With And Without Forestry Programs. Although Defor-Estation Was The Most Dominant Forest Cover Change Process In 2007-2018 In Zit ' Acuaro, Forest Recovery, Mostly In The Form Of Forest Densification, Occurred In Areas Of Comparable Size. However, The Causal Effect Of Forestry Programs On Forest Cover And Density Increase At The Agrarian Nuclei Level Was Negligible. The Passive Forest Regrowth Resulting From Agricultural Abandonment Or Postfire Regeneration Could Have Been More Determinant Of Forest Recovery In The Study Period. Detailed Qualitative Local Data Will Be Needed To Understand Factors And Reasons For Passive Recovery To Support This Process In The Future.
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Strohmenger, L., Sauquet, E., Bernard, C., Bonneau, J., Branger, F., Bresson, A., et al. (2023). On The Visual Detection Of Non-Natural Records In Streamflow Time Series: Challenges And Impacts. Hydrology And Earth System Sciences, 272(181), 3375–3391.
Abstract: Large Datasets Of Long-Term Streamflow Measurements Are Widely Used To Infer And Model Hydrological Processes. However, Streamflow Measurements May Suffer From What Users Can Consider Anomalies, I.E. Non-Natural Records That May Be Erroneous Streamflow Values Or Anthropogenic Influences That Can Lead To Misinterpretation Of Actual Hydrological Processes. Since Identifying Anomalies Is Time Consuming For Humans, No Study Has Investigated Their Proportion, Temporal Distribution, And Influence On Hydrological Indicators Over Large Datasets. This Study Summarizes The Results Of A Large Visual Inspection Campaign Of 674 Streamflow Time Series In France Made By 43 Evaluators, Who Were Asked To Identify Anomalies Falling Under Five Categories, Namely, Linear Interpolation, Drops, Noise, Point Anomalies, And Other. We Examined The Evaluators' Individual Behaviour In Terms Of Severity And Agreement With Other Evaluators, As Well As The Temporal Distributions Of The Anomalies And Their Influence On Commonly Used Hydrological Indicators. We Found That Inter-Evaluator Agreement Was Surprisingly Low, With An Average Of 12 % Of Overlapping Periods Reported As Anomalies. These Anomalies Were Mostly Identified As Linear Interpolation And Noise, And They Were More Frequently Reported During The Low-Flow Periods In Summer. The Impact Of Cleaning Data From The Identified Anomaly Values Was Higher On Low-Flow Indicators Than On High-Flow Indicators, With Change Rates Lower Than 5 % Most Of The Time. We Conclude That The Identification Of Anomalies In Streamflow Time Series Is Highly Dependent On The Aims And Skills Of Each Evaluator, Which Raises Questions About The Best Practices To Adopt For Data Cleaning.
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Sutherland, I., Van Vianen, J., Rowland, D., Palomo, I., Pascual, U., Mathys, A., et al. (2023). Use, Value, And Desire: Ecosystem Services Under Agricultural Intensification In A Changing Landscape In West Kalimantan (Indonesia). Regional Environmental Change, 232(4).
Abstract: A Fundamental Challenge Is To Understand And Navigate Trade-Offs Between Ecosystem Services (Es) In Dynamic Landscapes And To Account For Interactions Between Local People And Broad-Scale Drivers, Such As Agricultural Intensification. Many Analyses Of Es Trade-Offs Rely On Static Mapping And Biophysical Indicators While Disregarding The Multiple Uses, Values, And Desires For Es (Uvd-Es) That Local People Associate With Their Changing Landscapes. Here, A Participatory Uvd-Es Framework Was Applied To Assess Differences In The Use, Values, And Desire Of Es Between Three Zones With Different Land-Use Intensities (With Pre-Frontier, Frontier, And Post-Frontier Landscapes) In West Kalimantan (Indonesia). The Analysis Revealed That (1) Almost The Full Suite Of Es Uses Has Become Destabilized As A Result Of Agricultural Intensification; (2) Es More Closely Associated With Agricultural Intensification Were Largely Desired By Local People Yet They Still Valued A Diversity Of Traditional Es, Such As Those Derived From The Provision Of Non-Timber Forest Products, Fish, And Other Es Associated With Non-Material Aspects Including Those Tied To Traditional Culture; (3) The Mismatch In Used Es Versus Valued Es Increased With Agricultural Intensification Due To A Decrease In The Flow Of Non-Timber Forest Products, Aquatic, Regulating, And Non-Material (Cultural) Es. Together, Exploring Uvd-Es Patterns In A Participatory Way Helped To Reveal Locally Relevant Social-Ecological Drivers Of Es And A Multidimensional Perspective Of Es Trade-Offs. Our Uvd-Es Framework Offers An Opportunity To Foster Participation As A Way To Reconnect Global Environmental Research Agendas With Local And Regional Landscape Contexts.
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T Veld, M., Pandolfi, M., Amato, F., Perez, N., Reche, C., Dominutti, P., et al. (2023). Discovering Oxidative Potential (Op) Drivers Of Atmospheric Pm10, Pm2.5, And Pm1 Simultaneously In North-Eastern Spain. Science Of The Total Environment, 8578.
Abstract: Ambient Particulate Matter (Pm) Is A Major Contributor To Air Pollution, Leading To Adverse Health Effects On The Human Population. It Has Been Suggested That The Oxidative Potential (Op, As A Tracer Of Oxidative Stress) Of Pm Is A Possible Determinant Of Its Health Impact. In This Study, Samples Of Pm10, Pm2.5, And Pm1 Were Collected Roughly Every Four Days From January 2018 Until March 2019 At A Barcelona Urban Background Site And Montseny Rural Background Site In Northeastern Spain. We Determined The Chemical Composition Of Samples, Allowing Us To Perform Source Apportionment Using Positive Matrix Factorization. The Op Of Pm Was Determined By Measuring Reactive Oxygen Species Using Dithiothreitol And Ascorbic Acid Assays. Finally, To Link The Sources With The Measured Op, Both A Pearson'S Correlation And A Multiple Linear Regression Model Were Applied To The Dataset. The Results Showed That In Barcelona, The Op Of Pm10 Was Much Higher Than Those Of Pm2.5 And Pm1, Whereas In Montseny Results For All Pm Sizes Were In The Same Range, But Significantly Lower Than In Barcelona. In Barcelona, Several Anthropogenic Sources Were The Main Drivers Of Op In Pm10 (Combustion + Road Dust + Heavy Oil + Oc-Rich) And Pm2.5 (Road Dust + Combustion). In Contrast, Pm1 -Associated Op Was Driven By Industry, With A Much Lower Contribution To Pm10 And Pm2.5 Mass. Meanwhile, Montseny Exhibited No Clear Drivers For Op Evolution, Likely Explaining The Lack Of A Significant Difference In Op Between Pm10, Pm2.5, And Pm1. Overall, This Study Indicates That Size Fraction Matters For Op, As A Function Of The Environment Typology. In An Urban Context, Op Is Driven By The Pm10 And Pm1 Size Fractions, Whereas Only The Pm1 Fraction Is Involved In Rural Environments.
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Tall, M., Sylla, M., Dajuma, A., Almazroui, M., Houteta, D., Klutse, N., et al. (2023). Drought Variability, Changes And Hot Spots Across The African Continent During The Historical Period (1928-2017). International Journal Of Climatology, .
Abstract: The Spatiotemporal Variability Of Meteorological Droughts, Its Changes And Hot Spots Location Across Africa Are Analysed For The Period Spanning 1928-2017 Using The Standardized Precipitation Index (Spi) Applied To The Precipitation Products From The Climatic Research Unit (Cru), University Of Delaware (Udel) And Global Precipitation Climatology Centre (Gpcc). Spatially, An Analysis Based On Rotational Empirical Orthogonal Function Identifies Five Regions Of Similar Drought Variability, Namely The Sahel, East Africa, East Southern Africa, West Southern Africa And The Gulf Of Guinea. Temporally, The Most Common Periods Of Drought Occurrence Are The 1970S, The 1980S And, To A Lesser Extent, The 1990S. Changes In Drought Characteristics For The Intermediate Past (1958-1987) And Recent Past (1988-2017) Compared To The Far Past (1928-1957) Indicate Robust Increases Of Drought Duration, Frequency And Severity In The Sahel, And To A Lower Extent In The Gulf Of Guinea, Some Areas Of Central Africa, Part Of Southern Africa And Over Madagascar. These Changes Are Stronger (Weaker) Along The Sahel During The Intermediate Past (Recent Past) And Stronger (Weaker) Over Central And Southern Africa And Madagascar During The Recent Past (Intermediate Past). As A Consequence, Drought Hot Spots, Mostly Driven By Severity During The Regions' Wet Season, Are Identified In Areas Confined In The Sahel During The Intermediate Past And In Regions Mainly Over Central And Southern Africa And Madagascar During The Recent Past. Our Results Are Useful For Drought Disaster Risk Management Across Africa And Provide A Valuable Reference For Future Drought Analysis Under Global Warming Conditions.
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Tang, S., Vlug, A., Piao, S., Li, F., Wang, T., Krinner, G., et al. (2023). Regional And Tele-Connected Impacts Of The Tibetan Plateau Surface Darkening. Nature Communications, 141(1).
Abstract: Despite Knowledge Of The Presence Of The Tibetan Plateau (Tp) In Reorganizing Large-Scale Atmospheric Circulation, It Remains Unclear How Surface Albedo Darkening Over Tp Will Impact Local Glaciers And Remote Asian Monsoon Systems. Here, We Use A Coupled Land-Atmosphere Global Climate Model And A Glacier Model To Address These Questions. Under A High-Emission Scenario, Tp Surface Albedo Darkening Will Increase Local Temperature By 0.24 K By The End Of This Century. This Warming Will Strengthen The Elevated Heat Pump Of Tp, Increasing South Asian Monsoon Precipitation While Exacerbating The Current “South Flood-North Drought” Pattern Over East Asia. The Albedo Darkening-Induced Climate Change Also Leads To An Accompanying Tp Glacier Volume Loss Of 6.9%, Which Further Increases To 25.2% At The Equilibrium, With A Notable Loss In Western Tp. Our Findings Emphasize The Importance Of Land-Surface Change Responses In Projecting Future Water Resource Availability, With Important Implications For Water Management Policies. Impacts Of Tibetan Plateau Darkening Remain Unclear. Here Authors Show That Darkening Under The Rcp8.5 Scenario Will Increase South Asian Monsoon Precipitation And The “South Flood-North Drought” Pattern Over East Asia, While Lead To Local Glacier Loss.
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Tassone, A., Magand, O., Naccarato, A., Martino, M., Amico, D., Sprovieri, F., et al. (2023). Seven-Year Monitoring Of Mercury In Wet Precipitation And Atmosphere At The Amsterdam Island Gmos Station. Heliyon, 9(3).
Abstract: Mercury (Hg) Fate And Transport Research Requires More Effort To Obtain A Deep Knowledge Of Its Biogeochemical Cycle, Particularly In The Southern Hemisphere And Tropics That Are Still Missing Of Distributed Monitoring Sites.Continuous Monitoring Of Atmospheric Hg Concentrations And Trend Worldwide Is Relevant For The Effectiveness Evaluation Of The Minamata Convention On Mercury (Mcm) Actions. In This Context, Gaseous Elemental Mercury (Gem) And Total Mercury (Thg) In Precipitations Were Monitored From 2013 To 2019 At The Amsterdam Island Observatory (Ams -37 Degrees 48 ' S, 77 Degrees 34 ' E) To Provide Insights Into The Hg Pathway In The Remote Southern Indian Ocean, Also Considering Ancillary Dataset Of Rn-222, Co2, Co, And Ch4. Gem Average Concentration Was 1.06 +/- 0.07 Ng M- 3, With A Slight Increase During The Austral Winter Due To Both Higher Wind Speed Over The Surface Ocean And Contributions From Southern Africa. In Wet Depositions, Thg Average Concen-Tration Was 2.39 +/- 1.17 Ng L-1, Whereas The Annual Flux Averaged 2.04 +/- 0.80 Mu Gm- 2 Year -1. In General, Both Gem And Volume-Weighted Mean Concentration (Vwmc) Of Thg Did Not Show An Increasing/Decreasing Trend Over The Seven-Year Period, Suggesting A Substantial Lack Of Evolution About Emission Of Hg Reaching Ams.Air Masses Cluster Analysis And Potential Source Contribution Function Showed That Oceanic Evasion Was The Main Hg Contributor At Ams, While Further Contributions Were Attributable To Long-Range Transport Events From Southern Africa, Particularly When The Occurrence Of El Nin Similar To O Increased The Frequency Of Wildfires.
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Tebaldi, C., Adalgeirsdottir, G., Drijfhout, S., Dunne, J., Edwards, T., Fischer, E., et al. (2023). The Hazard Components Of Representative Key Risks. The Physical Climate Perspective. Climate Risk Management, .
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Termansen, M., Jacobs, S., Pandit, R., Mwampamba, T., Dendoncker, N., Schaafsma, M., et al. (2023). Five Steps Towards Transformative Valuation Of Nature. Current Opinion In Environmental Sustainability, 646.
Abstract: The Values Assessment (Va) Of The Intergovernmental Science Policy Platform On Biodiversity And Ecosystem Services Shows That While A Wide Range Of Valuation Methods Exist To Include Nature'S Values In Diverse Decision-Making Contexts, Uptake Of These Methods Remains Limited. Building On The Va, This Paper Reviews Five Critical Steps In The Evaluation Of Project Or Policy Proposals That Can Improve The Inclusion Of Nature'S Values In Decisions. Furthermore, Improving Valuation Practice Requires Guidelines That Utilise Quality Criteria For Valuation Of Nature And Ensure A Balance Between Them. This Paper Proposes Three Such Quality Criteria: Relevance, Robustness And Resource Efficiency. The Paper Argues That The Five Steps And Three Rs Can Generate A Practical Checklist To Support Commissioning, Evaluation And Performance Of More Plural Valuations. Such Guidelines Can Provide The Next Steps Needed To Improve Uptake Of Nature Valuation In Decision-Making.
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Tham, Y., Sarnela, N., Iyer, S., Li, Q., Angot, H., Quelever, L., et al. (2023). Widespread Detection Of Chlorine Oxyacids In The Arctic Atmosphere. Nature Communications, 141(1).
Abstract: Observations Are Reported Of Hclo3 And Hclo4 In The Atmosphere And Their Widespread Occurrence Over The Pan-Arctic During Spring, Providing Further Insights Into Atmospheric Chlorine Cycling In The Polar Environment. Chlorine Radicals Are Strong Atmospheric Oxidants Known To Play An Important Role In The Depletion Of Surface Ozone And The Degradation Of Methane In The Arctic Troposphere. Initial Oxidation Processes Of Chlorine Produce Chlorine Oxides, And It Has Been Speculated That The Final Oxidation Steps Lead To The Formation Of Chloric (Hclo3) And Perchloric (Hclo4) Acids, Although These Two Species Have Not Been Detected In The Atmosphere. Here, We Present Atmospheric Observations Of Gas-Phase Hclo3 And Hclo4. Significant Levels Of Hclo3 Were Observed During Springtime At Greenland (Villum Research Station), Ny-Angstrom Lesund Research Station And Over The Central Arctic Ocean, On-Board Research Vessel Polarstern During The Multidisciplinary Drifting Observatory For The Study Of The Arctic Climate (Mosaic) Campaign, With Estimated Concentrations Up To 7 X 10(6) Molecule Cm(-3). The Increase In Hclo3, Concomitantly With That In Hclo4, Was Linked To The Increase In Bromine Levels. These Observations Indicated That Bromine Chemistry Enhances The Formation Of Oclo, Which Is Subsequently Oxidized Into Hclo3 And Hclo4 By Hydroxyl Radicals. Hclo3 And Hclo4 Are Not Photoactive And Therefore Their Loss Through Heterogeneous Uptake On Aerosol And Snow Surfaces Can Function As A Previously Missing Atmospheric Sink For Reactive Chlorine, Thereby Reducing The Chlorine-Driven Oxidation Capacity In The Arctic Boundary Layer. Our Study Reveals Additional Chlorine Species In The Atmosphere, Providing Further Insights Into Atmospheric Chlorine Cycling In The Polar Environment.
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Thiria, S., Sorror, C., Archambault, T., Charantonis, A., Bereziat, D., Mejia, C., et al. (2023). Downscaling Of Ocean Fields By Fusion Of Heterogeneous Observations Using Deep Learning Algorithms. Ocean Modelling, 1821.
Abstract: We Present A Deep Learning Method To Downscale Low-Resolution Geophysical Fields By Merging Them With High-Resolution Data. The Downscaling Was Performed Using An Ensemble Of Convolutional Neural Networks (Cnns), Whose Prediction Values Are The Average Values Of The Outputs Of 20 Cnns. Academic Experiments Were Conducted On Simulated Ocean Data In The Gulf Stream Region, Given By The Outputs Of The Natl60 Model. The Cnns Forced With Low-Resolution (120 X 120 Km) Sea Surface High (Ssh) Data And Mesoscale Resolution (12 X 12 Km) Sea Surface Temperature (Sst) Data Allowed Us To Obtain Mesoscale Resolution Sea Surface Currents With Good Accuracy. Sensitivity Experiments Have Shown That Taking Sst Into Account Significantly Increases The Accuracy Of The High-Resolution Velocity Retrieval, Even When Noise Is Added To The Ssh Data. The Velocity Information Embedded In The Transport Equation Modeling The Sst Advection Is Taken Into Account By The Cnn, Which Greatly Increases The Resolution Of Ocean Currents Provided By Ssh. In The Present Work, We Only Consider Spatial Downscaling By Assuming That Ssh And Sst Are Daily Observations. The Method We Developed Is Generic And Can Be Used To Improve The Resolution Of A Wide Variety Of Large-Scale Fields By Merging Them With High-Resolution Fields.
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Thomas, D., Robson, B., & Racoviteanu, A. (2023). An Integrated Deep Learning And Object-Based Image Analysis Approach For Mapping Debris-Covered Glaciers. Frontiers In Remote Sensing, 4.
Abstract: Evaluating Glacial Change And The Subsequent Water Stores In High Mountains Is Becoming Increasingly Necessary, And In Order To Do This, Models Need Reliable And Consistent Glacier Data. These Often Come From Global Inventories, Usually Constructed From Multi-Temporal Satellite Imagery. However, There Are Limitations To These Datasets. While Clean Ice Can Be Mapped Relatively Easily Using Spectral Band Ratios, Mapping Debris-Covered Ice Is More Difficult Due To The Spectral Similarity Of Supraglacial Debris To The Surrounding Terrain. Therefore, Analysts Often Employ Manual Delineation, A Time-Consuming And Subjective Approach To Map Debris-Covered Ice Extents. Given The Increasing Prevalence Of Supraglacial Debris In High Mountain Regions, Such As High Mountain Asia, A Systematic, Objective Approach Is Needed. The Current Study Presents An Approach For Mapping Debris-Covered Glaciers That Integrates A Convolutional Neural Network And Object-Based Image Analysis Into One Seamless Classification Workflow, Applied To Freely Available And Globally Applicable Sentinel-2 Multispectral, Landsat-8 Thermal, Sentinel-1 Interferometric Coherence, And Geomorphometric Datasets. The Approach Is Applied To Three Different Domains In The Central Himalayan And The Karakoram Ranges Of High Mountain Asia That Exhibit Varying Climatic Regimes, Topographies And Debris-Covered Glacier Characteristics. We Evaluate The Performance Of The Approach By Comparison With A Manually Delineated Glacier Inventory, Achieving F-Score Classification Accuracies Of 89.2%-93.7%. We Also Tested The Performance Of This Approach On Declassified Panchromatic 1970 Corona Kh-4B Satellite Imagery In The Manaslu Region Of Nepal, Yielding Accuracies Of Up To 88.4%. We Find Our Approach To Be Robust, Transferable To Other Regions, And Accurate Over Regional (>4,000 Km(2)) Scales. Integrating Object-Based Image Analysis With Deep-Learning Within A Single Workflow Overcomes Shortcomings Associated With Convolutional Neural Network Classifications And Permits A More Flexible And Robust Approach For Mapping Debris-Covered Glaciers. The Novel Automated Processing Of Panchromatic Historical Imagery, Such As Corona Kh-4B, Opens The Possibility Of Exploiting A Wealth Of Multi-Temporal Data To Understand Past Glacier Changes.
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Torresani, L., Piton, G., & D'Agostino, V. (2023). Morphodynamics And Sediment Connectivity Index In An Unmanaged, Debris-Flow Prone Catchment: A Through Time Perspective. Journal Of Mountain Science, , 89188–91099.
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Trabattoni, A., Barruol, G., Dreo, R., & Boudraa, A. (2023). Ship Detection And Tracking From Single Ocean-Bottom Seismic And Hydroacoustic Stations. Journal Of The Acoustical Society Of America, 1531(1), 260–273.
Abstract: We Report In This Study How Ocean-Bottom Seismometers (Obs) Can Be Used As Passive Sonars To Automatically Detect, Localize, And Track Moving Acoustic Sources At The Ocean Surface. We Developed Single-Station Methods Based On Direction Of Arrival And On Multi-Path Interference Measurements Capable Of Handling Continuous Erratic Signals Emitted By Ships. Based On A Bayesian Mathematical Framework, We Developed An Azimuthal Detector And A Radial Detector And Combined Them Into A Fully Automatic Tracker. We Tested The Developed Algorithm On Seismic And Hydroacoustic Data Recorded In The Indian Ocean By An Obs Deployed At 4300 M Depth, 200 Km West Of La Reunion Island. We Quantified The Performances Using Archives Of Commercial-Vessel Trajectories In The Area Provided By The Automatic Identification System. Detectors Demonstrate Capabilities In The Detection Range Up To 100 Km From The Obs With Azimuthal Accuracies Of A Few Degrees And With Distance Accuracies Of A Few Hundred Of Meters. We Expect The Method To Be Easily Transposed To Any Other Kind Of Sources (Such As Marine Mammals).
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Treguier, A., Montegut, C., Bozec, A., Chassignet, E., Fox-Kemper, B., Hogg, A., et al. (2023). The Mixed-Layer Depth In The Ocean Model Intercomparison Project (Omip): Impact Of Resolving Mesoscale Eddies. Geoscientific Model Development, 161(131), 3849–3872.
Abstract: The Ocean Mixed Layer Is The Interface Between The Ocean Interior And The Atmosphere Or Sea Ice And Plays A Key Role In Climate Variability. It Is Thus Critical That Numerical Models Used In Climate Studies Are Capable Of A Good Representation Of The Mixed Layer, Especially Its Depth. Here We Evaluate The Mixed-Layer Depth (Mld) In Six Pairs Of Non Eddying (1 Degrees Grid Spacing) And Eddy-Rich (Up To 1/16 Degrees) Models From The Ocean Model Intercomparison Project (Omip), Forced By A Common Atmospheric State. For Model Evaluation, We Use An Updated Mld Dataset Computed From Observations Using The Omip Protocol (A Constant Density Threshold). In Winter, Low-Resolution Models Exhibit Large Biases In The Deep-Water Formation Regions. These Biases Are Reduced In Eddy-Rich Models But Not Uniformly Across Models And Regions. The Improvement Is Most Noticeable In The Mode Water Formation Regions Of The Northern Hemisphere. Results In The Southern Ocean Are More Contrasted, With Biases Of Either Sign Remaining At High Resolution. In Eddy-Rich Models, Mesoscale Eddies Control The Spatial Variability In Mld In Winter. Contrary To A Hypothesis That The Deepening Of The Mixed Layer In Anticyclones Would Make The Mld Larger Globally, Eddy-Rich Models Tend To Have A Shallower Mixed Layer At Most Latitudes Than Coarser Models Do. In Addition, Our Study Highlights The Sensitivity Of The Mld Computation To The Choice Of A Reference Level And The Spatio-Temporal Sampling, Which Motivates New Recommendations For Mld Computation In Future Model Intercomparison Projects.
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Uchida, T., Jamet, Q., Poje, A., Wienders, N., Dewar, W., & Deremble, B. (2023). Wavelet-Based Wavenumber Spectral Estimate Of Eddy Kinetic Energy: Idealized Quasi-Geostrophic Flow. Journal Of Advances In Modeling Earth Systems, 151(3).
Abstract: A Wavelet-Based Method Is Re-Introduced In An Oceanographic And Spectral Context To Estimate Wavenumber Spectrum And Spectral Flux Of Kinetic Energy And Enstrophy. We Apply This To A Numerical Simulation Of Idealized, Doubly Periodic Quasi-Geostrophic Flows, That Is, The Flow Is Constrained By The Coriolis Force And Vertical Stratification. The Double Periodicity Allows For A Straightforward Fourier Analysis As The Baseline Method. Our Wavelet Spectra Agree Well With The Canonical Fourier Approach But With The Additional Strengths Of Negating The Necessity For The Data To Be Periodic And Being Able To Extract Local Anisotropies In The Flow. Caution Is Warranted, However, When Computing Higher-Order Quantities, Such As Spectral Flux.
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Umlauft, J., Johnson, C., Roux, P., Trugman, D., Lecointre, A., Walpersdorf, A., et al. (2023). Mapping Glacier Basal Sliding Applying Machine Learning. Journal Of Geophysical Research-Earth Surface, 1281(111).
Abstract: During The Resolve Project (“High-Resolution Imaging In Subsurface Geophysics: Development Of A Multi-Instrument Platform For Interdisciplinary Research”), Continuous Surface Displacement And Seismic Array Observations Were Obtained On Glacier D'Argentiere In The French Alps For 35 Days In May 2018. The Data Set Is Used To Perform A Detailed Study Of Targeted Processes Within The Highly Dynamic Cryospheric Environment. In Particular, The Physical Processes Controlling Glacial Basal Motion Are Poorly Understood And Remain Challenging To Observe Directly. Especially In The Alpine Region For Temperate Based Glaciers Where The Ice Rapidly Responds To Changing Climatic Conditions And Thus, Processes Are Strongly Intermittent In Time And Heterogeneous In Space. Spatially Dense Seismic And Global Positioning System (Gps) Measurements Are Analyzed Applying Machine Learning To Gain Insight Into The Processes Controlling Glacial Motions Of Glacier D'Argentiere. Using Multiple Bandpass-Filtered Copies Of The Continuous Seismic Waveforms, We Compute Energy-Based Features, Develop A Matched Field Beamforming Catalog And Include Meteorological Observations. Features Describing The Data Are Analyzed With A Gradient Boosting Decision Tree Model To Directly Estimate The Gps Displacements From The Seismic Noise. We Posit That Features Of The Seismic Noise Provide Direct Access To The Dominant Parameters That Drive Displacement On The Highly Variable And Unsteady Surface Of The Glacier. The Machine Learning Model Infers Daily Fluctuations And Longer Term Trends. The Results Show On-Ice Displacement Rates Are Strongly Modulated By Activity At The Base Of The Glacier. The Techniques Presented Provide A New Approach To Study Glacial Basal Sliding And Discover Its Full Complexity.
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Valenzuela, J., Figueroa, M., Armijos, E., Espinoza, J., Wongchuig, S., & Ramirez-Avila, J. (2023). Flooding Risk Of Cropland Areas By Repiquetes In The Western Amazon Basin: A Case Study Of Peruvian Tamshiyacu City. Journal Of Hydrology-Regional Studies, 474.
Abstract: Study Region: The Western Amazon Basin At Tamshiyacu Gauging Station (Near The Iquitos City) Hosts Floodplain Agriculture That Can Be Affected By The Sudden Reversal In Direction Of Water Levels Known As “Repiquetes” That Produce Intermittent Flooding.Study Focus: This Study Assesses Repiquete Flooding Risk In Riparian Crop Areas Based On Statistical Analyses Of Repiquete Events Registered From 1996 To 2018, Hydraulic Modeling To Estimate Flooded Extension, And Assessment Of Climatological Characteristics During The Formation Of Repiquetes.New Hydrological Insights: Floods (& Ge; 20 Cm) Produced By Repiquetes In Riparian Crop Areas Between 83.00 And 88.00 M Above Sea Level (Masl) Occur 1.8 Times Per Year. However, Not All Elevation Ranges Have The Same Flooding Risk To Crops. Terrain Elevations Between 85.31 And 87.00 Masl Have A Reduced Flooding Risk Of 0.35 Per Year. Likewise, Areas With Elevations Between 87.00 And 88.00 Masl (43% Of The Total Area) Were Not Affected By Repiquetes. Extreme Repiquetes (Study Cases Of 2002 And 2008) Have Been Influenced By The Increase Of Atmospheric Moisture Flux Convergence And Precipitation Over Both The Northern Ucayali And Maran & Sim;& Prime;On Basins Through The Six Previous Days. Flood Impacts From The Extreme Event Of 2002 (2008) Could Have Reached 40% (25%) Of The Available Area For Agriculture At The Initiation Of The Repiquete.
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Valois, R., Derode, B., Vouillamoz, J., Kotchoni, D., Lawson, M., & Rau, G. (2023). Use Of Atmospheric Tides To Estimate The Hydraulic Conductivity Of Confined And Semi-Confined Aquifers. Hydrogeology Journal, .
Abstract: Characterizing Groundwater Responses To Natural Drivers Is Cost Effective And Offers Great Potential In Hydrogeological Inves-Tigations. However, There Is A Lack Of Method Development And Evaluation, For Example By Comparing Results With Those Derived From Using Conventional Methods. This Paper Presents A Modified Method To Calculate The Hydraulic Conductivity (K) Of Confined Aquifers Using The Well Water Response To Atmospheric Tides. The Approach Separates The Earth And Atmospheric Tide Influences On Filtered Well Water-Level Records In The Time Domain. The Resulting Ill-Posed Regression Deconvolution Problem Can Be Overcome By Constraining The Well Water Response To Atmospheric Tides In Order To Follow A Physically Real-Istic Semi-Diurnal Barometric Response Function (S-2-Brf), Or To Follow Directly A Modified Hydraulic Model (Be-Hvorslev) Similar To A Slug Test Evaluation. An Analysis With Synthetic Data Shows That K Up To 10(-4) M/S Can Be Estimated When Pressure Records With Short Sampling Intervals Are Available. Application To A Field Dataset From Cambodia And Benin, With 20-Minute To 60-Minute Sampling Intervals, Respectively, Results In K Values Of 5.82 Center Dot 10(-7) M/S And 2.9<Middle Dot>10(-7) M/S. This Agrees With Results Independently Derived From Pumping Tests For Both Confined Sediments And Semi-Confined Hard-Rock Conditions. This Method Offers A Promising And Low-Cost Approach To Derive K Solely From Monitoring Datasets In Confined Aquifers. This Is Especially Advantageous For Low-Conductivity Formations Where Hydraulic Testing Takes Time.
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Viallon-Galinier, L., Hagenmuller, P., & Eckert, N. (2023). Combining Modelled Snowpack Stability With Machine Learning To Predict Avalanche Activity. Cryosphere, , 224522–226022.
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Vincent, C., & Thibert, E. (2023). Brief Communication: Non-Linear Sensitivity Of Glacier Mass Balance To Climate Attested By Temperature-Index Models. Cryosphere, , 198911–199511.
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Von Schneidemesser, E., Mcdonald, B., Van Der Gon, H., Crippa, M., Guizzardi, D., Borbon, A., et al. (2023). Comparing Urban Anthropogenic Nmvoc Measurements With Representation In Emission Inventories-A Global Perspective. Journal Of Geophysical Research-Atmospheres, .
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Von Schuckmann, K., Miniere, A., Gues, F., Cuesta-Valero, F., Kirchengast, G., Adusumilli, S., et al. (2023). Heat Stored In The Earth System 1960-2020: Where Does The Energy Go? Earth System Science Data, , 167511–170911.
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Wang, Z., Chung, A., Steinhage, D., Parrenin, F., Freitag, J., & Eisen, O. (2023). Mapping Age And Basal Conditions Of Ice In The Dome Fuji Region, Antarctica, By Combining Radar Internal Layer Stratigraphy And Flow Modeling. Cryosphere, 171(101), 4297–4314.
Abstract: The Dome Fuji (Df) Region In Antarctica Is A Potential Site For An Ice Core With A Record Of Over 1 Myr. Here, We Combine Large-Scale Internal Airborne Radar Stratigraphy With A 1-D Model To Estimate The Age Of Basal Ice In The Df Region. The Radar Data Used In The Study Were Collected In A Survey During The 2016-2017 Antarctic Season. We Transfer The Latest Age-Depth Scales From The Df Ice Core To Isochrones Traced In Radargrams In The Surrounding 500 Km X 550 Km Region. At Each Point Of The Survey The 1-D Model Uses The Ages Of Isochrones To Construct The Age-Depth Scale At Depths Where Dated Isochrones Do Not Exist, The Surface Accumulation Rate And The Basal Thermal Condition, Including Melt Rate And The Thickness Of Stagnant Ice. Our Resulting Age Distribution And Age Density Suggest That Several Promising Sites With Ice Older Than 1.5 Myr In The Df Region Might Exist. The Deduced Melt Rates And Presence Of Stagnant Ice Provide More Constraints For Locating Sites With A Cold Base. The Accumulation Rates Range From 0.015 To 0.038 M A-1 Ice Equivalent. Based On Sensitivity Studies We Find That The Number And Depth Of Picked Isochrones And The Timescale Of The Ice Core Severely Affect The Model Results. Our Study Demonstrates That Constraints From Deep Radar Isochrones And A Trustworthy Timescale Could Improve The Model Estimation To Find Old Ice In The Df Region.
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Wharton, G., Phillips, J., Legout, C., & Grabowski, R. (2023). Preface: Understanding Fine Sediment Dynamics In Aquatic Systems. Journal Of Soils And Sediments, 232(101), 3567–3573.
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Willis, M., Lannuzel, D., Else, B., Angot, H., Campbell, K., Crabeck, O., et al. (2023). Polar Oceans And Sea Ice In A Changing Climate. Elementa-Science Of The Anthropocene, 111(1).
Abstract: Polar Oceans And Sea Ice Cover 15% Of The Earth'S Ocean Surface, And The Environment Is Changing Rapidly At Both Poles. Improving Knowledge On The Interactions Between The Atmospheric And Oceanic Realms In The Polar Regions, A Surface Ocean-Lower Atmosphere Study (Solas) Project Key Focus, Is Essential To Understanding The Earth System In The Context Of Climate Change. However, Our Ability To Monitor The Pace And Magnitude Of Changes In The Polar Regions And Evaluate Their Impacts For The Rest Of The Globe Is Limited By Both Remoteness And Sea-Ice Coverage. Sea Ice Not Only Supports Biological Activity And Mediates Gas And Aerosol Exchange But Can Also Hinder Some In-Situ And Remote Sensing Observations. While Satellite Remote Sensing Provides The Baseline Climate Record For Sea-Ice Properties And Extent, These Techniques Cannot Provide Key Variables Within And Below Sea Ice. Recent Robotics, Modeling, And In-Situ Measurement Advances Have Opened New Possibilities For Understanding The Ocean-Sea Ice-Atmosphere System, But Critical Knowledge Gaps Remain. Seasonal And Long-Term Observations Are Clearly Lacking Across All Variables And Phases. Observational And Modeling Efforts Across The Sea-Ice, Ocean, And Atmospheric Domains Must Be Better Linked To Achieve A System-Level Understanding Of Polar Ocean And Sea-Ice Environments. As Polar Oceans Are Warming And Sea Ice Is Becoming Thinner And More Ephemeral Than Before, Dramatic Changes Over A Suite Of Physicochemical And Biogeochemical Processes Are Expected, If Not Already Underway. These Changes In Sea-Ice And Ocean Conditions Will Affect Atmospheric Processes By Modifying The Production Of Aerosols, Aerosol Precursors, Reactive Halogens And Oxidants, And The Exchange Of Greenhouse Gases. Quantifying Which Processes Will Be Enhanced Or Reduced By Climate Change Calls For Tailored Monitoring Programs For High-Latitude Ocean Environments. Open Questions In This Coupled System Will Be Best Resolved By Leveraging Ongoing International And Multidisciplinary Programs, Such As Efforts Led By Solas, To Link Research Across The Ocean-Sea Ice-Atmosphere Interface.
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Wongchuig, S., Espinoza, J., Condom, T., Junquas, C., Sierra, J., Fita, L., et al. (2023). Changes In The Surface And Atmospheric Water Budget Due To Projected Amazon Deforestation: Lessons From A Fully Coupled Model Simulation. Journal Of Hydrology, 6256.
Abstract: The Amazon Forest Has A Complex Interaction With Climate At Different Spatial And Temporal Scales. This Means That Alterations In Land Use Could Modify The Regional Water Cycle, Including The Surface And Atmospheric Water Budget. However, Little Is Known About How These Changes Occur Seasonally And In A Spatially Distributed Manner In The Most Vulnerable Regions, Such As The Southern Amazon. In This Study, The Local To Regional Effects Of Future Amazon Deforestation On The Surface And Atmospheric Water Budget Components Are Investigated By Twin Numerical Experiments Using The Regional Earth System Model Of The 'Institute Pierre Simone Laplace' (Regipsl) For 19 Yr (2001-2019). The Results Show That Significant Changes In Precipitation And Actual Evapotranspiration In The Southern Amazon (South Of 5 Degrees S) Are Associated With Surrounding Areas With A Deforested Ratio Higher Than 40%. During The Onset Of The Wet Season (September-November) The Largest Changes In Convective Processes Are Manifested By Opposite Atmospheric Dynamic In Adjacent Regions (Dipole), Associated With. This Dynamic Is Associated With Wind Orientation And The Different Sizes Of The Straight Corridors Of Continuous Deforestation (Pathways). The Dipole Manifests Itself As A Suppression Of Convection In The Upwind Sector, While Convection Increases In The Downwind Sector Of The Deforestation Pathway. For Medium-Sized Deforestation Pathways (-350 Km) Convection Changes Are Related To Dynamic Processes (Decrease In Surface Roughness). In Large-Sized Pathways (-500 Km) The Mechanisms Causing Convective Changes Are Combined, Dynamic And Thermal (Increase In Surface Temperature). In Deforested Regions There Is An Average Increase Of Terrestrial Water Storage Dynamics And Runoff -10 Times Higher Than In Non-Deforested Regions. Furthermore, The Atmosphere Becomes -8 Times Drier In Deforested Regions Than In Non-Deforested Regions. Our Findings Indicate A New Perspective Regarding A Comprehensive Modeling Approach To Understand Potential Changes In The Surface And Atmospheric Water Cycle In Different Regions Of Amazonia And In Different Seasons Due To Future Deforestation And Thus Provide New Insights Into Their Spatial And Temporal Variability At Sub-Regional Scales.
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Xiong, J., Jiang, L., Qiu, Y., Wongchuig, S., Abishek, Guo, S., et al. (2023). On The Capabilities Of The Swot Satellite To Monitor The Lake Level Change Over The Third Pole. Environmental Research Letters, 181(4).
Abstract: The Lake Level Dynamics Of The Qinghai-Tibetan Plateau (Qtp, Also Called The 'Third Pole') Are A Crucial Indicator Of Climate Change And Human Activities; However, They Remain Poorly Measured Due To Extremely High Elevation And Cold Climate. The Existing Satellite Altimeters Also Suffer From Relatively Coarse Temporal Resolution Or Low Spatial Coverage, Preventing Effective Monitoring Of Lake Level Change At Such A Large Spatial Scale. The Recently Launched Surface Water And Ocean Topography (Swot) Mission Is Expected To Greatly Enhance The Current Lake Level Monitoring Capabilities. However, A Systematic Evaluation Is Still Lacking In The Region. To Elucidate This Potential, Here, We Generated Swot-Like Lake Products For 38 Major Lakes (>150 Km(2)) Over The Qtp During 2000-2018 Using A Large-Scale Swot Hydrology Simulator With The Input Of Satellite Altimetry And Water Mask Databases. The Comparative Assessments Between The Satellite Altimetry Data And Swot Simulations Using Various Statistical Metrics And Decomposed Time Series Components Demonstrate That Swot Can Successfully Monitor Both Short-Term Dynamics And Long-Term Trends. Extended Experiments To Derive Swot-Like Data Of 783 Lakes (>1 Km(2)) Based On The Synthetic Lake Level Series Present The Spatial Pattern Of Swot Performance That Tends To Improve With The Increasing Lake Area. Our Findings Provide Comprehensive Inferences And Confidence For Lake Level Monitoring In The Third Pole In The Early Period Of The Swot Satellite.
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Yue, F., Angot, H., Blomquist, B., Schmale, J., Hoppe, C., Lei, R., et al. (2023). The Marginal Ice Zone As A Dominant Source Region Of Atmospheric Mercury During Central Arctic Summertime. Nature Communications, 141(1).
Abstract: Atmospheric Gaseous Elemental Mercury (Gem) Concentrations In The Arctic Exhibit A Clear Summertime Maximum, While The Origin Of This Peak Is Still A Matter Of Debate In The Community. Based On Summertime Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition And A Modeling Approach, We Further Investigate The Sources Of Atmospheric Hg In The Central Arctic. Simulations With A Generalized Additive Model (Gam) Show That Long-Range Transport Of Anthropogenic And Terrestrial Hg From Lower Latitudes Is A Minor Contribution (Similar To 2%), And More Than 50% Of The Explained Gem Variability Is Caused By Oceanic Evasion. A Potential Source Contribution Function (Pscf) Analysis Further Shows That Oceanic Evasion Is Not Significant Throughout The Ice-Covered Central Arctic Ocean But Mainly Occurs In The Marginal Ice Zone (Miz) Due To The Specific Environmental Conditions In That Region. Our Results Suggest That This Regional Process Could Be The Leading Contributor To The Observed Summertime Gem Maximum. In The Context Of Rapid Arctic Warming And The Observed Increase In Width Of The Miz, Oceanic Hg Evasion May Become More Significant And Strengthen The Role Of The Central Arctic Ocean As A Summertime Source Of Atmospheric Hg.
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Yue, F., Angot, H., Blomquist, B., Schmale, J., Hoppe, C., Lei, R., et al. (2023). The Marginal Ice Zone As A Dominant Source Region Of Atmospheric Mercury During Central Arctic Summertime. Nature Communications, 141(1).
Abstract: Atmospheric Gaseous Elemental Mercury (Gem) Concentrations In The Arctic Exhibit A Clear Summertime Maximum, While The Origin Of This Peak Is Still A Matter Of Debate In The Community. Based On Summertime Observations During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition And A Modeling Approach, We Further Investigate The Sources Of Atmospheric Hg In The Central Arctic. Simulations With A Generalized Additive Model (Gam) Show That Long-Range Transport Of Anthropogenic And Terrestrial Hg From Lower Latitudes Is A Minor Contribution (Similar To 2%), And More Than 50% Of The Explained Gem Variability Is Caused By Oceanic Evasion. A Potential Source Contribution Function (Pscf) Analysis Further Shows That Oceanic Evasion Is Not Significant Throughout The Ice-Covered Central Arctic Ocean But Mainly Occurs In The Marginal Ice Zone (Miz) Due To The Specific Environmental Conditions In That Region. Our Results Suggest That This Regional Process Could Be The Leading Contributor To The Observed Summertime Gem Maximum. In The Context Of Rapid Arctic Warming And The Observed Increase In Width Of The Miz, Oceanic Hg Evasion May Become More Significant And Strengthen The Role Of The Central Arctic Ocean As A Summertime Source Of Atmospheric Hg.
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Zeiger, P., Frappart, F., Darrozes, J., Prigent, C., Jiménez, C., & Bourrel, L. (2023). Weekly Mapping Of Surface Water Extent In The Intertropical Wetlands Using Spaceborne Gnss Reflectometry. Journal Of Hydrology, 6266.
Abstract: As Of Today, The Uncertain Distribution And Dynamics Of Inundations In The Tropical Wetlands Cause Large Uncertainties In The Quantification Of The World'S Methane Emissions. Long-Term, Global Remote Sensing Observations Currently Rely On Optical Sensors, Affected By Cloud Cover And Vegetation, And On Passive Microwave Imagery With A Low Spatial Resolution. Global Navigation Satellite System Reflectometry (Gnss-R) L-Band Observations From Space Onboard The Cyclone Gnss (Cygnss) Mission Can Provide Information About The Dynamics Of Surface Water At Moderate To Low Spatial Resolution And With A Frequent Revisit. In This Article, We Propose A Methodology To Compute The Fraction Of Water Contained In 0.1 Degrees Pixels (Similar To 10 Km) Using Cygnss Reflectivity And Above Ground Biomass (Agb) Maps. We Produced A 1-Year Time Series Of Water Fractions With A Weekly Time Sampling For The Full Coverage Of Cygnss Between +/- 38 Degrees Of Latitude, From August 2018 To July 2019. We Evaluated The Results Against Regional Reference Maps Of Surface Water Based On Modis, Jers-1, And Palsar, And Against The Global Inundation Extent From Multi-Satellite (Giems) Dataset. Cygnss Water Fractions Represent Well The Spatial Distribution And The Seasonality Of Inundation Extent For Most Of The Tropical Wetlands, With A Global Rmsd Of 15.0 % Against Giems. We Found A Likely Overestimation When The Soil Moisture (Sm) Exceeds 0.3-0.4 Cm3/Cm3, I.E. For Saturated Soils Where Gnss-R Reflections Are Coherent, As The Sm Was Not Parameterized In Our Retrieval Model. Despite This, The Results Are Consistent In The Entire Intertropical Band Including Over Densely Vegetated Areas. These Weekly Water Fractions For 2018-2019 With A 0.1 Degrees Pixel Size Are Distributed To Contribute To Further Comparisons And Hydrological Researches.
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Zha, Q., Aliaga, D., Krejci, R., Sinclair, V., Wu, C., Ciarelli, G., et al. (2023). Oxidized Organic Molecules In The Tropical Free Troposphere Over Amazonia. National Science Review, .
Abstract: New Particle Formation (Npf) In The Tropical Free Troposphere (Ft) Is A Globally Important Source Of Cloud Condensation Nuclei, Affecting Cloud Properties And Climate. Oxidized Organic Molecules (Ooms) Produced From Biogenic Volatile Organic Compounds Are Believed To Contribute To Aerosol Formation In The Tropical Ft, But Without Direct Chemical Observations. We Performed In Situ Molecular-Level Ooms Measurements At The Bolivian Station Chacaltaya At 5240 M Above Sea Level, On The Western Edge Of Amazonia. For The First Time, We Demonstrate The Presence Of Ooms, Mainly With 4-5 Carbon Atoms, In Both Gas-Phase And Particle-Phase (In Terms Of Mass Contribution) Measurements In Tropical Ft Air From Amazonia. These Observations, Combined With Air Mass History Analyses, Indicate That The Observed Ooms Are Linked To Isoprene Emitted From The Rainforests Hundreds Of Kilometers Away. Based On Particle-Phase Measurements, We Find That These Compounds Can Contribute To Npf, At Least The Growth Of Newly Formed Nanoparticles, In The Tropical Ft On A Continental Scale. Thus, Our Study Is A Fundamental And Significant Step In Understanding The Aerosol Formation Process In The Tropical Ft. In-Situ Molecular-Level Measurements Demonstrate The Presence Of Oxidized Organic Molecules, Mainly With 4-5 Carbon Atoms, In Both Gas-Phase And Particle-Phase In Tropical Free Troposphere Air From Amazonia. These Molecules Are Linked To Isoprene Emitted From The Rainforests Hundreds Of Kilometers Away, And Can Contribute To New Particle Formation.
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Zha, Q., Huang, W., Aliaga, D., Perakyla, O., Heikkinen, L., Koenig, A., et al. (2023). Measurement Report: Molecular-Level Investigation Of Atmospheric Cluster Ions At The Tropical High-Altitude Research Station Chacaltaya (5240 M A.S.L.) In The Bolivian Andes. Atmospheric Chemistry And Physics, , 455944–457644.
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Zhang, S., Gan, T., Bush, A., Liu, J., Zolina, O., & Gelfan, A. (2023). Changes Of The Streamflow Of Northern River Basins Of Siberia And Their Teleconnections To Climate Patterns. International Journal Of Climatology, .
Abstract: The Arctic Rivers Contribute More Than One-Third Of The Total Freshwater Streamflow Into The Arctic Ocean And Play An Essential Role In The Heat And Mass Circulation Of The Arctic Atmosphere/Ocean System. As The Arctic Is Warming Faster Than The Global Average, The Streamflow From Arctic Basins Increases. This Study Analyzed The Streamflow Of The Three Largest Siberian Rivers: The Lena, Yenisei, And Ob', At Multiple Temporal Scales. Results Show That The Annual Streamflow Of Each River Basin Exhibits Statistically Significant Increasing Trends, While The Seasonal Streamflow Of Sub-Basins Generally Decreases In The Summer But Increases In The Winter. Both Autocorrelation And Long-Term Persistency Are Often Found In The Streamflow Time Series, Which Indicates Significant Changes In The Large-Scale Climatological Environment. Therefore, Wavelet Coherence Between The Streamflow And Large-Scale Climate Patterns, Including The El Nino-Southern Oscillation (Enso), North Pacific Pattern (Np), Arctic Oscillation (Ao), And The Pacific/North America Pattern (Pna), Have Been Conducted. Np And Enso Are Found To Have Positive Relationships With The Precipitation And The Ratio Of Potential Evapotranspiration Over The Precipitation. Ao And The Pna Are Found To Have Positive Relationships With The Streamflow Of The Ob' And Yenisei Rivers At Decadal And Multidecadal Scales. This Study Demonstrates That The Existence Of Nonstationarities Within The Siberian Streamflow As The Combined Impact Of Climate Change Alters The Hydroclimatological And Terrestrial Environment Of Siberia. These Findings Provide New Insights Into The Mechanisms Underlying The Hydrologic Changes To Warming Trends And Oscillations Of Climate Patterns, Which Contribute To Our Understanding And The Prediction Of Streamflow Of These Northern Rivers.
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Zhao, M., Ponte, R., & Penduff, T. (2023). Global-Scale Random Bottom Pressure Fluctuations From Oceanic Intrinsic Variability. Science Advances, 9(292).
Abstract: Intrinsic Processes Such As Mesoscale Turbulence Have Recently Been Proved As Important As Atmospheric Variability In Causing Variations In Ocean Bottom Pressure (P(B)). Intrinsic Processes Are Also Known To Generate Random Variability On Scales Larger Than The Mesoscale Through Inverse Energy Cascades Or Large-Scale Baroclinic Instability. Here, Model Analyses Reveal A Truly Global-Scale, Intrinsic P(B) Mode Of Variability At Monthly Time Scales That Relies On A Different Mechanism. The Intrinsic Mode Has Largest Amplitudes Around Drake Passage And Opposite Polarity Between The Southern Ocean And Atlantic/Arctic Oceans. Its Signature Is Consistent With Localized Eddy-Driven P(B) Anomalies Of Opposite Sign Near Drake Passage That Then Adjust Freely In The Rest Of The Ocean Via Barotropic Wave Processes. This Intrinsic Mode Seems Consistent With Observed P(B) Variability.
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Zheng, Y., Golledge, N., Gossart, A., Picard, G., & Leduc-Leballeur, M. (2023). Statistically Parameterizing And Evaluating A Positive Degree-Day Model To Estimate Surface Melt In Antarctica From 1979 To 2022. Cryosphere, 171(9), 3667–3694.
Abstract: Surface Melting Is One Of The Primary Drivers Of Ice Shelf Collapse In Antarctica And Is Expected To Increase In The Future As The Global Climate Continues To Warm Because There Is A Statistically Significant Positive Relationship Between Air Temperature And Melting. Enhanced Surface Melt Will Impact The Mass Balance Of The Antarctic Ice Sheet (Ais) And, Through Dynamic Feedbacks, Induce Changes In Global Mean Sea Level (Gmsl). However, The Current Understanding Of Surface Melt In Antarctica Remains Limited In Terms Of The Uncertainties In Quantifying Surface Melt And Understanding The Driving Processes Of Surface Melt In Past, Present And Future Contexts. Here, We Construct A Novel Grid-Cell-Level Spatially Distributed Positive Degree-Day (Pdd) Model, Forced With 2 M Air Temperature Reanalysis Data And Spatially Parameterized By Minimizing The Error With Respect To Satellite Estimates And Surface Energy Balance (Seb) Model Outputs On Each Computing Cell Over The Period 1979 To 2022. We Evaluate The Pdd Model By Performing A Goodness-Of-Fit Test And Cross-Validation. We Assess The Accuracy Of Our Parameterization Method, Based On The Performance Of The Pdd Model When Considering All Computing Cells As A Whole, Independently Of The Time Window Chosen For Parameterization. We Conduct A Sensitivity Experiment By Adding +/- 10 % To The Training Data (Satellite Estimates And Seb Model Outputs) Used For Pdd Parameterization And A Sensitivity Experiment By Adding Constant Temperature Perturbations ( + 1 , + 2 , + 3 , + 4 And + 5 Circle C) To The 2 M Air Temperature Field To Force The Pdd Model. We Find That The Pdd Melt Extent And Amounts Change Analogously To The Variations In The Training Data With Steady Statistically Significant Correlations And That The Pdd Melt Amounts Increase Nonlinearly With The Temperature Perturbations, Demonstrating The Consistency Of Our Parameterization And The Applicability Of The Pdd Model To Warmer Climate Scenarios. Within The Limitations Discussed, We Suggest That An Appropriately Parameterized Pdd Model Can Be A Valuable Tool For Exploring Antarctic Surface Melt Beyond The Satellite Era.
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Zou, X., Rowe, P., Gorodetskaya, I., Bromwich, D., Lazzara, M., Cordero, R., et al. (2023). Strong Warming Over The Antarctic Peninsula During Combined Atmospheric River And Foehn Events: Contribution Of Shortwave Radiation And Turbulence. Journal Of Geophysical Research-Atmospheres, 1281(161).
Abstract: The Antarctica Peninsula (Ap) Has Experienced More Frequent And Intense Surface Melting Recently, Jeopardizing The Stability Of Ice Shelves And Ultimately Leading To Ice Loss. Among The Key Phenomena That Can Initiate Surface Melting Are Atmospheric Rivers (Ars) And Leeside Foehn; The Combined Impact Of Ars And Foehn Led To Moderate Surface Warming Over The Ap In December 2018 And Record-Breaking Surface Melting In February 2022. Focusing On The More Intense 2022 Case, This Study Uses High-Resolution Polar Wrf Simulations With Advanced Model Configurations, Reference Elevation Model Of Antarctica Topography, And Observed Surface Albedo To Better Understand The Relationship Between Ars And Foehn And Their Impacts On Surface Warming. With An Intense Ar (Ar3) Intrusion During The 2022 Event, Weak Low-Level Blocking And Heavy Orographic Precipitation On The Upwind Side Resulted In Latent Heat Release, Which Led To A More Deep-Foehn Like Case. On The Leeside, Sensible Heat Flux Associated With The Foehn Magnitude Was The Major Driver During The Night And The Secondary Contributor During The Day Due To A Stationary Orographic Gravity Wave. Downward Shortwave Radiation Was Enhanced Via Cloud Clearance And Dominated Surface Melting During The Daytime, Especially After The Peak Of The Ar/Foehn Events. However, Due To The Complex Terrain Of The Ap, Ars Can Complicate The Foehn Event By Transporting Extra Moisture To The Leeside Via Gap Flows. During The Peak Of The 2022 Foehn Warming, Cloud Formation On The Leeside Hampered The Downward Shortwave Radiation And Slightly Increased The Downward Longwave Radiation.
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2022 |
Ackerer, J., Van Der Woerd, J., Meriaux, A., Ranchoux, C., Schafer, G., Delay, F., et al. (2022). Quantifying Geomorphological Evolution From Be-10 Denudation Rates: Insights From High-Resolution Depth Profiles, Topsoils, And Stream Sediments (Strengbach Czo, France). Earth Surface Processes And Landforms, .
Abstract: A Rare Dataset Of In-Situ Be-10 From High-Resolution Depth Profiles, Soils, Rock Outcrops, And Stream Sediments Is Combined With Geochemical Analysis And Modelling Of Regolith Evolution To Understand The Variability Of Denudation Rates In A Mountain Watershed (Strengbach Critical Zone Observatory). High-Resolution Depth Profiles Are Key To Detect The Presence Of Mobile Regolith And To Highlight How It Affects The Critical Zone Evolution. The Modelling Of Regolith Evolution And Be-10 Concentrations Along Depth Profiles Allow Us To Estimate Both The Cosmic Ray Exposure Age (19 Kyr) And The Mean Denudation Rate (22 Mm Kyr(-1)) Of The Regolith Without Any Steady-State Assumption On Be-10 Concentrations. Comparison With Maximum Denudation Rates Inferred From Topsoil Samples Collected From The Surface Of The Depth Profiles And Calculated Using The Temporal Steady-State Assumption Of Be-10 Concentrations Highlights An Overestimation Of Denudation By A Factor Of Two. Maximum Spatially Averaged Denudation Rates Determined From Stream Sediment Samples Also Likely Overestimate Denudation Rates By A Factor Of Two. These Biases Are Significant For Investigating The Geomorphological Evolution And We Propose A Method To Correct Denudation Rates Using The Inherited Be-10 Concentrations And The Cosmic Ray Exposure Age Deduced From The High-Resolution Depth Profiles. A Key Result Is Also That A Steady State Of Be-10 Concentrations And A Steady State Of Regolith Thickness Are Two Different Equilibrium States That Do Not Necessarily Coincide. The Comparison Between Locally Corrected And Spatially Averaged Denudation Rates Indicates That The Watershed Geomorphology Is Not In A Topographic Steady State But Is Modulated By Regressive Fluvial Erosion. Nonetheless, Our Study Demonstrates That Even In A Watershed Where The Steady-State Assumption Of Be-10 Concentrations Is Not Verified, The Spatial Variations Of In-Situ Be-10 Concentrations In Sediments Still Carry Qualitatively Relevant Information On The Geomorphological Evolution Of Landscapes.
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Ahmed, S., Thomas, J. L., Tuite, K., Stutz, J., Flocke, F., Orlando, J. J., et al. (2022). The Role of Snow in Controlling Halogen Chemistry and Boundary Layer Oxidation During Arctic Spring: A 1D Modeling Case Study. Journal Of Geophysical Research-Atmospheres, 1271(5).
Abstract: Reactive chlorine and bromine species emitted from snow and aerosols can significantly alter the oxidative capacity of the polar boundary layer. However, halogen production mechanisms from snow remain highly uncertain, making it difficult for most models to include descriptions of halogen snow emissions and to understand the impact on atmospheric chemistry. We investigate the influence of Arctic halogen emissions from snow on boundary layer oxidation processes using a one-dimensional atmospheric chemistry and transport model (PACT-1D). To understand the combined impact of snow emissions and boundary layer dynamics on atmospheric chemistry, we model Cl-2 and Br-2 primary emissions from snow and include heterogeneous recycling of halogens on both snow and aerosols. We focus on a 2-day case study from the 2009 Ocean-Atmosphere-Sea Ice-Snowpack campaign at Utqia & x121;vik, Alaska. The model reproduces both the diurnal cycle and high quantity of Cl-2 observed, along with the measured concentrations of Br-2, BrO, and HOBr. Due to the combined effects of emissions, recycling, vertical mixing, and atmospheric chemistry, reactive chlorine is typically confined to the lowest 15 m of the atmosphere, while bromine can impact chemistry up to and above the surface inversion height. Upon including halogen emissions and recycling, the concentration of HOx (HOx = OH + HO2) at the surface increases by as much as a factor of 30 at mid-day. The change in HOx due to halogen chemistry, as well as chlorine atoms derived from snow emissions, significantly reduce volatile organic compound lifetimes within a shallow layer near the surface.
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Al-Yaari, A., Ducharne, A., Thiery, W., Cheruy, F., & Lawrence, D. (2022). The Role Of Irrigation Expansion On Historical Climate Change: Insights From Cmip6. Earths Future, 101(111).
Abstract: To Produce Food For A Growing World Population, Irrigated Areas Have Increased From Approximately 0.63 Million Km(2) Of Land In 1900 To 3.1 Million Km(2) Of Land In 2005. Despite This Massive Expansion, Irrigation Is Still Overlooked In Most State-Of-The-Art Earth System Models (Esms) Involved In The Coupled Model Intercomparison Project Phase 6 (Cmip6). To Our Knowledge, Only Three Cmip6 Models Represent Irrigation Activities: Cesm2, Giss-E2-1-G, And Noresm2-Lm. Here, We Investigate The Role Of Irrigation On Historical Climate At Global And Regional Scales By Analyzing Trends Of Key Surface Climate Variables In Cmip6 Simulations During 1900-2014. The Three Models Including Irrigation Show Distinct Behavior From The 15 Models Without Irrigation Over Intensively Irrigated Areas (I.E., >50% Of Grid Cell Area Is Equipped By Irrigation): Both Annual (Months That Correspond To Monthly Air Temperature Higher Than 274 K) Mean Latent Heat Flux (Lhf) And Soil Moisture Increase Over Time, In Contrast To The Models Without Irrigation That Show No Trend Or Even A Negative Trend. The Positive Lhf Trend Over Intensively Irrigated Areas In The Irrigation-On Models Is Consistent With Three Satellite-Based Lhf Products. While Annual (Considering The Warmest Month In A Year) Warming Trends Are Found In These Regions For Most Of The No-Irrigation Models, The Increase In Lhf Induces A Cooling Trend For The Models With Irrigation, Which Was Not Confirmed By Observational Air Temperature Data Sets. These Findings, Supported By Satellite Data, Indicate The Importance Of Improved Representation Of Land Management In The Next Generation Of Esm.
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Aldana-Dominguez, J., Palomo, I., Arellana, J., & de la Rosa, C. G. (2022). Unpacking The Complexity Of Nature ' S Contributions To Human well-being: lessons to transform the Barranquilla Metropolitan Area into a BiodiverCity. Ecosystems And People, 181(1), 430–446.
Abstract: Rapid urbanization trends and urban lifestyles challenge urban populations to recognize ecosystems' contributions to their well-being, and urban planners to integrate nature at the core of urban development. This study assesses the relationships between ecosystems and people in the rapidly expanding Barranquilla Metropolitan Area (BMA) and extracts lessons for its planning as a BiodiverCity. Using 22 interviews and 400 face-to-face surveys we evaluated: 1) the perception of positive and negative contributions of specific types of ecosystems to human well-being (HWB); 2) the importance and vulnerability of multiple ecosystem services (ES) and disservices (EdS); and 3) the relationships between ES, EdS and relational values (RV), and the influence of socioeconomic factors in providing HWB, using a Structural Equation Model (SEM). Open-ended answers in the survey showed that rural and certain natural ecosystems, such as wetlands, mangroves and tropical dry forest were the least valued ecosystems and included some EdS. In contrast, urban and peri-urban ecosystems, namely the river, beaches, crops, urban green, and backyards, were the most valued. Overall, regulating ES were perceived as critical, as well as important and vulnerable. The results of the SEM model indicate that HWB is not only explained by socioeconomic factors such as income and education, but also by ES. We argue that the necessary sustainable socio-economic development of the BMA should be coupled with an urban planning that integrates ES and their contributions to HWB.
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Amraoui, S., Auroux, D., Blum, J., & Cosme, E. (2022). Back-And-Forth Nudging For The Quasi-Geostrophic Ocean Dynamics With Altimetry: Theoretical Convergence Study And Numerical Experiments With The Future Swot Observations. Discrete And Continuous Dynamical Systems-Series S, .
Abstract: In data assimilation for geophysical problems, the increasing amount of satellite data to analyze makes it more and more challenging to guarantee near real time forecasting. Thus, low time and memory consuming data assimilation methods become very attractive. The back-and-forth nudging (BFN) method is a non-classical data assimilation method that can be seen as a deterministic and smoothing version of the Kalman filter. From a practical point of view, the BFN method is very valuable for its simplicity of implementation (no optimization, no differentiation,...) and its rapidity of convergence. Under observability conditions, we prove the mathematical convergence of BFN at deep layers for a multi-layer quasi-geostrophic (MQG) ocean circulation model using an infinite dimensional variant of LaSalle's invariance principle. We also extend the BFN to the problem of joint state-parameter identification. The numerical experiments, performed on 120km large swath sea surface height (SSH) simulated data of the Surface Water Ocean Topography (SWOT) satellite, show the high robustness of the algorithm to uncertainties and the few iterations needed to reach convergence, whereas some problems remain due to non-reversibility properties in time. We also give a strategy to improve geophysical model accuracy, considering the large number of uncertain parameters inherent to models and their impacts on state estimation performance. We propose here a joint state-parameter estimation, tested on the baroclinic wavenumber as an unobserved parameter.
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Angot, H., Blomquist, B., Howard, D., Archer, S., Bariteau, L., Beck, I., et al. (2022). Year-Round Trace Gas Measurements In The Central Arctic During The Mosaic Expedition. Scientific Data, 9(1).
Abstract: Despite The Key Role Of The Arctic In The Global Earth System, Year-Round In-Situ Atmospheric Composition Observations Within The Arctic Are Sparse And Mostly Rely On Measurements At Ground-Based Coastal Stations. Measurements Of A Suite Of In-Situ Trace Gases Were Performed In The Central Arctic During The Multidisciplinary Drifting Observatory For The Study Of Arctic Climate (Mosaic) Expedition. These Observations Give A Comprehensive Picture Of Year-Round Near-Surface Atmospheric Abundances Of Key Greenhouse And Trace Gases, I.E., Carbon Dioxide, Methane, Nitrous Oxide, Ozone, Carbon Monoxide, Dimethylsulfide, Sulfur Dioxide, Elemental Mercury, And Selected Volatile Organic Compounds (Vocs). Redundancy In Certain Measurements Supported Continuity And Permitted Cross-Evaluation And Validation Of The Data. This Paper Gives An Overview Of The Trace Gas Measurements Conducted During Mosaic And Highlights The High Quality Of The Monitoring Activities. In Addition, In The Case Of Redundant Measurements, Merged Datasets Are Provided And Recommended For Further Use By The Scientific Community.
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Araujo, B., Osterwalder, S., Szponar, N., Lee, D., Petrova, M., Pernov, J., et al. (2022). Mercury Isotope Evidence For Arctic Summertime Re-Emission Of Mercury From The Cryosphere. Nature Communications, 131(1).
Abstract: During Arctic Springtime, Halogen Radicals Oxidize Atmospheric Elemental Mercury (Hg-0), Which Deposits To The Cryosphere. This Is Followed By A Summertime Atmospheric Hg-0 Peak That Is Thought To Result Mostly From Terrestrial Hg Inputs To The Arctic Ocean, Followed By Photoreduction And Emission To Air. The Large Terrestrial Hg Contribution To The Arctic Ocean And Global Atmosphere Has Raised Concern Over The Potential Release Of Permafrost Hg, Via Rivers And Coastal Erosion, With Arctic Warming. Here We Investigate Hg Isotope Variability Of Arctic Atmospheric, Marine, And Terrestrial Hg. We Observe Highly Characteristic Hg Isotope Signatures During The Summertime Peak That Reflect Re-Emission Of Hg Deposited To The Cryosphere During Spring. Air Mass Back Trajectories Support A Cryospheric Hg Emission Source But No Major Terrestrial Source. This Implies That Terrestrial Hg Inputs To The Arctic Ocean Remain In The Marine Ecosystem, Without Substantial Loss To The Global Atmosphere, But With Possible Effects On Food Webs. Arctic Warming Thaws Permafrost, Leading To Enhanced Soil Mercury Transport To The Arctic Ocean. Mercury Isotope Signatures In Arctic Rivers, Ocean And Atmosphere Suggest That Permafrost Mercury Is Buried In Marine Sediment And Not Emitted To The Global Atmosphere
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Argueso, D., Di Luca, A., Jourdain, N., Romero, R., & Homar, V. (2022). Mechanisms For Extreme Precipitation Changes In A Tropical Archipelago. Journal Of Climate, 353(171), 5519–5536.
Abstract: The Maritime Continent Is One Of The Most Challenging Regions For Atmospheric Models. Processes That Modulate Deep Convection Are Poorly Represented In Models, Which Affects Their Ability To Simulate Precipitation Features Accurately. Thus, Future Projections Of Precipitation Over The Region Are Prone To Large Uncertainties. One Of The Key Players In Modeling Tropical Precipitation Is The Convective Representation, And Hence Convection-Permitting Experiments Have Contributed To Improve Aspects Of Precipitation In Models. This Improvement Creates Opportunities To Explore The Physical Processes That Govern Rainfall In The Maritime Continent, As Well As Their Role In A Warming Climate. Here, We Examine The Response To Climate Change Of Models With Explicit And Parameterized Convection And How That Reflects In Precipitation Changes. We Focus On The Intensification Of Spatial Contrasts As Precursors Of Changes In Mean And Extreme Precipitation In The Tropical Archipelago. Our Results Show That The Broad Picture Is Similar In Both Model Setups, Where Islands Will Undergo An Increase In Mean And Extreme Precipitation In A Warmer Climate And The Ocean Will See Less Rain. However, The Magnitude And Spatial Structure Of Such Changes, As Well As The Projection Of Rainfall Percentiles, Are Different Across Model Experiments. We Suggest That While The Primary Effect Of Climate Change Is Thermodynamical And It Is Similarly Reproduced By Both Model Configurations, Dynamical Effects Are Represented Quite Differently In Explicit And Parameterized Convection Experiments. In This Study, We Link Such Differences To Horizontal And Vertical Spatial Contrasts And How Convective Representations Translate Them Into Precipitation Changes.
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Autin, P., Sicart, J. E., Rabatel, A., Soruco, A., & Hock, R. (2022). Climate Controls On The Interseasonal And Interannual Variability Of The Surface Mass and Energy Balances of a Tropical Glacier (Zongo Glacier, Bolivia, 16 degrees S): New Insights From the Multi-Year Application of a Distributed Energy Balance Model. Journal Of Geophysical Research-Atmospheres, 1271(7).
Abstract: The application of a distributed energy balance model over nine years at an hourly time step to a 20 x 20 m grid cell over Glacier Zongo (Bolivia, 16 degrees S) enabled assessment of the climate factors that control the interseasonal and interannual variability of its surface mass balance. The model was validated by comparing the measured and simulated discharge at the outlet, albedo at the Automatic Weather Station, surface state and annual mass balance both glacier-wide and as a function of altitude. Analysis of the mean monthly energy fluxes highlighted the importance of the meteorological conditions over October and November on the variability of the annual surface mass balance. Two sensitivity analyses are presented, one of the distribution of precipitation over time which maintains a physical coherence between the different meteorological variables and one of the impact of prolonged periods of intense cloud radiative forcing on the surface mass balance. The distribution of precipitation events over time and their associated amounts are the main drivers of the interannual variability of the surface mass balance via an albedo feedback effect. Additionally, prolonged periods of negative cloud radiative forcing, specifically over the month of November, notably reduce the melt rate.
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Aviles, G. P. F., Spadini, L., Sacchi, E., Rossier, Y., Savarino, J., Ramos, O. E., et al. (2022). Hydrogeochemical and nitrate isotopic evolution of a semiarid mountainous basin aquifer of glacial-fluvial and paleolacustrine origin (Lake Titicaca, Bolivia): the effects of natural processes and anthropogenic activities. Hydrogeology Journal, 303(1), 181–201.
Abstract: A hydrogeochemical and stable isotopic (delta(15) N-NO3 and delta O-18(NO3)) multitracer approach was combined with previous geological and hydrogeological knowledge in a groundwater-dominated basin, located within the semiarid region of the Bolivian Altiplano (SE of Lake Titicaca). Major natural processes and anthropogenic impacts controlling water chemistry and isotopic compositions of groundwater were identified and corresponding aquifer impacted zones determined. The main natural processes are, by following water flowlines, (1) silicate weathering in the piedmont subsystem (similar to 4,600-3,910 m asl, Ca(Mg)HCO3 facies), (2) Na-Ca exchange within glacial-fluvial deposits overlying paleolacustrine deposits (similar to 3,910 to 3,860 m asl, Na-HCO3 facies), and (3) evaporite dissolution in the confined zone of the lacustrine plain (similar to 3,860-3,810 m asl, Na-Cl-SO4 facies). The highest contributions of anthropogenic nitrate in groundwater have been observed at 3,960-3,860 m asl in the piedmont subsystem and were isotopically associated with leaching from areas influenced by manure piles, synthetic N fertilizers, and sewage collector pipes. In this subsystem, natural water-rock interactions could be deciphered with minimal anthropogenic impact, allowing nitrate sources to be clearly identified. Denitrification, occurring in the topographic lows of the piedmont subsystem, was identified as the main natural attenuation process. The multitracer approach provided a consistent understanding of the major processes that take place along the groundwater flow system and confirmed the significant role of anthropogenic nitrate. This aquifer system thus represents an ideal model of the region's hydrochemical evolution along the gravity-driven flow caused by natural water-rock interaction processes and the influence of anthropogenic contamination.
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Bakker, M., Legout, C., Gimbert, F., Nord, G., Boudevillain, B., & Freche, G. (2022). Seismic Modelling And Observations Of Rainfall. Journal Of Hydrology, 6106.
Abstract: Rainfall is a key driver of geomorphological processes ranging from impacting drops that lead to the small-scale dislodgement of soil particles to large-scale morphogenic floods and rainfall-induced hillslope processes. Although rainfall has been identified in seismic records, the associated power spectral density and its quantitative relation to the underlying physical processes have not yet been studied. Here, we analyze nearly 2 years of combined seismic and optical disdrometer measurements, where the latter enables the drop-based quantification of rainfall physical properties. Our measurements confirm the broadband observation of ground velocity power spectral density due to rainfall, allowing the seismic identification of rainfall at intensities as low as 1 mm/h. Seismic power, P, shows a power-law scaling with rainfall intensity, I, and kinetic energy, E: P proportional to I-2.1 and P proportional to E-1.6. The observed scaling relations are consistent between the three monitored sites although there are absolute differences in seismic power of about 1 order of magnitude, which are likely due to variability in landcover and subsurface seismic properties. With a physical model, we demonstrate that the observed power-law relations are set by an underlying linear relation between seismic power and rainfall impulse power, and that the associated exponent values of I and E are due to the covariance of the raindrop size distribution with the total number of drops. The largest raindrop fractions, whose relative contribution increases with rainfall intensity, dominate the seismic signal where, in our case, 90% of the seismic power is attributed to drops larger than 3 mm. Using our model, we estimate the contributing area of rainfall to seismic observations to be within a radial distance of -5-25 m. The spatially integrated nature of the seismic measurements and their sensitivity to large raindrops, which control the disaggregation and the mobilization of soil particles, make seismic records well-suited for the investigation of soil erosion processes. More generally, our work provides a basis for the temporally-resolved seismic quantification of rainfall that drives the dynamics of various hydro-geomorphological processes.
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Bakker, M., Legout, C., Gimbert, F., Nord, G., Boudevillain, B., & Freche, G. (2022). Seismic Modelling And Observations Of Rainfall. Journal Of Hydrology, 6106.
Abstract: Rainfall is a key driver of geomorphological processes ranging from impacting drops that lead to the small-scale dislodgement of soil particles to large-scale morphogenic floods and rainfall-induced hillslope processes. Although rainfall has been identified in seismic records, the associated power spectral density and its quantitative relation to the underlying physical processes have not yet been studied. Here, we analyze nearly 2 years of combined seismic and optical disdrometer measurements, where the latter enables the drop-based quantification of rainfall physical properties. Our measurements confirm the broadband observation of ground velocity power spectral density due to rainfall, allowing the seismic identification of rainfall at intensities as low as 1 mm/h. Seismic power, P, shows a power-law scaling with rainfall intensity, I, and kinetic energy, E: P proportional to I-2.1 and P proportional to E-1.6. The observed scaling relations are consistent between the three monitored sites although there are absolute differences in seismic power of about 1 order of magnitude, which are likely due to variability in landcover and subsurface seismic properties. With a physical model, we demonstrate that the observed power-law relations are set by an underlying linear relation between seismic power and rainfall impulse power, and that the associated exponent values of I and E are due to the covariance of the raindrop size distribution with the total number of drops. The largest raindrop fractions, whose relative contribution increases with rainfall intensity, dominate the seismic signal where, in our case, 90% of the seismic power is attributed to drops larger than 3 mm. Using our model, we estimate the contributing area of rainfall to seismic observations to be within a radial distance of -5-25 m. The spatially integrated nature of the seismic measurements and their sensitivity to large raindrops, which control the disaggregation and the mobilization of soil particles, make seismic records well-suited for the investigation of soil erosion processes. More generally, our work provides a basis for the temporally-resolved seismic quantification of rainfall that drives the dynamics of various hydro-geomorphological processes.
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Baladima, F., Thomas, J. L., Voisin, D., Dumont, M., Junquas, C., Kumar, R., et al. (2022). Modeling An Extreme Dust Deposition Event To The French Alpine Seasonal Snowpack in April 2018: Meteorological Context and Predictions of Dust Deposition. Journal Of Geophysical Research-Atmospheres, 1271(8).
Abstract: Mineral dust is an important aerosol in the atmosphere and is known to reduce snow albedo upon deposition. Model predictions of dust deposition events in snow covered mountain regions are challenging due to the complexity of aerosol-cloud interactions and the specifics of mountain meteorological systems. We use a case study of dust deposition between 30 March and 5 April 2018 to the French alpine snowpack to study the processes that control dust deposition to the seasonal snowpack. To understand processes controlling dust transport and deposition to snow, we use a combination of in situ observations at Col du Lautaret in the French Alps, satellite remote sensing, the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis global atmospheric composition, and the regional model WRF-Chem. Specifically, we investigate the role of increased model spatial resolution within WRF-Chem in capturing mountain meteorology, precipitation, and predicted dust deposition. Regional model results are also compared to the reanalysis global CAMS products including aerosols in the atmosphere and predicted dust deposition fluxes. We conclude that predicted mountain meteorology (e.g., precipitation) is better with increased model resolution (3 x 3 km resolution WRF-Chem domain). This improved meteorology has significant impacts on predicted dry and wet dust deposition to the alpine snowpack. Dry deposition is important in the western part of the French Alps at low altitudes, while wet deposition dominates over the complex higher altitude mountain terrain.
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Barbero, A., Grilli, R., Frey, M., Blouzon, C., Helmig, D., Caillon, N., et al. (2022). Summer Variability Of The Atmospheric No2 : No Ratio A Dome C On The East Antarctic Plateau. Atmospheric Chemistry And Physics, 222(181), 12025–12054.
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Basantes-Serrano, R., Rabatel, A., Francou, B., Vincent, C., Soruco, A., Condom, T., et al. (2022). New Insights Into The Decadal Variability In Glacier Volume Of A Tropical Ice Cap, Antisana (0 Degrees 29 ' S, 78 Degrees 09 ' W), Explained By The Morpho-Topographic And Climatic Context. Cryosphere, 161(111), 4659–4677.
Abstract: We Present A Comprehensive Study Of The Evolution Of The Glaciers On The Antisana Ice Cap (Tropical Andes) Over The Period 1956-2016. Based On Geodetic Observations Of Aerial Photographs And High-Resolution Satellite Images, We Explore The Effects Of Morpho-Topographic And Climate Variables On Glacier Volumes. Contrasting Behaviour Was Observed Over The Whole Period, With Two Periods Of Strong Mass Loss, 1956-1964 (-0.72 M W.E. Yr(-1)) And 1979-1997 (-0.82 M W.E. Yr(-1)), And Two Periods With Slight Mass Loss, 1965-1978 (0.10 M W.E. Yr(-1)) And 1998-2016 (-0.26 M W.E. Yr(-1)). There Was A 42 % Reduction In The Total Surface Area Of The Ice Cap. Individually, Glacier Responses Were Modulated By Morpho-Topographic Variables (E.G. Maximum And Median Altitude And Surface Area), Particularly In The Case Of The Small Tongues Located At Low Elevations (Glacier 1, 5 And 16) Which Have Been Undergoing Accelerated Disintegration Since The 1990S And Will Likely Disappear In The Coming Years. Moreover, Thanks To The Availability Of Aerial Data, A Surging Event Was Detected On The Antisana Glacier 8 (G8) In The 2009-2011 Period; Such An Event Is Extremely Rare In This Region And Deserves A Dedicated Study. Despite The Effect Of The Complex Topography, Glaciers Have Reacted In Agreement With Changes In Climate Forcing, With A Stepwise Transition Towards Warmer And Alternating Wet-Dry Conditions Since The Mid-1970S. Long-Term Decadal Variability Is Consistent With The Warm-Cold Conditions Observed In The Pacific Ocean Represented By The Southern Oscillation Index.
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Bayle, A., Roy, A., Dedieu, J. P., Boudreau, S., Choler, P., & Levesque, E. (2022). Two Distinct Waves Of Greening In Northeastern Canada: Summer Warming does not tell the whole story. Environmental Research Letters, 171(6).
Abstract: Arctic vegetation cover has been increasing over the last 40 years, which has been attributed mostly to increases in temperature. Yet, the temporal dimension of this greening remains overlooked as it is often viewed as a monotonic trend. Here, using 11 year long rolling windows on 30 m resolution Landsat data, we examined the temporal variations in greening in north-eastern Canada and its dependence on summer warming. We found two significant and distinct waves of greening, centred around 1996 and 2011, and observed in all land cover types (from boreal forest to arctic tundra). The first wave was more intense and correlated with increasing summer temperature while no such relation was found for the weaker second wave. More specifically, the greening lasted longer at higher elevation during the first wave which translates to a prolonged correlation between greening and summer warming compared to low-altitude vegetation. Our work explored a forsaken complexity of high latitude greening trends and associated drivers and has raised new questions that warrant further research highlighting the importance to include temporal dimension to greening analyses in conjunction with common spatial gradients.
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Becagli, S., Barbaro, E., Bonamano, S., Caiazzo, L., di Sarra, A., Feltracco, M., et al. (2022). Factors Controlling Atmospheric Dms And Its Oxidation Products (Msa And nssSO(4)(2-)) in the aerosol at Terra Nova Bay, Antarctica. Atmospheric Chemistry And Physics, 222(141), 9245–9263.
Abstract: This paper presents the results of simultaneous high time-resolution measurements of biogenic aerosol (methane sulfonic acid (MSA), non-sea salt sulfate nssSO(4)(2-)) with its gaseous precursor dimethylsulfide (DMS), performed at the Italian coastal base Mario Zucchelli Station (MZS) in Terra Nova Bay (MZS) during two summer campaigns (2018-2019 and 2019-2020). Data on atmospheric DMS concentration are scarce, especially in Antarctica. The DMS maximum at MZS occurs in December, one month earlier than at other Antarctic stations. The maximum of DMS concentration is connected with the phytoplanktonic senescent phase following the bloom of Phaeocystis antarctica that occurs in the polynya when sea ice opens up. The second plankton bloom occurs in January and, despite the high dimethylsufoniopropionate (DMSP) concentration in seawater, atmospheric DMS remains low, probably due to its fast biological turnover in seawater in this period. The intensity and timing of the DMS evolution during the two years suggest that only the portion of the polynya close to the sampling site produces a discernible effect on the measured DMS. The closeness to the DMS source area and the occurrence of air masses containing DMS and freshly formed oxidation products allow us to study the kinetic of biogenic aerosol formation and the reliable derivation of the branch ratio between MSA and nssSO(4)(2-) from DMS oxidation that is estimated to be 0.84 +/- 0.06. Conversely, for aged air masses with low DMS content, an enrichment of nssSO(4)(2-) with respect to MSA, is observed. We estimate that the mean contribution of freshly formed biogenic aerosol to PM10 is 17 % with a maximum of 56 %. The high contribution of biogenic aerosol to the total PM10 mass in summer in this area highlights the dominant role of the polynya on biogenic aerosol formation. Finally, due to the regional and year-to-year variability of DMS and related biogenic aerosol formation, we stress the need for long-term measurements of seawater and atmospheric DMS and biogenic aerosol along the Antarctic coast and in the Southern Ocean.
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Becquet, J., Lamouroux, N., Condom, T., Gouttevin, I., Forcellini, M., Launay, B., et al. (2022). Macroinvertebrate Distribution Associated With Environmental Variables In Alpine Streams. Freshwater Biology, .
Abstract: Ongoing Hydrological Alterations Due To Climate Change And Anthropogenic Uses Of Water Have Major Implications For Freshwater Biodiversity. Quantifying The Relative Effects Of Environmental Variables On Macroinvertebrates Is Required To Predict Biological Responses To Hydrological Alterations. To Date, No Study Simultaneously Examined The Effects Of Physico-Chemistry, Hydraulics, And Hydrology On The Distribution Of Alpine Macroinvertebrate Communities And Taxa. In This Study, We Aimed To Quantify The Relative Correlation Between These Environmental Variables And Macroinvertebrate Community Composition And Structure. We Sampled Macroinvertebrates At 66 Stream Sites Located In Three Catchments In The French Alps. We Characterised The Proximate Habitat At Each Site Using 11 Variables Describing Measured Physico-Chemistry And Hydraulics, And Simulation-Based Hydrology. We Described Relationships Between Community Structure And The Environment Using A Co-Inertia Analysis And Modelled Individual Taxa Abundance With Generalised Linear Mixed Models. The Co-Inertia Revealed A Significant Co-Structure Between The Environmental And Macroinvertebrate Matrices. Glacier-Influenced Sites With High Turbidity And Summer Flow Exhibited Similar Community Composition With Low Total Abundance. Sources At High Altitude And Sites With Low Glacial Influence, Exhibiting High Summer Flow And Flow Velocity, Were Dominated By Diamesinae, Rhithrogena Spp., Dictyogenus Spp., And Baetis Alpinus. Streams Fed By Rainfall/Snowmelt And Valley Sources, Associated With Higher Temperature, Conductivity, And Monthly Discharge Variability Were Characterised By Higher Richness And Abundances. Models Indicated That The Three Types Of Proximate Habitat Variables Significantly Contributed To The Macroinvertebrate Distribution. Turbidity Was Strongly Negatively Associated With Macroinvertebrate Abundances. Increasing Flow Velocity And Summer Flow Had Significant (Mainly Negative) Effect In 43% Of Models. The Co-Structure Between Communities And Proximate Habitat Variables Was Shared By The Three Catchments. For Most Individual Taxa, Catchment Identity Did Not Influence Abundance Models And Cross-Validations Indicated Transferable Effects Of Proximate Habitat Variables Among Alpine Catchments. Our Results Can Be Used To Infer Responses Of Alpine Macroinvertebrates To Multivariate Environmental Changes. Understanding The Relationships Between Macroinvertebrates And Environmental Variables Help To Predict How Communities And Taxa Will Be Affected By Habitat Alterations Due To Ongoing Hydrological Changes And Resulting Physico-Chemical Conditions.
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Benavent, N., Mahajan, A., Li, Q., Cuevas, C., Schmale, J., Angot, H., et al. (2022). Substantial Contribution Of Iodine To Arctic Ozone Destruction. Nature Geoscience, .
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Beraud, L., Cusicanqui, D., Rabatel, A., Brun, F., Vincent, C., & Six, D. (2022). Glacier-Wide Seasonal And Annual Geodetic Mass Balances From Pleiades Stereo Images: Application To The Glacier D'Argentiere, French Alps. Journal Of Glaciology, .
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Bernard, A., Hagenmuller, P., Montagnat, M., & Chambon, G. (2022). Disentangling Creep And Isothermal Metamorphism During Snow Settlement With X-Ray Tomography. Journal Of Glaciology, .
Abstract: Once Fallen, Snow Settles Due To The Combined Effects Of Metamorphism And Deformation Of The Ice Matrix Under Gravity. To Understand How These Coupled Processes Affect Snow Evolution, We Performed Oedometric Compression Tests And Continuously Monitored The Snow Microstructure.With X-Ray Tomography. Centimetric Samples With An Initial Density Between 200 And 300 Kgm(-3) Were Followed During An Initial Sintering Phase And Under Two Different Loads Of 2.1 And 4.7 Kpa At -8 Degrees C For Similar To 1 Week. The Microstructure Captured At A Voxel Size Of 8.5 Mu M Was Characterized By Density, Specific Surface Area (Ssa) And Two Metrics Related To Bond Network, Namely The Euler Characteristic And The Minimum Cut Surface. Load-Induced Creep Of The Ice Matrix Was Observed Only For Sufficiently Low Values Of Initial Density (<290 Kgm(-3) In Our Tests), And Was Shown To Be Associated To A Significant Increase Of The Number Of Bonds. Application Of The Load, However, Did Not Affect The Individual Bond Size Nor The Ssa, Which Appeared To Be Mainly Controlled By Isothermal Metamorphism. The Uniaxial Compression Did Not Induce Any Creation Of Anisotropy On The Microstructural Characteristics. Overall, Our Results Show That, For The Considered Conditions, The Deformation Of The Ice Matrix Mainly Leads To A Reduction Of The Pore Space And An Increase Of The Coordination Number, While Metamorphism Mainly Affects The Grain And Bond Sizes.
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Bessin, Z., Dedieu, J. P., Arnaud, Y., Wagnon, P., Brun, F., Esteves, M., et al. (2022). Processing of VEN μS Images of High Mountains: A Case Study for Cryospheric and Hydro-Climatic Applications in the Everest Region (Nepal). Remote Sensing, 141(5).
Abstract: In the Central Himalayas, glaciers and snowmelt play an important hydrological role, as they ensure the availability of surface water outside the monsoon period. To compensate for the lack of field measurements in glaciology and hydrology, high temporal and spatial resolution optical remotely sensed data are necessary. The French-Israeli VEN μS Earth observation mission has been able to complement field measurements since 2017. The aim of this paper is to evaluate the performance of different reflectance products over the Everest region for constraining the energy balance of glaciers and for cloud and snow cover mapping applied to hydrology. Firstly, the results indicate that a complete radiometric correction of slope effects such as the Gamma one (direct and diffuse illumination) provides better temporal and statistical metrics (R-2 = 0.73 and RMSE = 0.11) versus ground albedo datasets than a single cosine correction, even processed under a fine-resolution digital elevation model (DEM). Secondly, a mixed spectral-textural approach on the VEN μS images strongly improves the cloud mapping by 15% compared with a spectral mask thresholding process. These findings will improve the accuracy of snow cover mapping over the watershed areas downstream of the Everest region.
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Bianchi, F., Sinclair, V. A., Aliaga, D., Zha, Q. Z., Scholz, W., Wu, C., et al. (2022). The Saltena Experiment Comprehensive Observations Of Aerosol Sources, Formation, and Processes in the South American Andes. Bulletin Of The American Meteorological Society, 1031(2), E212–E229.
Abstract: This paper presents an introduction to the Southern Hemisphere High Altitude Experiment on Particle Nucleation and Growth (SALTENA). This field campaign took place between December 2017 and June 2018 (wet to dry season) at Chacaltaya (CHC), a GAW (Global Atmosphere Watch) station located at 5,240 m MSL in the Bolivian Andes. Concurrent measurements were conducted at two additional sites in El Alto (4,000 m MSL) and La Paz (3,600 m MSL). The overall goal of the campaign was to identify the sources, understand the formation mechanisms and transport, and characterize the properties of aerosol at these stations. State-of-the-art instruments were brought to the station complementing the ongoing permanent GAW measurements, to allow a comprehensive description of the chemical species of anthropogenic and biogenic origin impacting the station and contributing to new particle formation. In this overview we first provide an assessment of the complex meteorology, airmass origin, and boundary layer-free troposphere interactions during the campaign using a 6-month high-resolution Weather Research and Forecasting (WRF) simulation coupled with Flexible Particle dispersion model (FLEXPART). We then show some of the research highlights from the campaign, including (i) chemical transformation processes of anthropogenic pollution while the air masses are transported to the CHC station from the metropolitan area of La Paz- El Alto, (ii) volcanic emissions as an important source of atmospheric sulfur compounds in the region, (iii) the characterization of the compounds involved in new particle formation, and (iv) the identification of long-range-transported compounds from the Pacific or the Amazon basin. We conclude the article with a presentation of future research foci. The SALTENA dataset highlights the importance of comprehensive observations in strategic high-altitude locations, especially the undersampled Southern Hemisphere.
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Blanchet, J., & Creutin, J. D. (2022). Instrumental Agreement And Retrospective Analysis Of Trends In precipitation extremes in the French Mediterranean Region. Environmental Research Letters, 171(7).
Abstract: In this letter we show the emergence of an agreement between the instruments of a rain-gauge network to point toward a positive trend in daily precipitation extremes since 1960 in the French Mediterranean Region. We identify for each gauge the time varying parameters of the generalized extreme value distribution of annual maximum precipitation over incremental time-windows. These distributions provide for each station of the network a trend assessment over a chosen period that can be interpreted for instance as a trend of the mean or as the trend of a chosen quantile. The incremental window, i.e. a window containing the series of data available at a given date, mimics the annual assessment of the trends that could have been made through time. Each year we thus have one trend per gauge that we can look in distribution through the network in order to assess the level of consensus among instruments. We show how the increasing size of the datasets used over a period of possible climate non-stationarity progressively leads from a dissensus anarchically pointing to no trend (before the 2000s) to a consensus where a majority of gauges points toward a positive trend (after the 2000s). The detected trend in this Mediterranean Region is quite substantial. For instance the 20 year return period precipitation in 1960 turns out to become a 8 year return period precipitation in 2020. Using a simulation basis we try to characterize the effect of decadal variability that is quite readable in the consensus evolution. The proposed metrics is thought to be a good candidate for the assessment of the local time and rate of emergence of climate change that has important implications in regards to adaptation of human and natural systems.
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Boisson, E., Wilhelm, B., Garnier, E., Melo, A., Anquetin, S., & Ruin, I. (2022). Geo-historical database of flood impacts in Alpine catchments (HIFAVa database, Arve River, France, 1850-2015). Natural Hazards And Earth System Sciences, 222(3), 831–847.
Abstract: In France, flooding is the most common and damaging natural hazard (CCR, 2021). Global warming is expected to exacerbate flood risk and could be more pronounced in the European Alps which are experiencing a high warming rate, likely to lead to heavier rainfall events. Alpine valleys are densely populated, potentially increasing exposure and vulnerability to flood hazard. The study of historical records is highly relevant to understand long-term flood occurrence and related socio-economic impacts in relation to changes in the flood risk components (i.e. hazard, exposure and vulnerability). To this aim we introduce the newly constituted database of Historical Impacts of Floods in the Arve Valley (HIFAVa) located in the French northern Alps starting in 1850. This quite unique database reports historical impacts related to impact events occurrences in a well-documented Alpine catchment that encompasses both hydrological and socio-economical diversity. After a complete description of the database (collection, content and structure), we explore the distribution of the recorded impacts with respect to their characteristics and evolution in both time and space. The analysis reveals that small mountain streams and particularly glacial streams caused more impacts (67 %) than the main river. While an increase in heavy rainfall and ice melt are expected to enhance flood hazard in small Alpine catchments, this finding calls for greater attention to flood risk assessment and management in small catchments. The analysis also reveals an increasing occurrence of impacts from 1920 onwards, for which possible factors are discussed. Further work is, however, needed to conclude on the respective contribution of the source effect, the increase in flood hazard, or the exposure of goods and people.
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Bolibar, J., Rabatel, A., Gouttevin, I., Zekollari, H., & Galiez, C. (2022). Nonlinear sensitivity of glacier mass balance to future climate change unveiled by deep learning. Nature Communications, 131(1).
Abstract: Glaciers and ice caps are experiencing strong mass losses worldwide, challenging water availability, hydropower generation, and ecosystems. Here, we perform the first-ever glacier evolution projections based on deep learning by modelling the 21st century glacier evolution in the French Alps. By the end of the century, we predict a glacier volume loss between 75 and 88%. Deep learning captures a nonlinear response of glaciers to air temperature and precipitation, improving the representation of extreme mass balance rates compared to linear statistical and temperature-index models. Our results confirm an over-sensitivity of temperature-index models, often used by large-scale studies, to future warming. We argue that such models can be suitable for steep mountain glaciers. However, glacier projections under low-emission scenarios and the behaviour of flatter glaciers and ice caps are likely to be biased by mass balance models with linear sensitivities, introducing long-term biases in sea-level rise and water resources projections. Deep learning unveils a nonlinear sensitivity of glacier mass changes to future climate warming, with important implications for water resources and sea-level rise coming from glaciers and particularly ice caps.
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Bonino, G., Iovino, D., Brodeau, L., & Masina, S. (2022). The Bulk Parameterizations Of Turbulent Air-Sea Fluxes In Nemo4: The Origin Of Sea Surface Temperature Differences In A Global Model Study. Geoscientific Model Development, 151(171), 6873–6889.
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Borlaza, L., Uzu, G., Ouidir, M., Lyon-Caen, S., Marsal, A., Weber, S., et al. (2022). Personal Exposure To Pm2.5 Oxidative Potential And Its Association To Birth Outcomes. Journal Of Exposure Science And Environmental Epidemiology, .
Abstract: Background: Prenatal Exposure To Fine Particulate Matter (Pm2.5) Assessed Through Its Mass Concentration Has Been Associated With Foetal Growth Restriction In Studies Based On Outdoor Levels. Oxidative Potential Of Pm2.5 (Op) Is An Emerging Metric A Priori Relevant To Mechanisms Of Action Of Pm On Health, With Very Limited Evidence To Indicate Its Role On Birth Outcomes. Objectives: We Investigated The Association Of Op With Birth Outcomes And Compared It With That Of Pm2.5 Mass Concentration. Methods: 405 Pregnant Women From Sepages Cohort (Grenoble Area) Carried Pm2.5 Personal Dosimeters For One Or Two One-Week Periods. Op Was Measured Using Dithiothreitol (Dtt) And Ascorbic Acid (Aa) Assays From The Collected Filters. Associations Of Each Exposure Metric With Offspring Weight, Height, And Head Circumference At Birth Were Estimated Adjusting For Potential Confounders. Results: The Correlation Between Pm2.5 Mass Concentration And Opvdtt Was 0.7. An Interquartile Range Increase In – Was Associated With Reduced Weight (Adjusted Change, -64 G, -166 To -11, P = 0.02) And Height (-4 Mm, -6 To -1, P = 0.01) At Birth. Pm2.5 Mass Concentration Showed Similar Associations With Weight (-53 G, -99 To -8, P = 0.02) And Height (-2 Mm, -5 To 0, P = 0.05). In Birth Height Models Mutually Adjusted For The Two Exposure Metrics, The Association With Opvdtt Was Less Attenuated Than That With Mass Concentration, While For Weight Both Effect Sizes Attenuated Similarly. There Was No Clear Evidence Of Associations With Head Circumference For Any Metric, Nor For Opvaa With Any Growth Parameter. Impact: Pm2.5 Pregnancy Exposure Assessed From Personal Dosimeters Was Associated With Altered Foetal Growth. Personal Op Exposure Was Associated With Foetal Growth Restrictions, Specifically Decreased Weight And Height At Birth, Possibly To A Larger Extent Than Pm2.5 Mass Concentration Alone. These Results Support Op Assessed From Dtt As Being A Health-Relevant Metric. Larger Scale Cohort Studies Are Recommended To Support Our Findings.
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Borlaza, L. J., Weber, S., Marsal, A., Uzu, G., Jacob, V., Besombes, J. L., et al. (2022). Nine-Year Trends Of Pm10 Sources And Oxidative Potential In A Rural background site in France. Atmospheric Chemistry And Physics, 222(131), 8701–8723.
Abstract: Long-term monitoring at sites with relatively low particulate pollution could provide an opportunity to identify changes in pollutant concentration and potential effects of current air quality policies. In this study, 9-year sampling of PM10 (particles with an aerodynamic diameter below 10 μm) was performed in a rural background site in France (Observatoire Menne de l'Environnement or OPE) from 28 February 2012 to 22 December 2020. The positive matrix factorization (PMF) method was used to apportion sources of PME) based on quantified chemical constituents and specific chemical tracers analysed on collected filters. Oxidative potential (OP), an emerging health metric that measures PM capability to potentially cause anti-oxidant imbalance in the lung, was also measured using two acellular assays: dithiothreitol (DTT) and ascorbic acid (AA). The sources of OP were also estimated using multiple linear regression (MLR) analysis. In terms of mass contribution, the dominant sources are secondary aerosols (nitrate- and sulfate-rich) associated with long-range transport (LRT). However, in terms of OP contributions, the main drivers are traffic, mineral dust, and biomass burning factors. There is also some OP contribution apportioned to the sulfate- and nitrate-rich sources influenced by processes and ageing during LRT that could have encouraged mixing with other anthropogenic sources. The study indicates much lower OP values than in urban areas. A substantial decrease (58 % reduction from the year 2012 to 2020) in the mass contributions from the traffic factor was found, even though this is not clearly reflected in its OP contribution. Nevertheless, the findings in this long-term study at the OPE site could indicate effectiveness of implemented emission control policies, as also seen in other long-term studies conducted in Europe, mainly for urban areas.
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Box, J. E., Wehrle, A., van As, D., Fausto, R. S., Kjeldsen, K. K., Dachauer, A., et al. (2022). Greenland Ice Sheet Rainfall, Heat And Albedo Feedback Impacts From The Mid-August 2021 Atmospheric River. Geophysical Research Letters, 494(111).
Abstract: Rainfall at the Greenland ice sheet Summit 14 August 2021, was delivered by an atmospheric river (AR). Extreme surface ablation expanded the all-Greenland bare ice area to near-record-high with snowline climbing up to 788 +/- 90 m. Ice sheet wet snow extent reached 46%, a record high for the 15-31 August AMSR data since 2003. Heat-driven firn deflation averaged 0.14 +/- 0.05 m at four accumulation area automatic weather stations (AWSs). Energy budget calculations from AWS data indicate that surface heating from rainfall is much smaller than from either the sensible, latent, net-longwave or solar energy fluxes. Sensitivity tests show that without the heat-driven snow-darkening, melt at 1,840 m would have totaled 28% less. Similarly, at 1,270 m elevation, without the bare ice exposure, melting would have been 51% less. Proglacial river discharge was the highest on record since 2006 for late August and confirms the melt-sustaining effect of the albedo feedback.
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Brighty, A., Jacob, V., Uzu, G., Borlaza, L., Conil, S., Hueglin, C., et al. (2022). Cellulose In Atmospheric Particulate Matter At Rural And Urban Sites across France and Switzerland. Atmospheric Chemistry And Physics, 222(9), 6021–6043.
Abstract: The spatiotemporal variations in free-cellulose concentrations in atmospheric particles, as a proxy for plant debris, were investigated using an improved protocol with a high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD) method. Filter samples were taken from nine sites of varying characteristics across France and Switzerland, with sampling covering all seasons. Concentrations of cellulose, as well as carbonaceous aerosol and other source-specific chemical tracers (e.g. elemental carbon, EC; levoglucosan; polyols; trace metals; and glucose), were quantified. Annual mean free-cellulose concentrations within PM10 (particulate matter) ranged from 29 +/- 38 ng m(-3) at Basel (urban site) to 284 +/- 225 ng m(-3) at Payerne (rural site). Concentrations were considerably higher during episodes, with spikes exceeding 1150 and 2200 ng m(-3) at Payerne and ANDRA-OPE (Agence nationale pour la gestion des dechets radioactifs Observatoire Perenne de l'Environnement; rural site), respectively. A clear seasonality, with highest cellulose concentrations during summer and autumn, was observed at all rural and some urban sites. However, some urban locations exhibited a weakened seasonality. Contributions of cellulose carbon to total organic carbon are moderate on average (0.7 %-5.9 %) but much greater during “episodes”, reaching close to 20 % at Payerne. Cellulose concentrations correlated poorly between sites, even at ranges of about 10 km, indicating the localised nature of the sources of atmospheric plant debris. With regards to these sources, correlations between cellulose and typical biogenic chemical tracers (polyols and glucose) were moderate to strong (R-s = 0.28-0.78, p < 0.0001) across the nine sites. Seasonality was strongest at sites with stronger biogenic correlations, suggesting the main source of cellulose arises from biogenic origins. A second input to ambient plant debris concentrations was suggested via resuspension of plant matter at several urban sites, due to moderate cellulose correlations with mineral dust tracers, Ca2+, and Ti metal (R-s = 0.28-0.45, p < 0.007). No correlation was obtained with the biomass burning tracer (levoglucosan), an indication that this is not a source of atmospheric cellulose. Finally, an investigation into the interannual variability in atmospheric cellulose across the Grenoble metropole was completed. It was shown that concentrations and sources of ambient cellulose can vary considerably between years. All together, these results deeply improve our knowledge on the phenomenology of plant debris within ambient air.
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Burgard, C., Jourdain, N., Reese, R., Jenkins, A., & Mathiot, P. (2022). An Assessment Of Basal Melt Parameterisations For Antarctic Ice Shelves. Cryosphere, 161(121), 4931–4975.
Abstract: Ocean-Induced Ice-Shelf Melt Is One Of The Largest Uncertainty Factors In The Antarctic Contribution To Future Sea-Level Rise. Several Parameterisations Exist, Linking Oceanic Properties In Front Of The Ice Shelf To Melt At The Base Of The Ice Shelf, To Force Ice-Sheet Models. Here, We Assess The Potential Of A Range Of These Existing Basal Melt Parameterisations To Emulate Basal Melt Rates Simulated By A Cavity-Resolving Ocean Model On The Circum-Antarctic Scale. To Do So, We Perform Two Cross-Validations, Over Time And Over Ice Shelves Respectively, And Re-Tune The Parameterisations In A Perfect-Model Approach, To Compare The Melt Rates Produced By The Newly Tuned Parameterisations To The Melt Rates Simulated By The Ocean Model. We Find That The Quadratic Dependence Of Melt To Thermal Forcing Without Dependency On The Individual Ice-Shelf Slope And The Plume Parameterisation Yield The Best Compromise, In Terms Of Integrated Shelf Melt And Spatial Patterns. The Box Parameterisation, Which Separates The Sub-Shelf Circulation Into Boxes, The Picop Parameterisation, Which Combines The Box And Plume Parameterisation, And Quadratic Parameterisations With Dependency On The Ice Slope Yield Basal Melt Rates Further From The Model Reference. The Linear Parameterisation Cannot Be Recommended As The Resulting Integrated Ice-Shelf Melt Is Comparably Furthest From The Reference. When Using Offshore Hydrographic Input Fields In Comparison To Properties On The Continental Shelf, All Parameterisations Perform Worse; However, The Box And The Slope-Dependent Quadratic Parameterisations Yield The Comparably Best Results. In Addition To The New Tuning, We Provide Uncertainty Estimates For The Tuned Parameters.
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Cabrera, M., Moulatlet, G., Valencia, B., Maisincho, L., Rodriguez-Barroso, R., Albendin, G., et al. (2022). Microplastics in a tropical Andean Glacier: A transportation process across the Amazon basin? Science Of The Total Environment, 805.
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Calonne, N., Burr, A., Philip, A., Flin, F., & Geindreau, C. (2022). Effective coefficient of diffusion and permeability of firn at Dome C and Lock In, Antarctica, and of various snow types – estimates over the 100-850 kg m(-3) density range. Cryosphere, 161(3), 967–980.
Abstract: Modeling air transport through the entire firn column of polar ice sheets is needed to interpret climate archives. To this end, different regressions have been proposed in the past to estimate the effective coefficient of diffusion and permeability of firn. These regressions are often valid for specific depth or porosity ranges only. Also, they constitute a source of uncertainty as evaluations have been limited by the lack of reliable data of firn transport properties. To contribute with a new dataset, this study presents the effective coefficient of diffusion and the permeability at Dome C and Lock In, Antarctica, from the near-surface to the close-off (23 to 133 m depth). Also, microstructure is characterized based on density, specific surface area, closed porosity ratio, connectivity index, and structural anisotropy through the correlation lengths. All properties were estimated based on pore-scale computations from 3D tomographic images of firn samples. The normalized diffusion coefficient ranges from 1.9 x 10(-1) to 8.3 x 10(-5) , and permeability ranges from 1.2 x 10(-9) to 1.1 x 10(-12) m(2), for densities between 565 and 888 kg m(-3). No or little anisotropy is reported. Next, we investigate the relationship of the transport properties with density over the firn density range (550-850 kg m(-3)), as well as over the entire density range encountered in the ice sheets (100-850 kg m(-3)), by extending the datasets with transport properties of alpine and artificial snow from previous studies. Classical analytical models and regressions from literature are evaluated against the estimates from pore-scale simulations. For firn, good agreements are found for permeability and the diffusion coefficient with two existing regressions of the literature based on open porosity despite the rather different site conditions (Greenland). Over the entire 100-850 kg m(-3) density range, permeability is accurately reproduced by the Carman-Kozeny and self-consistent (spherical bi-composite) models when expressed in terms of a rescaled porosity, phi(res) = (phi – phi(off)) – (1 – phi(off)), to account for pore clo- sure, where q5off is the close-off porosity. For the normalized diffusion coefficient, none of the evaluated formulas were satisfactory, so we propose a new regression based on the rescaled porosity that reads D / D-air = (phi(res))(1.61).
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Camara, M., Diba, I., & Diedhiou, A. (2022). Effects of Land Cover Changes on Compound Extremes over West Africa Using the Regional Climate Model RegCM4. Atmosphere, 131(3).
Abstract: This study aims to characterize the impacts of the Sahel-Sahara interface reforestation on compound extremes in the Sahel region during the West African monsoon season (June-July-August-September, JJAS). For this purpose, we performed a simulation with the standard version of the RegCM4 model, and another simulation with the altered version of the same model, taking into account the incorporated forest. Results show that reforestation may strongly influence the frequency of individual extreme events (dry and warm days) by decreasing them over and off the reforested zone. The reduction in these extreme dry and warm days may be due partly to the strengthening of the atmospheric moisture content over most parts of the West African domain and the weakening of the sensible heat flux south of 16 degrees N. The analysis also shows an increase in extreme wet days over and off the reforested zone, which could be associated partly with the strengthening of evapotranspiration over most parts of the West African domain, including the reforested area. The analysis of compound extremes shows a strong occurrence of the compound dry/warm mode over the northern Sahel for both runs, probably due to the weak precipitation recorded in this zone. Both experiments also simulated a strong compound wet/warm mode occurrence over the Sahel due to a high rainfall occurrence over this region. When comparing both runs, the impact of the reforestation was to decrease (increase) the compound extreme dry/warm (wet/warm) mode over the reforested zone. The dry/warm mode decrease is consistent with that of individual extreme dry and warm days, while the compound wet/warm mode increase may be driven by that of the extreme wet days. Finally, when considering the seasonal cycle, the dry/warm mode exhibits a more substantial decrease in the beginning (June-July, JJ) than during the peak of the West African summer monsoon season (August-September, AS). Moreover, reforestation similarly affects the compound wet/warm mode in JJ and AS by increasing it in the reforested region and decreasing it over the Southern Sahel (south of 15 degrees N). This work suggests that reforestation may be a good solution for West African policymakers to mitigate climate change over the region and to develop better strategies for water resource management.
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Cao, Y., Jiang, Z., Alexander, B., Cole-Dai, J., Savarino, J., Erbland, J., et al. (2022). On The Potential Fingerprint Of The Antarctic Ozone Hole In Ice-Core Nitrate Isotopes: A Case Study Based On A South Pole Ice Core. Atmospheric Chemistry And Physics, 222(202), 13407–13422.
Abstract: Column Ozone Variability Has Important Implications For Surface Photochemistry And The Climate. Ice-Core Nitrate Isotopes Are Suspected To Be Influenced By Column Ozone Variability And Delta N-15(No3-) Has Been Sought To Serve As A Proxy Of Column Ozone Variability. In This Study, We Examined The Ability Of Ice-Core Nitrate Isotopes To Reflect Column Ozone Variability By Measuring Delta N-15(No3-) And Delta O-17(No3-) In A Shallow Ice Core Drilled At The South Pole. The Ice Core Covers The Period 1944-2005, And During This Period Delta N-15(No3-) Showed Large Annual Variability ((59.2 +/- 29.3)Parts Per Thousand), But With No Apparent Response To The Antarctic Ozone Hole. Utilizing A Snow Photochemical Model, We Estimated 6.9 Parts Per Thousand Additional Enrichments In Delta N-15(No3-) Could Be Caused By The Development Of The Ozone Hole. Nevertheless, This Enrichment Is Small And Masked By The Effects Of The Snow Accumulation Rate At The South Pole Over The Same Period Of The Ozone Hole. The Delta O-17(No3-) Record Has Displayed A Decreasing Trend By Similar To 3.4 Parts Per Thousand Since 1976. This Magnitude Of Change Cannot Be Caused By Enhanced Post-Depositional Processing Related To The Ozone Hole. Instead, The Delta O-17(No3-) Decrease Was More Likely Due To The Proposed Decreases In The O-3 / Hox Ratio In The Extratropical Southern Hemisphere. Our Results Suggest Ice-Core Delta N-15(No3-) Is More Sensitive To Snow Accumulation Rate Than To Column Ozone, But At Sites With A Relatively Constant Snow Accumulation Rate, Information Of Column Ozone Variability Embedded In Delta N-15(No3-) Should Be Retrievable.
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Chagnaud, G., Panthou, G., Vischel, T., & Lebel, T. (2022). A synthetic view of rainfall intensification in the West African Sahel. Environmental Research Letters, 171(4).
Abstract: The West African Sahel has been facing for more than 30 years an increase in extreme rainfall with strong socio-economic impacts. This situation challenges decision-makers to define adaptation strategies in a rapidly changing climate. The present study proposes (i) a quantitative characterization of the trends in extreme rainfall at the regional scale, (ii) the translation of the trends into metrics that can be used by hydrological risk managers, (iii) elements for understanding the link between the climatology of extreme and mean rainfall. Based on a regional non-stationary statistical model applied to in-situ daily rainfall data over the period 1983-2015, we show that the region-wide increasing trend in extreme rainfall is highly significant. The change in extreme value distribution reflects an increase in both the mean and variability, producing a 5%/decade increase in extreme rainfall intensity whatever the return period. The statistical framework provides operational elements for revising the design methods of hydraulic structures which most often assume a stationary climate. Finally, the study shows that the increase in annual maxima of daily rainfall is more attributable to stronger storm intensities (80%) than to more frequent storm occurrences (20%), reflecting a major rainfall regime shift in comparison to those observed in the region since 1950.
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Chamarande, T., Mathy, S., & Hingray, B. (2022). The Least Cost Design Of 100 % Solar Power Microgrids In Africa: Sensitivity To Meteorological And Economic Drivers And Possibility For Simple Pre- Sizing Rules. Energy For Sustainable Development, 696, 211–223.
Abstract: Autonomous Micro-Grids Based On Solar Photovoltaic (Pv) Are One Of The Most Promising Solutions To Provide Electricity Access In Many Regions Worldwide. Different Storage/Pv Capacities Can Produce The Same Level Of Quality Service, But An Optimal Design Is Typically Identified To Minimize The Levelized Cost Of Electricity. This Cost Optimization However Relies On Technical And Economic Hypothesis That Come With Large Uncertainties And/Or Spatial Disparities. This Article Explores The Sensitivity Of The Optimal Sizing To Variations And Uncertainties Of Such Parameters. Using Data From Heliosat And Era5, We Simulate The Solar Pv Production And Identify The Least Cost Configurations For 200 Locations In Africa. Our Results Show That The Optimal Configuration Is Highly Dependent On The Characteristics Of The Resource, And Especially On Its Co-Variability Structure With The Electric Demand On Different Timescales. It Is Conversely Rather Insensitive To Cost Hypotheses, Which Allow Us To Propose Simple Pre-Sizing Rules Based On The Only Characteristics Of The Solar Resource And Electricity Demand. The Optimal Storage Capacity Can Be Estimated From The 75Th Percentile Of The Daily Nocturnal Demand And The Optimal Pv Capacity From The Mean Demand And The Standard Deviation Of The Daily Power Difference Between Solar Production And Demand. (C) 2022 International Energy Initiative. Published By Elsevier Inc. All Rights Reserved.
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Charrier, L., Yan, Y., Trouve, E., Koeniguer, E., Mouginot, J., & Millan, R. (2022). Fusion Of Multitemporal Multisensor Velocities Using Temporal Closure Of Fractions Of Displacements. Ieee Geoscience And Remote Sensing Letters, 191.
Abstract: Numerous Glacier Velocity Observations, Derived From Spaceborne Imagery, Are Available Online, But It Remains Difficult To Analyze Them Because They Are Measured With Different Temporal Baselines, By Various Sensors. In This Study, We Propose A Novel Formulation Of The Temporal Closure To Fuse Multitemporal Multisensor Velocity Observations Without Prior Information On The Displacement Behavior And The Data Uncertainty. We Establish A System Of Linear Equations Between Combinations Of Displacement Observations And Fractions Of Estimated Displacements. The Proposed Approach Provides A Velocity Time-Series With A Regular And Optimal Temporal Sampling, The Latter Representing A Compromise Between The Temporal Resolution And The Signal-To-Noise Ratio. The Proposed Approach Is First Evaluated On Synthetic Datasets And Second On Sentinel-2 And Venus Velocity Observations Over The Fox Glacier In New Zealand. The Results Show The Intra-Annual Variability Of Fox Glacier Surface Velocity With A Reduced Uncertainty And Complete Temporal Coverage.
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Charrondiere, C., Brun, C., Hopfinger, E. J., Cohard, J. M., & Sicart, J. E. (2022). Mean Flow Structure Of Katabatic Winds And Turbulent Mixing Properties. Journal Of Fluid Mechanics, 9419.
Abstract: The recent field measurements of katabatic winds on steep alpine slopes provide a unique database for theoretical analysis of the mean flow development and the determination of mixing properties. The theory is based on the depth-integrated momentum and heat equations, and demonstrates an increase in mean velocity U with downstream distance x according to x(n) (n <= 1/2). An equation for the mean wind velocity is established, expressing its dependency on the buoyancy flux, related to the heat flux to the ground, entrainment and bottom friction. No ambient stratification, and ambient wind and constant ground surface temperature, lead to U similar to x(1/2), while constant heat flux to the ground leads to U similar to x(1/3) and requires that the reduced gravity decreases as x(-1/3). Stable ambient stratification N causes, in addition to small-amplitude mean flow oscillations, a decrease in reduced gravity with x, in which case the assumption of constant surface heat flux along x is only an approximation. The turbulent fluxes are a function of gradient Richardson number Ri with the ratio of turbulent diffusivity to viscosity K-h/K-m changing from nearly 1.4 to approximately 0.5 at Ri approximate to 0.5. A new mixing efficiency is introduced that includes turbulence kinetic energy production or consumption by along-slope turbulent buoyancy flux. It increases with Ri up to 0.25 at Ri approximate to 0.5 and then remains nearly constant. The measurements allowed us to determine the bottom drag coefficients and interfacial entrainment, with the ground surface heat flux being determined from the mean buoyancy flux.
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Cheng, G., Morlighem, M., Mouginot, J., & Cheng, D. (2022). Helheim Glacier's Terminus Position Controls Its Seasonal and Inter-Annual Ice Flow Variability. Geophysical Research Letters, 494(5).
Abstract: Over the past decade, one of the largest contributors to total ice discharge across the Greenland ice sheet, Helheim Glacier, has experienced large fluctuations in ice velocity. In this study, we simulate the dynamics of Helheim, from 2007 to 2020, using the Ice-sheet and Sea-level System Model to identify the drivers of these large changes in ice discharge. By quantifying the impact of individual external forcing and model parameters on Helheim's modeled velocity, we find that the position of the calving front alone explains the dynamic variability of the glacier, as it has a direct and large impact on Helheim's ice velocity. The seasonal to inter-annual variability of Helheim Glacier is, however, relatively insensitive to the choice of friction law or ice rheology factor. This study shows that more research on calving dynamics and ice-ocean interactions is required to project the future of this sector of Greenland.
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Chmiel, M., Godano, M., Piantini, M., Brigode, P., Gimbert, F., Bakker, M., et al. (2022). Brief Communication: Seismological Analysis Of Flood Dynamics And hydrologically triggered earthquake swarms associated with Storm Alex. Natural Hazards And Earth System Sciences, 222(5), 1541–1558.
Abstract: On 2 October 2020, the Maritime Alps in southern France were struck by the devastating Storm Alex, which caused locally more than 600 mm of rain in less than 24 h. The extreme rainfall and flooding destroyed regional rain and stream gauges. That hinders our understanding of the spatial and temporal dynamics of rainfall-runoff processes during the storm. Here, we show that seismological observations from permanent seismic stations constrain these processes at a catchment scale. The analysis of seismic power, peak frequency, and the back azimuth provides us with the timing and velocity of the propagation of flash-flood waves associated with bedload-dominated phases of the flood on the Vesubie River. Moreover, the combined short-term average to long-term average ratio and template-matching earthquake detection reveal that 114 local earthquakes between local magnitude M-L = -0.5 and M-L = 2 were triggered by the hydrological loading and/or the resulting in situ underground pore pressure increase. This study shows the impact of Storm Alex on the Earth's surface and deep-layer processes and paves the way for future works that can reveal further details of these processes.
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Colliander, A., Reichle, R., Crow, W., Cosh, M., Chen, F., Chan, S., et al. (2022). Validation of Soil Moisture Data Products From the NASA SMAP Mission. Ieee Journal Of Selected Topics In Applied Earth Observations And Remote Sensing, 15, 364–392.
Abstract: The National Aeronautics and Space Administration Soil Moisture Active Passive (SMAP) mission has been validating its soil moisture (SM) products since the start of data production on March 31, 2015. Prior to launch, the mission defined a set of criteria for core validation sites (CVS) that enable the testing of the key mission SM accuracy requirement (unbiased root-mean-square error <0.04 m(3)/m(3)). The validation approach also includes other (“sparse network”) in situ SM measurements, satellite SM products, model-based SM products, and field experiments. Over the past six years, the SMAP SM products have been analyzed with respect to these reference data, and the analysis approaches themselves have been scrutinized in an effort to best understand the products' performance. Validation of the most recent SMAP Level 2 and 3 SM retrieval products (R17000) shows that the L-band (1.4 GHz) radiometer-based SM record continues to meet mission requirements. The products are generally consistent with SM retrievals from the European Space Agency Soil Moisture Ocean Salinity mission, although there are differences in some regions. The high-resolution (3-km) SM retrieval product, generated by combining Copernicus Sentinel-1 data with SMAP observations, performs within expectations. Currently, however, there is limited availability of 3-km CVS data to support extensive validation at this spatial scale. The most recent (version 5) SMAP Level 4 SM data assimilation product providing surface and root-zone SM with complete spatio-temporal coverage at 9-km resolution also meets performance requirements. The SMAP SM validation program will continue throughout the mission life; future plans include expanding it to forested and high-latitude regions.
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Collow, A. B. M., Shields, C. A., Guan, B., Kim, S., Lora, J. M., McClenny, E. E., et al. (2022). An Overview Of Artmip'S Tier 2 Reanalysis Intercomparison: Uncertainty in the Detection of Atmospheric Rivers and Their Associated Precipitation. Journal Of Geophysical Research-Atmospheres, 1271(8).
Abstract: Atmospheric rivers, or long but narrow regions of enhanced water vapor transport, are an important component of the hydrologic cycle as they are responsible for much of the poleward transport of water vapor and result in precipitation, sometimes extreme in intensity. Despite their importance, much uncertainty remains in the detection of atmospheric rivers in large datasets such as reanalyses and century scale climate simulations. To understand this uncertainty, the Atmospheric River Tracking Method Intercomparison Project (ARTMIP) developed tiered experiments, including the Tier 2 Reanalysis Intercomparison that is presented here. Eleven detection algorithms submitted hourly tags--binary fields indicating the presence or absence of atmospheric rivers--of detected atmospheric rivers in the Modern Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) and European Centre for Medium-Range Weather Forecasts' Reanalysis Version 5 (ERA5) as well as six-hourly tags in the Japanese 55-year Reanalysis (JRA-55). Due to a higher climatological mean for integrated water vapor transport in MERRA-2, atmospheric rivers were detected more frequently relative to the other two reanalyses, particularly in algorithms that use a fixed threshold for water vapor transport. The finer horizontal resolution of ERA5 resulted in narrower atmospheric rivers and an ability to detect atmospheric rivers along resolved coastlines. The fraction of hemispheric area covered by ARs varies throughout the year in all three reanalyses, with different atmospheric river detection tools having different seasonal cycles.
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Conway, J., Abermann, J., Andreassen, L., Azam, M., Cullen, N., Fitzpatrick, N., et al. (2022). Cloud Forcing Of Surface Energy Balance From In Situ Measurements In Diverse Mountain Glacier Environments. Cryosphere, 161(8), 3331–3356.
Abstract: Clouds Are An Important Component Of The Climate System, Yet Our Understanding Of How They Directly And Indirectly Affect Glacier Melt In Different Climates Is Incomplete. Here We Analyse High-Quality Datasets From 16 Mountain Glaciers In Diverse Climates Around The Globe To Better Understand How Relationships Between Clouds And Near-Surface Meteorology, Radiation And Surface Energy Balance Vary. The Seasonal Cycle Of Cloud Frequency Varies Markedly Between Mountain Glacier Sites. During The Main Melt Season At Each Site, An Increase In Cloud Cover Is Associated With Increased Vapour Pressure And Relative Humidity, But Relationships To Wind Speed Are Site Specific. At Colder Sites (Average Near-Surface Air Temperature In The Melt Season <0 Degrees C), Air Temperature Generally Increases With Increasing Cloudiness, While For Warmer Sites (Average Near-Surface Air Temperature In The Melt Season >> 0 Degrees C), Air Temperature Decreases With Increasing Cloudiness. At All Sites, Surface Melt Is More Frequent In Cloudy Compared To Clear-Sky Conditions. The Proportion Of Melt From Temperature-Dependent Energy Fluxes (Incoming Longwave Radiation, Turbulent Sensible Heat And Latent Heat) Also Universally Increases In Cloudy Conditions. However, Cloud Cover Does Not Affect Daily Total Melt In A Universal Way, With Some Sites Showing Increased Melt Energy During Cloudy Conditions And Others Decreased Melt Energy. The Complex Association Of Clouds With Melt Energy Is Not Amenable To Simple Relationships Due To Many Interacting Physical Processes (Direct Radiative Forcing; Surface Albedo; And Co-Variance With Temperature, Humidity And Wind) But Is Most Closely Related To The Effect Of Clouds On Net Radiation. These Results Motivate The Use Of Physics-Based Surface Energy Balance Models For Representing Glacier-Climate Relationships In Regional- And Global-Scale Assessments Of Glacier Response To Climate Change.
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Creutin, J. D., Blanchet, J., Reverdy, A., Brochet, A., Lutoff, C., & Robert, Y. (2022). Reported Occurrence of Multiscale Flooding in an Alpine Conurbation over the Long Run (1850-2019). Water, 141(4).
Abstract: This paper deals with the identification of extreme multiscale flooding events in the Alpine conurbation of Grenoble, France. During such events, typically over one to several days, the organization in space and time of the generating hydrometeorological situation triggers the concurrent reaction of varied sets of torrents and main rivers and creates diverse socioeconomic damages and disruptions. Given the limits of instrumental data over the long run, in particular at the torrent scale, we explore the potential of a database of reported extreme flood events to study multiscale flooding over a Metropolitan domain. The definition of Metropolitan events is mainly based on the database built by the RTM (Restauration des Terrains de Montagne, a technical service of the French Forest Administration). Relying on expert reports, the RTM database covers the long lifetime of this French national service for the management of mountainous areas (1850-2019). It provides quantitative information about the time and place of inundation events as well as qualitative information about the generating phenomena and the consequent damages. The selection process to define Metropolitan events simply chronologically explores the RTM database and complements it with historical research data. It looks for concurrence between site events at the same date under a chosen set of criteria. All scales together, we selected 104 Metropolitan events between 1850 and 2019. Exploring the list of dates, we examine the homogeneity of the Metropolitan events over 1850-2019 and their space-time characteristics. We evidence the existence of multiscale flooding at the Metropolitan scale, and we discuss some implications for flood risk management.
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Crotti, I., Quiquet, A., Landais, A., Stenni, B., Wilson, D., Severi, M., et al. (2022). Wilkes Subglacial Basin Ice Sheet Response To Southern Ocean Warming During Late Pleistocene Interglacials. Nature Communications, 131(1).
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Danso, D. K., Anquetin, S., Diedhiou, A., Lavaysse, C., Hingray, B., Raynaud, D., et al. (2022). A CMIP6 assessment of the potential climate change impacts on solar photovoltaic energy and its atmospheric drivers in West Africa. Environmental Research Letters, 171(4).
Abstract: Many solar photovoltaic (PV) energy projects are currently being planned and/or developed in West Africa to sustainably bridge the increasing gap between electricity demand and supply. However, climate change will likely affect solar power generation and the atmospheric factors that control it. For the first time, the state-of-the-art CMIP climate models (CMIP6) are used to investigate the potential future evolution of solar power generation and its main atmospheric drivers in West Africa. A multi-model analyses carried out revealed a decrease of solar PV potential throughout West Africa in the 21st century, with an ensemble mean reduction reaching about 12% in southern parts of the region. In addition, the variability of future solar PV production is expected to increase with a higher frequency of lower production periods. The projected changes in the solar PV production and its variability are expected to be predominant in the June to August season. We found the decrease in the solar PV potential to be driven by a decrease of surface irradiance and an increase of near-surface air temperature. However, the decrease of the surface irradiance accounted for a substantially larger percentage of the projected solar PV potential. The decrease in surface irradiance was further linked to changes in both cloud cover and aerosol presence, although generally much more strongly for the former.
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Dao, T. S., Nguyen, V. T., Baduel, C., Bui, M. H., Tran, V. T., Pham, T. L., et al. (2022). Toxicity of di-2-ethylhexyl phthalate and tris (2-butoxyethyl) phosphate to a tropical micro-crustacean (Ceriodaphnia cornuta) is higher in Mekong River water than in standard laboratory medium. Environmental Science And Pollution Research, .
Abstract: Plasticizers such as di(2-ethylhexyl) phthalate (DEHP) and tris (2-butoxyethyl) phosphate (TBOEP) are manufactured chemicals produced in high volumes. These chemicals are frequently detected in the aquatic environment and cause toxic effects on organisms. In this study, we assessed the chronic impacts of DEHP and TBOEP, respectively, at the concentration of 100 μL-1 dissolved in the artificial medium (M4/4) and Mekong River water on life history traits of a tropical micro-crustacean, Ceriodaphnia cornuta, for 14 days. DEHP and TBOEP substantially reduced the survival of C. cornuta. In M4/4 medium, both plasticizers strongly enhanced reproduction but did not influence the growth of C. cornuta. Mekong River water, plasticizers-exposed C. cornuta produced less neonates than those in the control. The detrimental impacts of DEHP and TBOEP on the fitness of C. cornuta were much stronger in natural river water than in M4/4. Our results suggest that plasticizers can cause adverse effects on tropical freshwater cladocerans, particularly in natural water. These results are of a deep concern, as national and international regulatory guidelines which are based on ecotoxicological tests using standard media may not fully capture these effects.
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Dasari, S., & Widory, D. (2022). Radiocarbon (C-14) Analysis Of Carbonaceous Aerosols: Revisiting The Existing Analytical Techniques for Isolation of Black Carbon. Frontiers In Environmental Science, 101.
Abstract: Air pollution, a complex cocktail of different components, exerts an influence on climate/human; health both locally and away from source regions. The issue of air pollution is often closely linked; to carbonaceous aerosols, the assessment of climate/air quality/health impact of which remains associated with large uncertainties. Black carbon (BC)-a product of incomplete combustion-is a potent climate warming agent and one of the central components to this issue. An accurate; knowledge of BC emitting sources is necessary for devising appropriate mitigation strategies and; policies to reduce the associated climate/environmental burden. The radiocarbon isotope (C-14 or carbon-14) fingerprinting allows for an unambiguous and quantitative constraining of the BC sources and is therefore a well-popularized method. Here, we review the existing analytical techniques for the isolation of BC from a filter matrix for conducting C-14-based investigations. This work summarizes the protocols in use, provides an overarching perspective on the state-of- the-art and recommendations for certain aspects of future method development.
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Dasari, S., Paris, G., Saar, B., Pei, Q. M., Cong, Z. Y., & Widory, D. (2022). Sulfur Isotope Anomalies (Delta S-33) In Urban Air Pollution Linked To Mineral-Dust-Associated Sulfate. Environmental Science & Technology Letters, .
Abstract: Sulfur isotope analysis provides a unique probe for source-specific information and certain atmospheric reactions. Globally, atmospheric aerosols in urban locations exhibit significant sulfur mass-independent fractionation (i.e., S-MIF, Delta S-33 not equal 0). The origin(s) of these S-MIF anomalies remains unclear, thereby limiting the interpretation and/or application of such signals. Her; we conducted dual-isotope (Delta S-33 and delta S-34) fingerprinting of sulfate aerosols from summertime megacity Delhi in south Asia. A shift toward concomitantly high Delta S-33 (from 0.2 parts per thousand to 0.5 parts per thousand) and low delta S-34 (from 5 parts per thousand to 1 parts per thousand) values was observed with the influx of mineral dust. The Fe:Al ratio showed significant correlations with both sulfate loadings (R-2 = 0.84) and Delta S-33 signatures (R-2 = 0.77). Contrary to the prevailing paradigm, this observational evidence suggests that mineral-dust-associated sulfate exhibits S-MIF anomalies. Atmospheric processing of mineral dust plausibly leads to the production of these anomalies. Our evaluation suggests that an inherent mechanism(s) remains elusive. Although hindered by end-member uncertainties, we show that S-MIF signals can be source apportioned to quantitatively constrain the fraction of mineral-dust-associated sulfate in urban locations. The influx of mineral-dust-associated sulfate can influence urban air pollution affecting air quality and/or human health and as such requires monitoring. Urban Delta S-33 signals can therefore be used to trace this sulfate fraction, thereby improving our understanding of sulfate aerosol dynamics.
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de Lavenne, A., Andreassian, V., Crochemore, L., Lindstrom, G., & Arheimer, B. (2022). Quantifying Multi-Year Hydrological Memory With Catchment Forgetting Curves. Hydrology And Earth System Sciences, 262(101), 2715–2732.
Abstract: A climatic anomaly can potentially affect the hydrological behaviour of a catchment for several years. This article presents a new approach to quantifying this multi-year hydrological memory, using exclusively streamflow and climate data. Rather than providing a single value of catchment memory, we aim to describe how this memory fades over time. The precipitation-runoff relationship is analyzed through the concept of elasticity. Elasticity quantifies the change in one quantity caused by the change in another quantity. We analyze the elasticity of the relation between the annual anomalies of runoff yield and humidity index. We identify Catchment Forgetting Curves (CFC) to quantify multiyear catchment memory, considering not only the current year's humidity anomaly but also the anomalies of the preceding years. The variability of CFCs is investigated on a set of 158 Swedish and 527 French catchments. As expected, French catchments overlying large aquifers exhibit a long memory, i.e., with the impact of climate anomalies detected over several years. In Sweden, the expected effect of the lakes is less clear. For both countries, a relatively strong relationship between the humidity index and memory is identified, with drier regions exhibiting longer memory. Taking into account the multi-year memory has significantly improved the elasticity analysis for 15 % of the catchments. Our work thus underlines the need to account for catchment memory in order to produce meaningful and geographically coherent elasticity indices.
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Delrieu, G., Khanal, A. K., Cazenave, F., & Boudevillain, B. (2022). Sensitivity Analysis Of Attenuation In Convective Rainfall At X-Band frequency using the mountain reference technique. Atmospheric Measurement Techniques, 151(111), 3297–3314.
Abstract: The RadAlp experiment aims at improving quantitative precipitation estimation (QPE) in the Alps thanks to X-band polarimetric radars and in situ measurements deployed in the region of Grenoble, France. In this article, we revisit the physics of propagation and attenuation of microwaves in rain. We first derive four attenuation-reflectivity (AZ) algorithms constrained, or not, by path-integrated attenuations (PIAs) estimated from the decrease in the return of selected mountain targets when it rains compared to their dry weather levels (the so-called mountain reference technique – MRT). We also consider one simple polarimetric algorithm based on the profile of the total differential phase shift between the radar and the mountain targets. The central idea of the work is to implement these five algorithms all together in the framework of a generalized sensitivity analysis in order to establish useful parameterizations for attenuation correction. The parameter structure and the inherent mathematical ambiguity of the system of equations makes it necessary to organize the optimization procedure in a nested way. The core of the procedure consists of (i) exploring with classical sampling techniques the space of the parameters allowed to be variable from one target to the other and from one time step to the next, (ii) computing a cost function (CF) quantifying the proximity of the simulated profiles and (iii) selecting parameters sets for which a given CF threshold is exceeded. This core is activated for a series of values of parameters supposed to be fixed, e.g., the radar calibration error for a given event. The sensitivity analysis is performed for a set of three convective events using the 0 degrees elevation plan position indicator (PPI) measurements of the Meteo-France weather radar located on top of the Moucherotte mountain (altitude of 1901 ma.s.l. – above sea level). It allows the estimation of critical parameters for radar QPE using radar data alone. In addition to the radar calibration error, this includes the time series of radome attenuation and estimations of the coefficients of the power law models relating the specific attenuation and the reflectivity (A-Z relationship) on the one hand and the specific attenuation and the specific differential phase shift (A-K-dp relationship) on the other hand. It is noteworthy that the A-Z and A-K-dp relationships obtained are consistent with those derived from concomitant drop size distribution measurements at ground level, in particular with a slightly non-linear A-K-dp relationship (A = 0:28 K-dp(1.1)). X-Band radome attenuations as high as 15 dB were estimated, leading to the recommendation of avoiding the use of radomes for remote sensing of precipitation at such a frequency.
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Dewar, W., Parfitt, R., & Wienders, N. (2022). Routine Reversal Of The Amoc In An Ocean Model Ensemble. Geophysical Research Letters, 494(242).
Abstract: We Describe A Form Of Atlantic Meridional Overturning Circulation (Amoc) Variability That We Believe Has Not Previously Appeared In Observations Or Models. It Is Found In An Ensemble Of Eddy-Resolving North Atlantic Simulations That The Amoc Frequently Reverses In Sign At Similar To 35 Degrees N With Gyre-Wide Anomalies In Size And That Reach Throughout The Water Column. The Duration Of Each Reversal Is Roughly 1 Month. The Reversals Are Part Of The Annual Amoc Cycle Occurring In Boreal Winter, Although Not All Years Feature An Actual Reversal In Sign. The Occurrence Of The Reversals Appears In Our Ensemble Mean, Suggesting It Is A Forced Feature Of The Circulation. A Partial Explanation Is Found In An Ekman Response To Wind Stress Anomalies. Model Ensemble Simulations Run With Different Combinations Of Climatological And Realistic Forcings Argue That It Is The Atmospheric Forcing Specifically That Results In The Reversals, Despite The Signals Extending Into The Deep Ocean.
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Diba, I., Diedhiou, A., Famien, A., Camara, M., & Fotso-Nguemo, T. (2022). Changes In Compound Extremes Of Rainfall And Temperature Over West Africa Using Cmip5 Simulations. Environmental Research Communications, 4(101).
Abstract: This Study Aims To Characterize Changes In Compound Extremes Of Rainfall And Temperature Over West Africa. For This Purpose, Data From Chirps Observations, The Era5 Reanalysis, And Twenty-Four (24) Climate Models Involved In The Cmip5 Project Were Analyzed. First, Climate Models Were Evaluated In Terms Of Their Capacity To Simulate Summer Mean Climatology And Compound Extremes During The Historical Period (1981-2005), And Secondly, Changes In Compound Extremes Were Examined Under Rcp8.5 Emission Scenario Between The Near Future (2031-2055) And The Far Future (2071-2095) Relative To The Historical Period. Despite The Presence Of Some Biases, The Ensemble Mean Of The Models Well Reproduces The Compound Extremes Patterns Over West Africa At The Seasonal And Intraseasonal Timescales. The Analysis Over The Historical Period With Chirps/Era5 Dataset Shows A Strong Occurrence Of The Dry/Warm Mode Over The Northern Sahel During The June-July-August-September Period (Jjas; Main Rainy Season) And Over The Guinean Region During The February-March-April-May Season (Fmam; First And Main Rainy Season). These Strong Occurrences Are Due To A Weak And Highly Frequent Precipitation Recorded In These Zones. The Compound Wet/Warm Mode Is Frequent In Jjas Over The Sahel And The Sudanian Zone (Transition Area Between Sahel And Guinean Regions), While In Fmam, Its Occurrence Is Maximum Over The Guinean Region. The Study Also Shows That The Dry/Warm Mode Will Increase In The Whole Sahel (Western And Central) And In The Guinean Zone In The Near And Far Futures While The Compound Wet/Warm Mode Will Decrease In The Whole Region. This Study Suggests That The West Africa Region Will Be Prone To Drought Intensified By Warmer Temperatures And Calls For Climate Action And Adaptation Strategies To Mitigate The Risks On Rain-Fed Agriculture, Energy, And On Animals And Human Health.
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Dietz, R., Wilson, S., Loseto, L. L., Dommergue, A., Xie, Z. Q., Sonne, C., et al. (2022). Special Issue On The Amap 2021 Assessment Of Mercury In The Arctic. Science Of The Total Environment, 8438.
Abstract: This Editorial presents an overview of the Special Issue on advances in Arctic mercury (Hg) science synthesized from the 2021 assessment of the Arctic Monitoring and Assessment Programme (AMAP). Mercury continues to travel to Arctic environments and threaten wildlife and human health in this circumpolar region. Over the last decade, progress has been achieved in addressing policy-relevant uncertainties in environmental Hg contamination. This includes temporal trends of Hg, its transport to and within the Arctic, methylmercury cycling, climate change influences, biological effects of Hg on fish and wildlife, human exposure to Hg, and forecasting of Arctic responses to different future scenarios of anthropogenic Hg emissions. In addition, important contributions of Indigenous Peoples to Arctic research and monitoring of Hg are highlighted, including through projects of knowledge co-production. Finally, policy-relevant recommendations are summarized for future study of Arctic mercury. This series of scientific articles presents comprehensive information relevant to supporting effectiveness evaluation of the United Nations Minamata Convention on Mercury.
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Dofal, A., Michon, L., Fontaine, F., Rindraharisaona, E., Barruol, G., & Tkalcic, H. (2022). Imaging The Lithospheric Structure And Plumbing System Below Themayotte Volcanic Zone. Comptes Rendus Geoscience, 3543, 47–64.
Abstract: Teleseismic Receiver-Functions And Rayleigh-Wave Dispersion Curves Are Jointly Inverted For Quantifying S-Wave Velocity Profiles Beneath The Active Volcanic Zone Off Mayotte. We Show That The Lithosphere In The East-Northeast Quadrant Is Composed Of Fourmain Layers, Interpreted As The Volcanic Edifice, The Crust With Underplating, The Lithospheric Mantle, And The Asthenosphere, The Latter Two Presenting A Main Low-Velocity Zone. The Depths Of The Old (10-11 Km) And New Moho (28-31 Km) Coincide With The Two Magma Reservoirs Evidenced By Recent Seismological And Petrological Methods. We Propose That The Main Magma Reservoir Composed Of Mush With An Increasing Amount Of Liquid Extends Down To 54 Km Depth. This Magma Storage Develops From A Rheological Contrast Between The Ductile Lower And Brittle Upper Lithospheric Mantle And Accounts For Most Of The Volcanic Eruptionrelated Seismicity. Finally, The Abnormally Small Thickness Of The Lithosphericmantle (33 Km) Is Likely A Result Of A Thermal Thinning Since The Onset Of Cenozoic Magmatism.
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Domine, F., Fourteau, K., Picard, G., Lackner, G., Sarrazin, D., & Poirier, M. (2022). Permafrost Cooled In Winter By Thermal Bridging Through Snow-Covered shrub branches. Nature Geoscience, 151(7), 554–+.
Abstract: Considerable expansion of shrubs across the Arctic tundra has been observed in recent decades. These shrubs are thought to have a warming effect on permafrost by increasing snowpack thermal insulation, thereby limiting winter cooling and accelerating thaw. Here, we use ground temperature observations and heat transfer simulations to show that low shrubs can actually cool the ground in winter by providing a thermal bridge through the snowpack. Observations from unmanipulated herb tundra and shrub tundra sites on Bylot Island in the Canadian high Arctic reveal a 1.21 degrees C cooling effect between November and February. This is despite a snowpack that is twice as insulating in shrubs. The thermal bridging effect is reversed in spring when shrub branches absorb solar radiation and transfer heat to the ground. The overall thermal effect is likely to depend on snow and shrub characteristics and terrain aspect. The inclusion of these thermal bridging processes into climate models may have an important impact on projected greenhouse gas emissions by permafrost. Arctic shrubs cool permafrost in winter by acting as a thermal bridge through the snowpack, according to ground temperature observations and heat transfer simulations.
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Dominutti, P., Chevassus, E., Baray, J., Jaffrezo, J., Borbon, A., Colomb, A., et al. (2022). Evaluation Of The Sources, Precursors, And Processing Of Aerosols At A High-Altitude Tropical Site. Acs Earth And Space Chemistry, .
Abstract: This Work Presents The Results From A Set Of Aerosol- And Gas-Phase Measurements Collected During The Bio-Maido Field Campaign In Reunion Between March 8And April 5, 2019. Several Offline And Online Sampling Devices Were Installed At The Maido Observatory (Mo), A Remote High-Altitude Site In The Southern Hemisphere, Allowing The Physical And Chemical Characterization Of Atmospheric Aerosols And Gases. The Evaluation Of Short-Lived Gas-Phase Measurements Allows Us To Conclude That Air Masses Sampled During This Period Contained Little Or No Anthropogenic Influence. The Dominance Of Sulfate And Organic Species In The Submicron Fraction Of The Aerosol Is Similar To That Measured At Other Coastal Sites. Carboxylic Acids On Pm10 Showed A Significant Contribution Of Oxalic Acid, A Typical Tracer Of Aqueous Processed Air Masses, Increasing At The End Of The Campaign. This Result Agrees With The Positive Matrix Factorization Analysis Of The Submicron Organic Aerosol, Where More Oxidized Organic Aerosols (Mooas) Dominated The Organic Aerosol With An Increasing Contribution Toward The End Of The Campaign. Using A Combination Of Air Mass Trajectories (Model Predictions), It Was Possible To Assess The Impact Of Aqueous Phase Processing On The Formation Of Secondary Organic Aerosols (Soas). Our Results Show How Specific Chemical Signatures And Physical Properties Of Air Masses, Possibly Affected By Cloud Processing, Can Be Identified At Reunion. These Changes In Properties Are Represented By A Shift In Aerosol Size Distribution To Large Diameters And An Increased Contribution Of Secondary Sulfate And Organic Aerosols After Cloud Processing.
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Dominutti, P. A., Renard, P., Vaitilingom, M., Bianco, A., Baray, J. L., Borbon, A., et al. (2022). Insights into tropical cloud chemistry in Reunion (Indian Ocean): results from the BIO-MAiDO campaign. Atmospheric Chemistry And Physics, 222(1), 505–533.
Abstract: We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAiDO” (Bio-physico-chemistry of tropical clouds at Maido (Reunion Island): processes and impacts on secondary organic aerosols' formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March-April 2019 in Reunion (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. Comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-solubility volatile organic compounds, VOCs). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g. chloride, sodium) demonstrating ocean-cloud exchanges. Indeed, Na+ and Cl- dominate the inorganic composition contributing to 30 % and 27 %, respectively, to the average total ion content. The strong correlations between these species (r(2) = 0.87, p value: < 0.0001) suggest similar air mass origins. However, the average molar Cl-/Na+ ratio (0.85) is lower than the sea-salt one, reflecting a chloride depletion possibly associated with strong acids such as HNO3 and H2SO4. Additionally, the non-sea-salt fraction of sulfate varies between 38 % and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 +/- 18.4 mgCL-1), with levels reaching up to 62 mgCL(-1). This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with the land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Even though a minor contribution of VOCs (oxygenated and low-solubility VOCs) to the total dissolved organic carbon (DOC) (0.62 % and 0.06 %, respectively) has been observed, significant levels of biogenic VOC (20 to 180 nmolL(-1)) were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed by measurements obtained in both the gas and aqueous phases and deduced experimental gas-/aqueous-phase partitioning was compared with Henry's law equilibrium to evaluate potential supersaturation or unsaturation conditions. The evaluation reveals the supersaturation of low-solubility VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, evidencing a deviation from thermodynamically expected partitioning in the aqueous-phase chemistry in this highly impacted tropical area.
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Dommo, A., Vondou, D., Philippon, N., Eastman, R., Moron, V., & Aloysius, N. (2022). The Era5'S Diurnal Cycle Of Low-Level Clouds Over Western Central Africa During June-September: Dynamic And Thermodynamic Processes. Atmospheric Research, 2802.
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Dorschel, B., Hehemann, L., Viquerat, S., Warnke, F., Dreutter, S., Tenberge, Y. S., et al. (2022). The International Bathymetric Chart Of The Southern Ocean Version 2. Scientific Data, 9(1).
Abstract: The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60 degrees S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world's oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50 degrees S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50 degrees S.
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dos Santos, T. C., Dominutti, P., Pedrosa, G. S., Coelho, M. S., Nogueira, T., Borbon, A., et al. (2022). Isoprene in urban Atlantic forests: Variability, origin, and implications on the air quality of a subtropical megacity. Science Of The Total Environment, 8248.
Abstract: Biosphere-atmosphere interactions play a key role in urban chemistry because of biogenic volatile organic compound (BVOC) emissions. Of the BVOC, isoprene is the most emitted compound; however, it also has anthropogenic origins in urban areas. In this study, we aimed to investigate the spatio-temporal variability and atmospheric impacts of biogenic and anthropogenic isoprene in the subtropical megacity of Sao Paulo (MASP), Brazil. Several measurement campaigns were conducted in three different urban Atlantic forests (Matao, PEFI, and RMG), and an urban background site (IAG); this equated to a total of 268 samples for the 2018-2019 period. For all sampling points, daytime average concentrations of isoprene were two to three times higher during the rainy season (IAG: 1.75 +/- 0.93 ppb; Matao: 0.87 +/- 0.35 ppb; PEFI: 0.50 +/- 0.30 ppb; RMG: 0.37 +/- 0.18 ppb), than those observed during the dry season (IAG: 0.46 +/- 0.24 ppb; Matao: 0.31 +/- 0.17 ppb; PEFI: 0.17 +/- 0.11 ppb; RMG: 0.11 +/- 0.07 ppb). Average isoprene concentrations were similar to those observed in other places worldwide, with the exception of theAmazon forest. Our results indicate differences in isoprene concentrations between sites, suggesting that environmental conditions such as the urban heat island and vegetation types, may play a role in spatial variability. Estimates of the isoprene fraction indicated that the biogenic fraction (85%) surpassed the anthropogenic fraction during the rainy season. By contrast, the anthropogenic fraction (52%) exceeded the biogenic fraction during dry periods. These fractions have an impact on potentially forming secondary pollutants gaseous (ozone formation potential: 7.19-33.32 μg m(-3)), and aerosols (secondary organic aerosols formation potential: 0.41-1.88 μg m(-3)). These results highlight the role of biogenic isoprene and its potential impact on urban air quality in subtropicalmegacities; this requires further investigation under future climate change scenarios.
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Doscher, R., Acosta, M., Alessandri, A., Anthoni, P., Arsouze, T., Bergman, T., et al. (2022). The Ec-Earth3 Earth System Model For The Coupled Model Intercomparison Project 6. Geoscientific Model Development, 151(7), 2973–3020.
Abstract: The Earth system model EC-Earth3 for contributions to CMIP6 is documented here, with its flexible coupling framework, major model configurations, a methodology for ensuring the simulations are comparable across different high-performance computing (HPC) systems, and with the physical performance of base configurations over the historical period. The variety of possible configurations and sub-models reflects the broad interests in the EC-Earth community. EC-Earth3 key performance metrics demonstrate physical behavior and biases well within the frame known from recent CMIP models. With improved physical and dynamic features, new Earth system model (ESM) components, community tools, and largely improved physical performance compared to the CMIP5 version, EC-Earth3 represents a clear step forward for the only European community ESM. We demonstrate here that EC-Earth3 is suited for a range of tasks in CMIP6 and beyond.
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Durand, G., van den Broeke, M. R., Le Cozannet, G., Edwards, T. L., Holland, P. R., Jourdain, N. C., et al. (2022). Sea-Level Rise: From Global Perspectives to Local Services. Frontiers In Marine Science, 8.
Abstract: Coastal areas are highly diverse, ecologically rich, regions of key socio-economic activity, and are particularly sensitive to sea-level change. Over most of the 20th century, global mean sea level has risen mainly due to warming and subsequent expansion of the upper ocean layers as well as the melting of glaciers and ice caps. Over the last three decades, increased mass loss of the Greenland and Antarctic ice sheets has also started to contribute significantly to contemporary sea-level rise. The future mass loss of the two ice sheets, which combined represent a sea-level rise potential of similar to 65 m, constitutes the main source of uncertainty in long-term (centennial to millennial) sea-level rise projections. Improved knowledge of the magnitude and rate of future sea-level change is therefore of utmost importance. Moreover, sea level does not change uniformly across the globe and can differ greatly at both regional and local scales. The most appropriate and feasible sea level mitigation and adaptation measures in coastal regions strongly depend on local land use and associated risk aversion. Here, we advocate that addressing the problem of future sea-level rise and its impacts requires (i) bringing together a transdisciplinary scientific community, from climate and cryospheric scientists to coastal impact specialists, and (ii) interacting closely and iteratively with users and local stakeholders to co-design and co-build coastal climate services, including addressing the high-end risks.
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Ershadi, M. R., Drews, R., Martin, C., Eisen, O., Ritz, C., Corr, H., et al. (2022). Polarimetric Radar Reveals The Spatial Distribution Of Ice Fabric At domes and divides in East Antarctica. Cryosphere, 161(5), 1719–1739.
Abstract: Ice crystals are mechanically and dielectrically anisotropic. They progressively align under cumulative deformation, forming an ice-crystal-orientation fabric that, in turn, impacts ice deformation. However, almost all the observations of ice fabric are from ice core analysis, and its influence on the ice flow is unclear. Here, we present a non-linear inverse approach to process co- and cross-polarized phase-sensitive radar data. We estimate the continuous depth profile of georeferenced ice fabric orientation along with the reflection ratio and horizontal anisotropy of the ice column. Our method approximates the complete second-order orientation tensor and all the ice fabric eigenvalues. As a result, we infer the vertical ice fabric anisotropy, which is an essential factor to better understand ice deformation using anisotropic ice flow models. The approach is validated at two Antarctic ice core sites (EPICA (European Project for Ice Coring in Antarctica) Dome C and EPICA Dronning Maud Land) in contrasting flow regimes. Spatial variability in ice fabric characteristics in the dome-to-flank transition near Dome C is quantified with 20 more sites located along with a 36 km long cross-section. Local horizontal anisotropy increases under the dome summit and decreases away from the dome summit We suggest that this is a consequence of the nonlinear rheology of ice, also known as the Raymond effect. On larger spatial scales, horizontal anisotropy increases with increasing distance from the dome. At most of the sites, the main driver of ice fabric evolution is vertical compression, yet our data show that the horizontal distribution of the ice fabric is consistent with the present horizontal flow. This method uses polarimetric-radar data, which are suitable for profiling radar applications and are able to constrain ice fabric distribution on a spatial scale comparable to ice flow observations and models.
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Espinoza, J. C., Marengo, J. A., Schongart, J., & Jimenez, J. C. (2022). The New Historical Flood Of 2021 In The Amazon River Compared To Major floods of the 21st century: Atmospheric features in the context of the intensification of floods. Weather And Climate Extremes, 353.
Abstract: In June 2021 a new extreme flood was reported in the Amazon Basin, the largest hydrological system on Earth. During this event water level was above 29 m (the emergency threshold) for 91 days at Manaus station (Brazil), surpassing even the previous historical flood of 2012. Since the late 1990s, 9 extreme floods occurred, while only 8 events were reported from 1903 to 1998. Here we report that the 2021 flood is associated with an intensification of the atmospheric upward motion in the northern Amazonia (5?degrees S-5?degrees N), which is related to an intensification of the Walker circulations. This atmospheric feature is associated with an enhanced of deep convective clouds and intense rainfall over the northern Amazonia that produce positive anomalies of terrestrial water storage over northern Amazonia in the 2021 austral summer. The intensification of Walker circulation is associated with La Nina conditions that characterize the major floods observed in Amazonia during the 21st century (2009, 2012 and 2021). However, during the 2021 an intensification of the continental Hadley circulation is also observed. This feature produces simultaneous dry conditions over southern and southeastern Amazonia, where negative rainfall anomalies, low frequency of deep convective clouds and negative anomalies of terrestrial water storage are observed.
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Fain, X., Rhodes, R. H., Place, P., Petrenko, V. V., Fourteau, K., Chellman, N., et al. (2022). Northern Hemisphere atmospheric history of carbon monoxide since preindustrial times reconstructed from multiple Greenland ice cores. Climate Of The Past, 181(3), 631–647.
Abstract: Carbon monoxide (CO) is a regulated pollutant and one of the key components determining the oxidizing capacity of the atmosphere. Obtaining a reliable record of atmospheric CO mixing ratios ([CO]) since preindustrial times is necessary to evaluate climate-chemistry models under conditions different from today and to constrain past CO sources. We present high-resolution measurements of CO mixing ratios from ice cores drilled at five different sites on the Greenland ice sheet that experience a range of snow accumulation rates, mean surface temperatures, and different chemical compositions. An optical-feedback cavity-enhanced absorption spectrometer (OF-CEAS) was coupled with continuous melter systems and operated during four analytical campaigns conducted between 2013 and 2019. Overall, continuous flow analysis (CFA) of CO was carried out on over 700 m of ice. The CFA-based CO measurements exhibit excellent external precision (ranging from 3.3 to 6.6 ppbv, 1 sigma) and achieve consistently low blanks (ranging from 4.1 +/- 1.2 to 12.6 +/- 4.4 ppbv), enabling paleoatmospheric interpretations. However, the five CO records all exhibit variability that is too large and rapid to reflect past atmospheric mixing ratio changes. Complementary tests conducted on discrete ice samples demonstrate that these variations are not artifacts of the analytical method (i.e., production of CO from organics in the ice during melting) but are very likely related to in situ CO production within the ice before analysis. Evaluation of the signal resolution and co-investigation of high-resolution records of CO and total organic carbon (TOC) suggest that past atmospheric CO variations can be extracted from the records' baselines with accumulation rates higher than 20 cm w.e. yr(-1) (water equivalent per year). Consistent baseline CO records from four Greenland sites are combined to produce a multisite average ice core reconstruction of past atmospheric CO for the Northern Hemisphere high latitudes, covering the period from 1700 to 1957 CE. Such a reconstruction should be taken as an upper bound of past atmospheric CO abundance. From 1700 to 1875 CE, the record reveals stable or slightly increasing values in the 100-115 ppbv range. From 1875 to 1957 CE, the record indicates a monotonic increase from 114 +/- 4 to 147 +/- 6 ppbv. The ice core multisite CO record exhibits an excellent overlap with the atmospheric CO record from Green-land firn air which spans the 1950-2010 CE time period. The combined ice core and firn air CO history, spanning 1700-2010 CE, provides useful constraints for future model studies of atmospheric changes since the preindustrial period.
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Fan, L., Al-Yaari, A., Frappart, F., Peng, J., Wen, J. G., Xiao, Q., et al. (2022). Estimating High-Resolution Soil Moisture Over Mountainous Regions Using Remotely-Sensed Multispectral and Topographic Data. Ieee Journal Of Selected Topics In Applied Earth Observations And Remote SENSING, 151, 3637–3649.
Abstract: A surface soil moisture (SM) condition at high spatiotemportal resolutions is required by regional Earth system applications. Here, we mapped daily 1-km SM in the Babao River Basin in the northwest of China during the summers from 2013 to 2015 using a random forest (RF) method by merging SM information retrieved from in situ measurements, optical/thermal remote sensing, and topographical indices. Relative importance analysis was used to determine the optimal predictors for estimating high-resolution SM. A specific RF model (RFVI+sup) was constructed using the optimal predictors including remote sensing albedo, apparent thermal inertia (ATI), normalized difference vegetation index, normalized difference infrared index 5, soil adjusted vegetation index, and topographical indices (aspect and elevation). The RFVI+sup also accounted for missing observations of the thermal index (e.g., ATI) over the mountainous regions. In the comparison between the SM estimates using the new RFVI+sup model and other RF models, the spatial coverage of available estimates increased from 14% to 64% over the study region, the correlation coefficient values were improved to 0.75, the unbiased root-mean-squared difference values decreased to 0.032 m(3)/m(3). Thus, the proposed RF method provided accurate SM estimates with high spatiotemporal resolution over the mountainous regions, by merging multiresource datasets from in situ measurements, remotely-sensed, and topographical indices.
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Fang, G., Li, Z., Yang, J., Chen, Y., Duan, W., Amory, C., et al. (2022). Changes In Flooding In The Alpine Catchments Of The Tarim River Basin, Central Asia. Journal Of Flood Risk Management, .
Abstract: Floods Are One Of The Most Affective Climate-Related Disasters, And Climate Change Has Altered Their Intensity And Frequency Worldwide. This Study Examined Long-Term Changes In Flood Characteristics (Including Magnitude, Frequency, And Timing) In 30 Alpine Headwaters Of The Large Endorheic Tarim River Basin, Central Asia. The Contributions Of Climatic Factors To Flood (Magnitude And Timing) Changes Were Investigated Using Numerical Experiments In Combination With The Random Forest Approach. The Following Results Were Obtained: (1) Annual Maximum Flood Peaks Increased At Most Stations (89% Stations) During 1961-2015 With Increased Flood Frequency. Earlier Flood Peaks Were Observed In Spring With A Rate Of 1.38 Day Per Decade; For Other Seasons, Changes In The Occurrence Time Of Flood Peaks Showed Strong Spatial Variability. (2) Precipitation Was The Dominant Factor For The Increased Flood Magnitude In Most Catchments Of The Southern Slope Of The Tianshan Mountains, And Temperature Played A Greater Role In The Northern Kunlun Mountains. (3) For Flood Timing Changes, Melt Level Height And Precipitation Were The Most Influential Factors In The Alpine Catchments In The Tarim River Basin. The Results Provide Information On The Spatiotemporal Variations Of Floods And Their Driving Factors In This Alpine Basin Under Climate Change.
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Fang, G., Yang, J., Li, Z., Chen, Y., Duan, W., Amory, C., et al. (2022). Shifting In The Global Flood Timing. Scientific Reports, 121(1).
Abstract: Climate Change Will Have An Impact On Not Only Flood Magnitude But Also On Flood Timing. This Paper Studies The Shifting In Flood Timing At 6167 Gauging Stations From 1970 To 2010, Globally. The Shift In Flood Timing And Its Relationship With Three Influential Factors (Maximum 7-Day Precipitation, Soil Moisture Excess, And Snowmelt) Are Investigated. There Is A Clear Global Pattern In The Mean Flooding Date: Winter (Dec-Feb) Across The Western Coastal America, Western Europe And The Mediterranean Region, Summer (Jun-Aug) In The North America, The Alps, Indian Peninsula, Central Asia, Japan, And Austral Summer (Dec-Feb) In South Africa And North Australia Area. The Shift In Flood Timing Has A Trend From – 22 Days Per Decade (Earlier) To 28 Days Per Decade (Delayed). Earlier Floods Were Found Extensively In The North America, Europe And Northeast Australia While Delayed Floods Were Prevailing In The Amazon, Cerrado, South Africa, India And Japan. Earlier Flood Timing In The North America And Europe Was Caused By Earlier Snowmelt While Delayed Extreme Soil Moisture Excess And Precipitation Have Jointly Led To Delayed Floods Around The Monsoon Zone, Including South Africa, India And Japan. This Study Provides An Insight On The Shifting Mechanism Of Flood Timing, And Supports Decisions On The Global Flood Mitigation And The Impact From Future Climate Change.
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Fleurbaey, H., Campargue, A., Da Silva, Y. C. M., Grilli, R., Kassi, S., & Mondelain, D. (2022). Characterization Of The H2O + Co2 Continuum Within The Infrared transparency windows. Journal Of Quantitative Spectroscopy & Radiative Transfer, 2822.
Abstract: Absorption spectra of humidified CO2 have been recorded at room temperature by cavity enhanced absorption techniques (CRDS and OFCEAS): (i) in three spectral ranges of the 1.6 μm window (5720-6045 cm (-1); 6390-6460 cm (-1) and 6570-6665 cm -1), (ii) in four narrow spectral intervals of the 2.3 μm window (4243-4255 cm(-1); 4301.3-4302 cm(-1); 4 421.5-4 4 40 cm(-1)and 4518-4535 cm( -1)), and (iii) around 2853 cm( -1). All these spectral ranges are situated in transparency windows of both H2O and CO2. The binary absorption coefficients (BC O-2-H2O +BH2O-C O-2) are retrieved from low pressure spectra ( < 1 atm) recorded with different molar fractions of water vapor in CO2 after subtracting the H2O and CO2 local monomer contributions and the self-continuum contribution of each species (i.e. H2O -H2O and CO2-CO2). Experimental room temperature binary coefficients are then compared to the only available empirical model based on line shape profiles with chi-factors. This model well reproduces our experimental values on the low-and high-frequency edges of the 1.6 μm window and gives a relatively good agreement for the 2853 cm( -1) data point. Larger differences are observed in the 2.3 μm window where the calculated values are underestimated by a factor of 3. Around 60 0 0 cm( -1), an additional absorption peak is observed which is tentatively interpreted as a collision induced absorption band due to the simultaneous excitation of the H2O and CO2 molecules. (C)& nbsp;2022 Elsevier Ltd. All rights reserved.
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Fleurbaey, H., Campargue, A., Da Silva, Y. C. M., Grilli, R., Kassi, S., & Mondelain, D. (2022). Characterization Of The H2O + Co2 Continuum Within The Infrared transparency windows. Journal Of Quantitative Spectroscopy & Radiative Transfer, 2822.
Abstract: Absorption spectra of humidified CO2 have been recorded at room temperature by cavity enhanced absorption techniques (CRDS and OFCEAS): (i) in three spectral ranges of the 1.6 μm window (5720-6045 cm (-1); 6390-6460 cm (-1) and 6570-6665 cm -1), (ii) in four narrow spectral intervals of the 2.3 μm window (4243-4255 cm(-1); 4301.3-4302 cm(-1); 4 421.5-4 4 40 cm(-1)and 4518-4535 cm( -1)), and (iii) around 2853 cm( -1). All these spectral ranges are situated in transparency windows of both H2O and CO2. The binary absorption coefficients (BC O-2-H2O +BH2O-C O-2) are retrieved from low pressure spectra ( < 1 atm) recorded with different molar fractions of water vapor in CO2 after subtracting the H2O and CO2 local monomer contributions and the self-continuum contribution of each species (i.e. H2O -H2O and CO2-CO2). Experimental room temperature binary coefficients are then compared to the only available empirical model based on line shape profiles with chi-factors. This model well reproduces our experimental values on the low-and high-frequency edges of the 1.6 μm window and gives a relatively good agreement for the 2853 cm( -1) data point. Larger differences are observed in the 2.3 μm window where the calculated values are underestimated by a factor of 3. Around 60 0 0 cm( -1), an additional absorption peak is observed which is tentatively interpreted as a collision induced absorption band due to the simultaneous excitation of the H2O and CO2 molecules. (C)& nbsp;2022 Elsevier Ltd. All rights reserved.
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Fleurbaey, H., Grilli, R., Mondelain, D., & Campargue, A. (2022). Measurements of the water vapor continuum absorption by OFCEAS at 3.50 μm and 2.32 μm. Journal Of Quantitative Spectroscopy & Radiative Transfer, 2782.
Abstract: Measurements of the water vapor absorption cross-sections at two spectral points of the 2.1 μm and 4.0 μm transparency windows are performed by optical feedback cavity enhanced absorption spectroscopy (OFCEAS). The self-continuum cross-section, C-s, is measured for temperature values of 30 and 47 degrees C (303 and 320 K) at the 2853 cm(-1) spectral point, corresponding to the lowest opacity region of the 4.0 μm transparency window. The C-s values derived from the pressure squared dependence of the self-continuum, are found consistent with previous CEAS measurements in the considered window but significantly smaller than measurements by Fourier transform spectroscopy (FTS). The C-s temperature dependence is discussed in relation with FTS measurements at high temperature. Foreign-continuum cross-sections, C-F, are newly obtained from OFCEAS spectra of moist air in flow regime at the 4302 cm(-1) spectral point of the low energy edge of the 2.1 μm window. After subtraction of the monomer and self-continuum contributions, C-F values are derived from the linear variation of the foreign-continuum absorption with the product of the water vapor and air partial pressures. The measurements were performed for temperature values of 34 and 47 degrees C (307 and 320 K) and no significant temperature dependency was observed. The present C-F value at 4302 cm(-1) is gathered with previous CEAS measurements at seven spectral points of the 2.1 μm window. This consistent set of C-F values is used to derive from a polynomial fit, the empirical frequency dependence of C-F(v) over the 4250-5000 cm(-1) range. Overall, the semi-empirical MTCKD3.5 values of C-F are significantly underestimated in the centre of the considered window. (C) 2021 Elsevier Ltd. All rights reserved.
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Foret, G., Michoud, V., Kotthaus, S., Petit, J., Baudic, A., Siour, G., et al. (2022). The December 2016 Extreme Weather And Particulate Matter Pollution Episode In The Paris Region (France). Atmospheric Environment, 2912.
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Fotso-Nguemo, T., Vondou, D., Diallo, I., Diedhiou, A., Weber, T., Tanessong, R., et al. (2022). Potential impact of 1.5, 2 and 3 degrees C global warming levels on heat and discomfort indices changes over Central Africa. Science Of The Total Environment, 804.
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Francis, D., Fonseca, R., Nelli, N., Bozkurt, D., Picard, G., & Guan, B. (2022). Atmospheric rivers drive exceptional Saharan dust transport towards Europe. Atmospheric Research, 2662.
Abstract: This study highlights the occurrence of atmospheric rivers (ARs) over northwest Africa towards Europe, which were accompanied by intense episodes of Saharan dust transport all the way to Scandinavia, in the winter season. Using a combination of observational and reanalysis data, we investigate two extreme dusty AR events in February 2021 and assess their impact on snow melt in the Alps. The warm, moist, and dusty air mass (spatially-averaged 2-meter temperature and water vapour mixing ratio anomalies of up to 8 K and 3 g kg(-1), and aerosol optical depths and dust loadings of up to 0.85 and 11 g m (2), respectively) led to a 50% and 40% decrease in snow depth and surface albedo, respectively, in less than one month during the winter season. ARs over northwest Africa show increasing trends over the past 4 decades, with 78% of AR events associated with severe dust episodes over Europe.
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Frezat, H., Le Sommer, J., Fablet, R., Balarac, G., & Lguensat, R. (2022). A Posteriori Learning For Quasi-Geostrophic Turbulence Parametrization. Journal Of Advances In Modeling Earth Systems, 141(111).
Abstract: The Use Of Machine Learning To Build Subgrid Parametrizations For Climate Models Is Receiving Growing Attention. State-Of-The-Art Strategies Address The Problem As A Supervised Learning Task And Optimize Algorithms That Predict Subgrid Fluxes Based On Information From Coarse Resolution Models. In Practice, Training Data Are Generated From Higher Resolution Numerical Simulations Transformed In Order To Mimic Coarse Resolution Simulations. By Essence, These Strategies Optimize Subgrid Parametrizations To Meet So-Called A Priori Criteria. But The Actual Purpose Of A Subgrid Parametrization Is To Obtain Good Performance In Terms Of A Posteriori Metrics Which Imply Computing Entire Model Trajectories. In This Paper, We Focus On The Representation Of Energy Backscatter In Two-Dimensional Quasi-Geostrophic Turbulence And Compare Parametrizations Obtained With Different Learning Strategies At Fixed Computational Complexity. We Show That Strategies Based On A Priori Criteria Yield Parametrizations That Tend To Be Unstable In Direct Simulations And Describe How Subgrid Parametrizations Can Alternatively Be Trained End-To-End In Order To Meet A Posteriori Criteria. We Illustrate That End-To-End Learning Strategies Yield Parametrizations That Outperform Known Empirical And Data-Driven Schemes In Terms Of Performance, Stability, And Ability To Apply To Different Flow Configurations. These Results Support The Relevance Of Differentiable Programming Paradigms For Climate Models In The Future.
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Fugger, S., Fyffe, C. L., Fatichi, S., Miles, E., McCarthy, M., Shaw, T. E., et al. (2022). Understanding Monsoon Controls On The Energy And Mass Balance Of glaciers in the Central and Eastern Himalaya. Cryosphere, 161(5), 1631–1652.
Abstract: The Indian and East Asian summer monsoons shape the melt and accumulation patterns of glaciers in High Mountain Asia in complex ways due to the interaction of persistent cloud cover, large temperature ranges, high atmospheric water content and high precipitation rates. Glacier energy- and mass-balance modelling using in situ measurements offers insights into the ways in which surface processes are shaped by climatic regimes. In this study, we use a full energy- and mass-balance model and seven on-glacier automatic weather station datasets from different parts of the Central and Eastern Himalaya to investigate how monsoon conditions influence the glacier surface energy and mass balance. In particular, we look at how debris-covered and debris-free glaciers respond differently to monsoonal conditions. The radiation budget primarily controls the melt of cleanice glaciers, but turbulent fluxes play an important role in modulating the melt energy on debris-covered glaciers. The sensible heat flux decreases during core monsoon, but the latent heat flux cools the surface due to evaporation of liquid water. This interplay of radiative and turbulent fluxes causes debris-covered glacier melt rates to stay almost constant through the different phases of the monsoon. Ice melt under thin debris, on the other hand, is amplified by both the dark surface and the turbulent fluxes, which intensify melt during monsoon through surface heating and condensation. Pre-monsoon snow cover can considerably delay melt onset and have a strong impact on the seasonal mass balance. Intermittent monsoon snow cover lowers the melt rates at high elevation. This work is fundamental to the understanding of the present and future Himalayan cryosphere and water budget, while informing and motivating further glacier- and catchment-scale research using process-based models.
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Gaubert-Bastide, T., Garambois, S., Bordes, C., Voisin, C., Oxarango, L., Brito, D., et al. (2022). High-Resolution Monitoring Of Controlled Water Table Variations From Dense Seismic-Noise Acquisitions. Water Resources Research, 585(8).
Abstract: Water-Resource Management Has Become A Major Global Issue In A World Threatened By Climate Change. High-Resolution Geophysical Methods May Be Of Valuable Help In Monitoring The Water Masses, Both In Space And Time. Passive Seismic Interferometry Takes Advantage Of Ambient Seismic Noise To Recover The Variations In Seismic Wave Velocity Induced By Changes In Groundwater. We Present Hereafter The Time And Space Monitoring Of An Hydraulic Dome Artificially Formed To Prevent Biological And Chemical Pollutants From Entering The Exploitation Field Of Crepieux-Charmy (Lyon, France). We Use A Dense Seismic Network To Passively Monitor The Water Table Changes Induced By Infilling Of An Infiltration Basin At The Water Supply Facility For The Two Million Inhabitants Of The Lyon Metropolis (France). We Assess The Hourly Seismic Velocity Variations Over 19 Days, During Which Two Filling And Drainage Cycles Were Performed. The Use Of A Dense Three-Component Seismic Network Allows Fine Characterization Of The Seismic Wavefield, And Offers The Possibility To Include The Analysis Of 4,851 Raypaths In A Robust Inversion Algorithm Based On Ray Theory. The Velocity Variations Are Mapped With High Resolution. They Are Directly Related To The Water Table Variations And To Residual Water Saturation Changes Within The Unsaturated Zone. This Seismic Experiment Highlights The Three-Dimensional (3D) Implementation And Evolution Of A Hydraulic Dome Under The Infiltration Basin. This Dynamic Information Helps In The Understanding And Modeling Of Water Flows Between The Water Table And A River, Which Represents A Fundamental Issue For Discussions On The Effectiveness Of The Barrier.
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Gaubert-Bastide, T., Garambois, S., Bordes, C., Voisin, C., Oxarango, L., Brito, D., et al. (2022). High-Resolution Monitoring Of Controlled Water Table Variations From Dense Seismic-Noise Acquisitions. Water Resources Research, 585(8).
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Geindreau, C., Emeriault, F., Dadda, A., Yaba, O., Spadini, L., Filet, A., et al. (2022). Mechanical and Microstructural Changes of Biocemented Sand Subjected to an Acid Solution. International Journal Of Geomechanics, 22(3).
Abstract: An experimental study was performed to investigate the effects of an acid solution on the mechanical strength and the microstructure of biocemented sand. The tests were performed on small triaxial samples extracted from a large-scale model. An acid solution composed of hydrochloric acid and Tris buffer with an initial pH of 6.6 was injected in the triaxial apparatus in different amounts. The changes of the physical and mechanical properties of the sample were studied afterwards. Triaxial drained tests with constant confining pressures were performed on the chemically treated samples in order to determine the remaining strength of the samples. Moreover, several scanning electron microscope (SEM) and X-ray microtomography observations were performed on small subsamples in order to identify the changes in the microstructure due to the chemical dissolution. The experimental results point out that the strength of the treated specimens decreases dramatically compared with that of the initial untreated specimens. Typically, a 50% strength reduction has been found for 10% of total calcite dissolution. Furthermore, the microstructural observations have shown uniform calcite dissolution at the pore scale (no preferential locations). The calcite crystal structures were damaged randomly by the chemical solution. A reduction of the spatial densities and sizes of these crystals were found from SEM and X-ray microtomography observations. Overall, no hysteretic effects were observed on the mechanical (strength) and microstructural (contact surface area) properties between the biocementation and dissolution paths.
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Genthon, C., Veron, D. E., Vignon, E., Madeleine, J. B., & Piard, L. (2022). Water vapor in cold and clean atmosphere: a 3-year data set in the boundary layer of Dome C, East Antarctic Plateau. Earth System Science Data, 141(4), 1571–1580.
Abstract: The air at the surface of the high Antarctic Plateau is very cold, dry and clean. Under such conditions, the atmospheric moisture can significantly deviate from thermodynamic equilibrium, and supersaturation with respect to ice can occur. Most conventional humidity sensors for meteorological applications cannot report supersaturation in this environment. A simple approach for measuring supersaturation using conventional instruments, with one being operated in a heated airflow, is presented. Since 2018, this instrumental setup has been deployed at three levels in the lower similar to 40m above the surface at Dome C on the high Antarctic Plateau. A resulting 3-year (2018-2020) record (Genthon et al., 2021a) is presented and analyzed for features such as the frequency of supersaturation with respect to ice, diurnal and seasonal variability, and vertical distribution. As supercooled liquid water droplets are frequently observed in clouds at the temperatures experienced on the high Antarctic Plateau, the distribution of relative humidity with respect to liquid water at Dome C is also discussed. It is suggested that, while not strictly mimicking the conditions of the high troposphere, the surface atmosphere on the Antarctic Plateau is a convenient natural laboratory to test parametrizations of cold microphysics predominantly developed to handle the genesis of high tropospheric clouds. Data are available from the PANGAEA data repository at https://doi.org/10.1594/PANGAEA.939425 (Genthon et al., 2021a).
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Gilbert, A., Gimbert, F., Thogersen, K., Schuler, T. V., & Kaab, A. (2022). A Consistent Framework For Coupling Basal Friction With Subglacial Hydrology on Hard-Bedded Glaciers. Geophysical Research Letters, 494(131).
Abstract: Below hard-bedded glaciers, both basal friction and distributed subglacial drainage are thought to be controlled by a network of cavities. Previous coupled hydro-mechanical models, however, describe cavity-driven friction and hydraulic transmissivity independently, resulting in a physically inconsistent cavity evolution between the two components of the models. Here, we overcome this issue by describing the hydro-mechanical system using a common cavity-evolution description, that governs both transient friction and hydraulic transmissivity. We show that our coupling approach is superior to previous formulations in explaining a unique observation record of glacier sliding speed from the French Alps. We find that, at multi-day to multi-decadal timescales, sliding speed can be expressed as a direct function of basal shear stress and water discharge, without accounting for water pressure, which simply adjusts to maintain the cavitation ratio needed to accommodate the water supply.
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Gonzalez-Garcia, A., Palomo, I., Arboledas, M., Gonzalez, J., Mugica, M., Mata, R., et al. (2022). Protected Areas As A Double Edge Sword: An Analysis Of Factors Driving Urbanisation In Their Surroundings. Global Environmental Change-Human And Policy Dimensions, 747.
Abstract: Protected Areas (Pas) Are The Most Effective Tools To Protect Biodiversity And Ecosystem Services. They Have Proven To Be Effective In Stopping Extensive Land Use Conversion In Well-Conserved Terrestrial Ecosystems. However, Land Cover Changes Around Pas Threaten Biodiversity And Ecosystem Services Within Their Limits And Reduce Ecological Connectivity. In This Study, We Analysed The Urban Sprawls On The Boundaries Of 159 Pas (National, Regional, And Natural Parks) In Spain, Using 2.5 And 5 Km Non-Protected Buffer Zones From 1990 To 2018. We Clustered Pas Based On Biophysical And Socio-Economic Characteristics And Modelled Urban Sprawl In Different Buffers And Periods. Hierarchical Clustering Revealed Three Groups Of Pas: (A) Proximate Urban Parks, (B) Mountainous Parks, And (C) Parks In The Madrid Autonomous Region. We Found That Urbanisation In The Surroundings Of Pas In Spain Has Nearly Doubled Since 1990. General Linear Models Explained A Significant Proportion Of The Urbanisation Trends Observed, With The Number Of Municipalities In The Boundary Of The Pa, The Distance To A Main Road, And The Distance To A Big City Acting As The Most Important Drivers Of Urban Sprawl. Our Results Also Show That Some Pas Exert Significant Effects On Urbanisation Trends In Their Surroundings Through The Park-View Effect. Finally, We Highlight Three Coexisting Phenomena That Might Explain The Observed Urban Sprawl Processes: (A) Pas Attracting Urbanisation In Their Surroundings Due To The Park-View Effect, (B) Pas As A Deterrent For Urban Sprawl Within Their Limits, And (C) Pas Occupying Residual Areas Among Previously Urbanised Lands.
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Grange, S. K., Uzu, G., Weber, S., Jaffrezo, J. L., & Hueglin, C. (2022). Linking Switzerland'S Pm10 And Pm2.5 Oxidative Potential (Op) With emission sources. Atmospheric Chemistry And Physics, 222(101), 7029–7050.
Abstract: Particulate matter (PM) is the air pollutant that causes the greatest deleterious health effects across the world, so PM is routinely monitored within air quality networks, usually in respect to PM mass or number in different size fractions. However, such measurements do not provide information on the biological toxicity of PM. Oxidative potential (OP) is a complementary metric that aims to classify PM in respect to its oxidising ability in the lungs and is being increasingly reported due to its assumed relevance concerning human health. Between June 2018 and May 2019, an intensive filter-based PM sampling campaign was conducted across Switzerland in five locations, which involved the quantification of a large number of PM constituents and the OP for both PM10 and PM2.5. OP was quantified by three assays: ascorbic acid (AA), dithiothreitol (DTT), and dichlorofluorescein (DCFH). OPv (OP by air volume) was found to be variable over time and space: Bern-Bollwerk, an urban-traffic sampling site, had the greatest levels of OPv among the Swiss sites (especially when considering OPvAA ), with more rural locations such as Payerne experiencing a lower OPv. However, urban-background and suburban sites experienced a significant OPv enhancement, as did the rural Magadino-Cadenazzo site during wintertime because of high levels of wood smoke. The mean OP ranges for the sampling period were 0.4-4.1 nmolmin(-1)m(-3), 0.6-3.0 nmolmin(-1)m(-3), and 0.3-0.7 nmolH(2)O(2)m(-3) for OPvAA, OPDvTT, and OPvDCFH, respectively. A source allocation method using positive matrix factorisation (PMF) models indicated that although all PM10 and PM2.5 sources that were identified contributed to OPv, the anthropogenic road traffic and wood combustion sources had the greatest OPm potency (OP per PM mass) on average. A dimensionality reduction procedure coupled to multiple linear regression modelling consistently identified a handful of metals usually associated with nonexhaust emissions, namely copper, zinc, iron, tin, antimony, manganese, and cadmium, as well as three specific wood-burning-sourced organic tracers – levoglucosan, mannosan, and galactosan (or their metal substitutes: rubidium and potassium), as the most important PM components to explain and predict OPv. The combination of a metal and a wood-burning-specific tracer led to the best-performing linear models to explain OPv. Interestingly, within the non-exhaust and wood combustion emission groups, the exact choice of component was not critical; the models simply required a variable representing the emission source or process to be present. This analysis strongly suggests that anthropogenic and locally emitting road traffic and wood burning sources should be prioritised, targeted, and controlled to gain the most efficacious decrease in OPv and presumably biological harm reductions in Switzerland.
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Grey, L., Johnson, A. V., Matthews, T., Perry, L. B., Elmore, A. C., Khadka, A., et al. (2022). Mount Everest's photogenic weather during the post-monsoon. Weather, .
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Grima, C., Mouginot, J., Kofman, W., Herique, A., & Beck, P. (2022). The Basal Detectability of an Ice-Covered Mars by MARSIS. Geophysical Research Letters, 494(2).
Abstract: The detection of anomalously strong relative basal reflectivity beneath the Martian South Polar Layered Deposits (SPLD) from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) has led to hypotheses suggesting the presence of basal materials such as liquid water. Here, we propose a forward approach to assess whether such a high signal could be produced by a Martian terrain currently exposed at the surface without liquid water. We convert existing MARSIS surface reflectivity measurements into a basal reflectivity as if it were overlaid by an SPLD-like ice deposit. 0.3%-2% of the surface could produce basal reflections of magnitude similar to the SPLD measurements in the assumption of a 10% impure ice. An ice loss tangent > $ > $0.01 is required to prevent any of the current Martian surface from producing a bright SPLD-like basal reflection. The detected bright terrains are gathered within volcanic constructs of diverse geologic epoch.
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Hachgenei, N., Nord, G., Spadini, L., Mora, H., Courvoisier, F., Sutra, J. F., et al. (2022). A device to simulate contaminant transfer and surface and subsurface flow through intact soil monoliths. Vadose Zone Journal, .
Abstract: Many contaminants of agricultural origin are released into rural environments, particularly at the soil surface. Their fate has been extensively investigated in repacked soils, but only few studies have addressed their transport in structurally preserved natural soils. Much remains unknown about their fate and transfer within and between environmental compartments, while the susceptibility of these compartments to the contaminants adverse effects can vary considerably. The lack of studies regarding surface and subsurface transfer of contaminants through intact soil compared with studies on repacked soil led us to propose a device and protocol for sampling intact soil monoliths (60 x 30 x 22 cm(3), length, width, depth [LWD]) without heavy machinery. This is achieved by a modular design with removable top and bottom lid and a protocol of cutting the soil and replacing the affected bottom soil with a drainage layer of glass beads. The device allows the application of artificial rainfall events with simultaneous highly resolved quantification of infiltration excess overland flow and drainage discharge. It is designed to facilitate the collection of samples for physical, biological, and chemical analyses that fulfill cleanliness standards for organic contaminant analysis at trace levels using only poorly reactive stainless steel and glass materials. Testing of the device was performed by measuring the transfer of the antiparasitic drug ivermectin (IVM) through and over a silt-loam pasture soil. This test case illustrates how the device can be used to gain valuable information on the transfer of trace organic contaminants through topsoils.
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Hachgenei, N., Vaury, V., Nord, G., Spadini, L., & Duwig, C. (2022). Faster And More Precise Isotopic Water Analysis Of Discrete Samples By predicting the repetitions' asymptote instead of averaging last values. Methodsx, 9.
Abstract: Water stable isotope analysis using Cavity Ring-Down Spectroscopy (CRDS) has a strong between-sample memory effect. The classic approach to correct this memory effect is to inject the sample at least 6 times and ignore the first two to three injections. The average of the remaining injections is then used as measured value. This is in many cases insufficient to completely compensate the memory effect. We propose a simple approach to correct this memory effect by predicting the asymptote of consecutive repeated injections instead of averaging over them. The asymptote is predicted by fitting a y = a/x + b relation to the sample repetitions and keeping b as measured value. This allows to save analysis time by doing less injections while gaining precision. We provide a Python program applying this method and describe the steps necessary to implement this method in any other programming language. We also show validation data comparing this method to the classical method of averaging over the last couple of injections. The validation suggests a gain in time of a factor two while gaining in precision at the same time. The method does not have any specific requirements for the order of analysis and can therefore also be applied to an existing set of analyzes in retrospect. We fit a simple y = a/x + b relation to the sample repetitions of Picarro L2130-i isotopic water analyzer, in order to keep the asymptote (b) as measured value instead of using the average over the last couple of measurements. This allows a higher precision in the measured value with less repetitions of the injection saving precious time during analysis. We provide a sample code using Python, but generally this method is easy to implement in any automated data treatment protocol. (C) 2022 The Author(s). Published by Elsevier B.V.
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Haddad, H., Jodeau, M., Legout, C., Antoine, G., & Droppo, I. G. (2022). Spatial Variability Of The Erodibility Of Fine Sediments Deposited In two alpine gravel-bed rivers: The Isere and Galabre. Catena, 2122.
Abstract: In mountainous environments, high suspended sediment load during runoff or dam flushing events can lead to important amounts of fine deposits in gravel bed rivers. Fine sediment deposits may contribute to bar elevation, riparian vegetation growth and consequently to bar stabilization. Despite their contribution to the morphodynamic of mountain rivers, the erosion properties of fine sediments in this context is not fully understood.& nbsp;In order to investigate the dynamics of re-suspension of these deposits, field monitoring campaigns were performed to explore both the spatial variability and the controlling factors of the erodibility of fine deposits. A cohesive strength-meter (CSM), along with moisture, grain sizes, geographical position and elevation were used to evaluate both the critical bed shear stress for erosion and erosion rate of fine sediment deposits in two rivers of the French Alps: the Ise`re and Galabre.& nbsp;The results highlight a large variety of fine sediment deposition areas, which are discontinuous compared to those in estuaries and lowland rivers. A high spatial variability of erodibility was observed on the reach, the bar and the metric scale. While no upstream-downstream trend was observed at the scale of both studied reaches, the locations of the deposits, elevation from the river surface and their moisture were inter-related variables and with the highest correlations to erodibility. Measurements showed that both dry and humid deposits located at the highest and lowest elevation from the river surface respectively, were more easily eroded than intermediate deposits with medium moisture.
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Haddad, H., Legout, C., & Jodeau, M. (2022). Spatial Variability Of Erodibility Of Fine Sediments Deposited In Gravel River Beds: From Field Measurements To 2D Numerical Models. Journal Of Soils And Sediments, .
Abstract: Purposegravel-Bed Rivers Can Store Significant Amounts Of Fine Sediments, In The Gravel Matrix Or At The Bar Surface. The Contribution Of The Latter To Suspended Sediment Fluxes Depends On Their Erodibility Which Is Highly Variable Spatially. The Sensitivity Induced By This Spatial Variability On Outputs Of A 2D Hydro-Sedimentary Numerical Model Was Investigated And Recommendations For In Situ Erodibility Measurement Strategy Were Provided.Methodsthe Spatial Variability Of Fine Sediment Erodibility Was Determined Using The Cohesive Strength Meter (Csm) Device In A 1-Km-Long River Reach Of The Galabre River In The Southern French Alps. A 2D Hydro-Sedimentary Numerical Model Was Built On The Monitored Reach Displaying Three Deposit Zones With Distinct Erodibility Values. The Sensitivity Of The Modeled Eroded Masses To Sediment Erodibility Variability Was Assessed Through Ten Distinct Sediment Erodibility Settings And Three Schematic Flood Events, Based On The In Situ Monitoring Of The River.Results And Discussionthe Spatial Variability Of Fine Sediment Deposit Erodibility Was Significant. Marginal Deposits Were More Resistant Than Superficial Or Water-Saturated Ones. The Sensitivity Of The Modeled Eroded Mass To Erodibility Parameters Was Different Depending On The Set Of Measurements Used. When Considering The Entire Dataset, Which Exhaustively Characterizes The Fine Sediment Deposits, The Numerical Sensitivity Was Relatively Low. On The Other Hand, When A Partial Set Of Measurements Outside The Quartiles Was Considered, The Sensitivity Was More Significant Leading To Large Differences In Eroded Masses Between Spatially Distributed And Spatially Averaged Settings. Using Bootstrap Sampling, We Recommended Making 15 To 20 Measurements In Marginal And Superficial Zones To Adequately Capture The Distribution Of Erodibility.Conclusionsthis Work Provided Insight On The Spatial Variability Of Erodibility And The Sensitivity Induced In 2D Numerical Modeling Of Fine Sediments. The Proposed Methodology Could Be Applied To Other Environments (E.G., Reservoirs, Estuaries, Or Lowland Rivers) In Order To Adapt The Monitoring And Numerical Modeling Strategies.
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Hamal, K., Ghimire, S. K., Khadka, A., Dawadi, B., & Sharma, S. (2022). Interannual Variability Of Spring Fire In Southern Nepal. Atmospheric Science Letters, .
Abstract: Nepal is highly vulnerable to climate change with increased fire occurrences and fire burned areas in recent years; therefore, we accessed the climatic drivers for its variability using fire burned areas product of Moderate Resolution Imaging Spectroradiometer (MODIS) from 2001 and 2020. The peak fire burned areas were observed in the spring season (similar to 91%) from March to May, especially higher in the lowlands of the western and central parts. At the inter-annual timescale, low precipitation, humidity, soil moisture, and high temperature supported the existence of spring fire. Combining these factors induces drought conditions, enhancing evapotranspiration from vegetation and providing more combustible fuels. Furthermore, the El Nino phase in the central-eastern Pacific Ocean is related to the weakened westerly moisture transport and moisture divergence that creates dry and warm conditions leading to increased fire activities. Thus, this study could be helpful for preparedness, management, and policy-making to limit the multi-dimensional losses in the ecosystem and society due to fire.
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Han, C., Burn, L. J., Vallelonga, P., Do Hur, S., Boutron, C. F., Han, Y., et al. (2022). Lead Isotopic Constraints On The Provenance Of Antarctic Dust And Atmospheric Circulation Patterns Prior to the Mid-Brunhes Event (similar to 430 kyr ago). Molecules, 272(131).
Abstract: A lead (Pb) isotopic record, covering the two oldest glacial-interglacial cycles (similar to 572 to 801 kyr ago) characterized by lukewarm interglacials in the European Project for Ice Coring in Antarctica Dome C ice core, provides evidence for dust provenance in central East Antarctic ice prior to the Mid-Brunhes Event (MBE), similar to 430 kyr ago. Combined with published post-MBE data, distinct isotopic compositions, coupled with isotope mixing model results, suggest Patagonia/Tierra del Fuego (TdF) as the most important sources of dust during both pre-MBE and post-MBE cold and intermediate glacial periods. During interglacials, central-western Argentina emerges as a major contributor, resulting from reduced dust supply from Patagonia/TdF after the MBE, contrasting to the persistent dominance of dust from Patagonia/TdF before the MBE. The data also show a small fraction of volcanic Pb transferred from extra-Antarctic volcanoes during post-MBE interglacials, as opposed to abundant transfer prior to the MBE. These differences are most likely attributed to the enhanced wet removal efficiency with the hydrological cycle intensified over the Southern Ocean, associated with a poleward shift of the southern westerly winds (SWW) during warmer post-MBE interglacials, and vice versa during cooler pre-MBE ones. Our results highlight sensitive responses of the SWW and the associated atmospheric conditions to stepwise Antarctic warming.
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Haruna, A., Blanchet, J., & Favre, A. C. (2022). Performance-Based Comparison Of Regionalization Methods To Improve The at-site estimates of daily precipitation. Hydrology And Earth System Sciences, 262(101), 2797–2811.
Abstract: In this article, we compare the performance of three regionalization approaches in improving the at-site estimates of daily precipitation. The first method is built on the idea of conventional RFA (regional frequency analysis) but is based on a fast algorithm that defines distinct homogeneous regions relying on their upper-tail similarity. It uses only the precipitation data at hand without the need for any additional covariate. The second is based on the region-of-influence (ROI) approach in which neighborhoods, containing similar sites, are defined for each station. The third is a spatial method that adopts generalized additive model (GAM) forms for the model parameters. In line with our goal of modeling the whole range of positive precipitation, the chosen marginal distribution model is the extended generalized Pareto distribution (EGPD) to which we apply the three methods. We consider a dense network composed of 1176 daily stations located within Switzerland and in neighboring countries. We compute different criteria to assess the models' performance in the bulk of the distribution and the upper tail. The results show that all the regional methods offered improved robustness over the local EGPD model. While the GAM method is more robust and reliable in the upper tail, the ROI method is better in the bulk of the distribution.
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Haruna, A., Garambois, P., Roux, H., Javelle, P., & Jay-Allemand, M. (2022). Does Flash Flood Model Performance Increase With Complexity? Signature And Sensitivity-Based Comparison Of Conceptual And Process-Oriented Models On French Mediterranean Cases. Hydrology, 9(8).
Abstract: We Compare Three Hydrological Models Of Different Complexities, Gr4H (Lumped, Continuous), Smash (Distributed, Continuous), And Marine (Distributed, Event-Based), For Mediterranean Flash Flood Modeling. The Objective Was To Understand How Differently They Simulate The Catchment'S Behavior, In Terms Of Outlet Discharge And Internal Dynamics, And How These Can Help To Improve The Relevance Of The Models. The Methodology Involved Global Sensitivity Analysis, Calibration/Validation, And Signature Comparison At The Event Scale With Good Performances. For All Models, We Found Transfer Parameters To Be Sensitive In The Case Of Gardon And Production Parameters In The Case Of Ardeche. The Non-Conservative Flow Component Of Gr4H Was Found To Be Sensitive And Could Benefit The Distributed Models. At The Event Scale, The Process-Based Marine Model At Finer Resolution Outperformed The Two Continuous Hourly Models At Flood Peak And Its Timing. Smash, Followed By Gr4H, Performed Better In The Volume Of Water Exported. Using The Operational Surface Model Sim2 To Benchmark The Soil Moisture Simulated By The Three Models, Marine (Initialized With Sim1) Emerged As The Most Accurate. Gr4H Followed Closely, While Smash Was The Least Accurate. Flexible Modeling And Regionalization Should Be Developed Based On Multi-Source Signatures And Worldwide Physiographic Databases.
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Herbaut, C., Houssais, M. N., Blaizot, A. C., & Molines, J. M. (2022). A Role For The Ocean In The Winter Sea Ice Distribution North Of Svalbard. Journal Of Geophysical Research-Oceans, 1271(6).
Abstract: The ocean is suggested to play a major role in the ongoing winter decay of the sea ice cover in the western Eurasian Basin. Using a high-resolution sea ice-ocean model, we investigate the processes influencing the ice-ocean interactions in winter in the waters north of Svalbard, with a particular focus on those contributing to sea ice melt events of large amplitude. These short term events, lasting 5-10 days, are associated with locally large melt rates mostly found along the pathway of the Atlantic Water. The sum of all these events over the simulation period is found to contribute 40% of the total winter melt. Episodes of strong surface winds, occasionally associated with enhanced velocity shear at the mixed layer base, can trigger enhanced entrainment of Atlantic Water through the relatively shallow upper thermocline in the Atlantic Water boundary current, leading to substantial ocean heat transfer to the sea ice. In some cases, strengthening of the boundary current also contributes to fueling the heat transfer to the ice. Another type of large melt event, not linked to increased ocean vertical heat flux but due to ice being advected over warm surface waters, is also identified, sometimes associated with episodes of ice close-up. Sea ice budget calculations show that, overall, large melt events contribute significantly to the eastward retreat of the winter marginal ice zone on the upper slope east of Svalbard while episodes of northward advection of ice largely dominate the ice edge retreat over the shelf north of Svalbard.
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Heredia, C., Guedron, S., Point, D., Perrot, V., Campillo, S., Verin, C., et al. (2022). Anthropogenic Eutrophication Of Lake Titicaca (Bolivia) Revealed By Carbon And Nitrogen Stable Isotopes Fingerprinting. Science Of The Total Environment, 8458.
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Hoang, C., Magand, O., Brioude, J., Dimuro, A., Brunet, C., Ah-Peng, C., et al. (2022). Probing The Limits Of Sampling Gaseous Elemental Mercury Passively In The Remote Atmosphere. Environmental Science-Atmospheres, .
Abstract: Reliably Recording Very Low Ambient Concentrations Of Gaseous Elemental Mercury (Gem) In Remote Regions Is Often Required, For Example In The Context Of Evaluating How Effective The Minamata Convention Is In Reducing Global Hg Emissions. However, Sampling Over Extended Periods Of Time At Sites That Are Difficult To Access Can Be Very Challenging. In Order To Establish What Role Inexpensive And Easy-To-Use Passive Air Samplers May Play In This Regard, We Deployed A Sampler Using A Radiello Diffusive Barrier And Activated Carbon Sorbent For Periods Of Up To Three Years And With Sampling Periods Ranging From One To Three Months In Some Of The Most Extreme, Remote And Challenging Global Environments: At Concordia Station On The Antarctic Plateau, On Amsterdam Island In The Remote Southern Indian Ocean And At Several Sites On The Tropical Island Of La Reunion. The Ability To Reliably Record The Gem Concentrations At These Sites Was Strongly Influenced By The Size Of The Sequestered Amount Of Mercury Relative To The Extent And Variability Of The Contamination Of Field Blank Samples. In Some Cases, Acceptably Low And Consistent Field Blank Contamination Could Only Be Achieved By Storing Samplers In Sealed Glass Jars During Transport And Storage. The Size Of The Sequestered Amount Is Easily Increased By Extending Deployment Times, And The Experience Of The Current Study Suggests That Deployment Periods In Excess Of Two Months Are Advisable. Sampling In Antarctica Was Compromised By The Extreme Low Temperatures, Which Caused Unknown Sampling Rates, Hoar Frost Accumulation, Material Failure And Potential Failure Of Storage Seals. While Good Agreement With Gem Concentrations Measured With An Active Sampler Was Noted On Amsterdam Island, The Passive Sampler Derived Levels At The Maido Observatory In La Reunion Were Notably Higher Than Concentrations Measured Simultaneously With A Tekran Vapour Analyzer, Which Was Possibly Related To Sampling Rates Being Temporarily Elevated At The Very Beginning Of Deployment At Low Gem Concentrations.
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Hogg, A. M., Penduff, T., Close, S. E., Dewar, W. K., Constantinou, N. C., & Martinez-Moreno, J. (2022). Circumpolar Variations In The Chaotic Nature Of Southern Ocean Eddy Dynamics. Journal Of Geophysical Research-Oceans, 1271(5).
Abstract: Circulation in the Southern Ocean is unique. The strong wind stress forcing and buoyancy fluxes, in concert with the lack of continental boundaries, conspire to drive the Antarctic Circumpolar Current replete with an intense eddy field. The effect of Southern Ocean eddies on the ocean circulation is significant-they modulate the momentum balance of the zonal flow, and the meridional transport of tracers and mass. The strength of the eddy field is controlled by a combination of forcing (primarily thought to be wind stress) and intrinsic, chaotic, variability associated with the turbulent flow field itself. Here, we present results from an eddy-permitting ensemble of ocean model simulations to investigate the relative contribution of forced and intrinsic processes in governing the variability of Southern Ocean eddy kinetic energy. We find that variations of the eddy field are mostly random, even on longer (interannual) timescales. Where correlations between the wind stress forcing and the eddy field exist, these interactions are dominated by two distinct timescales-a fast baroclinic instability response; and a multi-year process owing to feedback between bathymetry and the mean flow. These results suggest that understanding Southern Ocean eddy dynamics and its larger-scale impacts requires an ensemble approach to eliminate intrinsic variability, and therefore may not yield robust conclusions from observations alone.
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Hogg, A. M., Penduff, T., Close, S. E., Dewar, W. K., Constantinou, N. C., & Martinez-Moreno, J. (2022). Circumpolar Variations In The Chaotic Nature Of Southern Ocean Eddy Dynamics. Journal Of Geophysical Research-Oceans, 1271(5).
Abstract: Circulation in the Southern Ocean is unique. The strong wind stress forcing and buoyancy fluxes, in concert with the lack of continental boundaries, conspire to drive the Antarctic Circumpolar Current replete with an intense eddy field. The effect of Southern Ocean eddies on the ocean circulation is significant-they modulate the momentum balance of the zonal flow, and the meridional transport of tracers and mass. The strength of the eddy field is controlled by a combination of forcing (primarily thought to be wind stress) and intrinsic, chaotic, variability associated with the turbulent flow field itself. Here, we present results from an eddy-permitting ensemble of ocean model simulations to investigate the relative contribution of forced and intrinsic processes in governing the variability of Southern Ocean eddy kinetic energy. We find that variations of the eddy field are mostly random, even on longer (interannual) timescales. Where correlations between the wind stress forcing and the eddy field exist, these interactions are dominated by two distinct timescales-a fast baroclinic instability response; and a multi-year process owing to feedback between bathymetry and the mean flow. These results suggest that understanding Southern Ocean eddy dynamics and its larger-scale impacts requires an ensemble approach to eliminate intrinsic variability, and therefore may not yield robust conclusions from observations alone.
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Hounsinou, M., Mamadou, O., Wudba, M., Kounouhewa, B., & Cohard, J. M. (2022). Integral turbulence characteristics over a clear woodland forest in northern Benin (West Africa). Atmospheric Research, 2682.
Abstract: This study aims at investigating whether the Integral Turbulence Characteristics (ITC) obey the Monin-Obukhov Similarity Theory (MOST) above a forest site in a Sudanian climate, and at identifying the appropriate ITC models for this ecosystem. Data were collected from a 18 m tower equipped with an Eddy Covariance system, above the clear forest close to Bellefoungou's village, Northwest of Benin, West Africa. The turbulence intensity parameters calculated for five years and half, were analyzed according to wind speed, stability conditions and seasons. From their relationships with the stability parameter, data driven models were then obtained by the nonlinear least squares. The results showed that, all similarity functions follow MOST with a 1/3 power law whatever the stratification of the atmosphere during all the seasons excepted the temperature which had a parabolic shape in near neutral condition (-0.05 < zeta < 0.1). A seasonal dependence of all ITCs was evidenced under stable conditions. We also showed that the heat transfer is relatively more efficient than H2O transfer under both stability conditions. The established temperature and CO2 similarity models are found to be closer, and for some given stratification conditions, to those already existing in literature. But a noteworthy finding is that the models often used to assign a quality criterion to turbulent fluxes showed an overestimation relatively to those established 'locally' for u and w through all atmospheric stratification.
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Hugonnet, R., Brun, F., Berthier, E., Dehecq, A., Mannerfelt, E., Eckert, N., et al. (2022). Uncertainty Analysis Of Digital Elevation Models By Spatial Inference From Stable Terrain. Ieee Journal Of Selected Topics In Applied Earth Observations And Remote Sensing, 151, 6456–6472.
Abstract: The Monitoring Of Earth'S And Planetary Surface Elevations At Larger And Finer Scales Is Rapidly Progressing Through The Increasing Availability And Resolution Of Digital Elevation Models (Dems). Surface Elevation Observations Are Being Used Across An Expanding Range Of Fields To Study Topographical Attributes And Their Changes Over Time, Notably In Glaciology, Hydrology, Volcanology, Seismology, Forestry, And Geomorphology. However, Dems Frequently Contain Large-Scale Instrument Noise And Varying Vertical Precision That Lead To Complex Patterns Of Errors. Here, We Present A Validated Statistical Workflow To Estimate, Model, And Propagate Uncertainties In Dems. We Review The State-Of-The-Art Of Dem Accuracy And Precision Analyses, And Define A Conceptual Framework To Consistently Address Those. We Show How To Characterize Dem Precision By Quantifying The Heteroscedasticity Of Elevation Measurements, I.E., Varying Vertical Precision With Terrain- Or Sensor-Dependent Variables, And The Spatial Correlation Of Errors That Can Occur Across Multiple Spatial Scales. With The Increasing Availability Of High-Precision Observations, Our Workflow Based On Independent Elevation Data Acquired On Stable Terrain Can Be Applied Almost Anywhere On Earth. We Illustrate How To Propagate Uncertainties For Both Pixel-Scale And Spatial Elevation Derivatives, Using Terrain Slope And Glacier Volume Changes As Examples. We Find That Uncertainties In Dems Are Largely Underestimated In The Literature, And Advocate That New Metrics Of Dem Precision Are Essential To Ensure The Reliability Of Future Land Elevation Assessments.
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Huot, P. V., Kittel, C., Fichefet, T., Jourdain, N. C., & Fettweis, X. (2022). Effects of ocean mesoscale eddies on atmosphere-sea ice-ocean interactions off Adelie Land, East Antarctica. Climate Dynamics, .
Abstract: Heat and momentum exchanges at the Southern Ocean surface are crucial for the Earth's Climate, but the importance of the small-scale spatial variability of these surface fluxes is poorly understood. Here, we explore how small-scale heterogeneities of the surface conditions due in particular to ocean eddies affect the atmosphere-sea ice-ocean interactions off Adelie Land, in East Antarctica. To this end, we use a high-resolution regional atmosphere-sea ice-ocean coupled model based on the NEMO-LIM and MAR models. We explore how the atmosphere responds to small-scale heterogeneity of the ocean or sea ice surface conditions, how eddies affect the sea ice and atmosphere, and how the eddy-driven surface fluxes impact the heat, freshwater, and momentum budget of the ocean. The atmosphere is found to be more sensitive to small-scale surface temperature gradients above the ice-covered than above the ice-free ocean. Sea ice concentration is found to be weaker above anticyclonic than cyclonic eddies due to increased sea ice melting or freezing (0.8 cm/day) partly compensated by sea ice convergence or divergence. The imprint of ice-free eddies on the atmosphere is weak, but in the presence of sea ice, air warming (+ 0.3 degrees C) and wind intensification (+ 0.1 m/s) are found above anticyclonic eddies, while cyclonic eddies have the opposite effects. Removing the interactions of eddies with the sea ice or atmosphere does not affect the total sea ice volume, but increases the ocean kinetic energy by 8% and weakens northward advection of sea ice, leading to a 15% decrease in freshwater flux north of 62.5 degrees S and weaker ocean restratification.
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Jacq, K., Rapuc, W., Benoit, A., Coquin, D., Fanget, B., Perrette, Y., et al. (2022). Sedimentary structure discrimination with hyperspectral imaging in sediment cores. Science Of The Total Environment, 8178.
Abstract: Hyperspectral imaging (HSI) isa non-destructive, high-resolution imaging technique that is currently under significant development for analyzing geological areas with remote devices or natural samples in a laboratory. In both cases, the hyperspectral image provides several sedimentary structures that must be separated to temporally and spatially de-scribe the sample. Sediment sequences are composed of successive deposits (strata, homogenite, flood) that are visible depending on sample properties. The classical methods to identify them are time-consuming, have a low spatial reso-lution (millimeters) and are generally based on naked-eye counting. In this study, we compare several supervised clas-sification algorithms to discriminate sedimentological structures in lake sediments. Instantaneous events in lake sediments are generally linked to extreme geodynamical events (e.g., floods, earthquakes), so their identification and counting are essential to understand long-term fluctuations and improve hazard assessments. Identification and counting are done by reconstructing a chronicle of event layer occurrence, including estimation of deposit thicknesses. Here, we applied two hyperspectral imaging sensors (Visible Near-Infrared, VNIR, 60 μm, 400-1000 nm; Short Wave Infrared, SWIR, 200 μm, 1000-2500 nm) on three sediment cores from different lake systems. We highlight that the SWIR sensor is the optimal one for creating robust classification models with discriminant analyses (prediction accu-racies of 0.87-0.98). Indeed, the VNIR sensor is impacted by the surface reliefs and structures that are not in the learn-ing set, which causes mis-classification. These observations are also valid for the combined sensor (VNIR-SWIR) and the RGB images. Several spatial and spectral pre-processing were also compared and enabled one to highlight discriminant information specific to a sample and a sensor. These works show that the combined use of hyperspectral imaging and machine learning improves the characterization of sedimentary structures compared to conventional methods.
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Jamet, Q., Leroux, S., Dewar, W., Penduff, T., Le Sommer, J., Molines, J., et al. (2022). Non-Local Eddy-Mean Kinetic Energy Transfers In Submesoscale-Permitting Ensemble Simulations. Journal Of Advances In Modeling Earth Systems, 141(101).
Abstract: Understanding Processes Associated With Eddy-Mean Flow Interactions Helps Our Interpretation Of Ocean Energetics, And Guides The Development Of Parameterizations. Here, We Focus On The Non-Local Nature Of Kinetic Energy (Ke) Transfers Between Mean And Turbulent Reservoirs. Transfers Are Interpreted As Non-Local When The Energy Extracted From The Mean Flow Does Not Locally Sustain An Growth Of Energy In The Turbulent Flow, Or Vice Versa. The Novelty Of Our Approach Is To Use Ensemble Statistics To Define The Mean And The Turbulent Flow. Based On Ke Budget Considerations, We First Rationalize The Eddy-Mean Separation In The Ensemble Framework, And Discuss The Interpretation Of A Mean Flow < U > Driven By The Prescribed (Surface And Boundary) Forcing And A Turbulent Flow U' Driven By Non-Linear Dynamics Sensitive To Initial Conditions. We Then Analyze 120-Day Long, 20-Member Ensemble Simulations Of The Western Mediterranean Basin Run At 1/60 Degrees Resolution. Our Main Contribution Is To Recognize The Prominent Contribution Of The Cross Energy Term < U(H)> . U(H)' To Explain Non-Local Energy Transfers, Which Provides A Strong Constraint On The Horizontal Organization Of Eddy-Mean Flow Ke Transfers Since The Cross Energy Term Vanishes Identically For Perturbations (U(H)') Orthogonal To The Mean Flow (< U(H)>). We Also Highlight The Prominent Contribution Of Vertical Turbulent Fluxes For Energy Transfers Within The Surface Mixed Layer. Analyzing The Scale Dependence Of Non-Local Energy Transfers Supports The Local Approximation Usually Made In The Development Of Meso-Scale, Energy-Aware Parameterizations For Non-Eddying Models, But Points Out To The Necessity Of Accounting For Non-Local Dynamics In The Meso-To-Submeso Scale Range. Plain Language Summary The Ocean Constantly Exchanges Energy Between Its Mean And Its Turbulent Reservoirs. However, We Are Still Lacking A Clear Understanding Of Eddy-Mean Flow Interactions, Which Limits Our Ability To Represent Them In Numerical Ocean Simulations That Require Turbulent Closures. In Particular, It Has Been Recently Shown That Instabilities Of Midlatitude Jets Do Not Necessarily Sustain The Growth Of Turbulent Eddies Locally. Instead, The Energy Released By The Jet Can Be Transported Over Significant Distances To Either Sustain Turbulence Or To Reinforce The Jet. Here, We Analyze Model Outputs Of Submesoscale-Permitting (Horizontal Resolution Of 1-2 Km) Ensemble Simulations Of The Western Mediterranean Basin With The View Of Better Understanding This Non-Local Dynamics. Starting From 20 Initial Conditions Perturbed By Small, Independent Perturbations, We Analyze The Development Of The Ensemble Spread During 120-Days Long Simulations Exposed To Identical Forcing. We Investigate The Spatiotemporal Structure Of Eddy-Mean Flow Interactions Through Their Kinetic Energy Expression. Our Main Contribution Is To Highlight Turbulent Fluxes Of The Cross Energy Term As A Driving Mechanism To Explain Non-Local Dynamics, A Process That Need To Be Accounted For In The Development Of Submesoscale Parametrizations.
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Jiang, Z., Savarino, J., Alexander, B., Erbland, J., Jaffrezo, J. L., & Geng, L. (2022). Impacts Of Post-Depositional Processing On Nitrate Isotopes In The Snow and the overlying atmosphere at Summit, Greenland. Cryosphere, 161(7), 2709–2724.
Abstract: The effect of post-depositional processing on the preservation of snow nitrate isotopes at Summit, Greenland, remains a subject of debate and is relevant to the quantitative interpretation of ice-core nitrate (isotopic) records at high snow accumulation sites. Here we present the first year-round observations of atmospheric nitrate and its isotopic compositions at Summit and compare them with published surface snow and snowpack observations. The atmospheric delta N-15(NO3-) remained negative throughout the year, ranging from -3.1 parts per thousand to -47.9 parts per thousand with a mean of (-14.8 +/- 7.3)parts per thousand (n = 54), and displayed minima in spring which are distinct from the observed spring delta N-15(NO3-) maxima in snowpack. The spring average atmospheric delta N-15(NO3-) was (-17.9 +/- 8.3) parts per thousand (n = 21), significantly depleted compared to the snowpack spring average of (4.6 +/- 2.1)parts per thousand, while the surface snow delta N-15(NO3-) of (-6.8 +/- 0.5)parts per thousand was in between the atmosphere and the snowpack. The differences in atmospheric, surface snow and snowpack delta N-15(NO3-) are best explained by the photo-driven post-depositional processing of snow nitrate, with potential contributions from fractionation during nitrate deposition. In contrast to delta N-15(NO3-) the atmospheric Delta O-1(7)(NO3-) was of a similar seasonal pattern and magnitude of change to that in the snowpack, suggesting little to no changes in Delta O-1(7)(NO3-) from photolysis, consistent with previous modeling results. The atmospheric delta O-18(NO3-) varied similarly to atmospheric Delta O-1(7)(NO3-), with summer low and winter high values. However, the difference between atmospheric and snow delta O-18(NO3-) was larger than that of Delta O-17(NO3-). We found a strong correlation between atmospheric delta O-18(NO3-) and Delta O-17(NO3-) that is very similar to previous measurements for surface snow at Summit, suggesting that atmospheric delta O-18(NO3-) versus Delta O-17(NO3-) relationships were conserved during deposition. However, we found the linear relationships between delta O-18 and Delta O-17(NO3-) were significantly different for snowpack compared to atmospheric samples. This likely suggests the oxygen isotopes are also affected before preservation in the snow at Summit, but the degree of change for delta O-18(NO3-) should be larger than that of Delta O-17(NO3-). This is because photolysis is a massdependent process that would directly affect delta O-18(NO3-) in snow but not Delta O-17(NO3-) as the latter is a mass-independent signal. Although there were uncertainties associated with the complied dataset, the results suggested that post-depositional processing at Summit can induce changes in nitrate isotopes, especially delta N-15(NO3-), consistent with a previous modeling study. This reinforces the importance of understanding the effects of post-depositional processing before ice-core nitrate isotope interpretation, even for sites with relatively high snow accumulation rates.
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Jomelli, V., Swingedouw, D., Vuille, M., Favier, V., Goehring, B., Shakun, J., et al. (2022). In-phase millennial-scale glacier changes in the tropics and North Atlantic regions during the Holocene. Nature Communications, 131(1).
Abstract: Glaciers showed a similar evolution in Greenland, Europe, the US and the tropical Andes during the Holocene. The authors propose the Atlantic Meridional Ocean Overturning Circulation as a key driver of this trend. Based on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the “AMOC-corrected” temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms.
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Jouberton, A., Shaw, T., Miles, E., Mccarthy, M., Fugger, S., Ren, S., et al. (2022). Warming-Induced Monsoon Precipitation Phase Change Intensifies Glacier Mass Loss In The Southeastern Tibetan Plateau. Proceedings Of The National Academy Of Sciences Of The United States Of America, .
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Jouberton, A., Shaw, T., Miles, E., Mccarthy, M., Fugger, S., Ren, S., et al. (2022). Warming-Induced Monsoon Precipitation Phase Change Intensifies Glacier Mass Loss In The Southeastern Tibetan Plateau. Proceedings Of The National Academy Of Sciences Of The United States Of America, 1191(373).
Abstract: Glaciers Are Key Components Of The Mountain Water Towers Of Asia And Are Vital For Downstream Domestic, Agricultural, And Industrial Uses. The Glacier Mass Loss Rate Over The Southeastern Tibetan Plateau Is Among The Highest In Asia And Has Accelerated In Recent Decades. This Acceleration Has Been Attributed To Increased Warming, But The Mechanisms Behind These Glaciers' High Sensitivity To Warming Remain Unclear, While The Influence Of Changes In Precipitation Over The Past Decades Is Poorly Quantified. Here, We Reconstruct Glacier Mass Changes And Catchment Runoff Since 1975 At A Benchmark Glacier, Parlung No. 4, To Shed Light On The Drivers Of Recent Mass Losses For The Monsoonal, Spring-Accumulation Glaciers Of The Tibetan Plateau. Our Modeling Demonstrates How A Temperature Increase (Mean Of 0.39 Degrees C Center Dot Dec(-1) Since 1990) Has Accelerated Mass Loss Rates By Altering Both The Ablation And Accumulation Regimes In A Complexmanner. The Majority Of The Post-2000 Mass Loss Occurred During Themonsoon Months, Caused By Simultaneous Decreases In The Solid Precipitation Ratio (From 0.70 To 0.56) And Precipitation Amount (-10%), Leading To Reduced Monsoon Accumulation (-26%). Higher Solid Precipitation In Spring (+18%) During The Last Two Decades Was Increasingly Important In Mitigating Glacier Mass Loss By Providing Mass To The Glacier And Protecting It From Melting In The Early Monsoon. With Bare Ice Exposed To Warmer Temperatures For Longer Periods, Icemelt And Catchment Discharge Have Unsustainably Intensified Since The Start Of The 21St Century, Raising Concerns For Long-Term Water Supply And Hazard Occurrence In The Region.
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Jourdain, N., Mathiot, P., Burgard, C., Caillet, J., & Kittel, C. (2022). Ice Shelf Basal Melt Rates In The Amundsen Sea At The End Of The 21St Century. Geophysical Research Letters, 494(222).
Abstract: Antarctic Ice Sheet Projections Show The Highest Sensitivity To Increased Basal Melting In The Amundsen Sea. However, Little Is Known About The Processes That Control Future Increase In Melt Rates. We Build An Ensemble Of Three Ocean-Sea-Ice-Ice-Shelf Simulations For Both The Recent Decades And The Late 21St Century, Constrained By Regional Atmosphere Simulations And The Multi-Model Mean Climate Change Of The Fifth Climate Model Intercomparison Project Under The Rcp8.5 Scenario. The Ice-Shelf Melt Rates Are Typically Multiplied By 1.4-2.2 From Present Day To Future, For A Total Basal Mass Loss Increased By 346 Gt Yr(-1) On Average. This Is Equally Explained By Advection Of Warmer Water From Remote Locations And Regional Changes In Ekman Downwelling And In The Ice-Shelf Melt-Induced Circulation, While Increased Iceberg Melt Plays No Significant Role. Our Simulations Suggest That High-End Melt Projections Previously Used To Constrain Recent Sea Level Projections May Have Been Significantly Overestimated.
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Junquas, C., Heredia, M. B., Condom, T., Ruiz-Hernandez, J. C., Campozano, L., Dudhia, J., et al. (2022). Regional climate modeling of the diurnal cycle of precipitation and associated atmospheric circulation patterns over an Andean glacier region (Antisana, Ecuador). Climate Dynamics, .
Abstract: A multi-experiment ensemble is performed using the WRF (Weather Research and Forecasting) model at high spatial resolution (1 km) over the Antisana glacier region (Ecuador), during the year 2005. Our goal is to identify the best model configurations to simulate atmospheric processes at diurnal and seasonal scales. The model is able to reproduce the complex zonal gradient of precipitation between the wet Amazon and the drier inter-Andean region. The main precipitation biases are (i) an overestimation in the afternoon (up to 6 mm/day) in the Antisana region related to local surface circulation patterns and (ii) a nighttime overestimation (up to 20 mm/day) in the Andes-Amazon transition zone associated with the regional circulation. Changing the microphysics scheme and/or the cumulus scheme primarily affect nighttime processes, while changing the topography forcing and activating slope radiation and shading options mostly affects afternoon processes. An adequate choice of the model configuration allows a correct representation of the diurnal cycle of precipitation, and in particular: (i) the mid-level easterly regional flow, (ii) the local moisture transport along and across the valleys, and (iii) the orographic mountain waves on the Antisana summit. For this specific area and year, the best configuration retained defined as “dSRTM_LRad” shows nighttime (daytime) precipitation biases smaller than 2 mm/day (3 mm/day); it is based on non-smoothed SRTM digital elevation model (dSRTM), Lin Purdue microphysics (L), and slope and shading radiation options (Rad). This 1-km resolution configuration requires the activation of the cumulus scheme, that improves the regional nighttime convection induced by the easterly regional flow on the Amazon-Andes transition region. It allows also a realistic strengthening of the daytime upward moisture transport. This study demonstrates that in the Antisana region, 1 km is a resolution still too coarse to deactivate cumulus schemes for a correct representation of cloud convection.
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Junqueira, R., Viola, M. R., Amorim, J. D., Wongchuig, S. C., de Mello, C. R., Vieira, M., et al. (2022). Hydrological Retrospective And Historical Drought Analysis In A Brazilian Savanna Basin. Water, 141(141).
Abstract: Analyzing historical droughts is essential to improve the assessment of future hydrological risks and to understand the effects of climate variability on streamflow. However, prolonged and consistent hydrological time series are scarce in the Brazilian savanna region. This study aimed to analyze the performance of climate reanalysis products in precipitation estimation, hydrological modeling, and historical drought analysis in a Brazilian savanna basin. For this purpose, precipitation data from the twentieth-century atmospheric model ensemble (ERA-20CM) and the land component of the fifth generation of European ReAnalysis (ERA5-Land) with bias correction were used. The weather variables were obtained from the Climatic Research Unit (CRU) and the hydrological modeling was performed using the Soil and Water Assessment Tool (SWAT). The Standardized Streamflow Index (SSI) was used to calculate hydrological drought in the basin. Overall, ERA5-Land performed satisfactorily in precipitation estimation, mainly on the monthly time scale, hydrological modeling, and drought prediction. Since ERA-20CM showed unsatisfactory values for the performance statistics in all analyses, the hydrologic drought (1950 to 2018) was performed with ERA5-Land. The results showed both an increase in the number of dry months and a decrease in wet months in recent decades.
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Kaushik, S., Ravanel, L., Magnin, F., Yan, Y., Trouve, E., & Cusicanqui, D. (2022). Effects Of Topographic And Meteorological Parameters On The Surface Area Loss Of Ice Aprons In The Mont Blanc Massif (European Alps). Cryosphere, 161(101), 4251–4271.
Abstract: Ice Aprons (Ias) Are Part Of The Critical Components Of The Alpine Cryosphere. As A Result Of The Changing Climate Over The Past Few Decades, Deglaciation Has Resulted In A Surface Decrease Of Ias, Which Has Not Yet Been Documented, Except For A Few Specific Examples. In This Study, We Quantify The Effects Of Climate Change On Ias Since The Mid-20Th Century In The Mont Blanc Massif (Western European Alps). We Then Evaluate The Role Of Meteorological Parameters And The Local Topography In The Behaviour Of Ias. We Precisely Mapped The Surface Areas Of 200 Ias Using High-Resolution Aerial And Satellite Photographs From 1952, 2001, 2012 And 2019. From The Latter Inventory, The Surface Area Of The Present Individual Ias Ranges From 0.001 To 0.04 Km(2). Ias Have Lost Their Surface Area Over The Past 70 Years, With An Alarming Increase Since The Early 2000S. The Total Area, From 7.93 Km(2) In 1952, Was Reduced To 5.91 Km(2) In 2001 (-25.5 %) Before Collapsing To 4.21 Km(2) In 2019 (-47 % Since 1952). We Performed A Regression Analysis Using Temperature And Precipitation Proxies To Better Understand The Effects Of Meteorological Parameters On Ia Surface Area Variations. We Found A Strong Correlation Between Both Proxies And The Relative Area Loss Of Ias, Indicating The Significant Influence Of The Changing Climate On The Evolution Of Ias. We Also Evaluated The Role Of The Local Topographic Factors In The Ia Area Loss. At A Regional Scale, Factors Like Direct Solar Radiation And Elevation Influence The Behaviour Of Ias, While Others Like Curvature, Slope And Size Of The Ias Seem To Be Rather Important On A Local Scale.
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Kenny, G., Hyde, W., Storey, M., Garde, A., Whitehouse, M., Beck, P., et al. (2022). Ar-40/Ar-39 And Zircon U-Pb Analyses Date The Hiawatha Impact Structure, Northwest Greenland, To The Late Paleocene. Meteoritics & Planetary Science, 575.
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Kenny, G. G., Hyde, W. R., Storey, M., Garde, A. A., Whitehouse, M. J., Beck, P., et al. (2022). A Late Paleocene age for Greenland's Hiawatha impact structure. Science Advances, 8(101).
Abstract: The similar to 31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted Ar-40/Ar-39 analyses on glaciofluvial sand and U-Pb analyses on zircon separated from glaciofluvial pebbles of impact melt rock, all sampled immediately downstream of Hiawatha Glacier. Unshocked zircon in the impact melt rocks dates to similar to 1915 million years (Ma), consistent with felsic intrusions found in local bedrock. The Ar-40/Ar-39 data indicate Late Paleocene resetting and shocked zircon dates to 57.99 +/- 0.54 Ma, which we interpret as the impact age. Consequently, the Hiawatha impact structure far predates Pleistocene glaciation and is unrelated to either the Paleocene-Eocene Thermal Maximum or flood basalt volcanism in east Greenland. However, it was contemporaneous with the Paleocene Carbon Isotope Maximum, although the impact's exact paleoenvironmental and climatic significance awaits further investigation.
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Keuschnig, C., Martins, J., Navel, A., Simonet, P., & Larose, C. (2022). Micro-Fractionation Shows Microbial Community Changes In Soil Particles Below 20 Mu M. Frontiers In Ecology And Evolution, 101.
Abstract: Introductionmicro-Scale Analysis Of Microbes In Soil Is Essential To The Overall Understanding Of Microbial Organization, Interactions, And Ecosystem Functioning. Soil Fractionation According To Its Aggregated Structure Has Been Used To Access Microbial Habitats. While Bacterial Communities Have Been Extensively Described, Little Is Known About The Fungal Communities At Scales Relevant To Microbial Interactions. Methodswe Applied A Gentle Soil Fractionation Method To Preserve Stable Aggregated Structures Within The Range Of Micro-Aggregates And Studied Fungal And Bacterial Communities As Well As Nitrogen Cycling Potentials In The Pristine Rothamsted Park Grass Soil (Bulk Soil) As Well As In Its Particle Size Fractions (Psfs; >250 Mu M, 250-63 Mu M, 63-20 Mu M, 20-2 Mu M, <2 Mu M, And Supernatant). Resultsoverall Bacterial And Fungal Community Structures Changed In Psfs Below 20 Mu M. The Relative Abundance Of Basidiomycota Decreased With Decreasing Particle Size Over The Entire Measure Range, While Ascomycota Showed An Increase And Mucoromycota Became More Prominent In Particles Below 20 Mu M. Bacterial Diversity Was Found Highest In The < 2 Mu M Fraction, But Only A Few Taxa Were Washed-Off During The Procedure And Found In Supernatant Samples. These Taxa Have Been Associated With Exopolysaccharide Production And Biofilm Formation (E.G., Pseudomonas, Massilia, Mucilaginibacter, Edaphobaculum, Duganella, Janthinobacterium, And Variovorax). The Potential For Nitrogen Reduction Was Found Elevated In Bigger Aggregates. Discussionthe Observed Changes Below 20 Mu M Particle Are In Line With Scales Where Microbes Operate And Interact, Highlighting The Potential To Focus On Little Researched Sub-Fractions Of Micro-Aggregates. The Applied Method Shows Potential For Use In Studies Focusing On The Role Of Microbial Biofilms In Soil And Might Also Be Adapted To Research Various Other Soil Microbial Functions. Technical Advances In Combination With Micro-Sampling Methods In Soil Promise Valuable Output In Soil Studies When Particles Below 20 Mu M Are Included.
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Khadka, A., Wagnon, P., Brun, F., Shrestha, D., Lejeune, Y., & Arnaud, Y. (2022). Evaluation Of Era5-Land And Harv2 Reanalysis Data At High Elevation In The Upper Dudh Koshi Basin (Everest Region, Nepal). Journal Of Applied Meteorology And Climatology, 616(8), 931–954.
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Khan, S., Choi, Y., Morlighem, M., Rignot, E., Helm, V., Humbert, A., et al. (2022). Extensive Inland Thinning And Speed-Up Of Northeast Greenland Ice Stream. Nature, 6116(79377), 727–+.
Abstract: Over The Past Two Decades, Ice Loss From The Greenland Ice Sheet (Gris) Has Increased Owing To Enhanced Surface Melting And Ice Discharge To The Ocean(1-5). Whether Continuing Increased Ice Loss Will Accelerate Further, And By How Much, Remains Contentious(6-9). A Main Contributor To Future Ice Loss Is The Northeast Greenland Ice Stream (Negis), Greenland'S Largest Basin And A Prominent Feature Of Fast-Flowing Ice That Reaches The Interior Of The Gris(10-)(12). Owing To Its Topographic Setting, This Sector Is Vulnerable To Rapid Retreat, Leading To Unstable Conditions Similar To Those In The Marine-Based Setting Of Ice Streams In Antarctica(13-20). Here We Show That Extensive Speed-Up And Thinning Triggered By Frontal Changes In 2012 Have Already Propagated More Than 200 Km Inland. We Use Unique Global Navigation Satellite System (Gnss) Observations, Combined With Surface Elevation Changes And Surface Speeds Obtained From Satellite Data, To Select The Correct Basal Conditions To Be Used In Ice Flow Numerical Models, Which We Then Use For Future Simulations. Our Model Results Indicate That This Marine-Based Sector Alone Will Contribute 13.5-15.5 Mm Sea-Level Rise By 2100 (Equivalent To The Contribution Of The Entire Ice Sheet Over The Past 50 Years) And Will Cause Precipitous Changes In The Coming Century. This Study Shows That Measurements Of Subtle Changes In The Ice Speed And Elevation Inland Help To Constrain Numerical Models Of The Future Mass Balance And Higher-End Projections Show Better Agreement With Observations.
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Kittel, C., Amory, C., Hofer, S., Agosta, C., Jourdain, N. C., Gilbert, E., et al. (2022). Clouds Drive Differences In Future Surface Melt Over The Antarctic Ice shelves. Cryosphere, 161(7), 2655–2669.
Abstract: Recent warm atmospheric conditions have damaged the ice shelves of the Antarctic Peninsula through surface melt and hydrofracturing and could potentially initiate future collapse of other Antarctic ice shelves. However, model projections with similar greenhouse gas scenarios suggest large differences in cumulative 21st-century surface melting. So far it remains unclear whether these differences are due to variations in warming rates in individual models or whether local feedback mechanisms of the surface energy budget could also play a notable role. Here we use the polar-oriented regional climate model MAR (Modele Atmospherique Regional) to study the physical mechanisms that would control future surface melt over the Antarctic ice shelves in high-emission scenarios RCP8.5 and SSP5-8.5. We show that clouds enhance future surface melt by increasing the atmospheric emissivity and longwave radiation towards the surface. Furthermore, we highlight that differences in meltwater production for the same climate warming rate depend on cloud properties and particularly cloud phase. Clouds containing a larger amount of supercooled liquid water lead to stronger melt, subsequently favouring the absorption of solar radiation due to the snowmelt-albedo feedback. As liquid-containing clouds are projected to increase the melt spread associated with a given warming rate, they could bea major source of uncertainties in projections of the future Antarctic contribution to sea level rise.
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Kochtitzky, W., Copland, L., Van Wychen, W., Hugonnet, R., Hock, R., Dowdeswell, J., et al. (2022). The Unquantified Mass Loss Of Northern Hemisphere Marine-Terminating Glaciers From 2000-2020. Nature Communications, 131(1).
Abstract: In The Northern Hemisphere, -1500 Glaciers, Accounting For 28% Of Glacierized Area Outside The Greenland Ice Sheet, Terminate In The Ocean. Glacier Mass Loss At Their Ice-Ocean Interface, Known As Frontal Ablation, Has Not Yet Been Comprehensively Quantified. Here, We Estimate Decadal Frontal Ablation From Measurements Of Ice Discharge And Terminus Position Change From 2000 To 2020. We Bias-Correct And Cross-Validate Estimates And Uncertainties Using Independent Sources. Frontal Ablation Of Marine-Terminating Glaciers Contributed An Average Of 44.47 +/- 6.23 Gt A(-1) Of Ice To The Ocean From 2000 To 2010, And 51.98 +/- 4.62 Gt A(-1) From 2010 To 2020. Ice Discharge From 2000 To 2020 Was Equivalent To 2.10 +/- 0.22 Mm Of Sea-Level Rise And Comprised Approximately 79% Of Frontal Ablation, With The Remainder From Terminus Retreat. Near-Coastal Areas Most Impacted Include Austfonna, Svalbard, And Central Severnaya Zemlya, The Russian Arctic, And A Few Alaskan Fjords.
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Koenig, A. M., Sonke, J. E., Magand, O., Andrade, M., Moreno, I., Velarde, F., et al. (2022). Evidence For Interhemispheric Mercury Exchange In The Pacific Ocean Upper Troposphere. Journal Of Geophysical Research-Atmospheres, 1271(101).
Abstract: Even though anthropogenic mercury (Hg) emissions to the atmosphere are similar to 2.5 times higher in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH), atmospheric Hg concentrations in the NH are only similar to 1.5 times higher than in the SH. Global Hg models attribute this apparent discrepancy to large SH oceanic Hg emissions or to interhemispheric exchange of Hg through the atmosphere. However, no observational data set exists to serve as a benchmark to validate whether these coarse-resolution models adequately represent the complex dynamics of interhemispheric Hg exchange. During the 2015-2016 El Nino, we observed at mount Chacaltaya in the tropical Andes a similar to 50% increase in ambient Hg compared to the year before, coinciding with a shift in synoptic transport pathways. Using this event as a case study, we investigate the impact of interhemispheric exchange on atmospheric Hg in tropical South America. We use HYSPLIT to link Hg observations to long-range transport and find that the observed Hg increase relates strongly to air masses from the tropical Pacific upper troposphere (UT), a region directly impacted by interhemispheric exchange. Inclusion of the modeled seasonality of interhemispheric air mass exchange strengthens this relationship significantly. We estimate that interhemispheric exchange drives Hg seasonality in the SH tropical Pacific UT, with strongly enhanced Hg between July and October. We validate this seasonality with previously published aircraft Hg observations. Our results suggest that the transport of NH-influenced air masses to tropical South America via the Pacific UT occurs regularly but became more detectable at Chacaltaya in 2015-2016 because of a westward shift in air mass origin.
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Kone, B., Diedhiou, A., Diawara, A., Anquetin, S., Toure, N. E., Bamba, A., et al. (2022). Influence of initial soil moisture in a regional climate model study over West Africa – Part 1: Impact on the climate mean. Hydrology And Earth System Sciences, 262(3), 711–730.
Abstract: The impact of soil moisture initial conditions on the mean climate over West Africa was examined using the latest version of the regional climate model of the International Centre for Theoretical Physics (RegCM4) at a 25 km horizontal resolution. The soil moisture reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis of the 20th century (ERA-20C) was used to initialize the control experiment, while its minimum and maximum values over the entire domain were used to establish the respective initial dry and wet soil moisture conditions (hereafter referred to as dry and wet experiments, respectively). For the respective control, wet and dry experiments, an ensemble of five runs from June to September was performed. In each experiment, we analyzed the two idealized simulations most sensitive to the dry and wet soil moisture initial conditions. The impact of soil moisture initial conditions on precipitation in West Africa is linear over the Central and West Sahel regions, where dry (wet) experiments lead to a rainfall decrease (increase). The strongest precipitation increase is found over the West Sahel for wet experiments, with a maximum change value of approximately 40 %, whereas the strongest precipitation decrease is found for dry experiments over the Central Sahel, with a peak change of approximately -4 %. The sensitivity of soil moisture initial conditions can persist for 3-4 months (90-120 d) depending on the region. However, the influence on precipitation is no longer than 1 month (between 15 and 30 d). The strongest temperature decrease is located over the Central and West Sahel, with a maximum change of approximately -1.5 degrees C in wet experiments, whereas the strongest temperature increase is found over the Guinea coast and Central Sahel for the dry experiments, with a maximum change of around 0.6 degrees degrees C. A significant impact of soil moisture initial conditions on the surface energy fluxes is noted: in the wet (dry) experiments, a cooling (warming) of the surface temperature is associated with a decrease (increase) in sensible heat flux, an increase (decrease) in latent heat flux and a decrease (increase) in the boundary layer depth. Part 2 of this study (Kone et al., 2022) investigates the influence of soil moisture initial conditions on climate extremes.
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Kone, B., Diedhiou, A., Diawara, A., Anquetin, S., Toure, N. E., Bamba, A., et al. (2022). Influence of initial soil moisture in a regional climate model study over West Africa – Part 2: Impact on the climate extremes. Hydrology And Earth System Sciences, 262(3), 731–754.
Abstract: The influence of soil moisture initial conditions on the climate extreme indices over West Africa was investigated using the fourth generation of the International Centre for Theoretical Physics regional climate model (non-hydrostatic) coupled with version 4.5 of the Community Land Model (RegCM4-CLM4.5) at a 25 km spatial resolution. We initialized the control experiments with the reanalysis soil moisture data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis of the 20th century (ERA-20C), while we initialized the dry and wet experiments with the maximum and minimum soil moisture values over the West Africa domain, respectively. For each experiment, an ensemble of five runs was performed for 5 years (2001-2005) with soil moisture initial conditions for the runs prescribed on 1 June and the simulations being performed over 4 months (122 d) from June to September. The performance of RegCM4-CLM4.5 with respect to simulating the 10 extreme rainfall and temperature indices used in this study is presented. The results are then discussed for the two idealized simulations that are most sensitive to the dry and wet soil moisture initial conditions in order to highlight the impacts beyond the limits of soil moisture internal forcing in the model. Over the Central Sahel, dry (wet) experiments lead to a decrease (increase) in precipitation extreme indices related to the number of events, but this was not seen for indices related to the intensity of the events. Soil moisture initial conditions unequally affect the daily minimum and maximum temperatures. The strongest impact is found on the maximum temperature: wet (dry) experiments decrease (increase) the maximum temperature over the whole region. Over the Central Sahel, wet (dry) experiments lead to a decrease (increase) in the maximum values of the minimum temperature.
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Kouadio, C. A., Kouassi, K. L., Diedhiou, A., Obahoundje, S., Amoussou, E., Kamagate, B., et al. (2022). Assessing The Hydropower Potential Using Hydrological Models And Geospatial Tools in the White Bandama Watershed (Cote d'Ivoire, West Africa). Frontiers In Water, 4.
Abstract: An assessment of hydropower potential at the watershed scale was conducted at the White Bandama Watershed (WBW) in Cote d'Ivoire (West Africa). The method used involves the application of a hydrological model [Soil and Water Assessment Tool (SWAT)] coupled with a Quantum Geographic Information System (QGIS), denoted as QSWAT, to assess the water resource availability and hydropower potential of streams and determine potential hydropower sites for future hydropower development in the watershed. Geospatial data about the topography, soil types, land use/land cover, weather, and discharge were considered in hydrological and hydro-geomorphological characterization of the watershed. Streamflow and climate data-enabled model operation and simulation of the hydrology of the watershed. The model performance and robustness were confirmed with the p-factor, r-factor, coefficient of determination R-2, and Nash-Sutcliffe (NS) efficiency coefficient. The hydropower potential of streams was evaluated by considering the simulated streamflow and water head. A total of 22 future hydropower sites was identified, geolocated, and classified with an estimated total production capacity of 538.56 MW.
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Labedz, C. R., Bartholomaus, T. C., Amundson, J. M., Gimbert, F., Karplus, M. S., Tsai, V. C. C., et al. (2022). Seismic Mapping of Subglacial Hydrology Reveals Previously Undetected Pressurization Event. Journal Of Geophysical Research-Earth Surface, 1271(3).
Abstract: Understanding the dynamic response of glaciers to climate change is vital for assessing water resources and hazards, and subglacial hydrology is a key player in glacier systems. Traditional observations of subglacial hydrology are spatially and temporally limited, but recent seismic deployments on and around glaciers show the potential for comprehensive observation of glacial hydrologic systems. We present results from a high-density seismic deployment spanning the surface of Lemon Creek Glacier, Alaska. Our study coincided with a marginal lake drainage event, which served as a natural experiment for seismic detection of changes in subglacial hydrology. We observed glaciohydraulic tremor across the surface of the glacier that was generated by the subglacial hydrologic system. During the lake drainage, the relative changes in seismic tremor power and water flux are consistent with pressurization of the subglacial system of only the upper part of the glacier. This event was not accompanied by a significant increase in glacier velocity; either some threshold necessary for rapid basal motion was not attained, or, plausibly, the geometry of Lemon Creek Glacier inhibited speedup. This pressurization event would have likely gone undetected without seismic observations, demonstrating the power of cryoseismology in testing assumptions about and mapping the spatial extent of subglacial pressurization.
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Labreuche, P., Staquet, C., & Le Sommer, J. (2022). Resonant Growth Of Inertial Oscillations From Lee Waves In The Deep Ocean. Geophysical And Astrophysical Fluid Dynamics, 1161(5-6), 351–373.
Abstract: The Interactions Between Inertial Oscillations (Io) And Lee Waves (Lw) Close To The Bottom Of The Ocean And The Role Of Io In Energy Dissipation Are Addressed For A Range Of Physical Parameters Typical Of Southern Ocean Conditions. Idealized Numerical Simulations In A Vertical Plane And Resonant Interaction Theory Are Combined For This Purpose. The Lee Waves Are Emitted By A Uniform Geostrophic Flow Over A Sinusoidal Topography For A Constant Buoyancy Frequency At Mid-Latitude. We Show That Io Can Grow By Triadic Resonant Interactions With The Lw. Two Triads Are Dominant, Which Involve Waves With Frequency Omega(Lw), F And Omega(Lw)-F, Where Omega(Lw) Is The Intrinsic Frequency Of The Lw And F The Coriolis Frequency (Assumed Positive). These Triads Differ By The Sign And Value Of The Io Vertical Wavenumber. Results From The Numerical Simulations Show That The Triad Associated With The Upward Phase Propagation Of The Io Is Selected, Consistent With Oceanic Observations, That A Good Agreement Is Obtained With The Io Growth Rate Predicted Theoretically And That The Io Develop In A Bottom Layer Of Height Less Than 1000 M. A Quasi-Steady Flow Regime Is Eventually Reached, With The Io Amplitude Being Of The Same Order As The Geostrophic Flow Speed. During This Regime, Depending Upon The Flow Parameters, The Io Kinetic Energy Is Equal To 30-70% Of The Lw Energy Flux During One Inertial Period. This Large Range Of Values Is Not Reflected In The Turbulent Kinetic Energy (Tke) Dissipation Rate, Which Is Comprised Between 10 And 30% Of The Lw Energy Flux, Whatever The Io Amplitude, Even If Vanishingly Small. Therefore, For The Set Of Parameters We Consider, The Tke Dissipation Rate Cannot Be Inferred From The Io Amplitude. Yet, The Nonlinear Interactions Between The Lee Waves And The Io Are Critical In Setting The Energy Spectrum, And Similarly For The Internal Tide And The Io At Low Latitudes According To The Literature. This Implies That Io Should Be Taken Into Account In The Parameterisation Of Mixing In The Ocean.
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Lambin, C., Fettweis, X., Kittel, C., Fonder, M., & Ernst, D. (2022). Assessment Of Future Wind Speed And Wind Power Changes Over South Greenland Using The Modele Atmospherique Regional Regional Climate Model. International Journal Of Climatology, .
Abstract: Wind Is An Infinitely Renewable Energy Source That Is Not Evenly Distributed In Space And Time. The Interconnection Of Energy-Demanding And Energyresourceful (Yet Remote) Regions Would Help Prevent Energy Scarcity In A World Where Fossil Fuels Are No Longer Used. Previous Studies Have Shown That South Greenland And West Europe Have Complementary Wind Regimes. In Particular, The Southern Tip Of Greenland, Cape Farewell, Has Gained Growing Interest For Wind Farm Development As It Is One Of The Windiest Places On Earth. In Order To Gain New Insights About Future Wind Speed Variations Over South Greenland, The Modele Atmospherique Regional (Mar), Validated Against In Situ Observations Over The Tundra Where Wind Turbines Are Most Likely To Be Installed, Is Used To Build Climate Projections Under The Emission Scenario Ssp5-8.5 By Downscaling An Ensemble Of Cmip6 Earth System Models (Esms). It Appeared That Between 1981 And 2100, The Wind Speed Is Projected To Decrease By Similar To-0.8 M.S(-1) At 100 M A.G.L. Over The Tundra Surrounding Cape Farewell. This Decrease Is Particularly Marked In Winter While In Summer, A Wind Speed Acceleration Is Projected Along The Ice Sheet Margins. An Analysis Of Twodimensional Wind Speed Changes At Different Vertical Levels Indicates That The Winter Decrease Is Likely Due To A Large-Scale Circulation Change While In Summer, The Katabatic Winds Flowing Down The Ice Sheet Are Expected To Increase Due To An Enhanced Temperature Contrast Between The Ice Sheet And The Surroundings. As For The Mean Annual Maximum Wind Power A Turbine Can Yield, A Decrease Of Similar To-178.1 W Is Projected At 100 M A.G.L. Again, The Decrease Is Especially Pronounced In Winter. Considering The Very High Winter Wind Speeds Occurring In South Greenland Which Can Cut Off Wind Turbines If Too Intense, The Projected Wind Speed Decrease Might Be Beneficial For The Establishment Of Wind Farms Near Cape Farewell.
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Lanzafame, G. M., Bessagnet, B., Srivastava, D., Jaffrezo, J. L., Favez, O., Albinet, A., et al. (2022). Modelling Aerosol Molecular Markers In A 3D Air Quality Model: Focus On anthropogenic organic markers. Science Of The Total Environment, 8358.
Abstract: aerosol markers including one primary anthropogenic marker (levoglucosan) and 4 secondary anthropogenic markers (nitrophenols, nitroguaiacols, methylnitrocatechols and phthalic acid). Modelled concentrations have been compared to measurements performed at 12 locations in France for levoglucosan in winter 2014-15, and at a sub-urban station in the Paris region over the whole year 2015 for secondary molecular markers. While a good estimation of levoglucosan concentrations by the model has been obtained for a few sites, a strong underestimation was simulated for most of the stations especially for western locations due to a probable underestimation of residential wood burning emissions. The simulated ratio between wood burning organic matter and particulate phase levoglucosan is constant only at high OM values (>10 μg m-3) indicating that using marker contribution ratio may be valid only under certain conditions. Concentrations of secondary markers were well reproduced by the model for nitrophenols and nitroguaiacols but were underestimated for methylnitrocatechols and phthalic acid highlighting missing formation pathways and/or precursor emissions. By comparing modelled to measured Gas/Particle Partitioning (GPP) of markers, the simulated partitioning of Semi-Volatile Organic Compounds (SVOCs) was evaluated. Except for nitroguaiacols and nitrophenols when ideality was assumed, the GPP for all the markers was underestimated and mainly driven by the hydrophilic partitioning. SVOCs GPP, and more generally of all SVOC contributing to the formation of SOA, could therefore be significantly
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Larbi, I., Nyamekye, C., Dotse, S. Q., Danso, D. K., Annor, T., Bessah, E., et al. (2022). Rainfall And Temperature Projections And The Implications On Streamflow and evapotranspiration in the near future at the Tano River Basin of Ghana. Scientific African, 151.
Abstract: Climate change is projected to negatively affect water security which is already a challenge in many areas of Ghana including the Tano river basin (TRB). This study assessed the projections of rainfall and temperature and its impact on streamflow and actual evapotranspiration (ET) in the TRB of Ghana for 2021-2050 relative to the period 1986-2015. The impact assessment focused on how climate change under Representative Concentration Pathways (RCP 4.5 and RCP8.5) based on an ensemble mean of two regional climate models (RCMs) would affect streamflow and ET using the Soil and Water Assessment Tool (SWAT) model. Trend analysis and quantification for the streamflow and ET were analyzed using the Mann-Kendall's and Sen's slope estimators. The results show that the mean annual rainfall of 1401.9 mm would increase slightly by 0.5 % with a decreasing trend (1.22mm/yr) under the RCP4.5 scenario, but would decrease by 3.2% with a decreasing trend (0.3m mm/yr) under the RCP8.5 scenario. The mean annual temperature showed an increase (2.1 degrees C and 2.6 degrees C) with a statistically significant increasing trend of 0.07 and 0.09 degrees C/yr under RCP 4.5 and RCP8.5 respectively. An increase in ET with a non-significant increasing trend at a rate of 0.74 and 1.07 mm/year under RCP4.5 and RCP8.5 scenarios respectively is also projected. The mean annual streamflow is projected to decrease, with the decrease been more pronounced under the RCP8.5 (37.5%) scenario compared to the RCP4.5 scenario (19.9%). In general, the outcome of this study presents a useful perspective on the vulnerability of water resources to climate change and the need for better planning and management of the water resources in the basin. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.
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Le Roux, E., Evin, G., Eckert, N., Blanchet, J., & Morin, S. (2022). A Non-Stationary Extreme-Value Approach For Climate Projection ensembles: application to snow loads in the French Alps. Earth System Dynamics, 131(3), 1059–1075.
Abstract: Anticipating risks related to climate extremes often relies on the quantification of large return levels (values exceeded with small probability) from climate projection ensembles. Current approaches based on multi-model ensembles (MMES) usually estimate return levels separately for each climate simulation of the MME. In contrast, using MME obtained with different combinations of general circulation model (GCM) and regional climate model (RCM), our approach estimates return levels together from the past observations and all GCM-RCM pairs, considering both historical and future periods. The proposed methodology seeks to provide estimates of projected return levels accounting for the variability of individual GCM-RCM trajectories, with a robust quantification of uncertainties. To this aim, we introduce a flexible non-stationary generalized extreme value (GEV) distribution that includes (i) piecewise linear functions to model the changes in the three GEV parameters and (ii) adjustment coefficients for the location and scale parameters to adjust the GEV distributions of the GCM-RCM pairs with respect to the GEV distribution of the past observations. Our application focuses on snow load at 1500 m elevation for the 23 massifs of the French Alps. Annual maxima are available for 20 adjusted GCM-RCM pairs from the EURO-CORDEX experiment under the scenario Representative Concentration Pathway (RCP) 8.5. Our results show with a model-as-truth experiment that at least two linear pieces should be considered for the piecewise linear functions. We also show, with a split-sample experiment, that eight massifs should consider adjustment coefficients. These two experiments help us select the GEV parameterizations for each massif. Finally, using these selected parameterizations, we find that the 50-year return level of snow load is projected to decrease in all massifs by -2.9 kN m(-2) (-50 %) on average between 1986-2005 and 2080-2099 at 1500 m elevation and RCP8.5. This paper extends the recent idea to constrain climate projection ensembles using past observations to climate extremes.
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Legchenko, A., Baltassat, J., Abbas, M., Isch, A., Amraoui, N., Azaroual, M., et al. (2022). Monitoring Unsaturated Water Flow Using Magnetic Resonance Soundings. Journal Of Hydrology, 6126.
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Legrand, M., McConnell, J. R., Preunkert, S., Bergametti, G., Chellman, N. J., Desboeufs, K., et al. (2022). Thallium Pollution In Europe Over The Twentieth Century Recorded In Alpine Ice: Contributions From Coal Burning and Cement Production. Geophysical Research Letters, 494(131).
Abstract: Emission inventories indicate that thallium, a highly toxic metal, is emitted during coal burning and cement production. These estimates have been established only for the 1980s and 1990s but up to now they have not been compared to long-term observations. Here we used alpine ice cores to document thallium pollution over Europe since similar to 1850. Ice-core thallium concentrations increased from 1890 to 1910, and decreased after 1965 to concentrations that were half 1890 levels. Comparison of ice-core trends, estimated past emissions, and state-of-the-art atmospheric aerosol transport modeling suggest that coal burning was responsible for thallium pollution in Europe, particularly from 1920 to 1965 because of high coal consumption at that time. The subsequent decline resulted from decreased coal consumption and reduced emissions following technological improvements. The ice-core data suggest that the rapid growth of cement production that took place in Europe after 1950 had a limited impact on thallium pollution.
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Lehmann, B., Anderson, R. S., Bodin, X., Cusicanqui, D., Valla, P. G., & Carcaillet, J. (2022). Alpine Rock Glacier Activity Over Holocene To Modern Timescales (Western French Alps). Earth Surface Dynamics, 101(3), 605–633.
Abstract: Active rock glaciers are some of the most frequent cryospheric landforms in midlatitude high-elevation mountain ranges. Their activity strongly influences the hydrology and geomorphology of alpine environments over short (years to decades) and long (centuries to millennia) timescales. Being conspicuous expressions of mountain permafrost and important water reserves in the form of ground ice, rock glaciers are seen as increasingly important actors in the geomorphological and hydrological evolution of mountain systems, especially in the context of current climate change. Over geological timescales, rock glaciers both reflect paleoclimate conditions and transport rock boulders produced by headwall erosion, and they therefore participate in shaping high mountain slopes. However, the dynamics of rock glaciers and their evolution over different timescales remain under-constrained. In this study, we adopt a multi-method approach, including field observations, remote sensing, and geochronology, to investigate the rock glacier system of the Vallon de la Route (Combeynot Massif, western French Alps). Remotely sensed images and correlation techniques are used to document the displacement field of the rock glacier over timescales ranging from days to decades. Additionally, to estimate displacement over periods from centuries to millennia, we employ terrestrial cosmogenic nuclide (quartz Be-10) surface-exposure dating on rock boulder surfaces located along the central flow line of the rock glacier, targeting different longitudinal positions from the headwall to the rock glacier terminus. The remote sensing analysis demonstrates that between 1960 and 2018 the two lower units of the rock glacier were motionless, the transitional unit presented an integrated surface velocity of 0.03 +/- 0.02 m a(-1), and the two upper active units above 2600 m a.s.l. showed a velocity between 0.14 +/- 0.08 and 0.15 +/- 0.05 m a(-1). Our results show Be-10 surface-exposure ages ranging from 13.10 +/- 0.51 to 1.88 +/- 0.14 ka. The spatial distribution of dated rock glacier boulders reveals a first-order inverse correlation between Be-10 surface-exposure age and elevation and a positive correlation with horizontal distance to the headwall. These observations support the hypothesis of rock boulders falling from the headwall and remaining on the glacier surface as they are transported down valley, and they may therefore be used to estimate rock glacier surface velocity over geological timescales. Our results also suggest that the rock glacier is characterized by two major phases of activity. The first phase, starting around 12 ka, displays a Be-10 age gradient with a rock glacier surface velocity of about 0.45 m a(-1), following a quiescent period between ca. 6.2 and 3.4 ka before the emplacement of the present-day upper two active units. Climatic conditions have favored an integrated rock glacier motion of around 0.18 m a(-1) between 3.4 ka and present day. These results allow us to quantify back-wearing rates of the headwall of between 1.0 and 2.5 mm a(-1), higher than catchment-integrated denudation rates estimated over millennial timescales. This suggests that the rock glacier system promotes the maintenance of high rock wall erosion by acting as debris conveyor and allowing freshly exposed bedrock surfaces to be affected by erosion processes.
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Leroux, S., Brankart, J., Albert, A., Brodeau, L., Molines, J., Jamet, Q., et al. (2022). Ensemble Quantification Of Short-Term Predictability Of The Ocean Dynamics At A Kilometric-Scale Resolution: A Western Mediterranean Test Case. Ocean Science, 181(6), 1619–1644.
Abstract: We Investigate The Predictability Properties Of The Ocean Dynamics Using An Ensemble Of Short-Term Numerical Regional Ocean Simulations Forced By Prescribed Atmospheric Conditions. In That Purpose, We Developed A Kilometric-Scale, Regional Model For The Western Mediterranean Sea (Med-West60, At 1/60 Degrees Horizontal Resolution). A Probabilistic Approach Is Then Followed, Where A Stochastic Parameterization Of Model Uncertainties Is Introduced In This Setup To Initialize Ensemble Predictability Experiments. A Set Of Three Ensemble Experiments (20 Members And 2 Months) Are Performed, One With The Deterministic Model Initiated With Perturbed Initial Conditions And Two With The Stochastic Model, For Two Different Amplitudes Of Stochastic Model Perturbations. In All Three Experiments, The Spread Of The Ensemble Is Shown To Emerge From The Smallest Scales (Kilometric Scale) And Progressively Upscales To The Largest Structures. After 2 Months, The Ensemble Variance Saturates Over Most Of The Spectrum, And The Small Scales (< 100 Km) Have Become Fully Decorrelated Across The Ensemble Members. These Ensemble Simulations Can Provide A Statistical Description Of The Dependence Between Initial Accuracy And Forecast Accuracy For Time Lags Between 1 And 20 D. The Predictability Properties Are Assessed Using A Cross-Validation Algorithm (I.E., Using Alternatively Each Ensemble Member As The Reference Truth And The Remaining 19 Members As The Ensemble Forecast) Together With A Given Statistical Score To Characterize The Initial And Forecast Accuracy. From The Joint Distribution Of Initial And Final Scores, It Is Then Possible To Quantify The Probability Distribution Of The Forecast Score Given The Initial Score Or Reciprocally To Derive Conditions On The Initial Accuracy To Obtain A Target Forecast Accuracy. The Misfit Between Ensemble Members Is Quantified In Terms Of Overall Accuracy (Crps Score), Geographical Position Of The Ocean Structures (Location Score) And Spatial Spectral Decorrelation Of The Sea Surface Height 2-D Fields (Decorrelation Score). With This Approach, We Estimate For Example That, In The Region And Period Of Interest, The Initial Location Accuracy Required (Necessary Condition) With A Perfect Model (No Model Uncertainty) To Obtain A Location Accuracy Of The Forecast Of 10 Km With A 95 % Confidence Is About 8 Km For A 1 D Forecast, 4 Km Fora 5 D Forecast And 1.5 Km Fora 10 D Forecast, And This Requirement Cannot Be Met With A 15 D Or Longer Forecast.
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Light, C. X., Arbic, B. K., Martin, P. E., Brodeau, L., Farrar, J. T., Griffies, S. M., et al. (2022). Effects of grid spacing on high-frequency precipitation variance in coupled high-resolution global ocean-atmosphere models. Climate Dynamics, .
Abstract: High-frequency precipitation variance is calculated in 12 different free-running (non-data-assimilative) coupled high resolution atmosphere-ocean model simulations, an assimilative coupled atmosphere-ocean weather forecast model, and an assimilative reanalysis. The results are compared with results from satellite estimates of precipitation and rain gauge observations. An analysis of irregular sub-daily fluctuations, which was applied by Covey et al. (Geophys Res Lett 45:12514-12522, 2018. http://doi.org/10.1029/2018GL078926) to satellite products and low-resolution climate models, is applied here to rain gauges and higher-resolution models. In contrast to lower-resolution climate simulations, which Covey et al. (2018) found to be lacking with respect to variance in irregular sub-daily fluctuations, the highest-resolution simulations examined here display an irregular sub-daily fluctuation variance that lies closer to that found in satellite products. Most of the simulations used here cannot be analyzed via the Covey et al. (2018) technique, because they do not output precipitation at sub-daily intervals. Thus the remainder of the paper focuses on frequency power spectral density of precipitation and on cumulative distribution functions over time scales (2-100 days) that are still relatively “high-frequency” in the context of climate modeling. Refined atmospheric or oceanic model grid spacing is generally found to increase high-frequency precipitation variance in simulations, approaching the values derived from observations. Mesoscale-eddy-rich ocean simulations significantly increase precipitation variance only when the atmosphere grid spacing is sufficiently fine (<0.5 degrees). Despite the improvements noted above, all of the simulations examined here suffer from the “drizzle effect”, in which precipitation is not temporally intermittent to the extent found in observations.
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Lim, S., Hwang, J., Lee, M., Czimczik, C. I., Xu, X. M., & Savarino, J. (2022). Robust Evidence Of C-14, C-13, And N-15 Analyses Indicating Fossil Fuel Sources for Total Carbon and Ammonium in Fine Aerosols in Seoul Megacity. Environmental Science & Technology, 565(111), 6894–6904.
Abstract: Carbon- and nitrogen-containing aerosols are ubiquitous in urban atmospheres and play important roles in air quality and climate change. We determined the C-14 fraction modern (f(M)) and delta C-13 of total carbon (TC) and delta N-15 of NH4+ in the PM2.5 collected in Seoul megacity during April 2018 to December 2019. The seasonal mean delta C-13 values were similar to -25.1% +/- 2.0% in warm and -24.2%+/- 0.82% in cold seasons. Mean delta N-15 values were higher in warm (16.4%+/- 2.8%) than in cold seasons (4.0%+/- 6.1%), highlighting the temperature effects on atmospheric NH3 levels and phase- equilibrium isotopic exchange during the conversion of NH3 to NH4+. While 37% +/- 10% of TC was apportioned to fossilfuel sources on the basis of f(M) values, delta N-15 indicated a higher contribution of emissions from vehicle exhausts and electricity generating units (power-plant NH3 slip) to NH3: 60% +/- 26% in warm season and 66% +/- 22% in cold season, based on a Bayesian isotope-mixing model. The collective evidence of multiple isotope analysis reasonably supports the major contribution of fossil-fuel-combustion sources to NH4+, in conjunction with TC, and an increased contribution from vehicle emissions during the severe PM2.5 pollution episodes. These findings demonstrate the efficacy of a multiple-isotope approach in providing better insight into the major sources of PM2.5 in the urban atmosphere.
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Lim, S., Lee, M., Savarino, J., & Laj, P. (2022). Oxidation Pathways And Emission Sources Of Atmospheric Particulate nitrate in Seoul: based on delta N-15 and Delta O-17 measurements. Atmospheric Chemistry And Physics, 222(8), 5099–5115.
Abstract: PM2.5 haze pollution driven by secondary inorganic NO3- has been a great concern in East Asia. It is, therefore, imperative to identify its sources and oxidation processes, for which nitrogen and oxygen stable isotopes are powerful tracers. Here, we determined the delta N-15 (NO3-) and Delta O-17 (NO3-) of PM2.5 in Seoul during the summer of 2018 and the winter of 2018-2019 and estimated quantitatively the relative contribution of oxidation pathways for particulate NO3- and investigated major NOx emission sources. In the range of PM2.5 mass concentration from 7.5 μg m(-3) (summer) to 139.0 μg m(-3) (winter), the mean delta N-15 was -0.7 parts per thousand +/- 3.3 parts per thousand and 3.8 parts per thousand +/- 3.7 parts per thousand, and the mean Delta O-17 was 23.2 parts per thousand +/- 2.2 parts per thousand and 27.7 parts per thousand +/- 2.2 parts per thousand in the summer and winter, respectively. While OH oxidation was the dominant pathway for NO3- during the summer (87 %), nighttime formation via N2O5 and NO3 was relatively more important (38 %) during the winter, when aerosol liquid water content (ALWC) and nitrogen oxidation ratio (NOR) were higher. Interestingly, the highest Delta O-17 was coupled with the lowest delta N-15 and highest NOR during the record-breaking winter PM2.5 episodes, revealing the critical role of photochemical oxidation process in severe winter haze development. For NOx sources, atmospheric delta N-15 (NOx) estimated from measured delta N-15 (NO3-) considering isotope fractionation effects indicates vehicle emissions as the most important emission source of NOx in Seoul. The contribution from biogenic soil and coal combustion was slightly increased in summer and winter, respectively. Our results built on a multiple-isotope approach provide the first explicit evidence for NO3- formation processes and major NOx emission sources in the Seoul megacity and suggest an effective mitigation measure to improve PM2.5 pollution.
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Llovel, W., Kolodziejczyk, N., Close, S., Penduff, T., Molines, J. M., & Terray, L. (2022). Imprint of intrinsic ocean variability on decadal trends of regional sea level and ocean heat content using synthetic profiles. Environmental Research Letters, 171(4).
Abstract: The global ocean is warming and has absorbed 90% of the Earth Energy Imbalance over 2010-2018 leading to global mean sea level rise. Both ocean heat content (OHC) and sea level trends show large regional deviations from their global means. Both quantities have been estimated from in-situ observations for years. However, in-situ profile coverage is spatially uneven, leading to uncertainties when assessing both OHC and sea level trends, especially at regional scale. Recently, a new possible driver of regional sea level and OHC trends has been highlighted using eddy-permitting ensemble ocean simulations over multiple decades: non-linear ocean processes produce chaotic fluctuations, which yield random contributions to regional decadal OHC and sea level trends. In-situ measurements capture a combination of the atmospherically-forced response and this intrinsic ocean variability. It is therefore important to understand the imprint of the chaotic ocean variability recorded by the in-situ measurement sampling in order to assess its impact and associated uncertainty on regional budgets. A possible approach to investigate this problem is to use a set of synthetic in-situ-like profiles extracted from an ensemble of forced ocean simulations started from different states and integrated with the same atmospheric forcing. Comparisons between the original ensemble outputs and the remapped, subsampled, in-situ-like profiles elucidate the contribution of chaotic ocean variability to OHC and regional sea level trends. Our results show that intrinsic variability may be large in eddy-active regions in the gridded model outputs, and remains substantial when using the in-situ sampling-based estimates. Using the latter, the same result is also found on large scales, for which atmospheric forcing has been identified as the main driver. Our results suggest accounting for this intrinsic ocean variability when assessing regional OHC and sea level trend budgets on decadal time scales.
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Maclennan, M., Lenaerts, J., Shields, C., & Wille, J. (2022). Contribution Of Atmospheric Rivers To Antarctic Precipitation. Geophysical Research Letters, 494(181).
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Maier, N., Gimbert, F., & Gillet-Chaulet, F. (2022). Threshold Response To Melt Drives Large-Scale Bed Weakening In Greenland. Nature, 6076(79207), 714–+.
Abstract: Ice speeds in Greenland are largely set by basal motion(1), which is modulated by meltwater delivery to the ice base(2-4). Evidence suggests that increasing melt rates enhance the subglacial drainage network's capacity to evacuate basal water, increasing bed friction and causing the ice to slow(5-10). This limits the potential of melt forcing to increase mass loss as temperatures increase(11). Here we show that melt forcing has a pronounced influence on dynamics, but factors besides melt rates primarily control its impact. Using a method to examine friction variability across the entirety of western Greenland, we show that the main impact of melt forcing is an abrupt north-to-south change in bed strength that cannot be explained by changes in melt production. The southern ablation zone is weakened by 20-40 per cent compared with regions with no melt, whereas in northern Greenland the ablation zone is strengthened. We show that the weakening is consistent with persistent basal water storage and that the threshold is linked to differences in sliding and hydropotential gradients, which exert primary control on the pressures within drainage pathways that dewater the bed. These characteristics are mainly set by whether a margin is land or marine terminating, suggesting that dynamic changes that increase mass loss are likely to occur in northern Greenland as temperatures increase. Our results point to physical representations of these findings that will improve simulated ice-sheet evolution at centennial scales.
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Mandal, A., Angchuk, T., Azam, M., Ramanathan, A., Wagnon, P., Soheb, M., et al. (2022). An 11-Year Record Of Wintertime Snow-Surface Energy Balance And Sublimation At 4863 M A.S.L. On The Chhota Shigri Glacier Moraine (Western Himalaya, India). Cryosphere, 161(9), 3775–3799.
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Mannerfelt, E., Dehecq, A., Hugonnet, R., Hodel, E., Huss, M., Bauder, A., et al. (2022). Halving Of Swiss Glacier Volume Since 1931 Observed From Terrestrial Image Photogrammetry. Cryosphere, 161(8), 3249–3268.
Abstract: The Monitoring Of Glaciers In Switzerland Has A Long Tradition, Yet Glacier Changes During The 20Th Century Are Only Known Through Sparse Observations. Here, We Estimate A Halving Of Swiss Glacier Volumes Between 1931 And 2016 By Mapping Historical Glacier Elevation Changes At High Resolution. Our Analysis Relies On A Terrestrial Image Archive Known As Terra, Which Covers About 86 % Of The Swiss Glacierised Area With 21 703 Images Acquired During The Period 1916-1947 (With A Median Date Of 1931). We Developed A Semi-Automated Workflow To Generate Digital Elevation Models (Dems) From These Images, Resulting In A 45 % Total Glacier Coverage. Using The Geodetic Method, We Estimate A Swisswide Glacier Mass Balance Of -0.52 +/- 0.09 M W.E. A(-1) Between 1931 And 2016. This Equates To A 51.5 +/- 8.0 % Loss In Glacier Volume. We Find That Low-Elevation, High-Debriscover, And Gently Sloping Glacier Termini Are Conducive To Particularly High Mass Losses. In Addition To These Glacier-Specific, Quasi-Centennial Elevation Changes, We Present A New Inventory Of Glacier Outlines With Known Timestamps And Complete Attributes From Around 1931. The Fragmented Spatial Coverage And Temporal Heterogeneity Of The Terra Archive Are The Largest Sources Of Uncertainty In Our Glacier-Specific Estimates, Reaching Up To 0.50 M W.E. A(-1). We Suggest That The High-Resolution Mapping Of Historical Surface Elevations Could Also Unlock Great Potential For Research Fields Other Than Glaciology.
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Marengo, J. A., Jimenez, J. C., Espinoza, J. C., Cunha, A. P., & Aragao, L. E. O. (2022). Increased climate pressure on the agricultural frontier in the Eastern Amazonia-Cerrado transition zone. Scientific Reports, 121(1).
Abstract: Several large-scale drivers of both anthropogenic and natural environmental changes are interacting nonlinearly in the transition zone between eastern Amazonia and the adjacent Cerrado, considered to be another Brazilian agricultural frontier. Land-use change for agrobusiness expansion together with climate change in the transition zone between eastern Amazonia and the adjacent Cerrado may have induced a worsening of severe drought conditions over the last decade. Here we show that the largest warming and drying trends over tropical South America during the last four decades are observed to be precisely in the eastern Amazonia-Cerrado transition region, where they induce delayed wet-season and worsen severe drought conditions over the last decade. Our results evidence an increase in temperature, vapor pressure deficit, subsidence, dry-day frequency, and a decrease in precipitation, humidity, and evaporation, plus a delay in the onset of the wet season, inducing a higher risk of fire during the dry-to-wet transition season. These findings provide observational evidence of the increasing climatic pressure in this area, which is sensitive for global food security, and the need to reconcile agricultural expansion and protection of natural tropical biomes.
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Masalaite, A., Bycenkien, S., Pauraite, J., Garbariene, I., Bozzetti, C., Besombes, J. L., et al. (2022). Seasonal Observation And Source Apportionment Of Carbonaceous Aerosol from forested rural site (Lithuania). Atmospheric Environment, 2722.
Abstract: In this work, we conducted a study of the stable carbon isotope ratios of total carbon (delta C-13(TC)) for submicron aerosol particles (< 1 μm) that were collected year round (2014) at a hemiboreal forest site in Lithuania. Higher delta C-13(TC) values characterised the seasonal variation in delta C-13(TC) during the cold season (average-26.9 +/- 0.7%o) with lower values observed during the warm season (-27.6 +/- 0.6%o). The total carbon (TC) concentration was below 8 μg/m3 during the one-year measurement period. There was one pollution event in autumn when concentrations reached up to 14.8 μg/m(3). In addition to the offline analysis of the filter samples, the online measurements of aerosol physical and chemical properties were conducted from 15 May to September 27, 2014 by operating the Aethalometer AE-31 and a quadrupole-type Aerosol Chemical Speciation Monitor (ACSM). Source apportionment was conducted by analysing the ACSM mass spectra using Positive Matrix Factorisation (PMF). Three main factors were derived, pointing to primary emissions from biomass burning along with the secondary formation of less and more oxygenated organic aerosol of biogenic origin. A comparative analysis of delta C-13(TC) with organic carbon (OC), elemental carbon (EC), and organic markers justified two dominant sources (biomass burning and fossil fuel combustion) of aerosol particles at the hemiboreal forest site during the cold season.
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Mateo, E. I., Mark, B. G., Hellstrom, R. A., Baraer, M., McKenzie, J. M., Condom, T., et al. (2022). High-Temporal-Resolution Hydrometeorological Data Collected In The tropical Cordillera Blanca, Peru (2004-2020). Earth System Science Data, 141(6), 2865–2882.
Abstract: This article presents a comprehensive hydrometeorological dataset collected over the past two decades throughout the Cordillera Blanca, Peru. The data-recording sites, located in the upper portion of the Rio Santa valley, also known as the Callejon de Huaylas, span an elevation range of 3738-4750ma.s.l. As many historical hydrological stations measuring daily discharge across the region became defunct after their installation in the 1950s, there was a need for new stations to be installed and an opportunity to increase the temporal resolution of the streamflow observations. Through inter-institutional collaboration, the hydrometeorological network described in this paper was deployed with the goal of evaluating how progressive glacier mass loss was impacting stream hydrology, and understanding better the local manifestation of climate change over diurnal to seasonal and interannual time scales. The four automatic weather stations supply detailed meteorological observations and are situated in a variety of mountain landscapes, with one on a high-mountain pass, another next to a glacial lake, and two in glacially carved valleys. Four additional temperature and relative humidity loggers complement the weather stations within the Llanganuco valley by providing these data across an elevation gradient. The six streamflow gauges are located in tributaries to the Rio Santa and collect high-temporal-resolution runoff data. The datasets presented here are available freely from https://doi.org/10.4211/hs.35a670e6c5824ff89b3b74fe45ca90e0 (Mateo et al., 2021). Combined, the hydrological and meteorological data collected throughout the Cordillera Blanca enable detailed research of atmospheric and hydrological processes in tropical high-mountain terrain.
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Milillo, P., Rignot, E., Rizzoli, P., Scheuchl, B., Mouginot, J., Bueso-Bello, J. L., et al. (2022). Rapid glacier retreat rates observed in West Antarctica. Nature Geoscience, 151(1), 48–+.
Abstract: The Pope, Smith and Kohler glaciers, in the Amundsen Sea Embayment of West Antarctica, have experienced enhanced ocean-induced ice-shelf melt, glacier acceleration, ice thinning and grounding-line retreat in the past 30 years. Here we present observations of the grounding-line retreat of these glaciers since 2014 using a constellation of interferometric radar satellites combined with precision surface elevation data. We find that the grounding lines develop spatially variable, kilometre-scale, tidally induced migration zones. After correction for tidal effects, we detect a sustained pattern of retreat coincident with high melt rates of ungrounded ice, marked by episodes of more rapid retreat. In 2017, Pope Glacier retreated 3.5 km in 3.6 months, or 11.7 km yr(-1). In 2016-2018, Smith West retreated at 2 km yr(-1) and Kohler at 1.3 km yr(-1). While the retreat slowed in 2018-2020, these retreat rates are faster than anticipated by numerical models on yearly timescales. We hypothesize that the rapid retreat is caused by unrepresented, vigorous ice-ocean interactions acting within newly formed cavities at the ice-ocean boundary. The Pope, Smith and Kohler glaciers in West Antarctica have exhibited faster than expected retreat rates in recent years, according to grounding-line observations from satellite radar interferometry.
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Millan, R., Mouginot, J., Rabatel, A., & Morlighem, M. (2022). Ice velocity and thickness of the world's glaciers. Nature Geoscience, 151(2), 124–+.
Abstract: The effect of climate change on water resources and sea-level rise is largely determined by the size of the ice reservoirs around the world and the ice thickness distribution, which remains uncertain. Here, we present a comprehensive high-resolution mapping of ice motion for 98% of the world's total glacier area during the period 2017-2018. We use this mapping of glacier flow to generate an estimate of global ice volume that reconciles ice thickness distribution with glacier dynamics and surface topography. The results suggest that the world's glaciers have a potential contribution to sea-level rise of 257 +/- 85 mm, which is 20% less than previously estimated. At low latitudes, our findings highlight notable changes in freshwater resources, with 37% more ice in the Himalayas and 27% less ice in the tropical Andes of South America, affecting water availability for local populations. This mapping of glacier flow and thickness redefines our understanding of global ice-volume distribution and has implications for the prediction of glacier evolution around the world, since accurate representations of glacier geometry and dynamics are of prime importance to glacier modelling. Potential sea-level rise from the world's glaciers is 20% less than previously thought, according to an estimate based on high-resolution maps of glacier ice velocity and thickness.
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Millan, R., Mouginot, J., Rabatel, A., & Morlighem, M. (2022). Ice Velocity And Thickness Of The World'S Glaciers (Vol 15, Pg 124, 2022). Nature Geoscience, .
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Moschos, V., Dzepina, K., Bhattu, D., Lamkaddam, H., Casotto, R., Daellenbach, K. R., et al. (2022). Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols. Nature Geoscience, .
Abstract: Organic aerosols in the Arctic are predominantly fuelled by anthropogenic sources in winter and natural sources in summer, according to observations from eight sites across the Arctic Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.
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Moschos, V., Schmale, J., Aas, W., Becagli, S., Calzolai, G., Eleftheriadis, K., et al. (2022). Elucidating the present-day chemical composition, seasonality and source regions of climate-relevant aerosols across the Arctic land surface. Environmental Research Letters, 171(3).
Abstract: The Arctic is warming two to three times faster than the global average, and the role of aerosols is not well constrained. Aerosol number concentrations can be very low in remote environments, rendering local cloud radiative properties highly sensitive to available aerosol. The composition and sources of the climate-relevant aerosols, affecting Arctic cloud formation and altering their microphysics, remain largely elusive due to a lack of harmonized concurrent multi-component, multi-site, and multi-season observations. Here, we present a dataset on the overall chemical composition and seasonal variability of the Arctic total particulate matter (with a size cut at 10 μm, PM10, or without any size cut) at eight observatories representing all Arctic sectors. Our holistic observational approach includes the Russian Arctic, a significant emission source area with less dedicated aerosol monitoring, and extends beyond the more traditionally studied summer period and black carbon/sulfate or fine-mode pollutants. The major airborne Arctic PM components in terms of dry mass are sea salt, secondary (non-sea-salt, nss) sulfate, and organic aerosol (OA), with minor contributions from elemental carbon (EC) and ammonium. We observe substantial spatiotemporal variability in component ratios, such as EC/OA, ammonium/nss-sulfate and OA/nss-sulfate, and fractional contributions to PM. When combined with component-specific back-trajectory analysis to identify marine or terrestrial origins, as well as the companion study by Moschos et al 2022 Nat. Geosci. focusing on OA, the composition analysis provides policy-guiding observational insights into sector-based differences in natural and anthropogenic Arctic aerosol sources. In this regard, we first reveal major source regions of inner-Arctic sea salt, biogenic sulfate, and natural organics, and highlight an underappreciated wintertime source of primary carbonaceous aerosols (EC and OA) in West Siberia, potentially associated with the oil and gas sector. The presented dataset can assist in reducing uncertainties in modelling pan-Arctic aerosol-climate interactions, as the major contributors to yearly aerosol mass can be constrained. These models can then be used to predict the future evolution of individual inner-Arctic atmospheric PM components in light of current and emerging pollution mitigation measures and improved region-specific emission inventories.
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Moseid, K., Schulz, M., Eichler, A., Schwikowski, M., Mcconnell, J., Olivie, D., et al. (2022). Using Ice Cores To Evaluate Cmip6 Aerosol Concentrations Over The Historical Era. Journal Of Geophysical Research-Atmospheres, 1271(181).
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Murfitt, J., Duguay, C., Picard, G., & Gunn, G. (2022). Investigating The Effect Of Lake Ice Properties On Multifrequency Backscatter Using The Snow Microwave Radiative Transfer Model. Ieee Transactions On Geoscience And Remote Sensing, 606.
Abstract: Recent Investigations Using Polarimetric Decomposition And Numerical Models Have Helped To Improve The Understanding Of How Radar Signals Interact With Lake Ice. However, Further Research Is Needed On How Radar Signals Are Impacted By Varying Lake Ice Properties. Radiative Transfer (Rt) Models Provide One Method Of Improving This Understanding. These Are The First Published Experiments Using The Snow Microwave Rt (Smrt) Model To Investigate The Response Of Different Frequencies (L-, C-, And X-Band) At Horizontal-Horizontal (Hh) And Vertical-Vertical (Vv) Polarizations Using Various Incidence Angles (20 Degrees, 30 Degrees, And 40 Degrees) To Changes In Ice Thickness, Porosity, Bubble Radius, And Ice-Water Interface Roughness. This Is Also The First Use Of Smrt In Combination With A Thermodynamic Lake Ice Model. Experiments Were For A Lake With Tubular Bubbles And One Without Tubular Bubbles Under Difference Scenarios. An Analysis Of The Backscatter Response To Different Properties Indicates That Increasing Ice Thickness And Layer Porosity Have Little Impact On Backscatter From Lake Ice. X-Band Backscatter Shows Increased Response To Surface Ice Layer Bubble Radius; However, This Was Limited To Other Frequencies Except At Shallower Incidence Angles (40 Degrees). All Three Frequencies Display The Largest Response To Increasing Root Mean Square (Rms) Height At The Ice-Water Interface, Which Supports Surface Scattering At The Ice-Water Interface As Being The Dominant Scattering Mechanism. These Results Demonstrate That The Smrt Is A Valuable Tool For Understanding The Response Of Backscatter To Changes In Freshwater Lake Ice Properties And Could Be Used In The Development Of Inversion Models.
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Nair, S., Kotnik, J., Gacnik, J., Zivkovic, I., Koenig, A., Mlakar, T., et al. (2022). Dispersion Of Airborne Mercury Species Emitted From The Cement Plant. Environmental Pollution, 3123.
Abstract: The Cement Industry Is The Second Largest Source Of Anthropogenic Mercury (Hg) Emissions In Europe, Accounting For 11% Of Global Anthropogenic Hg Emissions. The Main Objective Of This Study Was To Examine The Influence Of Hg Emissions From The Salonit Anhovo Cement Plant On Hg Levels Measured In The Ambient Air At Vodarna, 1 Km Downwind From The Flue Gas Chimney. The Findings Reveal That The Plant Raw Mill Operational Status Plays An Important Role In Hg Concentrations In The Flue Gas Emitted From The Plant. Emitted Total Gaseous Mercury Was, On Average, Higher (49.4 Mu G/M(3)) When Raw Mills Were In The Direct Mode (Both Raw Mills-Off) And Lower (23.4 Mu G/M(3)) In The Combined Mode (Both Raw Mills-On). The Average Hg Concentrations In Vodarna Were 3.14 Ng/M(3) For Gaseous Elemental Mercury, 53.7 Pg/M(3) For Gaseous Oxidised Mercury, And 41.9 Pg/M(3) For Particulate Bound Mercury For The Whole Measurement Period. Atmospheric Hg Speciation In Vodarna, Coupled With Plant Emissions And Wind Data, Has Revealed That The Total Gaseous Mercury Emitted From The Cement Plant Is Clearly Related To All Hg Species Measured In Vodarna. Wind Blowing From The Northeastern Quadrant (Mostly Ne, Ene) Is Responsible For The Elevated Hg Levels In Vodarna, Where Gaseous Oxidised Mercury Levels Are Highly Linked To The Cement Plant Emissions. However, Elevated Levels Of Hg Species In The Absence Of Northeastern Winds Indicate Potential Inputs From Other Unknown Local Sources As Well As Inputs From Regional And Global Transport Mechanisms.
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Nanni, U., Roux, P., Gimbert, F., & Lecointre, A. (2022). Dynamic Imaging Of Glacier Structures At High-Resolution Using Source Localization With a Dense Seismic Array. Geophysical Research Letters, 494(6).
Abstract: Dense seismic array monitoring combined with advanced processing can help retrieve and locate a variety of seismic sources with unprecedented resolution and spatial coverage. We present a methodology that goes beyond classical localization algorithms through gathering various types of sources (impulsive or continuous) using a single scheme based on a gradient-descent optimization and evaluating different levels of phase coherence. We apply our methodology on an Alpine glacier and demonstrate that we can retrieve the dynamics of active crevasses with a metric resolution using sources associated with high phase coherence; the presence of diffracting materials (e.g., rocks) trapped in transverse crevasses using sources with moderate phase coherence; and the two-dimensional time evolution of the subglacial hydrology system using sources with low phase coherence. Our study highlights the strength of using an appropriate and systematic seismological approach to image a wide range of subsurface structures and phenomena in settings with complex wavefields.
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Nguyen, A., Dao, T., Strady, E., Nguyen, T., Aime, J., Gratiot, N., et al. (2022). Phytoplankton characterization in a tropical tidal river impacted by a megacity: the case of the Saigon River (Southern Vietnam). Environmental Science And Pollution Research, .
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Nguyen, A. T., Nemery, J., Gratiot, N., Dao, T. S., Le, T. T. M., Baduel, C., et al. (2022). Does Eutrophication Enhance Greenhouse Gas Emissions In Urbanized tropical estuaries? Environmental Pollution, 3033.
Abstract: Estuaries are considered as important sources of the global emission of greenhouse gases (GHGs). Urbanized estuaries often experience eutrophication under strong anthropogenic activities. Eutrophication can enhance phytoplankton abundance, leading to carbon dioxide (CO2) consumption in the water column. Only a few studies have evaluated the relationship between GHGs and eutrophication in estuaries. In this study, we assessed the concentrations and fluxes of CO2, methane (CH4) and nitrous oxide (N2O) in combination with a suite of biogeochemical variables in four sampling campaigns over two years in a highly urbanized tropical estuary in Southeast Asia (the Saigon River Estuary, Vietnam). The impact of eutrophication on GHGs was evaluated through several statistical methods and interpreted by biological processes. The average concentrations of CO2, CH4 and N2O at the Saigon River in 2019-2020 were 3174 +/- 1725 μgC-CO2 L-1, 5.9 +/- 16.8 μgC-CH4 L-1 and 3.0 +/- 4.8 μgN-N2O L-1, respectively. Their concentrations were 13-18 times, 52-332 times, and 9-37 times higher than the global mean concentrations of GHGs, respectively. While CO2 concentration had no clear seasonal pattern, N2O and CH(4 )concentrations significantly differed between the dry and the rainy seasons. The increase in eutrophication status along the dense urban area was linearly correlated with the increase in GHGs concentrations. The presence of both nitrification and denitrification resulted in elevated N2O concentrations in this urban area of the estuary. The high concentration of CO2 was contributed by the high concentration of organic carbon and mineralization process. GHGs fluxes at the Saigon River Estuary were comparable to other urbanized estuaries regardless of climatic condition. Control of eutrophication in urbanized estuaries through the implantation of efficient wastewater treatment facilities will be an effective solution in mitigating the global warming potential caused by estuarine emissions.
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Nguyen, A. T., Nemery, J., Gratiot, N., Dao, T. S., Le, T. T. M., Baduel, C., et al. (2022). Does Eutrophication Enhance Greenhouse Gas Emissions In Urbanized tropical estuaries? Environmental Pollution, 3033.
Abstract: Estuaries are considered as important sources of the global emission of greenhouse gases (GHGs). Urbanized estuaries often experience eutrophication under strong anthropogenic activities. Eutrophication can enhance phytoplankton abundance, leading to carbon dioxide (CO2) consumption in the water column. Only a few studies have evaluated the relationship between GHGs and eutrophication in estuaries. In this study, we assessed the concentrations and fluxes of CO2, methane (CH4) and nitrous oxide (N2O) in combination with a suite of biogeochemical variables in four sampling campaigns over two years in a highly urbanized tropical estuary in Southeast Asia (the Saigon River Estuary, Vietnam). The impact of eutrophication on GHGs was evaluated through several statistical methods and interpreted by biological processes. The average concentrations of CO2, CH4 and N2O at the Saigon River in 2019-2020 were 3174 +/- 1725 μgC-CO2 L-1, 5.9 +/- 16.8 μgC-CH4 L-1 and 3.0 +/- 4.8 μgN-N2O L-1, respectively. Their concentrations were 13-18 times, 52-332 times, and 9-37 times higher than the global mean concentrations of GHGs, respectively. While CO2 concentration had no clear seasonal pattern, N2O and CH(4 )concentrations significantly differed between the dry and the rainy seasons. The increase in eutrophication status along the dense urban area was linearly correlated with the increase in GHGs concentrations. The presence of both nitrification and denitrification resulted in elevated N2O concentrations in this urban area of the estuary. The high concentration of CO2 was contributed by the high concentration of organic carbon and mineralization process. GHGs fluxes at the Saigon River Estuary were comparable to other urbanized estuaries regardless of climatic condition. Control of eutrophication in urbanized estuaries through the implantation of efficient wastewater treatment facilities will be an effective solution in mitigating the global warming potential caused by estuarine emissions.
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Nicolaus, M., Perovich, D. K., Spreen, G., Granskog, M. A., von Albedyll, L., Angelopoulos, M., et al. (2022). Overview of the MOSAiC expedition: Snow and sea ice. Elementa-Science Of The Anthropocene, 101(1).
Abstract: Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice-ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice.
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Noe, S. M., Tabakova, K., Mahura, A., Lappalainen, H. K., Kosmale, M., Heilimo, J., et al. (2022). Arctic Observations And Sustainable Development Goals – Contributions and examples from ERA-PLANET iCUPE data. Environmental Science & Policy, 1321, 323–336.
Abstract: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) project developed 24 novel datasets utilizing in-situ observational capacities within the Arctic or remote sensing observations from ground or from space. The datasets covered atmospheric, cryospheric, marine, and terrestrial domains. This paper connects the iCUPE datasets to United Nations' Sustainable Development Goals and showcases the use of selected datasets as knowledge provision services for policy- and decision-making actions. Inclusion of indigenous and societal knowledge into the data processing pipelines enables a feedback mechanism that facilitates data driven public services.
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Nsangou, D., Kpoumie, A., Mfonka, Z., Ngouh, A. N., Fossi, D. H., Jourdan, C., et al. (2022). Urban Flood Susceptibility Modelling Using Ahp And Gis Approach: Case Of the Mfoundi watershed at Yaounde in the South-Cameroon plateau. Scientific African, 151.
Abstract: Floods are considered as the natural hazards that affect the world's major metropolises the most. Thus, the present study aimed at evaluating the sensitivity to flood risks of the Mfoundi watershed (96.5 km(2)) located in the heart of the Cameroonian political capital in a tropical humid forest zone, more precisely in the South Cameroon plateau. The methodological approach adopted was to identify the factors that most favor the risk of flooding in the area from intense literature review and field investigations; the analysis of these factors and the calculation of the Flood Harzard Index (FHI) using the Analytical Hierarchy Process (AHP) approach coupled with the Geographical Information System (GIS) environment. The results reveal that among the ten parameters of the natural environment (elevation, drainage density, rainfall, slope, distance from the river, topographic humidity, hydraulic conductivity, groundwater level, geology and land cover) selected, the land cover, elevation and the geology are the factors that most influences the flooding phenomenon in the area. The value of Flood Hazard Index (FHI) varied from 4.16 to 9.16, the higher the value, the more sensitive the area is to the risk of flooding. Five main classes of flood susceptibility are highlighted: very low, low, moderate, high and very high, representing 9.50, 26, 23, 22 and 19.5%, respectively of the study area. To validate the efficiency of the obtained flood susceptibility map, the adopted Area Under the Curve (AUC) method shows a very good accuracy (0.84 or 84%). The results of this study constitute a basic tool for decision-making for environmental management by public authorities and decentralised territorial authorities with territorial jurisdiction. (C) 2021 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.
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Obahoundje, S., & Diedhiou, A. (2022). Potential impacts of climate, land use and land cover changes on hydropower generation in West Africa: a review. Environmental Research Letters, 171(4).
Abstract: This study aims to review the existing literature on the past and future effects of climate, land use, and land cover changes on hydropower generation in West Africa (WA), based on listings in the Scopus and Google Scholar databases. This review shows that several African hydropower plants have experienced repeated power disruptions over the last three decades due to climate change and variability but it is less documented how increasing land use and land cover changes around the major dams have impacted the hydrological system and the hydropower generation. In the future, the risks of hydropower in WA may not be equally distributed within a country or region. Despite uncertainties in precipitation and on impacts on streamflow and water level in major basins, climate change is likely to reduce the available water over the range of 10%-20% (15%-40%) for the RCP4.5 (RCP8.5) scenario by 2050, which may considerably affect the water demand across all sectors, including hydropower. However, in the Kainji dam (Niger River basin), models project an increase in rainfall favorable to hydropower production for both RCP4.5 and RCP8.5. In contrast, within the Black Volta sub-basin, the intensification of land use is predicted to favor runoff and, consequently, an increase in the generation of Bui hydropower in the near future, even though models predict a rainfall decrease. This increase in land use for agriculture to feed a growing population has other adverse effects that need to be assessed, namely sedimentation and siltation, which are harmful to hydropower plants. Finally, the combined impact of climate and land use changes on the efficiency of hydroelectric infrastructure in WA is not well documented, while sustainable planning and investments in the hydropower sector require consideration of the nexus between climate, land use changes, and water.
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Obahoundje, S., Diedhiou, A., Dubus, L., Alamou, E., Amoussou, E., Akpoti, K., et al. (2022). Modeling Climate Change Impact On Inflow And Hydropower Generation Of Nangbeto Dam In West Africa Using Multi-Model Cordex Ensemble And Ensemble Machine Learning. Applied Energy, 3253.
Abstract: Climate Change (Cc) Poses A Threat To Renewable Hydropower, Which Continues To Play A Significant Role In Energy Generation In West Africa (Wa). Thus, The Assessment Of The Impacts Of Climate Change And Climate Variability On Hydropower Generation Is Critical For Dam Management. This Study Develops A Framework Based On Ensemble Climate Models And Ensemble Machine Learning Methods To Assess The Projected Impacts Of Cc On Inflow To The Reservoir And Hydropower Generation At The Nangbeto Hydropower Plant In Wa. Inflow To Reservoir And Energy Generation For The Future (2020-2099) Is Modeled Using Climate Models Output Data From Coordi-Nated Regional Downscaling Experiment To Produce A Publicly Accessible Hydropower Dataset From 1980 To 2099. The Bias-Adjusted Ensemble Mean Of Eleven Climate Models For Representative Concentration Pathways (Rc4.5 And Rcp8.5) Are Used. The Added Value Of This Approach Is To Use Fewer Input Data (Temperature And Precipi-Tation) While Focusing On Their Lagged Effect On Inflow And Energy. Generally, The Model Output Strongly Cor-Relates With The Observation (1986-2005) With A Pearson Correlation Of 0.86 For Energy And 0.82 For Inflow While The Mean Absolute Error Is 2.97% For Energy And 9.73% For Inflow. The Results Reveals That Both Inflow And Energy Simulated Over The Future Periods (2020-2039, 2040-2059, 2060-2079, And 2080-2099) Will Decrease Relative To The Historical Period (1986-2005) For Both Rcps In The Range Of (2.5-20.5% And 1-8.5% For Inflow And Energy, Respectively), At Annual, Monthly And Seasonal Time Scales. Therefore, These Results Should Be Considered By Decision-Makers When Assessing The Best Option For The Energy Mix Development Plan.
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Obahoundje, S., Diedhiou, A., Kouassi, K. L., Ta, M. Y., Mortey, E. M., Roudier, P., et al. (2022). Analysis Of Hydroclimatic Trends And Variability And Their Impacts On hydropower generation in two river basins in Cote d'Ivoire (West Africa) during 1981-2017. Environmental Research Communications, 4(6).
Abstract: Climate change (CC) and variability impacts on hydroelectric generation have become critical for hydropower management. The trends of inflow, outflow, reservoir water level, and storage as well as hydraulicity indices of three main dams in Cote d'Ivoire, namely Kossou and Taabo in the Bandama basin and Buyo in the Sassandra basin were examined during 1981-2017 and their impacts on hydropower generation were analyzed. Moreover, the hydropower generation sensitivity to CC of these dams was assessed using statistical analysis. The results reveal that the inflow is highly dependent on rainfall while the water level is highly influenced by the outflow, which is a function of the inflow to the reservoirs and water management policy. Furthermore, the Mann Kendall test revealed that temperature and potential evapotranspiration have increased significantly in all three sub-basins while precipitation shows a significant upward trend only within the Taabo dam catchment area. Meanwhile, inflow to reservoir increased significantly and greatly than precipitation probably due to land use/cover change. Precipitation and inflow show a strong correlation as energy generation is significantly and strongly correlated to outflow (inflow) in all stations (except Kossou). Furthermore, the energy generation at Buyo and Taabo dams is more sensitive to reservoir inflow, while that of Kossou dam is more affected by water level. In addition, the power of a given year is also dependent on the total rainfall of that year and/or the previous year depending on the plant.
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Obahoundje, S., N'Guessan, V., Diedhiou, A., Kravitz, B., & Moore, J. (2022). Influence Of Stratospheric Aerosol Geoengineering On Temperature Mean And Precipitation Extremes Indices In Africa. International Journal Of Climate Change Strategies And Management, 141(4), 399–423.
Abstract: Purpose Three Coupled Model Intercomparison Project Phase 5 Models Involved In The G4 Experiment Of The Geoengineering Model Inter-Comparison Project (Geomip) Project Were Used To Investigate The Impact Of Stratospheric Aerosol Injection (Sai) On The Mean Surface Air Temperature And Precipitation Extremes In Africa. Design/Methodology/Approach This Impact Was Examined Under G4 And Representative Concentration Pathway (Rcp) 4.5 Scenarios On The Total Precipitation, The Number Of Rainy Days (Rr1) And Of Days With Heavy Rainfall (R20 Mm), The Rainfall Intensity (Sdii), The Maximum Length Of Consecutive Wet (Cwd) And Dry (Cdd) Days And On The Maximum Rainfall In Five Consecutive Days (Rx5Day) Across Four Regions: Western Africa (Waf), Eastern Africa (Eaf), Northern Africa And Southern Africa (Saf). Findings During The 50 Years (2020-2069) Of Sai, Mean Continental Warming Is -0.40 Degrees C Lower In G4 Than Under Rcp4.5. During The Post-Injection Period (2070-2090), The Temperature Continues To Increase, But At A Lower Rate (-0.19 Degrees C) Than In Rcp4.5. During Sai, Annual Rainfall In G4 Is Significantly Greater Than In Rcp4.5 Over The High Latitudes (Especially Over Saf) And Lower Over The Tropics. The Termination Of Sai Leads To A Significant Increase Of Rainfall Over Sahel And Eaf And A Decrease Over Saf And Guinea Coast (Waf). Practical Implications Compared To Rcp4.5, Sai Will Contribute To Reducing Significantly Regional Warming But With A Significant Decrease Of Rainfall In The Tropics Where Rainfed Agriculture Account For A Large Part Of The Economies. After The Sai Period, The Risk Of Drought Over The Extratropical Regions (Especially In Saf) Will Be Mitigated, While The Risk Of Floods Will Be Exacerbated In The Central Sahel. Originality/Value To Meet The Paris Agreement, African Countries Will Implement Mitigation Measures To Contribute To Keep The Surface Air Temperature Below 2 Degrees C. Geoengineering With Sai Is Suggested As An Option To Meet This Challenge, But Its Implication On The African Climate System Needs A Deep Investigation In The Aim To Understand The Impacts On Temperature And Precipitation Extremes. To The Best Of The Authors' Knowledge, This Study Is The First To Investigate The Potential Impact Of Sai Using The G4 Experiment Of Geomip On Temperature And Precipitation Extremes Of The African Continent.
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Olmo, M. E., Espinoza, J. C., Bettolli, M. L., Sierra, J. P., Junquas, C., Arias, P. A., et al. (2022). Circulation Patterns And Associated Rainfall Over South Tropical South America: GCMs Evaluation During the Dry-To-Wet Transition Season. Journal Of Geophysical Research-Atmospheres, 1271(121).
Abstract: The representation of the South American Monsoon System (SAMS) by general circulation models (GCMs) is of key relevance for a better understanding of the physical rationale behind the recent climate changes over South Tropical South America (STSA) and their expected changes in a global warming scenario. During the last four decades, STSA experienced a lengthening of the dry season associated with diverse forcings. In this work, a set of 16 GCMs historical Coupled Model Intercomparison Project Phase 6 coupled simulations were evaluated during 1979-2014 in terms of how well they reproduced the atmospheric circulation over STSA through a circulation-patterns (CPs) approach. Nine CPs were first identified based on low-level winds from the ERA5 reanalysis. Focus was put on the representation of CPs during the dry-to-wet transition season (July-October). Model performance depended on the seasonal cycle and spatial structure of the CPs. GCMs adequately reproduced the different CPs, with lower skills in the transition seasons. GCMs tended to go from dry to wet conditions too quickly, evidencing deficiencies in the representation of the SAMS onset, related to a poor representation of the southerly wind intrusions to STSA and the variability of the South American low-level jet. Some GCMs were able to associate the occurrence of anomalous dry and wet years with specific CPs, suggesting well-represented physical mechanisms controlling precipitation variability. This study could identify a few GCMs that adequately simulated the CPs in STSA (among them, CESM2, CMCC-CM2-HR4 and MPI-ESM1-2-HR), which is relevant for driving high-resolution models and the analysis of future projections.
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Oyabu, I., Kawamura, K., Buizert, C., Parrenin, F., Orsi, A., Kitamura, K., et al. (2022). The Dome Fuji Ice Core Df2021 Chronology (0-207 Kyr Bp). Quaternary Science Reviews, .
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Papazian, S., D'Agostino, L. A., Sadiktsis, I., Froment, J., Bonnefille, B., Sdougkou, K., et al. (2022). Nontarget mass spectrometry and in silico molecular characterization of air pollution from the Indian subcontinent. Communications Earth & Environment, 3(1).
Abstract: A combination of high-resolution mass spectrometry and computational molecular characterization techniques can structurally annotate up to 17% of organic compounds in fine particulate matter in highly polluted air sampled in the Maldives. Fine particulate-matter is an important component of air pollution that impacts health and climate, and which delivers anthropogenic contaminants to remote global regions. The complex composition of organic molecules in atmospheric particulates is poorly constrained, but has important implications for understanding pollutant sources, climate-aerosol interactions, and health risks of air pollution exposure. Here, comprehensive nontarget high-resolution mass spectrometry was combined with in silico structural prediction to achieve greater molecular-level insight for fine particulate samples (n = 40) collected at a remote receptor site in the Maldives during January to April 2018. Spectral database matching identified 0.5% of 60,030 molecular features observed, while a conservative computational workflow enabled structural annotation of 17% of organic structures among the remaining molecular dark matter. Compared to clean air from the southern Indian Ocean, molecular structures from highly-polluted regions were dominated by organic nitrogen compounds, many with computed physicochemical properties of high toxicological and climate relevance. We conclude that combining nontarget analysis with computational mass spectrometry can advance molecular-level understanding of the sources and impacts of polluted air.
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Pellarin, T., Zoppis, A., Roman-Cascon, C., Kerr, Y. H., Rodriguez-Fernandez, N., Panthou, G., et al. (2022). From SMOS Soil Moisture to 3-hour Precipitation Estimates at 0.1 degrees Resolution in Africa. Remote Sensing, 141(3).
Abstract: Several recent studies have shown that knowledge of the spatiotemporal dynamics of soil moisture intrinsically contains information on precipitation. In this study, we show how SMOS measurements can be used to generate a near-real-time precipitation product with a spatial resolution of 0.1 degrees and a temporal resolution of 3 h. The principle consists of assimilating the SMOS data into a model that simulates the evolution of soil moisture, which is forced by a satellite precipitation product. The assimilation of SMOS soil moisture leads to an adjustment of the satellite precipitation rates. Using data from more than 200 rain gauges set up in Africa between 2010 and 2021, we show that the PrISM algorithm (for Precipitation Inferred from Soil Moisture) almost systematically improves the initial precipitation product. One of the original features of this study is that we used the IMERG-Early satellite precipitation product, which has a finer spatial resolution (0.1 degrees) than SMOS (~0.25 degrees). Despite this, the methodology reduces both the RMSE and bias of IMERG-Early. The RMSE is reduced from 8.0 to 6.3 mm/day, and the absolute bias is reduced from 0.81 to 0.63 mm/day on average over the 200 rain gauges. PrISM performs even slightly better on average than IMERG-Final in terms of RMSE (6.8 mm/day for IMERG-Final) but better scores are obtained by IMERG-Final in terms of absolute bias (0.35 mm/day), which utilizes a network of field measurements to correct the biases of the IMERG-Early product with a 2.5-month delay. Therefore, the use of SMOS soil moisture measurements for Africa can be an advantageous alternative to the use of gauge measurements for debiasing rainfall satellite products in real time.
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Pelletier, C., Fichefet, T., Goosse, H., Haubner, K., Helsen, S., Huot, P. V., et al. (2022). PARASO, a circum-Antarctic fully coupled ice-sheet-ocean-sea-ice-atmosphere-land model involving f.ETISh1.7, NEMO3.6, LIM3.6, COSM05.0 and CLM4.5. Geoscientific Model Development, 151(2), 553–594.
Abstract: We introduce PARASO, a novel five-component fully coupled regional climate model over an Antarctic circumpolar domain covering the full Southern Ocean. The state-of-the-art models used are the fast Elementary Thermomechanical Ice Sheet model (f.ETISh) v1.7 (ice sheet), the Nucleus for European Modelling of the Ocean (NEMO) v3.6 (ocean), the Louvain-la-Neuve sea-ice model (LIM) v3.6 (sea ice), the COnsortium for Small-scale MOdeling (COSMO) model v5.0 (atmosphere) and its CLimate Mode (CLM) v4.5 (land), which are here run at a horizontal resolution close to 1/4 degrees. One key feature of this tool resides in a novel two-way coupling interface for representing ocean- ice-sheet interactions, through explicitly resolved ice-shelf cavities. The impact of atmospheric processes on the Antarctic ice sheet is also conveyed through computed COSMO-CLM-f.ETISh surface mass exchange. In this technical paper, we briefly introduce each model's configuration and document the developments that were carried out in order to establish PARASO. The new offline-based NEMO-f.ETISh coupling interface is thoroughly described. Our developments also include a new surface tiling approach to combine open-ocean and sea-ice-covered cells within COSMO, which was required to make this model relevant in the context of coupled simulations in polar regions. We present results from a 2000-2001 coupled 2-year experiment. PARASO is numerically stable and fully operational. The 2-year simulation conducted without fine tuning of the model reproduced the main expected features, although remaining systematic biases provide perspectives for further adjustment and development.
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Philippon, N., Ouhechou, A., Camberlin, P., Trentmann, J., Fink, A. H., Maloba, J. D., et al. (2022). Characterization Of Sunshine Duration In Western Equatorial Africa: In Situ Measurements versus SARAH-2 Satellite Estimates. Journal Of Applied Meteorology And Climatology, 616(2), 185–201.
Abstract: Western Equatorial Africa is one of the least sunny areas in the world. Yet, this has attracted little research so far. As in many other parts of Africa, light availability is mainly estimated using in situ measurements of sunshine duration (SDU). Therefore, this study conducts the first characterization of SDU evolution during the annual cycle for the region. It also evaluates the skill of satellite-based estimates of SDU from the Surface Solar Radiation Data Set-Heliosat, edition 2.1 (SARAH-2.1). Mean annual SDU levels are low: less than 5 h day21 at the regional scale, with the sunniest stations in the northeast (Cameroon and Central African Republic) and the least sunny in an similar to 150-km-wide coastal strip in Gabon and Republic of the Congo (RoC). For most of the stations except the southeast ones in the Democratic Republic of Congo, the lowest SDU levels are recorded in July-September, during the main dry season, with persistent overcast conditions. They are as low as 2.5 h day21, especially on the windward slopes of the Massifs du Chaillu and du Mayombe, nd of the Bateke Plateaus in Gabon and RoC. Although the mean annual and monthly spatial patterns are well reproduced in SARAH-2.1, SDU levels are systematically overestimated by 1-2 h day21. The largest positive biases are recorded during the December-February dry season, especially at the northernmost stations. Analyses at the daily time scale show that SARAH-2.1 biases arise from a twofold problem: the number of dark days (SDU, 1 h day21) is 50% lower than observed whereas that of sunny days (SDU. 9 h day21) is 50% higher than observed.
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Piantini, M., Gimbert, F., Bakker, M., Recking, A., & Nanni, U. (2022). Using A Dense Seismic Array To Study Fluvial Processes In A Braided river reach under flood conditions. Lhb-Hydroscience Journal, , 2053314.
Abstract: Dense seismic array monitoring has recently allowed the detailed investigation of sources of ground vibrations and their spatiotemporal dynamics. In a context where traditional monitoring techniques for fluvial processes often do not provide data with adequate temporal and spatial resolution, the use of dense arrays could allow the identification and tracking of different sources of river-induced seismic ground vibrations (e.g. turbulence and bedload transport). Here, we study the potential of dense seismic array monitoring by investigating a high-flow event that occurred in summer 2019 along a 600-m-long braided reach of the Severaisse River (French Alps). We use a network of 80 seismometers deployed on both river banks, and we supplement the seismic observations with flow gauging measurements and time-lapse imagery. During this event, we observe impulsive signals that are coherently detected over the array, and which we interpret as being associated with the bedload transport of clusters of coarse grains (blocks). Through phase-delay analysis we are able to locate these seismic events on the bend apex of an active branch of the reach. These results demonstrate the capability of such a method to locate bedload activity at high spatiotemporal resolution, providing crucial information for geomorphological investigations and natural risk management.
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Piantini, M., Gimbert, F., Bakker, M., Recking, A., & Nanni, U. (2022). Using A Dense Seismic Array To Study Fluvial Processes In A Braided river reach under flood conditions. Lhb-Hydroscience Journal, .
Abstract: Dense seismic array monitoring has recently allowed the detailed investigation of sources of ground vibrations and their spatiotemporal dynamics. In a context where traditional monitoring techniques for fluvial processes often do not provide data with adequate temporal and spatial resolution, the use of dense arrays could allow the identification and tracking of different sources of river-induced seismic ground vibrations (e.g. turbulence and bedload transport). Here, we study the potential of dense seismic array monitoring by investigating a high-flow event that occurred in summer 2019 along a 600-m-long braided reach of the Severaisse River (French Alps). We use a network of 80 seismometers deployed on both river banks, and we supplement the seismic observations with flow gauging measurements and time-lapse imagery. During this event, we observe impulsive signals that are coherently detected over the array, and which we interpret as being associated with the bedload transport of clusters of coarse grains (blocks). Through phase-delay analysis we are able to locate these seismic events on the bend apex of an active branch of the reach. These results demonstrate the capability of such a method to locate bedload activity at high spatiotemporal resolution, providing crucial information for geomorphological investigations and natural risk management.
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Picard, G., Leduc-Leballeur, M., Banwell, A., Brucker, L., & Macelloni, G. (2022). The Sensitivity Of Satellite Microwave Observations To Liquid Water In The Antarctic Snowpack. Cryosphere, 161(121), 5061–5083.
Abstract: Surface Melting On The Antarctic Ice Sheet Has Been Monitored By Satellite Microwave Radiometry For Over 40 Years. Despite This Long Perspective, Our Understanding Of The Microwave Emission From Wet Snow Is Still Limited, Preventing The Full Exploitation Of These Observations To Study Supraglacial Hydrology. Using The Snow Microwave Radiative Transfer (Smrt) Model, This Study Investigates The Sensitivity Of Microwave Brightness Temperature To Snow Liquid Water Content At Frequencies From 1.4 To 37 Ghz. We First Determine The Snowpack Properties For Eight Selected Coastal Sites By Retrieving Profiles Of Density, Grain Size And Ice Layers From Microwave Observations When The Snowpack Is Dry During Wintertime. Second, A Series Of Brightness Temperature Simulations Is Run With Added Water. The Results Show That (I) A Small Quantity Of Liquid Water (P-Center Dot 0.5 Kgm(-2)) Can Be Detected, But The Actual Quantity Cannot Be Retrieved Out Of The Full Range Of Possible Water Quantities; (Ii) The Detection Of A Buried Wet Layer Is Possible Up To A Maximum Depth Of 1 To 6 M Depending On The Frequency (6-37 Ghz) And On The Snow Properties (Grain Size, Density) At Each Site; (Iii) Surface Ponds And Water-Saturated Areas May Prevent Melt Detection, But The Current Coverage Of These Waterbodies In The Large Satellite Field Of View Is Presently Too Small In Antarctica To Have Noticeable Effects; And (Iv) At 1.4 Ghz, While The Simulations Are Less Reliable, We Found A Weaker Sensitivity To Liquid Water And The Maximal Depth Of Detection Is Relatively Shallow (< 10 M) Compared To The Typical Radiation Penetration Depth In Dry Firn (Asymptotic To 1000 M) At This Low Frequency. These Numerical Results Pave The Way For The Development Of Improved Multi Frequency Algorithms To Detect Melt Intensity And The Depth Of Liquid Water Below The Surface In The Antarctic Snowpack.
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Picard, G., Lowe, H., Domine, F., Arnaud, L., Larue, F., Favier, V., et al. (2022). The Microwave Snow Grain Size: A New Concept To Predict Satellite Observations Over Snow-Covered Regions. Agu Advances, 3(4).
Abstract: Satellite observations of snow-covered regions in the microwave range have the potential to retrieve essential climate variables such as snow height. This requires a precise understanding of how microwave scattering is linked to snow microstructural properties (density, grain size, grain shape and arrangement). This link has so far relied on empirical adjustments of the theories, precluding the development of robust retrieval algorithms. Here we solve this problem by introducing a new microstructural parameter able to consistently predict scattering. This “microwave grain size” is demonstrated to be proportional to the measurable optical grain size and to a new factor describing the chord length dispersion in the microstructure, a geometrical property known as polydispersity. By assuming that the polydispersity depends on the snow grain type only, we retrieve its value for rounded and faceted grains by optimization of microwave satellite observations in 18 Antarctic sites, and for depth hoar in 86 Canadian sites using ground-based observations. The value for the convex grains (0.6) compares favorably to the polydispersity calculated from 3D micro-computed tomography images for alpine grains, while values for depth hoar show wider variations (1.2-1.9) and are larger in Canada than in the Alps. Nevertheless, using one value for each grain type, the microwave observations in Antarctica and in Canada can be simulated from in-situ measurements with good accuracy with a fully physical model. These findings improve snow scattering modeling, enabling future more accurate uses of satellite observations in snow hydrological and meteorological applications.
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Picard, G., Lowe, H., & Matzler, C. (2022). Brief Communication: A Continuous Formulation Of Microwave Scattering From Fresh Snow To Bubbly Ice From First Principles. Cryosphere, 161(9), 3861–3866.
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Prieur, C., Rabatel, A., Thomas, J., Farup, I., & Chanussot, J. (2022). Machine Learning Approaches To Automatically Detect Glacier Snow Lines On Multi-Spectral Satellite Images. Remote Sensing, 141(161).
Abstract: Documenting The Inter-Annual Variability And The Long-Term Trend Of The Glacier Snow Line Altitude Is Highly Relevant To Document The Evolution Of Glacier Mass Changes. Automatically Identifying The Snow Line On Glaciers Is Challenging; Recent Developments In Machine Learning Approaches Show Promise To Tackle This Issue. This Manuscript Presents A Proof Of Concept Of Machine Learning Approaches Applied To Multi-Spectral Images To Detect The Snow Line And Quantify Its Average Altitude. The Tested Approaches Include The Combination Of Different Image Processing And Classification Methods, And Takes Into Account Cast Shadows. The Efficiency Of These Approaches Is Evaluated On Mountain Glaciers In The European Alps By Comparing The Results With Manually Annotated Data. Solutions Provided By The Different Approaches Are Robust When Compared To The Ground Truth'S Snow Lines, With A Pearson'S Correlation Ranging From 79% To 96% Depending On The Method. However, The Tested Approaches May Fail When Snow Lines Are Not Continuous Or Exhibit A Strong Change Of Elevation. The Major Advantage Over The State Of The Art Is That The Proposed Approach Does Not Require One Calibration Per Glacier.
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Racoviteanu, A. E., Glasser, N. F., Robson, B. A., Harrison, S., Millan, R., Kayastha, R. B., et al. (2022). Recent Evolution Of Glaciers In The Manaslu Region Of Nepal From Satellite Imagery and UAV Data (1970-2019). Frontiers In Earth Science, 9.
Abstract: Glacierized mountain ranges such as the Himalaya comprise a variety of glacier types, including clean and debris-covered glaciers. Monitoring their behaviour over time requires an assessment of changes in area and elevation along with surface features and geomorphology. In this paper we quantify the surface evolution of glacier systems in the Manaslu region of Nepal over the last five decades using 2013/2019 multi-sensor imagery and elevation data constructed from 1970 declassified Corona imagery and 1970 declassified Corona imagery. We investigate area changes, glacier thickness, geodetic glacier mass balance and surface velocity changes at regional scales and focus on the Ponkar Glacier and Thulagi Glacier and Lake for an in-depth assessment of surface geomorphology and surface feature dynamics (ponds, vegetation and ice cliffs). The time series of surface elevation changes for the lower ablation area of Ponkar Glacier is extended using 2019 UAV-based imagery and field-based ablation rates measured over the period 2016-2019. Glaciers in the Manaslu region experienced a mean area loss of -0.26 +/- 0.0001% a(-1) between 1970 and 2019. The mean surface lowering was -0.20 +/- 0.02 ma(-1) over the period 1970 to 2013, corresponding to a regional geodetic mass balance of -0.17 +/- 0.03 m w. e.a(-1). Overall, debris-covered glaciers had slightly higher thinning rates compared to clean ice glaciers; lake-terminating glaciers had double thinning rates compared to land-terminating glaciers. Individual glacier mass balance was negatively controlled by glacier slope and mean glacier elevation. During the period 1970 to 2013, Ponkar Glacier had a geodetic mass balance of -0.06 +/- 0.01 m w. e.a(-1), inversely correlated with parts of the central trunk thickening. Between 2013 and 2019 there was a nine-fold increase in the thinning rates over the lower parts of the glacier tongue relative to the period 1970-2013. Ice-surface morphology changes between 1970 and 2019 on Ponkar Glacier include a decrease in ogives and open crevasses, an increase in ice cliffs and ponds and the expansion of the supraglacial debris and ice-surface vegetation. These changes point to reduced ice-dynamic activity and are commensurate with the observed recession and negative glacier mass balance over the last five decades.
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Range, M., Arbic, B., Johnson, B., Moore, T., Titov, V., Adcroft, A., et al. (2022). The Chicxulub Impact Produced A Powerful Global Tsunami. Agu Advances, 3(5).
Abstract: The Chicxulub Crater Is The Site Of An Asteroid Impact Linked With The Cretaceous-Paleogene (K-Pg) Mass Extinction At Similar To 66 Ma. This Asteroid Struck In Shallow Water And Caused A Large Tsunami. Here We Present The First Global Simulation Of The Chicxulub Impact Tsunami From Initial Contact Of The Projectile To Global Propagation. We Use A Hydrocode To Model The Displacement Of Water, Sediment, And Crust Over The First 10 Min, And A Shallow-Water Ocean Model From That Point Onwards. The Impact Tsunami Was Up To 30,000 Times More Energetic Than The 26 December 2004 Indian Ocean Tsunami, One Of The Largest Tsunamis In The Modern Record. Flow Velocities Exceeded 20 Cm/S Along Shorelines Worldwide, As Well As In Open-Ocean Regions In The North Atlantic, Equatorial South Atlantic, Southern Pacific And The Central American Seaway, And Therefore Likely Scoured The Seafloor And Disturbed Sediments Over 10,000 Km From The Impact Origin. The Distribution Of Erosion And Hiatuses In The Uppermost Cretaceous Marine Sediments Are Consistent With Model Results.
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Ravanel, L., Lacroix, E., Le Meur, E., Batoux, P., & Malet, E. (2022). Multiparameter Monitoring Of Crevasses On An Alpine Glacier To Understand Formation And Evolution Of Snow Bridges. Cold Regions Science And Technology, 2032.
Abstract: On Glaciers, The Snow Bridges That Form Above Crevasses Have Hardly Been Considered By Researchers Up To Now, Despite Their Importance For High Mountain Activities (Skiing, Mountaineering) And The Risks That Their Possible Failure Poses To Practitioners. In Order To Improve Our Understanding Of The Formation And Evolution Of These Fragile Snow Structures, We Monitored During Two Years A Succession Of Three Crevasses Located At 3450 M A.S.L. In The Mont-Blanc Massif (France) Using A Set Of Sensors Including An Automatic Camera, Air Temperature Sensors, A Wind Vane-Anemometer, And An Extensometer. Geophysical Profiles (Ground Penetrating Radar) Were Also Carried Out To Clarify The Glacial Context. Despite Particularly Extreme Monitoring Conditions, At The Level Of A Bump Formed By The Bedrock Under An Ice Thickness Of C. 25 M, We Have Shown That A Wind Event Parallel To The Crevasse Favours Its Filling By Snow While A Strong Wind Making A Significant Angle With The Crevasse Under Largely Negative Temperatures Can Rapidly Create A Snow Bridge By Cornice Accretion That Grows By Extending Leeward. High Temperatures Are Responsible For Most Of The Natural Failures Of Sbs. These Elements Are Already Used For Risk Mitigation.
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Reveillet, M., Dumont, M., Gascoin, S., Lafaysse, M., Nabat, P., Ribes, A., et al. (2022). Black Carbon And Dust Alter The Response Of Mountain Snow Cover Under Climate Change. Nature Communications, 131(1).
Abstract: Black Carbon And Dust Deposition Advanced The End Of The Snow Season By 17 Days On Average Over The Last 40 Years In The French Alps And The Pyrenees. The Warming-Induced Snow Cover Decline Was Partly Offset By Decreases In Black Carbon Deposition Observed Since The 1980S. By Darkening The Snow Surface, Mineral Dust And Black Carbon (Bc) Deposition Enhances Snowmelt And Triggers Numerous Feedbacks. Assessments Of Their Long-Term Impact At The Regional Scale Are Still Largely Missing Despite The Environmental And Socio-Economic Implications Of Snow Cover Changes. Here We Show, Using Numerical Simulations, That Dust And Bc Deposition Advanced Snowmelt By 17 +/- 6 Days On Average In The French Alps And The Pyrenees Over The 1979-2018 Period. Bc And Dust Also Advanced By 10-15 Days The Peak Melt Water Runoff, A Substantial Effect On The Timing Of Water Resources Availability. We Also Demonstrate That The Decrease In Bc Deposition Since The 1980S Moderates The Impact Of Current Warming On Snow Cover Decline. Hence, Accounting For Changes In Light-Absorbing Particles Deposition Is Required To Improve The Accuracy Of Snow Cover Reanalyses And Climate Projections, That Are Crucial For Better Understanding The Past And Future Evolution Of Mountain Social-Ecological Systems.
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Rignot, E., Mouginot, J., Scheuchl, B., & Jeong, S. (2022). Changes In Antarctic Ice Sheet Motion Derived From Satellite Radar Interferometry Between 1995 And 2022. Geophysical Research Letters, 494(232).
Abstract: Ice Motion And Boundaries Are Critical Information For Ice Sheet Models That Project Ice Evolution In A Warming Climate. We Present Four Historical, Continent-Wide, Maps Of Antarctic-Wide Ice Motion And Boundaries For The Time Period 1995-2022. The Results Reveal No Change In The Interior Region Of East Antarctica, Iceberg Detachments At Ice Shelf Fronts, And Widespread Glacier Speedup That Propagates 100 Km'S Inland In West Antarctica And The Antarctic Peninsula. Speedup Affects The Entire Drainage Of The Amundsen Sea Embayment Sector; The Entire West Coast Of The Antarctic Peninsula Down To Georgevi Ice Shelf; The East Coast Down To Larsen C Ice Shelf; Getz Ice Shelf, Hull And Land Glaciers In West Antarctica; Matusevitch, Ninnis, Mertz And Denman Glaciers, Glaciers In Porpoise And Vincennes Bay; And Robert, Wilma And Rayner Glaciers In Enderby Land, In East Antarctica. We Attribute The Observed Glacier Changes To Increased Melting By Warmer Ocean Waters.
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Rindraharisaona, E., Rechou, A., Fontaine, F., Barruol, G., Stamenoff, P., Boudevillain, B., et al. (2022). Seismic Signature Of Rain And Wind Inferred From Seismic Data. Earth And Space Science, 9(101).
Abstract: Seismic Stations Are Increasingly Used To Monitor River Activity And To Quantify Sediment Transport During Flood Events. In Tropical Regions, Cyclone-Induced Floods Are Often Associated With Heavy Rain And Strong Wind Episodes, Generating Complex Seismic Records Involving The Simultaneous Signature Of Water, Sediment, Rainfall And Wind. Hence, Seismic Characterization Of Rain And Wind Is Then Required To Better Decipher Each Process And Improve Our Understanding Of The River Seismic Signature. In This Study, We Investigate Experimentally The Seismic Response Of Rain And Wind Using Data Recorded By Geophones Deployed In Various Soil Types And At Different Burial Depth (Bd), Co-Located With Various Meteorological Instruments. Our Results Show That The Power Spectral Density (Psd) Of The Seismic Noise Intensifies At A Frequency Between 60 And 500 Hz For Rain And 5 And 500 Hz For Wind, In The Presence Of Rain Precipitation As Low As 0.025 Mm/Min And/Or Wind Speed >= 3 M/S. Psd Analysis Indicates That The Seismic Signal Associated With Rain Decreases With The Bd With A Value Of Similar To 2-5 Db In A Depth Difference Of 10 Cm. We Also Observe That Each Soil Type Has Its Own Seismic Signature. The 4-Min Root Mean Square Correlation Between The Seismic Signal Amplitude And The Rain Precipitation Suggests That They Best Correlate With Pearson Coefficient >0.90 At Bd Of 30 Cm. The Transfer Function Between The Precipitation Rate (Or Kinetic Energy) And The Seismic Signal Amplitude Shows That The Signal Recorded By The Geophone Can Be Used As A Robust Proxy For These Parameters. Plain Language Summary In Addition To Recording Deep Earth Activity Such As Earthquakes Or Volcanic Eruptions, Seismic Sensors Can Measure Numbers Of Naturally-Induced Ground Vibrations Such As Those Generated By Rivers Activities. In Tropical Areas During Cyclonic Events, Heavy Rain (And Strong Wind) Leads To The Presence Of Severe Flooding, During Which Several Activities In And On The River (E.G., Sediment Transport, Wind, Water, And Rain) Generate Ground Vibration, Making The Overall Signals Recorded By Seismic Sensors Complex To Interpret. To Better Decipher The River Seismic Signature, Investigating The Wind And Rain Signatures Are Then Essential. In This Study, We Investigate Experimentally The Seismic Response Of Rain And Wind From Data Recorded By Geophones And Complemented By Different Meteorological Sensors. The Obtained Results Show That (A) The Strength Of The Seismic Noise Intensifies With Frequency For Rain And Wind; (B) The Seismic Signal Associated With Rain Decreases With The Burying Depth Of The Sensor; (C) The Amplitude Of The Seismic Signal Correlates With Rain Precipitation When The Sensor Is Well Buried And (D) The Signal Recorded By The Geophone Can Be Used As A Robust Proxy For Rain Precipitation.
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Rivoire, P., Le Gall, P., Favre, A., Naveau, P., & Martius, O. (2022). High Return Level Estimates Of Daily Era-5 Precipitation In Europe Estimated Using Regionalized Extreme Value Distributions. Weather And Climate Extremes, 383.
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Robledano, A., Picard, G., Arnaud, L., Larue, F., & Ollivier, I. (2022). Modelling surface temperature and radiation budget of snow-covered complex terrain. Cryosphere, 161(2), 559–579.
Abstract: The surface temperature controls the temporal evolution of the snowpack, playing a key role in metamorphism and snowmelt. It shows large spatial variations in mountainous areas because the surface energy budget is affected by the topography, for instance because of the modulation of the short-wave irradiance by the local slope and the shadows and the short-wave and long-wave re-illumination of the surface from surrounding slopes. These topographic effects are often neglected in large-scale models considering the surface to be flat and smooth. Here we aim at estimating the surface temperature of snow-covered mountainous terrain in clear-sky conditions in order to evaluate the relative importance of the different processes that control the spatial variations. For this, a modelling chain is implemented to compute the surface temperature in a kilometre-wide area from local radiometric and meteorological measurements at a single station. The first component of this chain is the Rough Surface Ray-Tracing (RSRT) model. Based on a photon transport Monte Carlo algorithm, this model quantifies the incident and reflected short-wave radiation on every facet of the mesh describing the snow-covered terrain. The second component is a surface scheme that estimates the terms of the surface energy budget from which the surface temperature is eventually estimated. To assess the modelling chain performance, we use in situ measurements of surface temperature and satellite thermal observations (Landsat 8) in the Col du Lautaret area, in the French Alps. The results of the simulations show (i) an agreement between the simulated and measured surface temperature at the station for a diurnal cycle in winter within 0.2 degrees C; (ii) that the spatial variations in surface temperature are on the order of 5 to 10 degrees C in the domain and are well represented by the model; and (iii) that the topographic effects ranked by importance are the modulation of solar irradiance by the local slope, followed by the altitudinal variations in air temperature (lapse rate), the re-illumination by long-wave thermal emission from surrounding terrain, and the spectral dependence of snow albedo. The changes in the downward long-wave flux because of variations in altitude and the absorption enhancement due to multiple bounces of photons in steep terrain play a less significant role. These results show the necessity of considering the topography to correctly assess the energy budget and the surface temperature of snow-covered complex terrain.
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Rocco, M., Baray, J. L., Colomb, A., Borbon, A., Dominutti, P., Tulet, P., et al. (2022). High Resolution Dynamical Analysis Of Volatile Organic. Compounds (Voc) Measurements During the BIO-MAIDO Field Campaign (Reunion Island, Indian Ocean). Journal Of Geophysical Research-Atmospheres, 1271(4).
Abstract: This study presents a high-resolution dynamical analysis of Volatile Organic Compound (VOC) concentrations measured from March 11 to April 4 2019 at Reunion Island during the BIO-MAIDO (Bio-physicochemistry of tropical clouds at Maido: processes and impacts on secondary organic aerosols formation) campaign. We detail the dynamical and chemical processes that govern atmospheric VOC concentrations at two targeted sites of the western slope of Reunion Island: Petite France (PF), 950 m above sea level (a.s.l.) and Maido Observatory (MO), 2150 m a.s.l. A dynamical connection between PF and MO is found during four selected days: March 28 and 31, April 1 and 3. Trajectory calculations using the coupling of Meso-Computing Advection-interpolation of atmospheric parameters and Trajectory tool (CAT) (100 m horizontal resolution of Meso-NH high-resolution non-hydrostatic model and the CAT trajectory model) Lagrangian transport model showed that air masses were dynamically linked between the two measurements sites for 19% of the time during the complete campaign. Trajectories from the Meso-CAT model combined with the Corine Land Cover-2018 register shows that backward-trajectories are frequently located above biogenic area (mixed forest, 3%-46% of total number trajectory point) and cultures area (e.g., sugar cane plantation, 1%-17%). Regarding VOCs concentrations, air masses coming from downhill MO are associated with significant measured concentrations of isoprene, isoprene oxidation products and benzene. Averaged concentration daytime ratios of isoprene and isoprene oxidation products from PF to MO are 0.73 +/- 1.01 and 0.26 +/- 0.26 respectively illustrating a loss of these VOCs due to deposition, oxidation, or possibility dilution on clouds.
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Rohmer, J., Thieblemont, R., Le Cozannet, G., Goelzer, H., & Durand, G. (2022). Improving Interpretation Of Sea-Level Projections Through A Machine-Learning-Based Local Explanation Approach. Cryosphere, 161(111), 4637–4657.
Abstract: Process-Based Projections Of The Sea-Level Contribution From Land Ice Components Are Often Obtained From Simulations Using A Complex Chain Of Numerical Models. Because Of Their Importance In Supporting The Decision-Making Process For Coastal Risk Assessment And Adaptation, Improving The Interpretability Of These Projections Is Of Great Interest. To This End, We Adopt The Local Attribution Approach Developed In The Machine Learning Community Known As “Shap” (Shapley Additive Explanations). We Apply Our Methodology To A Subset Of The Multi-Model Ensemble Study Of The Future Contribution Of The Greenland Ice Sheet To Sea Level, Taking Into Account Different Modelling Choices Related To (1) Numerical Implementation, (2) Initial Conditions, (3) Modelling Of Ice-Sheet Processes, And (4) Environmental Forcing. This Allows Us To Quantify The Influence Of Particular Modelling Decisions, Which Is Directly Expressed In Terms Of Sea-Level Change Contribution. This Type Of Diagnosis Can Be Performed On Any Member Of The Ensemble, And We Show In The Greenland Case How The Aggregation Of The Local Attribution Analyses Can Help Guide Future Model Development As Well As Scientific Interpretation, Particularly With Regard To Spatial Model Resolution And To Retreat Parametrisation.
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Rosales, A. G., Junquas, C., da Rocha, R. P., Condom, T., & Espinoza, J. C. (2022). Valley-Mountain Circulation Associated with the Diurnal Cycle of Precipitation in the Tropical Andes (Santa River Basin, Peru). Atmosphere, 131(2).
Abstract: The Cordillera Blanca (central Andes of Peru) represents the largest concentration of tropical glaciers in the world. The atmospheric processes related to precipitations are still scarcely studied in this region. The main objective of this study is to understand the atmospheric processes of interaction between local and regional scales controlling the diurnal cycle of precipitation over the Santa River basin located between the Cordillera Blanca and the Cordillera Negra. The rainy season (December-March) of 2012-2013 is chosen to perform simulations with the WRF (Weather Research and Forecasting) model, with two domains at 6 km (WRF-6 km) and 2 km (WRF-2 km) horizontal resolutions, forced by ERA5. WRF-2 km precipitation shows a clear improvement over WRF-6 km in terms of the daily mean and diurnal cycle, compared to in situ observations. WRF-2 km shows that the moisture from the Pacific Ocean is a key process modulating the diurnal cycle of precipitation over the Santa River basin in interaction with moisture fluxes from the Amazon basin. In particular, a channeling thermally orographic flow is described as controlling the afternoon precipitation along the Santa valley. In addition, in the highest parts of the Santa River basin (in both cordilleras) and the southern part, maximum precipitation occurs earlier than the lowest parts and the bottom of the valley in the central part of the basin, associated with the intensification of the channeling flow by upslope cross-valley winds during mid-afternoon and its decrease during late afternoon/early night.
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Saks, T., Pohl, E., Machguth, H., Dehecq, A., Barandun, M., Kenzhebaev, R., et al. (2022). Glacier Runoff Variation Since 1981 in the Upper Naryn River Catchments, Central Tien Shan. Frontiers In Environmental Science, 9.
Abstract: Water resources in Central Asia strongly depend on glaciers, which in turn adjust their size in response to climate variations. We investigate glacier runoff in the period 1981-2019 in the upper Naryn basin, Kyrgyzstan. The basins contain more than 1,000 glaciers, which cover a total area of 776 km(2). We model the mass balance and runoff contribution of all glaciers with a simplified energy balance melt model and distributed accumulation model driven by ERA5 LAND re-analysis data for the time period of 1981-2019. The results are evaluated against discharge records, satellite-derived snow cover, stake readings from individual glaciers, and geodetic mass balances. Modelled glacier volume decreased by approximately 6.7 km(3) or 14%, and the majority of the mass loss took place from 1996 until 2019. The decreasing trend is the result of increasingly negative summer mass balances whereas winter mass balances show no substantial trend. Analysis of the discharge data suggests an increasing runoff for the past two decades, which is, however only partly reflected in an increase of glacier melt. Moreover, the strongest increase in discharge is observed in winter, suggesting either a prolonged melting period and/or increased groundwater discharge. The average runoff from the glacierized areas in summer months (June to August) constitutes approximately 23% of the total contributions to the basin's runoff. The results highlight the strong regional variability in glacier-climate interactions in Central Asia.
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Saks, T., Pohl, E., Machguth, H., Dehecq, A., Barandun, M., Kenzhebaev, R., et al. (2022). Glacier Runoff Variation Since 1981 In The Upper Naryn River Catchments, Central Tien Shan (Vol 9, 780466, 2022). Frontiers In Environmental Science, 101.
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Sanchez-Cid, C., Tignat-Perrier, R., Franqueville, L., Delauriere, L., Schagat, T., & Vogel, T. M. (2022). Sequencing Depth Has a Stronger Effect than DNA Extraction on Soil Bacterial Richness Discovery. Biomolecules, 121(3).
Abstract: Although Next-Generation Sequencing techniques have increased our access to the soil microbiome, each step of soil metagenomics presents inherent biases that prevent the accurate definition of the soil microbiome and its ecosystem function. In this study, we compared the effects of DNA extraction and sequencing depth on bacterial richness discovery from two soil samples. Four DNA extraction methods were used, and sequencing duplicates were generated for each DNA sample. The V3-V4 region of the 16S rRNA gene was sequenced to determine the taxonomical richness measured by each method at the amplicon sequence variant (ASV) level. Both the overall functional richness and antibiotic resistance gene (ARG) richness were evaluated by metagenomics sequencing. Despite variable DNA extraction methods, sequencing depth had a greater influence on bacterial richness discovery at both the taxonomical and functional levels. Sequencing duplicates from the same sample provided access to different portions of bacterial richness, and this was related to differences in the sequencing depth. Thus, the sequencing depth introduced biases in the comparison of DNA extraction methods. An optimisation of the soil metagenomics workflow is needed in order to sequence at a sufficient and equal depth. This would improve the accuracy of metagenomic comparisons and soil microbiome profiles.
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Saunderson, D., Mackintosh, A., Mccormack, F., Jones, R., & Picard, G. (2022). Surface Melt On The Shackleton Ice Shelf, East Antarctica (2003-2021). Cryosphere, 161(101), 4553–4569.
Abstract: Melt On The Surface Of Antarctic Ice Shelves Can Potentially Lead To Their Disintegration, Accelerating The Flow Of Grounded Ice To The Ocean And Raising Global Sea Levels. However, The Current Understanding Of The Processes Driving Surface Melt Is Incomplete, Increasing Uncertainty In Predictions Of Ice Shelf Stability And Thus Of Antarctica'S Contribution To Sea-Level Rise. Previous Studies Of Surface Melt In Antarctica Have Usually Focused On Either A Process-Level Understanding Of Melt Through Energy-Balance Investigations Or Used Metrics Such As The Annual Number Of Melt Days To Quantify Spatiotemporal Variability In Satellite Observations Of Surface Melt. Here, We Help Bridge The Gap Between Work At These Two Scales. Using Daily Passive Microwave Observations From The Amsr-E And Amsr-2 Sensors And The Machine Learning Approach Of A Self-Organising Map, We Identify Nine Representative Spatial Distributions (“Patterns”) Of Surface Melt On The Shackleton Ice Shelf In East Antarctica From 2002/03-2020/21. Combined With Output From The Racmo2.3P3 Regional Climate Model And Surface Topography From The Rema Digital Elevation Model, Our Results Point To A Significant Role For Surface Air Temperatures In Controlling The Interannual Variability In Summer Melt And Also Reveal The Influence Of Localised Controls On Melt. In Particular, Prolonged Melt Along The Grounding Line Shows The Importance Of Katabatic Winds And Surface Albedo. Our Approach Highlights The Necessity Of Understanding Both Local And Large-Scale Controls On Surface Melt And Demonstrates That Self-Organising Maps Can Be Used To Investigate The Variability In Surface Melt On Antarctic Ice Shelves.
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Schmeller, D., Urbach, D., Bates, K., Catalan, J., Cogalniceanu, D., Fisher, M., et al. (2022). Scientists' Warning Of Threats To Mountains. Science Of The Total Environment, 8538.
Abstract: Mountains Are An Essential Component Of The Global Life-Support System. They Are Characterized By A Rugged, Heterog-Enous Landscape With Rapidly Changing Environmental Conditions Providing Myriad Ecological Niches Over Relativelysmall Spatial Scales. Although Montane Species Are Well Adapted To Life At Extremes, They Are Highly Vulnerable To Human Derived Ecosystem Threats. Here We Build On The Manifesto'World Scientists' Warning To Humanity',Issuedbythe Alliance Of World Scientists, To Outline The Major Threats To Mountain Ecosystems. We Highlight Climate Change Asthe Greatest Threat To Mountain Ecosystems, Which Are More Impacted Than Their Lowland Counterparts. We Further Dis-Cuss The Cascade Of“Knock-On”Effects Of Climate Change Such As Increased Uv Radiation, Altered Hydrological Cycles,And Altered Pollution Profiles; Highlighting The Biological And Socio-Economic Consequences. Finally, We Presenthow Intensified Use Of Mountains Leads To Overexploitation And Abstraction Of Water, Driving Changes In Carbonstock, Reducing Biodiversity, And Impacting Ecosystem Functioning. These Perturbations Can Provide Opportunitiesfor Invasive Species, Parasites And Pathogens To Colonize These Fragile Habitats, Driving Further Changes And Losses Ofmicro- And Macro-Biodiversity, As Well Further Impacting Ecosystem Services. Ultimately, Imbalances In The Normalfunctioning Of Mountain Ecosystems Will Lead To Changes In Vital Biological, Biochemical, And Chemical Processes, Crit-Ically Reducing Ecosystem Health With Widespread Repercussions For Animal And Human Wellbeing. Developing Tools Inspecies/Habitat Conservation And Future Restoration Is Therefore Essential If We Are To Effectively Mitigate Against The Declining Health Of Mountains
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Segura, H., Espinoza, J. C., Junquas, C., Lebel, T., Vuille, M., & Condom, T. (2022). Extreme austral winter precipitation events over the South-American Altiplano: regional atmospheric features. Climate Dynamics, .
Abstract: The South American Altiplano has a marked dry season during the austral winter (June to August, JJA). However, during this season synoptic meteorological conditions triggering heavy precipitation can damage socioeconomic activities, often causing the loss of human lives. Using daily in-situ precipitation data from 39 rain-gauge stations over the northern Altiplano (18 degrees S -15 degrees S; > 3000 m.a.s.l.) for the JJA season, we computed the historical percentile 90 (p90) and we identified extreme rainy days with precipitation higher than p90 in the 1980-2010 period. We identified 100 winter extreme precipitation events (WEPEs) over this region that can last between one to 16 days. The K-means analysis was applied to anomalies of geopotential height at 500 hPa from ERA-Interim data during the initial day or Day(0) of WEPEs lasting 1 day (42 cases), 2 days (19) and more than 2 days (39). We found 59 WEPEs characterized by an upper-level trough over the Peruvian-Chilean coast. At 850 hPa, these 59 WEPEs are also associated with cold surges along the eastern Central Andes, indicating an association between the upper-level trough and the cold surge in developing deep convection over the northern Altiplano. A lead-lag composite analysis further showed a significant lower- and mid-tropospheric moistening over the western Amazon 2 days before the onset of these 59 WEPEs, due to low-level northerly wind anomalies originating over equatorial South America. The other 41 WEPEs are associated with a low-level southerly wind regime crossing the equator and a mid-and upper-level low-pressure system over the Peruvian-Chilean coast. While the low-level southerly regime enhances mid-tropospheric moisture transport from the equator towards the Altiplano due to the developed shallow meridional circulation when propagating equatorward, a low-pressure system promotes intensification of upward motion, boosting the upslope moisture transport from the lowlands to the east of the Central Andes towards the Altiplano.
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Serrano-Vincenti, S., Condom, T., Campozano, L., Escobar, L., Walpersdorf, A., Carchipulla-Morales, D., et al. (2022). Harmonic Analysis Of The Relationship Between Gnss Precipitable Water Vapor And Heavy Rainfall Over The Northwest Equatorial Coast, Andes, And Amazon Regions. Atmosphere, 131(111).
Abstract: This Study Finds The Relationship Between Increases In Precipitable Water Vapor (Pwv), And Intense Rainfall Events In Four Different Climatological Regions Of South America'S Equatorial Northwest: The Coast, Andes Valley, High Mountains, And Amazon. First, The Pwv Was Derived From Tropospheric Zenith Delay Measured By Global Navigation Satellite System (Gnss) Instrumentation Located Near Meteorological Stations Within The Regions Of Interest Using Hourly Data From The Year 2014. A Harmonic Analysis Approach Through Continuous Wavelet Cross-Spectrum And Coherence, As Well As Discrete Wavelets, Was Used To Determine A Measure Of The Lags Found Between Pwv And Specific Heavy Rain Events And Then Compared With Satellite Ir Images And Meteorological Anomalies. The Link Between Pwv Peaks And Rainfall Was The Most Evident On The Coast, And Less Discernible In The Other Stations Possibly Due To Local Dynamic Factors. The Results Showed A Lag Of 11 H Between The Preceding Pwv Increase And An Intense Rainfall Event. This Was Apparent In All Of The Stations, Except In Amazon Where It Was 6 H, With The Highest Precision At The Coast And With The Largest Dispersion In The High Mountains. The Interpretation Of This Lag For Each Region Is Also Discussed.
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Shahne, M. Z., Arhami, M., El Haddad, I., Abbaszade, G., Schnelle-Kreis, J., Jaffrezo, J. L., et al. (2022). Particulate emissions of real-world light-duty gasoline vehicle fleet in Iran (vol 292, 118303, 2022). Environmental Pollution, 3003.
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Shangguan, Y. F., Zhuang, X. G., Querol, X., Li, B. Q., Moreno, N., Trechera, P., et al. (2022). Characterization Of Deposited Dust And Its Respirable Fractions In underground coal mines: Implications for oxidative potential-driving species and source apportionment. International Journal Of Coal Geology, 2582.
Abstract: Oxidative potential (OP) is considered to be an efficient indicator of particulate matter (PM) to induce oxidative stress in the lungs and is increasingly considered to be a relevant health metric. In this study, two complementary OP assays were deployed, including dithiothreitol (DTT) and ascorbic acid (AA) assays, to investigate the po-tential toxicity (as generators of oxidative stress) of respirable fractions (DD4, < 4 μm) of deposited dust (DD500, < 500 μm) in underground low-S and low-pyrite coal mines in Henan Province, Central China. The OPDTT of DD4 is higher than that reported for other types of atmospheric PM, whereas the OPAA of DD4 is similar and/or slightly higher. Cross-correlation and multilinear regression analyses are applied using datasets of major mineral and geochemical patterns in the DD4 samples and the respective OP values to identify the major drivers for OP in respirable coal dust. Thereafter, the patterns of DD4 are compared with those of DD500 and the parent coals to determine the sources of OP-relevant substances. OP(DTT )is mainly governed by some trace elements (Sb, As, Li, B, Sr, and Pb) and minor minerals (anatase, quartz, siderite), and their synergistic effect may be one of the reasons for the high DTT consumption. For OPAA, quartz, total clay (sum of illite, kaolinite, tobelite, and clinochlore) and Ni, Cr, Co, Si, and S, play an important role in regulating the OPAA of pyrite-free DD4 samples. These OP-relevant substances have three sources: coal dust, which has a similar composition in DD4, DD500, and the parent coal (such as siderite and its associated elements); gangue dust, which does not occur in the parent coal but is widely detected in DD4 and DD500 (such as quartz, kaolinite, and relevant elements); and cement dust (from gunite galleries), which is mainly calcite-and calcite-associated elements.
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Sharma, R., Chaudhary, A., Seemanth, M., Bhowmick, S. A., Agarwal, N., Verron, J., et al. (2022). SARAL/AltiKa data analysis for oceanographic research: Impact of drifting and post star sensor anomaly phases. Advances In Space Research, 696(6), 2349–2361.
Abstract: Y AltiKa, first ever high frequency Ka-band altimeter on board SARAL (Satellite with ARgos and ALtiKa) has gone through different phases of operations, viz. Exact Repeat Mission, (ERM, March 2013 – July 2016), Drifting phase, (DP, July 2016 – January 2018) and then to Mispointing phase, (MP, February 2018 – till date). A detailed assessment of Sea level anomaly (SLA), Significant Wave Height (SWH) and Ocean Surface Wind Speed (WS) has been carried out during these different phases with a focus on the North Indian Ocean. Crossover analysis using the Jason series of satellites available during various phases of SARAL suggest high quality of SARAL/AltiKa data during the ERM and DP with root mean square differences of the order of 0.080 m, 0.25 m and 1 m/s for SLA, SWH and WS respectively. These differences are more during MP, being 0.095 m, 0.45 m and 1.72 m/s for SLA, SWH and WS respectively. Wavenumber Power spectrum computed from the along-track AltiKa SLA reveals that slopes in the mesoscale band (70-250 km) in different phases of operations are not very different. Errors in gridded SARAL/AltiKa SLA with respect to standard AVISO product remains unchanged during DP, but degrade by nearly 9.3% in the MP as compared to ERM. To assess the effect of assimilating along track SWH and SLA from different phases, two set of wave and circulation model simulations, with and without SARAL AltiKa data assimilation, were performed. Assimilation of SWH improved the wave height simulation by similar to 12.8% during the DP and similar to 8% during ERM and MP. As regards to circulation modeling, no significant difference of assimilating SLA from different phases was observed in the mesoscale range. These results indicate the usefulness of SLA from SARAL AltiKa during DP and MP for studying the mesoscale dynamics. (C) 2021 COSPAR. Published by Elsevier B.V. All rights reserved.
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Shupe, M. D., Rex, M., Blomquist, B., Persson, P. O. G., Schmale, J., Uttal, T., et al. (2022). Overview of the MOSAiC expedition-Atmosphere INTRODUCTION. Elementa-Science Of The Anthropocene, 101(1).
Abstract: With the Arctic rapidly changing, the needs to observe, understand, and model the changes are essential. To support these needs, an annual cycle of observations of atmospheric properties, processes, and interactions were made while drifting with the sea ice across the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition from October 2019 to September 2020. An international team designed and implemented the comprehensive program to document and characterize all aspects of the Arctic atmospheric system in unprecedented detail, using a variety of approaches, and across multiple scales. These measurements were coordinated with other observational teams to explore crosscutting and coupled interactions with the Arctic Ocean, sea ice, and ecosystem through a variety of physical and biogeochemical processes. This overview outlines the breadth and complexity of the atmospheric research program, which was organized into 4 subgroups: atmospheric state, clouds and precipitation, gases and aerosols, and energy budgets. Atmospheric variability over the annual cycle revealed important influences from a persistent large-scale winter circulation pattern, leading to some storms with pressure and winds that were outside the interquartile range of past conditions suggested by long-term reanalysis. Similarly, the MOSAiC location was warmer and wetter in summer than the reanalysis climatology, in part due to its close proximity to the sea ice edge. The comprehensiveness of the observational program for characterizing and analyzing atmospheric phenomena is demonstrated via a winter case study examining air mass transitions and a summer case study examining vertical atmospheric evolution. Overall, the MOSAiC atmospheric program successfully met its objectives and was the most comprehensive atmospheric measurement program to date conducted over the Arctic sea ice. The obtained data will support a broad range of coupled-system scientific research and provide an important foundation for advancing multiscale modeling capabilities in the Arctic.
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Siahaan, A., Smith, R., Holland, P., Jenkins, A., Gregory, J., Lee, V., et al. (2022). The Antarctic Contribution To 21St-Century Sea-Level Rise Predicted By The Uk Earth System Model With An Interactive Ice Sheet. Cryosphere, 161(101), 4053–4086.
Abstract: The Antarctic Ice Sheet Will Play A Crucial Role In The Evolution Of Global Mean Sea Level As The Climate Warms. An Interactively Coupled Climate And Ice Sheet Model Is Needed To Understand The Impacts Of Ice-Climate Feed-Backs During This Evolution. Here We Use A Two-Way Coupling Between The Uk Earth System Model And The Bisicles (Berkeley Ice Sheet Initiative For Climate At Extreme Scales) Dynamic Ice Sheet Model To Investigate Antarctic Ice-Climate Interactions Under Two Climate Change Scenarios. We Perform Ensembles Of Ssp1-1.9 And Ssp5-8.5 (Shared Socioeconomic Pathway) Scenario Simulations To 2100, Which We Believe Are The First Such Simulations With A Climate Model That Include Two-Way Coupling Of Atmosphere And Ocean Models To Dynamic Models Of The Greenland And Antarctic Ice Sheets. We Focus Our Analysis On The Latter. In Ssp1-1.9 Simulations, Ice Shelf Basal Melting And Grounded Ice Mass Loss From The Antarctic Ice Sheet Are Generally Lower Than Present Rates During The Entire Simulation Period. In Contrast, The Responses To Ssp5-8.5 Forcing Are Strong. By The End Of The 21St Century, These Simulations Feature Order-Of-Magnitude Increases In Basal Melting Of The Ross And Filchner-Ronne Ice Shelves, Caused By Intrusions Of Masses Of Warm Ocean Water. Due To The Slow Response Of Ice Sheet Drawdown, This Strong Melting Does Not Cause A Substantial Increase In Ice Discharge During The Simulations. The Surface Mass Balance In Ssp5-8.5 Simulations Shows A Pattern Of Strong Decrease On Ice Shelves, Caused By Increased Melting, And Strong Increase On Grounded Ice, Caused By Increased Snowfall. Despite Strong Surface And Basal Melting Of The Ice Shelves, Increased Snowfall Dominates The Mass Budget Of The Grounded Ice, Leading To An Ensemble Mean Antarctic Contribution To Global Mean Sea Level Of A Fall Of 22 Mm By 2100 In The Ssp5-8.5 Scenario. We Hypothesise That This Signal Would Revert To Sea-Level Rise On Longer Timescales, Caused By The Ice Sheet Dynamic Response To Ice Shelf Thinning These Results Demonstrate The Need For Fully Coupled Ice-Climate Models In Reducing The Substantial Uncertainty In Sea-Level Rise From The Antarctic Ice Sheet.
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Smith, A., Jahn, A., Burgard, C., & Notz, D. (2022). Improving Model-Satellite Comparisons Of Sea Ice Melt Onset With A Satellite Simulator. Cryosphere, 161(8), 3235–3248.
Abstract: Seasonal Transitions In Arctic Sea Ice, Such As The Melt Onset, Have Been Found To Be Useful Metrics For Evaluating Sea Ice In Climate Models Against Observations. However, Comparisons Of Melt Onset Dates Between Climate Models And Satellite Observations Are Indirect. Satellite Data Products Of Melt Onset Rely On Observed Brightness Temperatures, While Climate Models Do Not Currently Simulate Brightness Temperatures, And Must Therefore Define Melt Onset With Other Modeled Variables. Here We Adapt A Passive Microwave Sea Ice Satellite Simulator, The Arctic Ocean Observation Operator (Arc3O), To Produce Simulated Brightness Temperatures That Can Be Used To Diagnose The Timing Of The Earliest Snowmelt In Climate Models, As We Show Here Using Community Earth System Model Version 2 (Cesm2) Ocean-Ice Hindcasts. By Producing Simulated Brightness Temperatures And Earliest Snowmelt Estimation Dates Using Cesm2 And Arc3O, We Facilitate New And Previously Impossible Comparisons Between The Model And Satellite Observations By Removing The Uncertainty That Arises Due To Definition Differences. Direct Comparisons Between The Model And Satellite Data Allow Us To Identify An Early Bias Across Large Areas Of The Arctic At The Beginning Of The Cesm2 Ocean-Ice Hindcast Melt Season, As Well As Improve Our Understanding Of The Physical Processes Underlying Seasonal Changes In Brightness Temperatures. In Particular, The Arc3O Allows Us To Show That Satellite Algorithm-Based Melt Onset Dates Likely Occur After Significant Snowmelt Has Already Taken Place.
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Soriot, C., Picard, G., Prigent, C., Frappart, F., & Domine, F. (2022). Year-Round Sea Ice And Snow Characterization From Combined Passive And active microwave observations and radiative transfer modeling. Remote Sensing Of Environment, 2782.
Abstract: Satellite microwave observations from 1.4 to 36 GHz already showed sensitivity to several geophysical parameters of sea ice such as Sea Ice Concentration (SIC), Sea Ice Thickness (SIT) or snow depth. The main goal of this article is to provide a realistic and comprehensive characterization of the sea ice and its snow cover that explains the microwave observations during a whole year using a radiative transfer model. For this purpose, we construct a unique dataset of passive microwave observations, to mimic the future Copernicus Imaging Microwave Radiometer (CIMR), along with the active microwave scatterometer data (ASCAT). CIMR database is used to classify sea ice microwave signatures in their spectral dimension with a machine learning technique while ASCAT data are used to help interpret the results of the classification. Classification results are then interpreted with a state-of-art sea ice and Snow Microwave Radiative Transfer model (SMRT) for all highlighted signatures and all seasons. Results make it possible to identify the specific behaviors from the observation co-variabilities for SIC, SIT, and snow structure. Our analysis underlined the role of the depth hoar over multi-year ice, for the interpretation of scattering signals in winter. Scattering signals that appear in late summer are explained by the presence of superimposed ice. This characterization will benefit from future advances in SMRT development, as well as the improved observations of future satellite missions.
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Steensen, B. M., Marelle, L., Hodnebrog, O., & Myhre, G. (2022). Future urban heat island influence on precipitation. Climate Dynamics, .
Abstract: Urbanization and global warming are two of the major human impacts on the environment. The Urban Heat Island (UHI) effect can change precipitation patterns. Global warming also leads to changes in precipitation and especially an increase in intensity and frequency of extreme precipitation. With urbanization expected to grow in the future, the role of UHI in a warmer climate is an important research question. We present results from 20-year long regional convection-permitting model simulations that include the UHI effect, run for historical and future climates for two megacities, Paris and Shanghai. In the warmer future climate, urban-induced precipitation is found to decrease compared to the historical climate, for both mean and extreme precipitation, with large uncertainties due to natural variability. The mean precipitation increase due to UHI in Paris is 2.2 +/- 1.4% and 1.8 +/- 1.3% for historical and future conditions, respectively. Shanghai has slightly weaker mean precipitation change than Paris at present and no change in the future. The future reduction of the urban effect is found to be caused by a decrease in summer precipitation for both cities. Interannual variability in precipitation due to UHI is larger for Shanghai than Paris. The UHI effect on extreme precipitation is also reduced in the future climate and the area with precipitation increase is more concentrated. The general increase in extreme precipitation due to global warming, in combination with the precipitation redistribution due to UHI, underline the importance for future urban planning to mitigate damage caused by extreme precipitation events.
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Stokes, C., Abram, N., Bentley, M., Edwards, T., England, M., Foppert, A., et al. (2022). Response Of The East Antarctic Ice Sheet To Past And Future Climate Change. Nature, 6086(79227), 275–+.
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Strom, J., Svensson, J., Honkanen, H., Asmi, E., Dkhar, N. B., Tayal, S., et al. (2022). Snow Albedo And Its Sensitivity To Changes In Deposited Light-Absorbing particles estimated from ambient temperature and snow depth observations at a high-altitude site in the Himalaya. Elementa-Science Of The Anthropocene, 101(1).
Abstract: Snow darkening by deposited light-absorbing particles (LAP) accelerates snowmelt and shifts the snow meltout date (MOD). Here, we present a simple approach to estimate the snow albedo variability due to LAP deposition and test this method with data for 2 seasons (February-May 2016 and December 2016-June 2017) at a high-altitude valley site in the Central Himalayas, India. We derive a parameterization for the snow albedo that only depends on the daily observations of average ambient temperature and change in snow depth, as well as an assumed average concentration of LAP in snow precipitation. Linear regression between observed and parameterized albedo for the base case assuming an equivalent elemental carbon concentration [ECeq] of 100 ng g(-1) in snow precipitation yields a slope of 0.75 and a Pearson correlation coefficient r(2) of 0.76. However, comparing the integrated amount of shortwave radiation absorbed during the winter season using observed albedo versus base case albedo resulted in rather small differences of 11% and 4% at the end of Seasons 1 and 2, respectively. The enhanced energy absorbed due to LAP at the end of the 2 seasons for the base case scenario (assuming an [ECeq] of 100 ng g(-1) in snow precipitation) was 40% and 36% compared to pristine snow. A numerical evaluation with different assumed [ECeq] in snow precipitation suggests that the relative sensitivity of snow albedo to changes in [ECeq] remains rather constant for the 2 seasons. Doubling [ECeq] augments the absorption by less than 20%, highlighting that the impact on a MOD is small even for a doubling of average LAP in snow precipitation.
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Sulca, J., Takahashi, K., Tacza, J., Espinoza, J., & Dong, B. (2022). Decadal Variability In The Austral Summer Precipitation Over The Central Andes: Observations And The Empirical-Statistical Downscaling Model. International Journal Of Climatology, .
Abstract: The Decadal Variability In Summer Precipitation Over The Central Andes (10 Degrees-30 Degrees S) Is Investigated From 1921 To 2010 Using Low-Pass Filtered Time Series Of The Central And Eastern El Nino-Southern Oscillation (Enso) Pacific (C And E) Indices, The South Pacific Convergence Zone (Spcz) Index, The Atlantic Sst Indices, Atlantic Multidecadal Oscillation (Amo) Index, North Atlantic Oscillation (Nao) Index, And Era-20C Reanalysis. Additionally, An Empirical-Statistical Downscaling (Esd) Model Was Built. A Rotated Empirical Orthogonal Function (Reof) Analysis Shows That The First Leading Mode Of Precipitation (Rpc1) Represents 38.2% Of The Total Decadal Variance. Rpc2, Rcp3, And Rpc4 Represent 18.8, 12.8, And 9.7% Of The Total Decadal Variance, Respectively. Furthermore, Rpc1 Features Highest Loadings Over Most Of The Region. Rpc2 Features A Dipole Of Highest Loadings Over The Southernmost Bolivian Altiplano And Lowest Loadings Over The Northwestern Argentinian Andes. Conversely, Rpc3 Presents Highest Loadings Over The Eastern-Central Bolivian Altiplano And Northwestern Argentinian Andes. Rpc4 Features Highest Loadings Over The Southern Bolivian Andes. Rpc1 And Rpc3 Wet Summers Are Associated With Moisture Transport From The Amazon Basin, But Rpc1 Features The Strengthening Upper-Level Bolivian High-Nordeste Low System Over South America. Conversely, Rpc2 And Rpc4 Wet Summers Are Associated With Local Processes Induced By Southward Displacement Of The South Atlantic Convergence Zone And Warm Sea Surface Temperature (Sst) Anomalies Over The Indian Ocean, Respectively. According To The Esd Model, The Decadal Variability In The Central And Eastern Pacific (Cp And Ep) And Atlantic Ocean Reproduces The Decadal Component Of The Djf Precipitation Over Most Of The Central Andes.
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Swanson, W., Holmes, C., Simpson, W., Confer, K., Marelle, L., Thomas, J., et al. (2022). Comparison Of Model And Ground Observations Finds Snowpack And Blowing Snow Aerosols Both Contribute To Arctic Tropospheric Reactive Bromine. Atmospheric Chemistry And Physics, 222(222), 14467–14488.
Abstract: Reactive Halogens Play A Prominent Role In The Atmospheric Chemistry Of The Arctic During Springtime. Field Measurements And Modeling Studies Suggest That Halogens Are Emitted Into The Atmosphere From Snowpack And Reactions On Wind-Blown Snow-Sourced Aerosols. The Relative Importance Of Snowpack And Blowing Snow Sources Is Still Debated, Both At Local Scales And Regionally Throughout The Arctic. To Understand The Implications Of These Halogen Sources On A Pan-Arctic Scale, We Simulate Arctic Reactive Bromine Chemistry In The Atmospheric Chemical Transport Model Geos-Chem. Two Mechanisms Are Included: (1) A Blowing Snow Sea Salt Aerosol Formation Mechanism And (2) A Snowpack Mechanism Assuming Uniform Molecular Bromine Production From All Snow Surfaces. We Compare Simulations Including Neither Mechanism, Each Mechanism Individually, And Both Mechanisms To Examine Conditions Where One Process May Dominate Or The Mechanisms May Interact. We Compare The Models Using These Mechanisms To Observations Of Bromine Monoxide (Bro) Derived From Multiple-Axis Differential Optical Absorption Spectroscopy (Max-Doas) Instruments On O-Buoy Platforms On The Sea Ice And At A Coastal Site In Utqiagvik, Alaska, During Spring 2015. Model Estimations Of Hourly And Monthly Average Bro Are Improved By Assuming A Constant Yield Of 0.1 % Molecular Bromine From All Snowpack Surfaces On Ozone Deposition. The Blowing Snow Aerosol Mechanism Increases Modeled Bro By Providing More Bromide-Rich Aerosol Surface Area For Reactive Bromine Recycling. The Snowpack Mechanism Led To Increased Model Bro Across The Arctic Ocean With Maximum Production In Coastal Regions, Whereas The Blowing Snow Aerosol Mechanism Increases Bro In Specific Areas Due To High Surface Wind Speeds. Our Uniform Snowpack Source Has A Greater Impact On Bro Mixing Ratios Than The Blowing Snow Source. Model Results Best Replicate Several Features Of Bro Observations During Spring 2015 When Using Both Mechanisms In Conjunction, Adding Evidence That These Mechanisms Are Both Active During The Arctic Spring. Extending Our Transport Model Throughout The Entire Year Leads To Predictions Of Enhanced Fall Bro That Are Not Supported By Observations.
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Thera, B., Dominutti, P., Colomb, A., Michoud, V., Doussin, J. F., Beekmann, M., et al. (2022). O-3-Noy Photochemistry In Boundary Layer Polluted Plumes: Insights From the MEGAPOLI (Paris), ChArMEx/SAFMED (North West Mediterranean) and DACCIWA (southern West Africa) aircraft campaigns. Environmental Science-Atmospheres, 2(4), 659–686.
Abstract: The ozone-NOy photochemistry is explored in contrasting polluted plumes sampled with the Safire ATR 42 research aircraft during three summer field international campaigns in the megacity Paris, the North West Mediterranean basin (WMB) and southern West Africa (SWA). Various metrics derived from the photostationary steady state (PSS) and the ozone production efficiency (OPE) are calculated from airborne observations. A new metric, the oxidant production rate normalized to carbon monoxide (PROx), is introduced and quantified as a function of the processing time of the plume. In most of the polluted plumes, it is found that the Leighton ratio (phi) characterizing the equilibrium between O-3 and NOx is, on average, within the PSS range ([1 +/- 0.32]) or greater. The positive dependence of O-x to NO usually indicates a VOC-sensitive regime inside the plumes with some exceptions. In Paris, under oceanic westerly winds, and during DACCIWA, the plumes show a rural-like chemistry behaviour at moderate NOx levels (NOx-sensitive). Intense and frequent rapid changes in J(NO2), NO and NO2 explain the deviations from the PSS. The OPE for Paris plume suggests that the VOC-sensitive regime extends far beyond the urban plume. The mean ozone production is higher downwind of Paris (30 ppb h(-1) on average) compared to SWA (20 ppb h(-1)) and WMB (6 ppb h(-1)). PROx values vary between 0 (no oxidant production) and 0.27 ppb([Ox]) ppb([CO])(-1) h(-1). The determined uncertainty on the Leighton ratio value could affect the differences in the estimation of the photochemical oxidant production by PO3 and PROx. The emissions of CO along the flight path and the presence of vegetation and high humidity levels might shape the oxidant production depending on the explored environment. While limited in number, PROx values set a benchmark for future photochemical studies to compare with: Paris as representative of an anthropogenic urban plume and WMB as representative of a biogenic continental plume.
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Tilinina, N., Ivonin, D., Gavrikov, A., Sharmar, V., Gulev, S., Suslov, A., et al. (2022). Wind Waves In The North Atlantic From Ship Navigational Radar: Seavision Development And Its Validation With The Spotter Wave Buoy And Wavewatch Iii. Earth System Science Data, 141(8), 3615–3633.
Abstract: Wind Waves Play An Important Role In The Climate System, Modulating The Energy Exchange Between The Ocean And The Atmosphere And Effecting Ocean Mixing. However, Existing Ship-Based Observational Networks Of Wind Waves Are Still Sparse, Limiting Therefore The Possibilities Of Validating Satellite Missions And Model Simulations. In This Paper We Present Data Collected On Three Research Cruises In The North Atlantic And Arctic In 2020 And 2021 And The Seavision System For Measuring Wind Wave Characteristics Over The Open Ocean With A Standard Marine Navigation X-Band Radar. Simultaneously With The Seavision Wind Wave Characteristic Measurements, We Also Collected Data From The Spotter Wave Buoy At The Same Locations, And We Ran The Wavewatch Iii Model In A Very High-Resolution Configuration Over The Observational Domain Seavision Measurements Were Validated Against Co-Located Spotter Wave Buoy Data And Intercompared With The Output Of Wavewatch Iii Simulations. Observations Of The Wind Waves With The Navigation X-Band Radar Were Found To Be In Good Agreement With Buoy Data And Model Simulations With The Best Match For The Wave Propagation Directions. Supporting Datasets Consist Of Significant Wave Heights, Wave Directions, Wave Periods And Wave Energy Frequency Spectra Derived From Both Seavision And The Spotter Buoy. All Supporting Data Are Available Through The Pangaea Repository – Https://Doi.Org/10.1594/Pangaea.939620 (Gavrikov Et Al., 2021). The Dataset Can Be Further Used For Validation Of Satellite Missions And Regional Wave Model Experiments. Our Study Shows The Potential Of Ship Navigation X-Band Radars (When Assembled With Seavision Or Similar Systems) For The Development Of A New Near-Global Observational Network Providing A Much Larger Number Of Wind Wave Observations Compared To E.G. Voluntary Observing Ship (Vos) Data And Research Vessel Campaigns.
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Tu, T., Tweed, S., Dan, N., Descloitres, M., Quang, K., Nemery, J., et al. (2022). Localized Recharge Processes In The Ne Mekong Delta And Implications For Groundwater Quality. Science Of The Total Environment, 8458.
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Uchida, T., Deremble, B., & Popinet, S. (2022). Deterministic Model Of The Eddy Dynamics For A Midlatitude Ocean Model. Journal Of Physical Oceanography, 525(6), 1133–1154.
Abstract: Mesoscale Eddies, Although Being On Scales Of O(20-100) Km, Have A Disproportionate Role In Shaping The Mean Stratification, Which Varies On The Scale Of O(1000) Km. With The Increase In Computational Power, We Are Now Able To Partially Resolve The Eddies In Basin-Scale And Global Ocean Simulations, A Model Resolution Often Referred To As Mesoscale Permitting. It Is Well Known, However, That Due To Gridscale Numerical Viscosity, Mesoscale-Permitting Simulations Have Less Energetic Eddies And Consequently Weaker Eddy Feedback Onto The Mean Flow. In This Study, We Run A Quasigeostrophic Model At Mesoscale-Resolving Resolution In A Double Gyre Configuration And Formulate A Deterministic Closure For The Eddy Rectification Term Of Potential Vorticity (Pv), Namely, The Eddy Pv Flux Divergence. Our Closure Successfully Reproduces The Spatial Patterns And Magnitude Of Eddy Kinetic And Potential Energy Diagnosed From The Mesoscale-Resolving Model. One Novel Point About Our Approach Is That We Account For Nonlocal Eddy Feedbacks Onto The Mean Flow By Solving The “Subgrid” Eddy Pv Equation Prognostically In Addition To The Mean Pv.
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Uchida, T., Jamet, Q., Dewar, W. K., Le Sommer, J., Penduff, T., & Balwada, D. (2022). Diagnosing The Thickness-Weighted Averaged Eddy-Mean Flow Interaction From an Eddying North Atlantic Ensemble: The Eliassen-Palm Flux. Journal Of Advances In Modeling Earth Systems, 141(5).
Abstract: The thickness-weighted average (TWA) framework, which treats the residual-mean flow as the prognostic variable, provides a clear theoretical formulation of the eddy feedback onto the residual-mean flow. The averaging operator involved in the TWA framework, although in theory being an ensemble mean, in practice has often been approximated by a temporal mean. Here, we analyze an ensemble of North Atlantic simulations at mesoscale-permitting resolution (1/12 degrees). We therefore recognize means and eddies in terms of ensemble means and fluctuations about those means. The ensemble dimension being orthogonal to the temporal and spatial dimensions negates the necessity for an arbitrary temporal or spatial scale in defining the eddies. Eddy-mean flow feedbacks are encapsulated in the Eliassen-Palm (E-P) flux tensor and its convergence indicates that eddy momentum fluxes dominate in the separated Gulf Stream. The eddies can be interpreted to contribute to the zonal meandering of the Gulf Stream and a northward migration of it in the meridional direction. Downstream of the separated Gulf Stream in the North Atlantic Current region, the interfacial form stress convergence becomes leading order in the E-P flux convergence.
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Uchida, T., Jamet, Q., Dewar, W. K., Le Sommer, J., Penduff, T., & Balwada, D. (2022). Diagnosing The Thickness-Weighted Averaged Eddy-Mean Flow Interaction From an Eddying North Atlantic Ensemble: The Eliassen-Palm Flux. Journal Of Advances In Modeling Earth Systems, 141(5).
Abstract: The thickness-weighted average (TWA) framework, which treats the residual-mean flow as the prognostic variable, provides a clear theoretical formulation of the eddy feedback onto the residual-mean flow. The averaging operator involved in the TWA framework, although in theory being an ensemble mean, in practice has often been approximated by a temporal mean. Here, we analyze an ensemble of North Atlantic simulations at mesoscale-permitting resolution (1/12 degrees). We therefore recognize means and eddies in terms of ensemble means and fluctuations about those means. The ensemble dimension being orthogonal to the temporal and spatial dimensions negates the necessity for an arbitrary temporal or spatial scale in defining the eddies. Eddy-mean flow feedbacks are encapsulated in the Eliassen-Palm (E-P) flux tensor and its convergence indicates that eddy momentum fluxes dominate in the separated Gulf Stream. The eddies can be interpreted to contribute to the zonal meandering of the Gulf Stream and a northward migration of it in the meridional direction. Downstream of the separated Gulf Stream in the North Atlantic Current region, the interfacial form stress convergence becomes leading order in the E-P flux convergence.
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Uchida, T., Jamet, Q., Poje, A., & Dewar, W. K. (2022). An Ensemble-Based Eddy and Spectral Analysis, With Application to the Gulf Stream. Journal Of Advances In Modeling Earth Systems, 141(4).
Abstract: The “eddying” ocean, recognized for several decades, has been the focus of much observational and theoretical research. We here describe a generalization for the analysis of eddy energy, based on the use of ensembles, that addresses two key related issues: the definition of an “eddy” and the general computation of energy spectra. An ensemble identifies eddies as the unpredictable component of the flow, and permits the scale decomposition of their energy in inhomogeneous and non-stationary settings. We present two distinct, but equally valid, spectral estimates: one is similar to classical Fourier spectra, the other reminiscent of classical empirical orthogonal function analysis. Both satisfy Parseval's equality and thus can be interpreted as length-scale dependent energy decompositions. The issue of “tapering” or “windowing” of the data, used in traditional approaches, is also discussed. We apply the analyses to a mesoscale “resolving” (1/12 degrees) ensemble of the separated North Atlantic Gulf Stream. Our results reveal highly anisotropic spectra in the Gulf Stream and zones of both agreement and disagreement with theoretically expected spectral shapes. In general, we find spectral slopes that fall off faster than the steepest slope expected from quasi-geostrophic theory.
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Uchida, T., Le Sommer, J., Stern, C., Abernathey, R., Holdgraf, C., Albert, A., et al. (2022). Cloud-Based Framework For Inter-Comparing Submesoscale-Permitting Realistic Ocean Models. Geoscientific Model Development, 151(141), 5829–5856.
Abstract: With The Increase In Computational Power, Ocean Models With Kilometer-Scale Resolution Have Emerged Over The Last Decade. These Models Have Been Used For Quantifying The Energetic Exchanges Between Spatial Scales, Informing The Design Of Eddy Parametrizations, And Preparing Observing Networks. The Increase In Resolution, However, Has Drastically Increased The Size Of Model Outputs, Making It Difficult To Transfer And Analyze The Data. It Remains, Nonetheless, Of Primary Importance To Assess More Systematically The Realism Of These Models. Here, We Showcase A Cloud-Based Analysis Framework Proposed By The Pangeo Project That Aims To Tackle Such Distribution And Analysis Challenges. We Analyze The Output Of Eight Submesoscale-Permitting Simulations, All On The Cloud, For A Crossover Region Of The Upcoming Surface Water And Ocean Topography (Swot) Altimeter Mission Near The Gulf Stream Separation. The Cloud-Based Analysis Framework (I) Minimizes The Cost Of Duplicating And Storing Ghost Copies Of Data And (Ii) Allows For Seamless Sharing Of Analysis Results Amongst Collaborators. We Describe The Framework And Provide Example Analyses (E.G., Sea-Surface Height Variability, Submesoscale Vertical Buoyancy Fluxes, And Comparison To Predictions From The Mixed-Layer Instability Parametrization). Basin- To Global-Scale, Submesoscale-Permitting Models Are Still At Their Early Stage Of Development; Their Cost And Carbon Footprints Are Also Rather Large. It Would, Therefore, Benefit The Community To Document The Different Model Configurations For Future Best Practices. We Also Argue That An Emphasis On Data Analysis Strategies Would Be Crucial For Improving The Models Themselves.
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Vandecrux, B., Box, J. E., Wehrle, A., Kokhanovsky, A. A., Picard, G., Niwano, M., et al. (2022). The Determination of the Snow Optical Grain Diameter and Snowmelt Area on the Greenland Ice Sheet Using Spaceborne Optical Observations. Remote Sensing, 141(4).
Abstract: The optical diameter of the surface snow grains impacts the amount of energy absorbed by the surface and therefore the onset and magnitude of surface melt. Snow grains respond to surface heating through grain metamorphism and growth. During melt, liquid water between the grains markedly increases the optical grain size, as wet snow grain clusters are optically equivalent to large grains. We present daily surface snow grain optical diameters (d(opt)) retrieved from the Greenland ice sheet at 1 km resolution for 2017-2019 using observations from Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A. The retrieved d(opt) are evaluated against 3 years of in situ measurements in Northeast Greenland. We show that higher d(opt) are indicative of surface melt as calculated from meteorological measurements at four PROMICE automatic weather stations. We deduce a threshold value of 0.64 mm in d(opt) allowing categorization of the days either as melting or nonmelting. We apply this simple melt detection technique in Northeast Greenland and compare the derived melting areas with the conventional passive microwave MEaSUREs melt flag for June 2019. The two flags show generally consistent evolution of the melt extent although we highlight areas where large grain diameters are strong indicators of melt but are missed by the MEaSUREs melt flag. While spatial resolution of the optical grain diameter-based melt flag is higher than passive microwave, it is hampered by clouds. Our retrieval remains suitable to study melt at a local to regional scales and could be in the future combined with passive microwave melt flags for increased coverage.
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Verfaillie, D., Pelletier, C., Goosse, H., Jourdain, N. C., Bull, C. Y. S., Dalaiden, Q., et al. (2022). The Circum-Antarctic Ice-Shelves Respond To A More Positive Southern Annular Mode with regionally varied melting. Communications Earth & Environment, 3(1).
Abstract: The Southern Hemisphere cryosphere has recently shown regionally-contrasted responses to climate change, in particular to the positive phases of the Southern Annular Mode. However, the understanding of the impacts of this mode on ice-shelf basal melt at a circum-Antarctic scale is still limited. Here, we performed idealized experiments with a pan-Antarctic regional ice-shelf cavity-resolving ocean-sea-ice model for different phases of the Southern Annular Mode. We show that positive phases lead to increased upwelling and subsurface ocean temperature and salinity close to ice shelves, while the opposite occurs for negative phases. A one-standard-deviation increase of the Southern Annular Mode leads to a net basal mass loss of 40 Gt yr(-1), with strong regional contrasts: increased ice-shelf basal melt in the Bellingshausen and Western Pacific sectors and the opposite response in the Amundsen sector. Estimates of 1000-1200 and 2090-2100 ice-shelf basal melt changes due to the Southern Annular Mode are -86.6 Gt yr(-1) and 55.0 to 164.9 Gt yr(-1), respectively, compared to the present. Positive phases of the Southern Annular Mode lead to enhanced basal melt overall in the Antarctic ice shelves, with strong losses in the Bellingshausen and Western Pacific sectors and gains in the Amundsen Sea, according to ice-ocean model experiments.
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Verin, G., Domine, F., Babin, M., Picard, G., & Arnaud, L. (2022). Metamorphism Of Snow On Arctic Sea Ice During The Melt Season: Impact On Spectral Albedo And Radiative Fluxes Through Snow. Cryosphere, 161(9), 3431–3449.
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Vincent, C., Gilbert, A., Walpersdorf, A., Gimbert, F., Gagliardini, O., Jourdain, B., et al. (2022). Evidence Of Seasonal Uplift In The Argentiere Glacier (Mont Blanc Area, France). Journal Of Geophysical Research-Earth Surface, 1271(7).
Abstract: The hydromechanical processes by which basal water controls sliding at the glacier bed are poorly known, despite glacier basal motion being responsible for a large part of ice flux in temperate alpine glaciers. Previous studies suggest that sliding strongly relates to the quantity of water being stored at the ice-bedrock interface. However, this water storage is difficult to quantify accurately on the basis of surface-motion observations, given that uplift can also be affected by changes in vertical-strain rates and sliding velocity change. Here, we use a comprehensive data set of in situ measurements performed over 2 years on the Argentiere Glacier in the French Alps to investigate the relationships between horizontal and vertical velocities, basal sliding, subglacial runoff and bed separation. We observe strikingly large uplifts varying spatially between 0.20 and 0.90 m over the winter/spring seasons between January and June and with a consistent spatial pattern from 1 year to another. We show, based on observations and three dimensional ice-flow modeling, that these large uplifts cannot be explained solely by changes in strain rates or in sliding up an inclined bed. Our results reveal that more than 80% of the observed uplift is related to enhanced bed separation through cavitation, allowing us to estimate the volume occupied by water-filled subglacial cavities. Our interpretation of uplift being mainly caused by increased cavitation is also consistent with an associated increase in the observed surface horizontal velocity. These findings provide important observational constraints for testing subglacial hydrological models.
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Viviroli, D., Sikorska-Senoner, A., Evin, G., Staudinger, M., Kauzlaric, M., Chardon, J., et al. (2022). Comprehensive Space-Time Hydrometeorological Simulations For Estimating Very Rare Floods At Multiple Sites In A Large River Basin. Natural Hazards And Earth System Sciences, 222(9), 2891–2920.
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Voglimacci-Stephanopoli, J., Wendleder, A., Lantuit, H., Langlois, A., Stettner, S., Schmitt, A., et al. (2022). Potential Of X-Band Polarimetric Synthetic Aperture Radar Co-Polar Phase difference for arctic snow depth estimation. Cryosphere, 161(6).
Abstract: Changes in snowpack associated with climatic warming has drastic impacts on surface energy balance in the cryosphere. Yet, traditional monitoring techniques, such as punctual measurements in the field, do not cover the full snowpack spatial and temporal variability, which hampers efforts to upscale measurements to the global scale. This variability is one of the primary constraints in model development. In terms of spatial resolution, active microwaves (synthetic aperture radar – SAR) can address the issue and outperform methods based on passive microwaves. Thus, high-spatial-resolution monitoring of snow depth (SD) would allow for better parameterization of local processes that drive the spatial variability of snow. The overall objective of this study is to evaluate the potential of the TerraSAR-X (TSX) SAR sensor and the wave co-polar phase difference (CPD) method for characterizing snow cover at high spatial resolution. Consequently, we first (1) investigate SD and depth hoar fraction (DHF) variability between different vegetation classes in the Ice Creek catchment (Qikiqtaruk/Herschel Island, Yukon, Canada) using in situ measurements collected over the course of a field campaign in 2019; (2) evaluate linkages between snow characteristics and CPD distribution over the 2019 dataset; and (3) determine CPD seasonality considering meteorological data over the 2015-2019 period. SD could be extracted using the CPD when certain conditions are met. A high incidence angle (>30 circle) with a high topographic wetness index (TWI) (>7.0) showed correlation between SD and CPD (R2 up to 0.72). Further, future work should address a threshold of sensitivity to TWI and incidence angle to map snow depth in such environments and assess the potential of using interpolation tools to fill in gaps in SD information on drier vegetation types.
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Wever, N., Keenan, E., Amory, C., Lehning, M., Sigmund, A., Huwald, H., et al. (2022). Observations And Simulations Of New Snow Density In The Drifting Snow-Dominated Environment Of Antarctica. Journal Of Glaciology, .
Abstract: Owing To Drifting Snow Processes, Snow Accumulation And Surface Density In Polar Environments Are Variable In Space And Time. We Present New Field Data Of Manual Measurements, Repeat Terrestrial Laser Scanning And Snow Micro-Penetrometry From Dronning Maud Land, Antarctica, Showing The Density Of New Snow Accumulations. We Combine These Data With Published Drifting Snow Mass Flux Observations, To Evaluate The Performance Of The 1-D, Detailed, Physics-Based Snow Cover Model Snowpack In Representing Drifting Snow And Surface Density. For Two Sites In East Antarctica With Multiple Years Of Data, We Found A Coefficient Of Determination For The Simulated Drifting Snow Of R(2) = 0.42 And R(2) = 0.50, Respectively. The Field Observations Show The Existence Of Low-Density Snow Accumulations During Low Wind Conditions. Successive High Wind Speed Events Generally Erode These Low-Density Layers While Producing Spatially Variable Erosion/Deposition Patterns With Typical Length Scales Of A Few Metres. We Found That A Model Setup That Is Able To Represent Low-Density Snow Accumulating During Low Wind Speed Conditions, As Well As Subsequent Snow Erosion And Redeposition At Higher Densities During Drifting Snow Events Was Mostly Able To Describe The Observed Temporal Variability Of Surface Density In The Field.
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Wilhelm, B., Amann, B., Corella, J. P., Rapuc, W., Giguet-Covex, C., Merz, B., et al. (2022). Reconstructing Paleoflood Occurrence and Magnitude from Lake Sediments. Quaternary, 5(1).
Abstract: Lake sediments are a valuable archive to document past flood occurrence and magnitude, and their evolution over centuries to millennia. This information has the potential to greatly improve current flood design and risk assessment approaches, which are hampered by the shortness and scarcity of gauge records. For this reason, paleoflood hydrology from lake sediments received fast-growing attention over the last decade. This allowed an extensive development of experience and methodologies and, thereby, the reconstruction of paleoflood series with increasingly higher accuracy. In this review, we provide up-to-date knowledge on flood sedimentary processes and systems, as well as on state-of-the-art methods for reconstructing and interpreting paleoflood records. We also discuss possible perspectives in the field of paleoflood hydrology from lake sediments by highlighting the remaining challenges. This review intends to guide the research interest in documenting past floods from lake sediments. In particular, we offer here guidance supported by the literature in how: to choose the most appropriate lake in a given region, to find the best suited sedimentary environments to take the cores, to identify flood deposits in the sedimentary sequence, to distinguish them from other instantaneous deposits, and finally, to rigorously interpret the flood chronicle thus produced.
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Wilhelm, B., Rapuc, W., Amann, B., Anselmetti, F. S., Arnaud, F., Blanchet, J., et al. (2022). Impact of warmer climate periods on flood hazard in the European Alps. Nature Geoscience, 151(2), 118–+.
Abstract: Flooding is a pervasive natural hazard-costly in both human and economic terms-and climate change will probably exacerbate risks around the world. Mountainous areas, such as the densely populated European Alps, are of particular concern as topography and atmospheric conditions can result in large and sudden floods. In addition, the Alps are experiencing a high warming rate, which is probably leading to more heavy rainfall events. Here, we compile palaeoflood records to test the still uncertain impact these climatic trends might have on flood frequency and magnitude in the European Alps. We demonstrate that a warming of 0.5-1.2 degrees C, whether naturally or anthropogenically forced, led to a 25-50% decrease in the frequency of large (>= 10 yr return period) floods. This decreasing trend is not conclusive in records covering less than 200 years but persistent in those ranging from 200 to 9,000 years. By contrast, extreme (>100 yr) floods may increase with a similar degree of warming in certain small alpine catchments impacted by local intensification of extreme rainfall. Our results show how long, continuous palaeoflood records can be used to disentangle complex climate-flooding relationships and assist in improving risk assessment and management at a regional scale. Moderate flooding in the European Alps declined during past warmer periods, whereas extreme floods both increased and decreased, according to an analysis of palaeoflood records.
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2021 |
Abdalla, S., Kolahchi, A., Ablain, M., Adusumilli, S., Bhowmick, S., Alou-Font, E., et al. (2021). Altimetry for the future: Building on 25 years of progress. Advances In Space Research, 68(2), 319–363.
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Abdou, M., Vandervaere, J., Descroix, L., & Moussa, I. (2021). Comparative hydrodynamic study of granitic and sedimentary catchments in Western Niger. Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, .
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Ajayi, A., Le Sommer, J., Chassignet, E., Molines, J., Xu, X., Albert, A., et al. (2021). Diagnosing Cross-Scale Kinetic Energy Exchanges From Two Submesoscale Permitting Ocean Models. Journal Of Advances In Modeling Earth Systems, 13(6).
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Albertin, S., Savarino, J., Bekki, S., Barbero, A., & Caillon, N. (2021). Measurement report: Nitrogen isotopes (delta N-15) and first quantification of oxygen isotope anomalies (Delta O-17, delta O-18) in atmospheric nitrogen dioxide. Atmospheric Chemistry And Physics, 21(13), 10477–10497.
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Alemany, O., Talalay, P., Boissonneau, P., Chappellaz, J., Chemin, J., Duphil, R., et al. (2021). The SUBGLACIOR drilling probe: hydraulic considerations. Annals Of Glaciology, 62(84), 131–142.
Abstract: Using significant technological breakthroughs and unconventional approaches, the goal of the in situ probing of glacier ice for a better understanding of the orbital response of climate (SUBGLACIOR) project is to advance ice core research by inventing, constructing and testing an in situ probe to evaluate if a target site is suitable for recovering ice as old as 1.5 million years. Embedding a laser spectrometer, the probe is intended to make its own way down into the ice and to measure, in real time and down to the bedrock, the depth profiles of the ice delta D water isotopes as well as the trapped CH4 gas concentration and dust concentration. The probe descent is achieved through electromechanical drilling combined with continuous meltwater sample production using a central melting finger in the drill head. A key aspect of the project lies in the design and implementation of an efficient method to continuously transfer to the surface the ice chips being produced by the drill head and from the refreezed water expulsed downstream from the melting finger, into the borehole. This paper presents a detailed calculation and analysis of the flow rates and pressure conditions required to overcome friction losses of the drilling fluid and to effectively transport ice chips to the surface.
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Aliaga, D., Sinclair, V., Andrade, M., Artaxo, P., Carbone, S., Kadantsev, E., et al. (2021). Identifying source regions of air masses sampled at the tropical high-altitude site of Chacaltaya using WRF-FLEXPART and cluster analysis. Atmospheric Chemistry And Physics, 21(21), 16453–16477.
Abstract: Observations of aerosol and trace gases in the remote troposphere are vital to quantify background concentrations and identify long-term trends in atmospheric composition on large spatial scales. Measurements made at high altitude are often used to study free-tropospheric air; however such high-altitude sites can be influenced by boundary layer air masses. Thus, accurate information on air mass origin and transport pathways to high-altitude sites is required. Here we present a new method, based on the source-receptor relationship (SRR) obtained from backwards WRF-FLEXPART simulations and a k-means clustering approach, to identify source regions of air masses arriving at measurement sites. Our method is tailored to areas of complex terrain and to stations influenced by both local and long-range sources. We have applied this method to the Chacaltaya (CHC) GAW station (5240 m a.s.l.; 16.35 degrees S, 68.13 degrees W) for the 6-month duration of the “Southern Hemisphere high-altitude experiment on particle nucleation and growth” (SALILNA) to identify where sampled air masses originate and to quantify the influence of the surface and the free troposphere. A key aspect of our method is that it is probabilistic, and for each observation time, more than one air mass (cluster) can influence the station, and the percentage influence of each air mass can be quantified. This is in contrast to binary methods, which label each observation time as influenced by either boundary layer or free-troposphere air masses. Air sampled at CHC is a mix of different provenance. We find that on average 9 % of the air, at any given observation time, has been in contact with the surface within 4 d prior to arriving at CHC. Furthermore, 24 % of the air has been located within the first 1.5 km above ground level (surface included). Consequently, 76 % of the air sampled at CHC originates from the free troposphere. However, pure free-tropospheric influences are rare, and often samples are concurrently influenced by both boundary layer and free-tropospheric air masses. A clear diurnal cycle is present, with very few air masses that have been in contact with the surface being detected at night. The 6-month analysis also shows that the most dominant air mass (cluster) originates in the Amazon and is responsible for 29 % of the sampled air. Furthermore, short-range clusters (origins within 100 km of CHC) have high temporal frequency modulated by local meteorology driven by the diurnal cycle, whereas the mid- and long-range clusters' (> 200 km) variability occurs on timescales governed by synoptic-scale dynamics. To verify the reliability of our method, in situ sulfate observations from CHC are combined with the SRR clusters to correctly identify the (pre-known) source of the sulfate: the Sabancaya volcano located 400 km north-west from the station.
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Allen, S., Allen, D., Baladima, F., Phoenix, V., Thomas, J., Le Roux, G., et al. (2021). Evidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory. Nature Communications, 12(1).
Abstract: Microplastics are found in the environment globally, but their atmospheric transport is not well understood. Here the authors report atmospheric microplastic pollution at the Pic du Midi Observatory, suggesting free long range transport in the troposphere. The emerging threat of atmospheric microplastic pollution has prompted researchers to study areas previously considered beyond the reach of plastic. Investigating the range of atmospheric microplastic transport is key to understanding the global extent of this problem. While atmospheric microplastics have been discovered in the planetary boundary layer, their occurrence in the free troposphere is relatively unexplored. Confronting this is important because their presence in the free troposphere would facilitate transport over greater distances and thus the potential to reach more distal and remote parts of the planet. Here we show evidence of 0.09-0.66 microplastics particles/m(3) over 4 summer months from the Pic du Midi Observatory at 2877 meters above sea level. These results exhibit true free tropospheric transport of microplastic, and high altitude microplastic particles <50 μm (aerodynamic diameter). Analysis of air/particle history modelling shows intercontinental and trans-oceanic transport of microplastics illustrating the potential for global aerosol microplastic transport.
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Amory, C., Kittel, C., Le Toumelin, L., Agosta, C., Delhasse, A., Favier, V., et al. (2021). Performance of MAR (v3.11) in simulating the drifting-snow climate and surface mass balance of Adelie Land, East Antarctica. Geoscientific Model Development, 14(6), 3487–3510.
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An, L., Rignot, E., Wood, M., Willis, J., Mouginot, J., & Khan, S. (2021). Ocean melting of the Zachariae Isstrom and Nioghalvfjerdsfjorden glaciers, northeast Greenland. Proceedings Of The National Academy Of Sciences Of The United States Of America, 118(2).
Abstract: Zachariae Isstrom (ZI) and Nioghalvfjerdsfjorden (79N) are marine-terminating glaciers in northeast Greenland that hold an ice volume equivalent to a 1.1-m global sea level rise. ZI lost its floating ice shelf, sped up, retreated at 650 m/y, and experienced a 5-gigaton/y mass loss. Glacier 79N has been more stable despite its exposure to the same climate forcing. We analyze the impact of ocean thermal forcing on the glaciers. A three-dimensional inversion of airborne gravity data reveals an 800-m-deep, broad channel that allows subsurface, warm, Atlantic Intermediate Water (AIW) (+1.25 degrees C) to reach the front of ZI via two sills at 350-m depth. Subsurface ocean temperature in that channel has warmed by 1.3 +/- 0.5 degrees C since 1979. Using an ocean model, we calculate a rate of ice removal at the grounding line by the ocean that increased from 108 m/y to 185 m/y in 1979-2019. Observed ice thinning caused a retreat of its flotation line to increase from 105 m/y to 217 m/y, for a combined grounding line retreat of 13 km in 41 y that matches independent observations within 14%. In contrast, the limited access of AIW to 79N via a narrower passage yields lower grounded ice removal (53 m/y to 99 m/y) and thinning-induced retreat (27 m/y to 50 m/y) for a combined retreat of 4.4 km, also within 12% of observations. Ocean-induced removal of ice at the grounding line, modulated by bathymetric barriers, is therefore a main driver of ice sheet retreat, but it is not incorporated in most ice sheet models.
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Anthelme, F., Cauvy-Fraunie, S., Francou, B., Caceres, B., & Dangles, O. (2021). Living at the Edge: Increasing Stress for Plants 2-13 Years After the Retreat of a Tropical Glacier. Frontiers In Ecology And Evolution, 9.
Abstract: Rapid warming is a major threat for the alpine biodiversity but, at the same time, accelerated glacial retreat constitutes an opportunity for taxa and communities to escape range contraction or extinction. We explored the first steps of plant primary succession after accelerated glacial retreat under the assumption that the first few years are critical for the success of plant establishment. To this end, we examined plant succession along a very short post-glacial chronosequence in the tropical Andes of Ecuador (2-13 years after glacial retreat). We recorded the location of all plant individuals within an area of 4,200 m(2) divided into plots of 1 m(2). This sampling made it possible to measure the responses of the microenvironment, plant diversity and plants traits to time since the glacial retreat. It also made it possible to produce species-area curves and to estimate positive interactions between species. Decreases in soil temperature, soil moisture, and soil macronutrients revealed increasing abiotic stress for plants between two and 13 years after glacial retreat. This increasing stress seemingly explained the lack of positive correlation between plant diversity and time since the glacial retreat. It might explain the decreasing performance of plants at both the population (lower plant height) and the community levels (lower species richness and lower accumulation of species per area). Meanwhile, infrequent spatial associations among plants indicated a facilitation deficit and animal-dispersed plants were almost absent. Although the presence of 21 species on such a small sampled area seven years after glacial retreat could look like a colonization success in the first place, the increasing abiotic stress may partly erase this success, reducing species richness to 13 species after 13 years and increasing the frequency of patches without vegetation. This fine-grain distribution study sheds new light on nature's responses to the effects of climate change in cold biomes, suggesting that faster glacial retreat would not necessarily result in accelerated plant colonization. Results are exploratory and require site replications for generalization.
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Archundia, D., Martins, J., Lehembre, F., Morel, M., & Duwig, C. (2021). Sulfamethoxazole biodegradation and impacts on soil microbial communities in a Bolivian arid high altitude catchment. Chemosphere, 284.
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Arias, P., Garreaud, R., Poveda, G., Espinoza, J., Molina-Carpio, J., Masiokas, M., et al. (2021). Hydroclimate of the Andes Part II: Hydroclimate Variability and Sub-Continental Patterns. Frontiers In Earth Science, 8.
Abstract: This paper provides an updated review of the most relevant scientific literature related to the hydroclimate of the Andes. The Andes, the longest cordillera in the world, faces major challenges regarding climate variability and climate change, which impose several threats to sustainable development, including water supply and the sustainability of ecosystem services. This review focuses on hydroclimate variability of the Andes at a sub-continental scale. The annual water cycle and long-term water balance along the Andes are addressed first, followed by the examination of the effects of orography on convective and frontal precipitation through the study of precipitation gradients in the tropical, subtropical and extratropical Andes. In addition, a review is presented of the current scientific literature on the climate variability in the Andes at different timescales. Finally, open research questions are presented in the last section of this article.
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Arienzo, M., Legrand, M., Preunkert, S., Stohl, A., Chellman, N., Eckhardt, S., et al. (2021). Alpine Ice-Core Evidence of a Large Increase in Vanadium and Molybdenum Pollution in Western Europe During the 20th Century. Journal Of Geophysical Research-Atmospheres, 126(4).
Abstract: Pollutants emitted by industrial processes are deposited across the landscape. Ice core records from mid-latitude glaciers located close to emission sources document the history of local-to-regional pollution since preindustrial times. Such records underpin attribution of pollutants to specific emission sources critical to developing abatement policies. Previous ice core studies from the Alps document the overall magnitude and timing of pollution related to nitrogen and sulfur-derived species, as well as a few metals including lead. Here, we used subannually resolved measurements of vanadium (V) and molybdenum (Mo) in two ice cores from Col du Dome (French Alps), as well as atmospheric transport and deposition modeling, to investigate sources of pollution in the free European troposphere. The noncrustal V and Mo (ncV, ncMo) components were calculated by subtracting the crustal component from the total concentration. These ice core results showed a 32-fold increase in ncV and a 69-fold increase in ncMo from the preindustrial era (pre-1860) to the industrial concentration peaks. Anthropogenic V and Mo emissions in Europe were estimated using emission factors from oil and coal consumption and atmospheric transport and deposition modeling. When comparing ice core data to estimated anthropogenic V and Mo emissions in Europe, V was found to be sourced primarily from oil combustion emissions. Conversely, coal and oil combustion estimated emissions did not agree with the measured ice core Mo concentrations, suggesting that other anthropogenic Mo sources dominated coal-burning emissions, particularly after the 1950s. Noncoal-burning sources of Mo may include metallurgy although emission factors are poorly known.
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Bahar, T., Oxarango, L., Castebrunet, H., Rossier, Y., & Mermillod-Blondin, F. (2021). 3D modelling of solute transport and mixing during managed aquifer recharge with an infiltration basin. Journal Of Contaminant Hydrology, 237.
Abstract: Artificial basins are used to recharge groundwater by many municipalities to improve the sustainability of storm water management. Despite its increasing operational implementation, artificial recharge still raises numerous questions related to its impact on groundwater quality. In this paper, a 3D numerical model of MAR basin/ aquifer system was implemented in order to simulate the fate of water and pollutants. It was used to illustrate the complex distribution in time and space of a tracer contaminant injected in the basin. The model was based on a well instrumented storm water infiltration basin located in Chassieu (Lyon area, France). The well-known Richards model was used to simulate the water flow in the saturated and unsaturated zone of the study site. The transfer of solutes in the basin/aquifer system was modelled by the advection-dispersion-equation (ADE). The model was calibrated during a rain event using hydraulic head and electric conductivity data from a set of piezometers located around the basin. The flow model was validated on a one month period of basin operation presenting several rain events. The model was then used to simulate the fate of a solute pollutant considered as a tracer during a high intensity rain event. This simplified test case illustrated the mechanism of capillary trapping in the vadose zone and the effect of sampling point location on concentration measurements. Three main results were obtained: (1) capillary trapping promoted a retention of up to 20% of the injected tracer in the vadose zone, (2) 0 to 24% of the injected solute concentration could be recovered depending on the piezometer location, (3) the averaged concentration decreased by 50% if the measuring device is lowered by 5 m under the water table. These results were strongly site and event dependant but observed trends should be considered while discussing punctual water quality measurements used to monitor MAR systems. It also allowed to suggest some guidelines for sampling point positioning.
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Bailey, H., Hubbard, A., Klein, E., Mustonen, K., Akers, P., Marttila, H., et al. (2021). Arctic sea-ice loss fuels extreme European snowfall. Nature Geoscience, .
Abstract: The loss of Arctic sea-ice enhances evaporation and fuels extreme European winter snowfall, according to an analysis of atmospheric water vapour isotope measurements. The loss of Arctic sea-ice has been implicated with severe cold and snowy mid-latitude winters. However, the mechanisms and a direct link remain elusive due to limited observational evidence. Here we present atmospheric water vapour isotope measurements from Arctic Finland during 'the Beast from the East'-a severe anticyclonic outbreak that brought heavy snowfall and freezing across Europe in February 2018. We find that an anomalously warm Barents Sea, with a 60% ice-free surface, supplied up to 9.3 mm d(-1) moisture flux to this cold northeasterly airflow. We demonstrate that approximately 140 gigatonnes of water was evaporated from the Barents Sea during the event, potentially supplying up to 88% of the corresponding fresh snow over northern Europe. Reanalysis data show that from 1979 to 2020, net March evaporation across the Barents Sea increased by approximately 70 kg per square metre of sea-ice lost (r(2) = 0.73, P < 0.01), concurrent with a 1.6 mm (water equivalent) per year increase in Europe's maximum snowfall. Our analysis directly links Arctic sea-ice loss with increased evaporation and extreme snowfall, and signifies that by 2080, an Atlantified ice-free Barents Sea will be a major source of winter moisture for continental Europe.
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Ballabio, C., Jiskra, M., Osterwalder, S., Borrelli, P., Montanarella, L., & Panagos, P. (2021). A spatial assessment of mercury content in the European Union topsoil. Science Of The Total Environment, 769.
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Banwell, A., Datta, R., Dell, R., Moussavi, M., Brucker, L., Picard, G., et al. (2021). The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula. Cryosphere, 15(2), 909–925.
Abstract: In the 2019/2020 austral summer, the surface melt duration and extent on the northern George VI Ice Shelf (GVIIS) was exceptional compared to the 31 previous summers of distinctly lower melt. This finding is based on analysis of near-continuous 41-year satellite microwave radiometer and scatterometer data, which are sensitive to meltwater on the ice shelf surface and in the near-surface snow. Using optical satellite imagery from Landsat 8 (2013 to 2020) and Sentinel-2 (2017 to 2020), record volumes of surface meltwater ponding were also observed on the northern GVIIS in 2019/2020, with 23% of the surface area covered by 0.62 km(3) of ponded meltwater on 19 January. These exceptional melt and surface ponding conditions in 2019/2020 were driven by sustained air temperatures >= 0 degrees C for anomalously long periods (55 to 90 h) from late November onwards, which limited meltwater refreezing. The sustained warm periods were likely driven by warm, low-speed (<= 7.5 m s(-1)) northwesterly and northeasterly winds and not by foehn wind conditions, which were only present for 9 h total in the 2019/2020 melt season. Increased surface ponding on ice shelves may threaten their stability through increased potential for hydrofracture initiation; a risk that may increase due to firn air content depletion in response to near-surface melting.
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Barbero, A., Savarino, J., Grilli, R., Blouzon, C., Picard, G., Frey, M., et al. (2021). New Estimation of the NOx Snow-Source on the Antarctic Plateau. Journal Of Geophysical Research-Atmospheres, 126(20).
Abstract: To fully decipher the role of nitrate photolysis on the atmospheric oxidative capacity in snow-covered regions, NOx flux must be determined with more precision than existing estimates. Here, we introduce a method based on dynamic flux chamber measurements for evaluating the NOx production by photolysis of snowpack nitrate in Antarctica. Flux chamber experiments were conducted for the first time in Antarctica, at the French-Italian station Concordia, Dome C (75 degrees 06'S, 123 degrees 20'E, 3233 m a.s.l) during the 2019-2020 summer campaign. Measurements were gathered with several snow samples of different ages ranging from newly formed drifted snow to 6-year-old firn. Contrary to existing literature expectations, the daily average photolysis rate coefficient, JNO3 over bar , did not significantly vary between differently aged snow samples, suggesting that the photolabile nitrate in snow behaves as a single-family source with common photochemical properties, where a JNO3 over bar = (2.37 +/- 0.35) x 10(-8) s(-1) (1 sigma) has been calculated from December 10(th) 2019 to January 7(th) 2020. At Dome C summer daily average NOx flux, FNOx, based on measured NOx production rates was estimated to be (4.3 +/- 1.2) x 10(8) molecules cm(-2) s(-1), which is 1.5-7 times less than the net NOx flux observed previously above snow at Dome C using the gradient flux method. Using these results, we extrapolated an annual continental snow sourced NOx budget of 0.017 +/- 0.003 Tg center dot N y(-1), similar to 2 times the nitrogen budget, (N-budget), of the stratospheric denitrification previously estimated for Antarctica. These quantifications of nitrate photolysis using flux chamber experiments provide a road-map toward a new parameterization of the sigma NO3-(lambda,T)phi(T,pH) product that can improve future global and regional models of atmospheric chemistry.
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Barraza, F., Schreck, E., Uzu, G., Leveque, T., Zouiten, C., Boidot, M., et al. (2021). Beyond cadmium accumulation: Distribution of other trace elements in soils and cacao beans in Ecuador. Environmental Research, 192.
Abstract: Since cacao beans accumulate Cd in high levels and restrictions have been imposed on safe levels of chocolate consumption, concern about whether or not cacao trees store other toxic elements seems to be inevitable. Following a previous study in Ecuador examining Cd content in five cacao varieties collected in pristine areas and in places impacted by oil activities, we present here the concentrations of 11 trace elements (TEs) (As, Ba, Co, Cu, Cr, Mo, Mn, Ni, Pb, V and Zn) in soils, cacao tissues (leaves, pod husks, beans) and cocoa liquor (CL). Several TEs showed concentrations in topsoils above the Ecuadorian limits, and may have a mixed natural and anthropogenic origin. Ba and Mo concentrations in cacao tissues are slightly higher than those reported in other surveys, but this was not the case for toxic elements (As and Pb). TE contents are lower in CL, than in beans, except for Pb and Co, but no risk was identified for human health. Compared with control areas, Enrichment Factors were below 2 in impacted areas, except for Ba. Transfer factors (from soils to cacao) indicated that cacao does not accumulate TEs. A positive correlation was found between Cd and Zn in topsoils and cacao tissues for the CCN-51 variety, and between Cd and Ni for the Nacional variety. Identifying patterns of TE distribution and potential interactions in order to explain plant internal mechanisms, which is also dependent on the cacao variety, is a difficult task and needs further research.
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Barree, M., Mialon, A., Pellarin, T., Parrens, M., Biron, R., Lemaitre, F., et al. (2021). Soil moisture and vegetation optical depth retrievals over heterogeneous scenes using LEWIS L-band radiometer. International Journal Of Applied Earth Observation And Geoinformation, 102.
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Basse, J., Sabaly, H., Diba, I., Sarr, A., Camara, M., & Diedhiou, A. (2021). Synoptic variability associated with wet and dry spells in the Western Sahel. Theoretical And Applied Climatology, .
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Beaumet, J., Deque, M., Krinner, G., Agosta, C., Alias, A., & Favier, V. (2021). Significant additional Antarctic warming in atmospheric bias-corrected ARPEGE projections with respect to control run. Cryosphere, 15(8), 3615–3635.
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Beaumet, J., Menegoz, M., Morin, S., Gallee, H., Fettweis, X., Six, D., et al. (2021). Twentieth century temperature and snow cover changes in the French Alps. Regional Environmental Change, 21(4).
Abstract: Changes in snow cover associated with the warming of the French Alps greatly influence social-ecological systems through their impact on water resources, mountain ecosystems, economic activities, and glacier mass balance. In this study, we investigated trends in snow cover and temperature over the twentieth century using climate model and reanalysis data. The evolution of temperature, precipitation and snow cover in the European Alps has been simulated with the Modele Atmospherique Regional (MAR) applied with a 7-km horizontal resolution and driven by ERA-20C (1902-2010) and ERA5 (1981-2018) reanalyses data. Snow cover duration and snow water equivalent (SWE) simulated with MAR are compared to the SAFRAN – SURFEX-ISBA-Crocus – MEPRA meteorological and snow cover reanalysis (S2M) data across the French Alps (1958-2018) and in situ glacier mass balance measurements. MAR outputs provide a realistic distribution of SWE and snow cover duration as a function of elevation in the French Alps. Large disagreements are found between the datasets in terms of absolute warming trends over the second part of the twentieth century. MAR and S2M trends are in relatively good agreement for the decrease in snow cover duration, with higher decreases at low elevation (similar to 5-10%/decade). Consistent with other studies, the highest warming rates in MAR occur at low elevations (< 1000 m a.s.l) in winter, whereas they are found at high elevations (> 2000 m a.s.l) in summer. In spring, warming trends show a maximum at intermediate elevations (1500 to 1800 m). Our results suggest that higher warming at these elevations is mostly linked to the snow-albedo feedback in spring and summer caused by the disappearance of snow cover at higher elevation during these seasons. This work has evidenced that depending on the season and the period considered, enhanced warming at higher elevations may or may not be found. Additional analysis in a physically comprehensive way and more high-quality dataset, especially at high elevations, are still required to better constrain and quantify climate change impacts in the Alps and its relation to elevation.
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Belke-Brea, M., Domine, F., Picard, G., Barrere, M., & Arnaud, L. (2021). On the influence of erect shrubs on the irradiance profile in snow. Biogeosciences, 18(21), 5851–5869.
Abstract: The warming-induced expansion of shrubs in the Arctic is transforming snowpacks into a mixture of snow, impurities and buried branches. Because snow is a translucent medium into which light penetrates up to tens of centimetres, buried branches may alter the snowpack radiation budget with important consequences for the snow thermal regime and microstructure. To characterize the influence of buried branches on radiative transfer in snow, irradiance profiles were measured in snowpacks with and without shrubs near Umiujaq in the Canadian Low Arctic (56.5 degrees N, 76.5 degrees W) in November and December 2015. Using the irradiance profiles measured in shrub-free snowpacks in combination with a Monte Carlo radiative transfer model revealed that the dominant impurity type was black carbon (BC) in variable concentrations up to 185 ng g(-1). This allowed the separation of the radiative effects of impurities and buried branches. Irradiance profiles measured in snowpacks with shrubs showed that the impact of buried branches was local (i.e. a few centimetres around branches) and only observable in layers where branches were also visible in snowpit photographs. The local-effect hypothesis was further supported by observations of localized melting and depth hoar pockets that formed in the vicinity of branches. Buried branches therefore affect snowpack properties, with possible impacts on Arctic flora and fauna and on the thermal regime of permafrost. Lastly, the unexpectedly high BC concentrations in snow are likely caused by nearby open-air waste burning, suggesting that cleaner waste management plans are required for northern community and ecosystem protection.
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Berto, M., Cappelletti, D., Barbaro, E., Varin, C., Gallet, J., Markowicz, K., et al. (2021). Variability in black carbon mass concentration in surface snow at Svalbard. Atmospheric Chemistry And Physics, 21(16), 12479–12493.
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Bianchi, F., Junninen, H., Bigi, A., Sinclair, V., Dada, L., Hoyle, C., et al. (2021). Biogenic particles formed in the Himalaya as an important source of free tropospheric aerosols. Nature Geoscience, .
Abstract: Aerosols of biogenic and anthropogenic origin affect the total radiative forcing of global climate. Poor knowledge of the pre-industrial aerosol concentration and composition, in particular of particles formed directly in the atmosphere from gaseous precursors, constitutes a large uncertainty in the anthropogenic radiative forcing. Investigations of new particle formation at pre-industrial-like conditions can contribute to the reduction of this uncertainty. Here we present observations taken at the remote Nepal Climate Observatory Pyramid station at 5,079 m above sea level, a few kilometres from the summit of Everest. We show that up-valley winds funnel gaseous aerosol precursors to higher altitudes. During this transport, these are oxidized into compounds of very low volatility, which rapidly form a large number of aerosol particles. These are then transported into the free troposphere, which suggests that the whole Himalayan region may act as an 'aerosol factory' and contribute substantially to the free tropospheric aerosol population. Aerosol production in this region occurs mainly via organic precursors of biogenic origin with little evidence of the involvement of anthropogenic pollutants. This process is therefore likely to be essentially unchanged since the pre-industrial period, and may have been one of the major sources that contributes to the upper tropospheric aerosol population during that time. Newly formed biogenic particles in the Himalaya increase free-tropospheric background aerosol concentration by a factor of up to two.
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Blanc, A., Blanchet, J., & Creutin, J. (2021). Characterizing large-scale circulations driving extreme precipitation in the Northern French Alps. International Journal Of Climatology, .
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Blanc, A., Blanchet, J., & Creutin, J. (2021). Linking Large-Scale Circulation Descriptors to Precipitation Variability in the Northern French Alps. Geophysical Research Letters, 48(15).
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Blanchet, J., Blanc, A., & Creutin, J. (2021). Explaining recent trends in extreme precipitation in the Southwestern Alps by changes in atmospheric influences. Weather And Climate Extremes, 33.
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Blanchet, J., Creutin, J., & Blanc, A. (2021). Retreating winter and strengthening autumn Mediterranean influence on extreme precipitation in the Southwestern Alps over the last 60 years. Environmental Research Letters, 16(3).
Abstract: This article analyzes the large-scale circulations producing daily precipitation extremes in the Southwestern Alps and their trends from 1958 to 2017. We consider a high-resolution precipitation data set of 1 x 1 km(2) and the weather patterns associated to the precipitation seasonal maxima at each grid point. The high-resolution allows us to analyze in details the atmospheric influences triggering seasonal maxima. Four influences are considered-the Atlantic influence, the Mediterranean influence, the northeast circulation and the Anticyclonic situation. We show that influences on maxima are very well organized in space but their organization depends on the season. Maxima are very mainly triggered by two types of influences in the region-the Atlantic influence and the Mediterranean influence. Trends in weather patterns producing maxima are also organized in space, with opposite trends for the Atlantic and the Mediterranean influences. The Mediterranean influence retreated very significantly over the period in winter and spring, while the Atlantic influence significantly extended further south. In autumn the Mediterranean influence strengthened where it was already dominant.
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Borlaza, L., Weber, S., Uzu, G., Jacob, V., Canete, T., Micallef, S., et al. (2021). Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 1: Source apportionment at three neighbouring sites. Atmospheric Chemistry And Physics, 21(7), 5415–5437.
Abstract: A fine-scale source apportionment of PM10 was conducted in three different urban sites (background, hypercenter, and peri-urban) within 15 km of the city in Grenoble, France using Positive Matrix Factorization (PMF 5.0) on measured chemical species from collected filters (24 h) from February 2017 to March 2018. To improve the PMF solution, several new organic tracers (3-MBTCA, pinic acid, phthalic acid, MSA, and cellulose) were additionally used in order to identify sources that are commonly unresolved by classic PMF methodologies. An 11-factor solution was obtained in all sites, including commonly identified sources from primary traffic (13 %), nitrate-rich (17 %), sulfate-rich (17 %), industrial (1 %), biomass burning (22 %), aged sea salt (4 %), sea/road salt (3 %), and mineral dust (7 %), and the newly found sources from primary biogenic (4 %), secondary biogenic oxidation (10 %), and MSA-rich (3 %). Generally, the chemical species exhibiting similar temporal trends and strong correlations showed uniformly distributed emission sources in the Grenoble basin. The improved PMF model was able to obtain and differentiate chemical profiles of specific sources even at high proximity of receptor locations, confirming its applicability in a fine-scale resolution. In order to test the similarities between the PMF-resolved sources, the Pearson distance and standardized identity distance (PD-SID) of the factors in each site were compared. The PD-SID metric determined whether a given source is homogeneous (i.e., with similar chemical profiles) or heterogeneous over the three sites, thereby allowing better discrimination of localized characteristics of specific sources. Overall, the addition of the new tracers allowed the identification of substantial sources (especially in the SOA fraction) that would not have been identified or possibly mixed with other factors, resulting in an enhanced resolution and sound source profile of urban air quality at a city scale.
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Braunig, J., Baduel, C., Barnes, C., & Mueller, J. (2021). Sorbent assisted immobilisation of perfluoroalkyl acids in soils & ndash; effect on leaching and bioavailability. Journal Of Hazardous Materials, 412.
Abstract: Contamination of soils and groundwater with perfluoroalkyl acids (PFAAs) is widespread due to their use in aqueous film-forming foams (AFFF). In this study the effectiveness of RemBind?, a sorbent containing activated carbon and aluminium oxyhydroxides was tested, as a tool to reduce the leaching and bioavailability of 12 PFAAs in soils, by amending contaminated soils with 5?30% (by weight) of the sorbents. Batch tests were used to determine the leaching of PFAAs. Their bioavailability to earthworms and wheat grass was assessed in greenhouse microcosms. Leaching and bioavailability of PFOS was reduced by up to 99.9%, at most sorbent application rates. Lowest reduction of leaching was found for shorter perfluoroalkyl chain length chemicals. The specific formulation of RemBind?, which is available in a basic and superior formulation, as well as the application rate were parameters for increasing effectiveness of the treatment. Furthermore, differences in leaching as well as bioavailability were seen depending on the perfluoroalkyl chain length. A preliminary assessment of the long-term stability of the treatment, assessed after a three-year curing period, suggested that the sorbent continued to be effective in reducing PFAAs in leachates, thus showing the potential of this sorbent to hinder further environmental contamination.
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Buizert, C., Fudge, T., Roberts, W., Steig, E., Sherriff-Tadano, S., Ritz, C., et al. (2021). Antarctic surface temperature and elevation during the Last Glacial Maximum. Science, 372(6546), 1097–+.
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Bull, C., Jenkins, A., Jourdain, N., Vankova, I., Holland, P., Mathiot, P., et al. (2021). Remote Control of Filchner-Ronne Ice Shelf Melt Rates by the Antarctic Slope Current. Journal Of Geophysical Research-Oceans, 126(2).
Abstract: Recent work on the Filchner-Ronne Ice Shelf (FRIS) system has shown that a redirection of the coastal current in the southeastern Weddell Sea could lead to a regime change in which an intrusion of warm Modified Circumpolar Deep Water results in large increases in the basal melt rate. Work to date has mostly focused on how increases in the Modified Circumpolar Deep Water crossing the continental shelf break leads directly to heat driven changes in melting in the ice-shelf cavity. In this study, we introduce a Weddell Sea regional ocean model configuration with static ice shelves. We evaluate a reference simulation against radar observations of melting, and find good agreement between the simulated and observed mean melt rates. We analyze 28 sensitivity experiments that simulate the influence of changes in remote water properties of the Antarctic Slope Current on basal melting in the FRIS. We find that remote changes in salinity quasi-linearly modulate the mean FRIS net melt rate. Changes in remote temperature quadratically vary the FRIS net melt rate. In both salinity and temperature perturbations, the response is rapid and transient, with a recovery time-scale of 5-15 years dependent on the size/type of perturbation. We show that the two types of perturbations lead to different changes on the continental shelf, and that ultimately different factors modulate the melt rates in the FRIS cavity. We discuss how these results, are relevant for ocean hindcast simulations, sea level, and melt rate projections of the FRIS.
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Cairns, W., Turetta, C., Maffezzoli, N., Magand, O., Araujo, B., Angot, H., et al. (2021). Mercury in precipitated and surface snow at Dome C and a first estimate of mercury depositional fluxes during the Austral summer on the high Antarctic plateau. Atmospheric Environment, 262.
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Camenen, B., Gratiot, N., Cohard, J., Gard, F., Tran, V., Nguyen, A., et al. (2021). Monitoring discharge in a tidal river using water level observations: Application to the Saigon River, Vietnam. Science Of The Total Environment, 761.
Abstract: The hydrological dynamics of the Saigon River is ruled by a complex combination of factors, which need to be disentangled to prevent and limit risks of flooding and salt intrusion. In particular, the Saigon water discharge is highly influenced by tidal cycles with a relatively low net discharge. This study proposes a low-cost technique to estimate river discharge at high frequency (every 10 min in this study). It is based on a stage-fall-discharge (SFD) rating curve adapted from the general Manning Strickler law, and calibrated thanks to two ADCP campaigns. Two pressure sensors were placed at different locations of the river in September 2016: one at the centre of Ho Chi Minh City and one in Phu Cuong, 40 km upstream approximately. The instantaneous water discharge data were used to evaluate the net residual discharge and to highlight seasonal and inter-annual trends. Both water level and water discharge show a seasonal behaviour. Rainfall, including during the Usagi typhoon that hit the megalopolis in November 2018, has no clear and direct impact on water level and water discharge due to the delta flat morphology and complex response between main channel and side channel network and ground water in this estuarine system under tidal influence. However, we found some evidences of interactions between precipitation, groundwater, the river network and possibly coastal waters. This paper can be seen as a proof of concept to (1) present a low-cost discharge method that can be applied to other tidal rivers, and (2) demonstrate how the high-frequency discharge data obtained with this method can be used to evaluate discharge dynamics in tidal river systems. (C) 2020 Elsevier B.V. All rights reserved.
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Campozano, L., Robaina, L., Gualco, L., Maisincho, L., Villacis, M., Condom, T., et al. (2021). Parsimonious Models of Precipitation Phase Derived from Random Forest Knowledge: Intercomparing Logistic Models, Neural Networks, and Random Forest Models. Water, 13(21).
Abstract: The precipitation phase (PP) affects the hydrologic cycle which in turn affects the climate system. A lower ratio of snow to rain due to climate change affects timing and duration of the stream flow. Thus, more knowledge about the PP occurrence and drivers is necessary and especially important in cities dependent on water coming from glaciers, such as Quito, the capital of Ecuador (2.5 million inhabitants), depending in part on the Antisana glacier. The logistic models (LM) of PP rely only on air temperature and relative humidity to predict PP. However, the processes related to PP are far more complex. The aims of this study were threefold: (i) to compare the performance of random forest (RF) and artificial neural networks (ANN) to derive PP in relation to LM; (ii) to identify the main drivers of PP occurrence using RF; and (iii) to develop LM using meteorological drivers derived from RF. The results show that RF and ANN outperformed LM in predicting PP in 8 out of 10 metrics. RF indicated that temperature, dew point temperature, and specific humidity are more important than wind or radiation for PP occurrence. With these predictors, parsimonious and efficient models were developed showing that data mining may help in understanding complex processes and complements expert knowledge.</p>
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Capron, E., Rasmussen, S., Popp, T., Erhardt, T., Fischer, H., Landais, A., et al. (2021). The anatomy of past abrupt warmings recorded in Greenland ice. Nature Communications, 12(1).
Abstract: Data availability and temporal resolution make it challenging to unravel the anatomy (duration and temporal phasing) of the Last Glacial abrupt climate changes. Here, we address these limitations by investigating the anatomy of abrupt changes using sub-decadal-scale records from Greenland ice cores. We highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters. This diversity in the sequence of changes seen in ice-core data is also observed in climate parameters derived from numerical simulations which exhibit self-sustained abrupt variability arising from internal atmosphere-ice-ocean interactions. Our analysis of two ice cores shows that the diversity of abrupt warming transitions represents variability inherent to the climate system and not archive-specific noise. Our results hint that during these abrupt events, it may not be possible to infer statistically-robust leads and lags between the different components of the climate system because of their tight coupling. Palaeodata resolution and dating limit the study of the sequence of changes across Earth during past abrupt warmings. Here, the authors show tight decadal-scale coupling between Greenland climate, North Atlantic sea ice and atmospheric circulation during these past events using two highly resolved ice-core records.
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Carret, A., Llovel, W., Penduff, T., & Molines, J. (2021). Atmospherically Forced and Chaotic Interannual Variability of Regional Sea Level and Its Components Over 1993-2015. Journal Of Geophysical Research-Oceans, 126(4).
Abstract: Satellite altimetry data have revealed a global mean sea level rise of 3.1 mm/yr since 1993 with large regional sea level variability. These remote data highlight complex structures especially in strongly eddying regions. A recent study showed that over 38% of the global ocean area, the chaotic variability may hinder the attribution to the atmospheric forcing of regional sea level trends from 1993 to 2015. This study aims to complement this work by focusing on the atmospherically forced and chaotic interannual variability of regional sea level and its components. At interannual time scales, variability can hamper the detection of regional sea level trends. A global 1/4 degrees ocean/sea-ice 50-member ensemble simulation is analyzed to disentangle the imprints of the atmospheric forcing and of the chaotic ocean variability on the interannual variability of regional sea level and of its steric and manometric components over 1993-2015. The atmospherically forced and chaotic interannual variabilities of sea level mainly have a steric origin, except in coastal areas. The chaotic part of the interannual variability of sea level and its components is stronger in the Pacific and Atlantic Oceans than in the Indian Ocean. The chaotic part of the interannual variance of sea level and of its steric component exceeds 20% over 48% of the global ocean area; this fractional area reduces to 26% for the manometric component. These results confirm the substantial imprint of the chaotic interannual variability on sea level components, questioning in several regions the attribution of their observed evolution to atmospheric causes. Plain Language Summary Since the early 1990s, satellite altimetry has become the main observing system for continuously measuring the sea level variations with a near global coverage. It has revealed a global mean sea level rise of 3.1 mm/yr since 1993 with large regional sea level variability that differs from the mean estimate. These measurements highlight complex structures especially for the western boundary currents (Gulf Stream or Kuroshio) or the Antarctic Circumpolar Current. Recent studies based on numerical modeling showed that the ocean spontaneously generates a chaotic intrinsic variability that substantially impacts the sea level interannual-to-decadal variability and its long-term trends. It is important to note that sea level observations simultaneously record these chaotic variations in the ocean but also the response to the atmospheric forcings. Here, we use a 50-member ensemble ocean simulation to disentangle the atmospherically forced and chaotic parts of the interannual variability of sea level and of its steric and manometric components. We found that, in several regions, the chaotic interannual variability has a large imprint on sea level components. While these results do not question the anthropic origin of global mean sea level rise, they give new insights into the oceanic vs. nonoceanic origin of regional interannual variability.
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Casado, M., Landais, A., Picard, G., Arnaud, L., Dreossi, G., Stenni, B., et al. (2021). Water Isotopic Signature of Surface Snow Metamorphism in Antarctica. Geophysical Research Letters, 48(17).
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Cavitte, M., Young, D., Mulvaney, R., Ritz, C., Greenbaum, J., Ng, G., et al. (2021). A detailed radiostratigraphic data set for the central East Antarctic Plateau spanning from the Holocene to the mid-Pleistocene. Earth System Science Data, 13(10), 4759–4777.
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Chagnaud, G., Panthou, G., Vischel, T., Blanchet, J., & Lebel, T. (2021). A unified statistical framework for detecting trends in multi-timescale precipitation extremes: application to non-stationary intensity-duration-frequency curves. Theoretical And Applied Climatology, .
Abstract: There is a large agreement that global warming induces changes of precipitation regimes of different nature and amplitude depending on the timescale considered. This question is of special concern regarding extreme rainfall that might have critical socio-environmental consequences. A unified framework is proposed here for detecting trends in extreme rainfall. It is based on the GEV distribution, whose parameters depend both on a simple scaling formulation to account for multiple time durations of rainfall and on time to account for the non-stationarity deriving from climatic trends. The implementation of the model is illustrated in the Sahel region by analyzing 30 in situ rainfall series of 28 years measured at time-steps from 2 to 24 h. While the separate analysis of the point series proves inconclusive for detecting trends at any of the time-steps considered, the inclusion of all the series and time-steps into the proposed unified model allows trends to be detected at a high level of confidence (p-value < 1%). This trend essentially appears in the scale parameter of the regional GEV distribution, involving a 15 to 20% increase of the 10-year rainfall in 28 years, and a 23 to 30% increase of the 100-year rainfall. The main advantages of the proposed framework are (i) its parsimony, allowing for reducing the uncertainty associated with the model inference; (ii) its capacity for detecting trends either in the mean and/or in the variability of the extreme events; and (iii) its ability for producing non-stationary Intensity-Duration-Frequency curves that are coherent over a range of durations of accumulation.
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Charrondiere, C., Brun, C., Cohard, J., Sicart, J., Obligado, M., Biron, R., et al. (2021). Katabatic Winds over Steep Slopes: Overview of a Field Experiment Designed to Investigate Slope-Normal Velocity and Near-Surface Turbulence. Boundary-Layer Meteorology, .
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Charton, J., Jomelli, V., Schimmelpfennig, I., Verfaillie, D., Favier, V., Mokadem, F., et al. (2021). A debris-covered glacier at Kerguelen (49 degrees S, 69 degrees E) over the past 15 000 years. Antarctic Science, 33(1), 103–115.
Abstract: Debris-covered glaciers constitute a large part of the world's cryosphere. However, little is known about their long-term response to multi-millennial climate variability, in particular in the Southern Hemisphere. Here, we provide first insights into the response of a debris-covered glacier to multi-millennial climate variability in the sub-Antarctic Kerguelen Archipelago, which can be compared to that of recently investigated debris-free glaciers. We focus on the Gentil Glacier and present 13 new Cl-36 cosmic-ray exposure ages from moraine boulders. The Gentil Glacier experienced at least two glacial advances: the first one during the Late Glacial (19.0-11.6 ka) at similar to 14.3 ka and the second one during the Late Holocene at similar to 2.6 ka. Both debris-covered and debris-free glaciers advanced broadly synchronously during the Late Glacial, most probably during the Antarctic Cold Reversal event (14.5-12.9 ka). This suggests that both glacier types at Kerguelen were sensitive to abrupt temperature changes recorded in Antarctic ice cores, associated with increased moisture. However, during the Late Holocene, the advance at similar to 2.6 ka was not observed in other glaciers and seems to be an original feature of the debris-covered Gentil Glacier, related to either distinct dynamics or to distinct sensitivity to precipitation changes.
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Charton, J., Verfaillie, D., Jomelli, V., & Francou, B. (2021). Early Holocene rock glacier stabilisation at col du Lautaret (French Alps): Palaeoclimatic implications. Geomorphology, 394.
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Cluzet, B., Lafaysse, M., Cosme, E., Albergel, C., Meunier, L., & Dumont, M. (2021). CrocO_v1.0: a particle filter to assimilate snowpack observations in a spatialised framework. Geoscientific Model Development, 14(3), 1595–1614.
Abstract: Monitoring the evolution of snowpack properties in mountainous areas is crucial for avalanche hazard forecasting and water resources management. In situ and remotely sensed observations provide precious information on the state of the snowpack but usually offer limited spatiotemporal coverage of bulk or surface variables only. In particular, visible-near-infrared (Vis-NIR) reflectance observations can provide information about the snowpack surface properties but are limited by terrain shading and clouds. Snowpack modelling enables the estimation of any physical variable virtually anywhere, but it is affected by large errors and uncertainties. Data assimilation offers a way to combine both sources of information and to propagate information from observed areas to non-observed areas. Here, we present CrocO (Crocus-Observations), an ensemble data assimilation system able to ingest any snowpack observation (applied as a first step to the height of snow (HS) and Vis-NIR reflectances) in a spatialised geometry. CrocO uses an ensemble of snowpack simulations to represent modelling uncertainties and a particle filter (PF) to reduce them. The PF is prone to collapse when assimilating too many observations. Two variants of the PF were specifically implemented to ensure that observational information is propagated in space while tackling this issue. The global algorithm ingests all available observations with an iterative inflation of observation errors, while the klocal algorithm is a localised approach performing a selection of the observations to assimilate based on background correlation patterns. Feasibility testing experiments are carried out in an identical twin experiment setup, with synthetic observations of HS and Vis-NIR reflectances available in only one-sixth of the simulation domain. Results show that compared against runs without assimilation, analyses exhibit an average improvement of the snow water equivalent continuous rank probability score (CRPS) of 60 % when assimilating HS with a 40-member ensemble and an average 20 % CRPS improvement when assimilating reflectance with a 160-member ensemble. Significant improvements are also obtained outside the observation domain. These promising results open a possibility for the assimilation of real observations of reflectance or of any snowpack observations in a spatialised context.
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Conway, J., Helgason, W., Pomeroy, J., & Sicart, J. (2021). Icefield Breezes: Mesoscale Diurnal Circulation in the Atmospheric Boundary Layer Over an Outlet of the Columbia Icefield, Canadian Rockies. Journal Of Geophysical Research-Atmospheres, 126(6).
Abstract: Atmospheric boundary layer (ABL) dynamics over glaciers mediate the response of glacier mass balance to large-scale climate forcing. Despite this, very few ABL observations are available over mountain glaciers in complex terrain. An intensive field campaign was conducted in June 2015 at the Athabasca Glacier outlet of Columbia Icefield in the Canadian Rockies. Observations of wind and temperature profiles with novel kite and radio-acoustic sounding systems showed a well-defined mesoscale circulation developed between the glacier and snow-free valley in fair weather. The typical vertical ABL structure above the glacier differed from that expected for “glacier winds”; strong daytime down-glacier winds extended through the lowest 200 m with no up-valley return flow aloft. This structure suggests external forcing at mesoscale scales or greater and is provisionally termed an “icefield breeze.” A wind speed maximum near the surface, characteristic of a “glacier wind,” was only observed during night-time and one afternoon. Lapse rates of air temperature down the glacier centerline show the interaction of down-glacier cooling driven by sensible heat loss into the ice, entrainment and periodic disruption and warming. Down-glacier cooling was weaker in “icefield breeze” conditions, while in “glacier wind” conditions, stronger down-glacier cooling enabled large increases in near-surface temperature on the lower glacier during periods of surface boundary layer (SBL) disruption. These results raise several questions, including the impact of Columbia Icefield on the ABL and melt of Athabasca Glacier. Future work should use these observations as a testbed for modeling spatio-temporal variations in the ABL and SBL within complex glaciated terrain.
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Cook, S., Christoffersen, P., Truffer, M., Chudley, T., & Abellan, A. (2021). Calving of a Large Greenlandic Tidewater Glacier has Complex Links to Meltwater Plumes and Melange. Journal Of Geophysical Research-Earth Surface, 126(4).
Abstract: Calving and solid ice discharge into fjords account for approximately half of the annual net ice loss from the Greenland ice sheet, but these processes are rarely observed. To gain insights into the spatiotemporal nature of calving, we use a terrestrial radar interferometer to derive a 3-week record of 8,026 calving events from Sermeq Kujalleq (Store Glacier, West Greenland), including the transition between a melange-filled and ice-free fjord. We show that calving rates double across this transition and that the interferometer record is in good agreement with volumetric estimates of calving losses from contemporaneous unmanned aerial vehicle surveys. We report significant variations in calving activity over time, which obfuscate any simple power-law relationship. While there is a statistically significant relationship between surface melt and the number of calving events, no such relationship exists between surface melt and the volume of these events. Similarly, we find a 70% increase in the number of calving events in the presence of visible meltwater plumes but only a 3% increase in calving volumes. While calving losses appear to have no clear single control, we find a bimodal distribution of iceberg sizes due to small blocks breaking off the subaerial part of the glacier front and large capsizing icebergs forming by full-thickness failure. Whereas previous work has hypothesized that tidewater glaciers can be grouped according to whether they calve predominantly by the former or latter mechanism, our observations indicate that calving here inherently comprises both and that the dominant process can change over relatively short periods.
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Cook, S. J., Christoffersen, P., & Todd, J. (2021). A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving. Journal Of Glaciology, .
Abstract: We present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland from the terminus and up to 41 and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year in which Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between types of behaviour. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store Glacier.
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Corella, J., Benito, G., Monteoliva, A., Sigro, J., Calle, M., Valero-Garces, B., et al. (2021). A 1400-years flood frequency reconstruction for the Basque country (N Spain): Integrating geological, historical and instrumental datasets. Quaternary Science Reviews, 262.
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Corella, J., Sierra, M., Garralon, A., Millan, R., Rodriguez-Alonso, J., Mata, M., et al. (2021). Recent and historical pollution legacy in high altitude Lake Marbore (Central Pyrenees): A record of mining and smelting since pre-Roman times in the Iberian Peninsula. Science Of The Total Environment, 751.
Abstract: We have analyzed potential harmful trace elements (PHTE; Pb, Hg, Zn, As and Cu) on sediment cores retrieved from lake Marbore (LM) (2612 m a.s.l, 42 degrees 41 ' N; 0 degrees 2 ' E). PHTE variability allowed us to reconstruct the timing and magnitude of trace metal pollutants fluxes over the last 3000 years in the Central Pyrenees. A statistical treatment of the dataset (PCA) enabled us to discern the depositional processes of PHTE, that reach the lake via direct atmospheric deposition. Indeed, the location of LM above the atmospheric boundary layer makes this lake an exceptional site to record the long-range transport of atmospheric pollutants in the free troposphere. Air masses back-trajectories analyses enabled us to understand the transport pathways of atmospheric pollutants while lead isotopic analyses contributed to evaluate the source areas of metal pollution in SW Europe during the Late Holocene. PHTE variability, shows a clear agreement with the main exploitation phases of metal resources in Southern Europe during the Pre-Industrial Period. We observed an abrupt lead enrichment from 20 to 375 yrs CE mostly associated to silver and lead mining and smelting practices in Southern Iberia during the Roman Empire. This geochemical data suggests that regional atmospheric metal pollution during the Roman times rivalled the Industrial Period. PHTE also increased during the High and Late Middle Ages (10-15th centuries) associated to a reactivation of mining and metallurgy activities in high altitude Pyrenean mining sites during climate amelioration phases. Atmospheric mercury deposition in the Lake Marbore record mostly reflects global emissions, particularly from Almaden mines (central Spain) and slightly fluctuates during the last three millennia with a significant increase during the last five centuries. Our findings reveal a strong mining-related pollution legacy in alpine lakes and watersheds that needs to be considered in management plans for mountain ecosystems as global warming and human pressure effects may contribute to their future degradation. (C) 2020 Elsevier B.V. All rights reserved.
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Coulibaly, H., Honore, C., Naga, C., Kouadio, K., Didi, S., Diedhiou, A., et al. (2021). Groundwater exploration using extraction of lineaments from SRTM DEM and water flows in Bere region. Egyptian Journal Of Remote Sensing And Space Sciences, 24(3), 391–400.
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Cravatte, S., Serazin, G., Penduff, T., & Menkes, C. (2021). Imprint of chaotic ocean variability on transports in the southwestern Pacific at interannual timescales. Ocean Science, 17(2), 487–507.
Abstract: The southwestern Pacific Ocean sits at a bifurcation where southern subtropical waters are redistributed equatorward and poleward by different ocean currents. The processes governing the interannual variability of these currents are not completely understood. This issue is investigated using a probabilistic modeling strategy that allows disentangling the atmospherically forced deterministic ocean variability and the chaotic intrinsic ocean variability. A large ensemble of 50 simulations performed with the same ocean general circulation model (OGCM) driven by the same realistic atmospheric forcing and only differing by a small initial perturbation is analyzed over 1980-2015. Our results show that, in the southwestern Pacific, the interannual variability of the transports is strongly dominated by chaotic ocean variability south of 20 degrees S. In the tropics, while the interannual variability of transports and eddy kinetic energy modulation are largely deterministic and explained by the El Nino-Southern Oscillation (ENSO), ocean nonlinear processes still explain 10% to 20% of their interannual variance at large scale. Regions of strong chaotic variance generally coincide with regions of high mesoscale activity, suggesting that a spontaneous inverse cascade is at work from the mesoscale toward lower frequencies and larger scales. The spatiotemporal features of the low-frequency oceanic chaotic variability are complex but spatially coherent within certain regions. In the Subtropical Countercurrent area, they appear as interannually varying, zonally elongated alternating current structures, while in the EAC (East Australian Current) region, they are eddy-shaped. Given this strong imprint of large-scale chaotic oceanic fluctuations, our results question the attribution of interannual variability to the atmospheric forcing in the region from pointwise observations and one-member simulations.
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Crick, L., Burke, A., Hutchison, W., Kohno, M., Moore, K., Savarino, J., et al. (2021). New insights into the similar to 74 ka Toba eruption from sulfur isotopes of polar ice cores. Climate Of The Past, 17(5), 2119–2137.
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Crockart, C., Vance, T., Fraser, A., Abram, N., Criscitiello, A., Curran, M., et al. (2021). El Nino-Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South. Climate Of The Past, 17(5), 1795–1818.
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Crotti, I., Landais, A., Stenni, B., Bazin, L., Parrenin, F., Frezzotti, M., et al. (2021). An extension of the TALDICE ice core age scale reaching back to MIS 10.1. Quaternary Science Reviews, 266.
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Cusicanqui, D., Rabatel, A., Vincent, C., Bodin, X., Thibert, E., & Francou, B. (2021). Interpretation of Volume and Flux Changes of the Laurichard Rock Glacier Between 1952 and 2019, French Alps. Journal Of Geophysical Research-Earth Surface, 126(9).
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Daher, H., Arbic, B., Williams, J., Ansong, J., Boggs, D., Muller, M., et al. (2021). Long-Term Earth-Moon Evolution With High-Level Orbit and Ocean Tide Models. Journal Of Geophysical Research-Planets, 126(12).
Abstract: Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows Earth ' s rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are “high-level” (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and Earth ' s rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded today ' s rate due to a closer Moon. Prior to similar to 3 Ga, evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation.
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Danso, D., Francois, B., Hingray, B., & Diedhiou, A. (2021). Assessing hydropower flexibility for integrating solar and wind energy in West Africa using dynamic programming and sensitivity analysis. Illustration with the Akosombo reservoir, Ghana. Journal Of Cleaner Production, 287.
Abstract: The flexibility of hydropower plants with large reservoirs is frequently exploited to integrate large shares of variable and intermittent renewable energy sources in electricity systems. In this study, we assess the flexibility that could be provided by large hydropower reservoirs in West Africa to cope with planned future solar and wind energy generation in the region. Reservoir operations are estimated via Dynamic Programming with the objective to minimize the variability of the residual demand that commonly needs to be supplied by conventional generation means at high monetary and carbon costs. The analysis framework is demonstrated for the Akosombo hydropower reservoir in Ghana for which a number of future scenarios of increased electricity demand are considered. Different combinations of solar and wind energy development are considered to match the increase in demand. The results show that the Akosombo hydropower reservoir can smooth out the variability of the residual electricity demand when the increase in electricity demand is below 25% and the corresponding contribution of solar and wind energy to the total electricity generation does not exceed 20%. For larger increases in demand and thus larger solar and wind generation, the Akosombo reservoir cannot fully smooth-out the variability of the subsequent residual demand, although, the performance varies with the relative contribution of solar and wind in the energy mix. However, we found that the use of an additional short-term storage helps to further reduce the variability of the residual demand. (c) 2020 Elsevier Ltd. All rights reserved.
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Dasari, S., Andersson, A., Popa, M., Rockmann, T., Holmstrand, H., Budhavant, K., et al. (2021). Observational Evidence of Large Contribution from Primary Sources for Carbon Monoxide in the South Asian Outflow. Environmental Science & Technology, .
Abstract: South Asian air is among the most polluted in the world, causing premature death of millions and asserting a strong perturbation of the regional climate. A central component is carbon monoxide (CO), which is a key modulator of the oxidizing capacity of the atmosphere and a potent indirect greenhouse gas. While CO concentrations are declining elsewhere, South Asia exhibits an increasing trend for unresolved reasons. In this paper, we use dual-isotope (delta C-13 and (delta O-18) fingerprinting of CO intercepted in the South Asian outflow to constrain the relative contributions from primary and secondary CO sources. Results show that combustion-derived primary sources dominate the wintertime continental CO fingerprint (f(primary) similar to 79 +/- 4%), significantly higher than the pnmr global estimate (f(primary) similar to 55 +/- 5%). Satellite-based inventory estimates match isotope-constrained f(primary)-CO, suggesting observational convergence in source characterization and a prospect for model-observation reconciliation. This “ground-truthing” emphasizes the pressing need to mitigate incomplete combustion activities for climate/air quality benefits in South Asia.
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Davtian, N., Bard, E., Darfeuil, S., Menot, G., & Rostek, F. (2021). The Novel Hydroxylated Tetraether Index RI-OH ' as a Sea Surface Temperature Proxy for the 160-45 ka BP Period Off the Iberian Margin. Paleoceanography And Paleoclimatology, 36(3).
Abstract: RI-OH ' and RI-OH (ring index of hydroxylated tetraethers) are two novel organic paleothermometers which could either complement or replace more established paleothermometric proxies, such as U-K '(37) (C-37 ketone unsaturation ratio) and TEX86 (TetraEther indeX of tetraethers consisting of 86 carbon atoms). Despite a few promising attempts, the paleothermometric potential of RI-OH ' and RI-OH is not fully constrained. Here we present new high-resolution temperature records over the 160-45 ka BP (before present = year 1950 CE) period using four organic proxies (RI-OH ', RI-OH, TEX86, and U-K '(37)) from three deep sea sediment cores located in a north-south transect along the Iberian Margin. We analyzed all organic proxies from a single set of lipid extracts to optimize proxy-proxy comparisons and phase relationship studies. RI-OH ' responds to Dansgaard-Oeschger and Heinrich events, better resembles U-K '(37) than TEX86, and better records the influence of (sub)polar waters during Heinrich events than does RI-OH. While RI-OH ' gives realistic sea surface temperatures and latitudinal gradients coherent with those from independent paleothermometers, a more extensive RI-OH '-temperature calibration for the North Atlantic is clearly needed. However, the absence of a significant warm bias in RI-OH '-based temperatures compared to a shallow sea site suggests that endemic, deep-dwelling archeal communities affect TEX86 but not RI-OH ' in the Iberian Margin. TEX86 leads RI-OH ' and U-K '(37) during four Heinrich-like events, potentially due to background fluxes from deep waters for nonhydroxylated tetraethers summed with primary productivity dependent fluxes from surface waters for all investigated lipid classes. Relationships with Greenland temperatures further support RI-OH '-based paleothermometry.
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Derkacheva, A., Gillet-Chaulet, F., Mouginot, J., Jager, E., Maier, N., & Cook, S. (2021). Seasonal evolution of basal environment conditions of Russell sector, West Greenland, inverted from satellite observation of surface flow. Cryosphere, 15(12), 5675–5704.
Abstract: Due to increasing surface melting on the Greenland ice sheet, better constraints on seasonally evolving basal water pressure and sliding speed are required by models. Here we assess the potential of using inverse methods on a dense time series of surface speeds to recover the seasonal evolution of the basal conditions in a well-documented region in southwest Greenland. Using data compiled from multiple satellite missions, we document seasonally evolving surface velocities with a temporal resolution of 2 weeks between 2015 and 2019. We then apply the inverse control method using the ice flow model Elmer/Ice to infer the basal sliding and friction corresponding to each of the 24 surface velocity data sets. Near the margin where the uncertainty in the velocity and bed topography are small, we obtain clear seasonal variations that can be mostly interpreted in terms of an effective-pressure-based hard-bed friction law. We find for valley bottoms or “troughs” in the bed topography that the changes in modelled basal conditions directly respond to local modelled water pressure variations, while the link is more complex for subglacial “ridges” which are often non-locally forced. At the catchment scale, in-phase variations in the water pressure, surface velocities, and surface runoff variations are found. Our results show that time series inversions of observed surface velocities can be used to understand the evolution of basal conditions over different timescales and could therefore serve as an intermediate validation for subglacial hydrology models to achieve better coupling with ice flow models.
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Diba, I., Basse, J., Ndiaye, M., Sabaly, H., Diedhiou, A., & Camara, M. (2021). Potential Dust Induced Changes on the Seasonal Variability of Temperature Extremes Over the Sahel: A Regional Climate Modeling Study. Frontiers In Earth Science, 8.
Abstract: The aim of this study is to simulate the impact of mineral dust emissions from the Sahel-Saharan zone on temperature extremes over the Sahel. To achieve this goal, we performed two numerical simulations: one with the standard version of the regional climate model RegCM4 (no dust run) and another one with the same version of this model incorporating a dust module (dust run). The difference between both versions of the model allowed to isolate the impacts of mineral dust emissions on temperature extremes. The results show that the accumulation of mineral dust into the atmosphere leads to a decrease of the frequency of warm days, very warm days, and warm nights over the Sahel. This decrease is higher during the MAM (March-April-May) and JJA (June-July-August) periods especially in the northern and western parts of the Sahel. The impact of the mineral dust emissions is also manifested by a decrease of the frequency of tropical nights especially during MAM in the northern Sahel. When considering the warm spells, mineral particles tend to weaken them especially in MAM and JJA in the northern Sahel. To estimate the potential impacts of the mineral dust accumulation on heat stress, the heat index and the humidex are used. The analysis of the heat index shows that the dust impact is to reduce the health risks particularly in the northern Sahel during the MAM period, in the western Sahel during JJA, and in the southern and the northeastern parts of the Sahel during the SON (September-October-November) period. As for the humidex, it is characterized by a decrease especially in the northern Sahel for all seasons. This reduction of the occurrence of thermal extremes may have a positive effect on the energy demand for cooling and on global health. However, the accumulation of dust particles in the atmosphere may also increase the meningitis incidence and prevalence.
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Donat-Magnin, M., Jourdain, N., Kittel, C., Agosta, C., Amory, C., Gallee, H., et al. (2021). Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet. Cryosphere, 15(2), 571–593.
Abstract: We present projections of West Antarctic surface mass balance (SMB) and surface melt to 2080-2100 under the RCP8.5 scenario and based on a regional model at 10 km resolution. Our projections are built by adding a CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model-mean seasonal climate-change anomaly to the present-day model boundary conditions. Using an anomaly has the advantage to reduce CMIP5 model biases, and a perfect-model test reveals that our approach captures most characteristics of future changes despite a 16 %-17 % underestimation of projected SMB and melt rates. SMB over the grounded ice sheet in the sector between Getz and Abbot increases from 336 Gt yr(-1) in 1989-2009 to 455 Gt yr(-1) in 2080-2100, which would reduce the global sea level changing rate by 0.33 mm yr(-1). Snowfall indeed increases by 7.4 % degrees C-1 to 8.9 % degrees C-1 of near-surface warming due to increasing saturation water vapour pressure in warmer conditions, reduced sea-ice concentrations, and more marine air intrusion. Ice-shelf surface melt rates increase by an order of magnitude in the 21st century mostly due to higher downward radiation from increased humidity and to reduced albedo in the presence of melting. There is a net production of surface liquid water over eastern ice shelves (Abbot, Cosgrove, and Pine Island) but not over western ice shelves (Thwaites, Crosson, Dotson, and Getz). This is explained by the evolution of the melt-to-snowfall ratio: below a threshold of 0.60 to 0.85 in our simulations, firn air is not entirely depleted by melt water, while entire depletion and net production of surface liquid water occur for higher ratios. This suggests that western ice shelves might remain unaffected by hydrofracturing for more than a century under RCP8.5, while eastern ice shelves have a high potential for hydrofracturing before the end of this century.
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Doumbia, M., Kouassi, A., Silue, S., Yoboue, V., Liousse, C., Diedhiou, A., et al. (2021). Road Traffic Emission Inventory in an Urban Zone of West Africa: Case of Yopougon City (Abidjan, Cote d'Ivoire). Energies, 14(4).
Abstract: Road traffic emission inventories based on bottom-up methodology, are calculated for each road segment from fuel consumption and traffic volume data obtained during field measurements in Yopougon. High emissions of black carbon (BC) from vehicles are observed at major road intersections, in areas surrounding industrial zones and on highways. Highest emission values from road traffic are observed for carbon monoxide (CO) (14.8 t/d) and nitrogen oxides (NOx) (7.9 t/d), usually considered as the major traffic pollution tracers. Furthermore, peak values of CO emissions due to personal cars (PCs) are mainly linked to the old age of the vehicle fleet with high emission factors. The highest emitting type of vehicle for BC on the highway is PC (70.2%), followed by inter-communal taxis (TAs) (13.1%), heavy vehicles (HVs) (9.8%), minibuses (GBs) (6.4%) and intra-communal taxis (WRs) (0.4%). While for organic carbon (OC) emissions on the main roads, PCs represent 46.7%, followed by 20.3% for WRs, 14.9% for TAs, 11.4% for GB and 6.7% for HVs. This work provides new key information on local pollutant emissions and may be useful to guide mitigation strategies such as modernizing the vehicle fleet and reorganizing public transportation, to reduce emissions and improve public health.
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Du Roscoat, S., Ivankovic, T., Lenoir, N., Dekic, S., Martins, J., & Geindreau, C. (2021). First visualisation of bacterial biofilms in 3D porous media with neutron microtomography without contrast agent. Journal Of Microscopy, .
Abstract: Characterising bacterial biofilm growth in porous media is important for developing reliable numerical models of biofouling in industrial biofilters. One of the promising imaging methods to do that has been a recent successful application of X-ray microtomography. However, this technique requires a contrast agent (1-chloronaphtalene, for example) to distinguish biofilm from the liquid phase, which raises concern about biofilm disruption and impaired image interpretation. To overcome these drawbacks, we tested a new approach based on neutron tomography (NT), which does not need a contrast agent, by imaging two types of porous media (polytetrafluoroethylene – PTFE – and clay beads of various diameters) in glass or PTFE tubes in which bacterial biofilms were grown for 7 days and by comparing these images with the ones obtained with X-ray microtomography. NT images showed that the biofilm formed preferentially around the beads and at bead/bead interface. Visual comparison of both imaging techniques showed consistent biofilm spatial distributions and that the contrasting agent did not significantly disrupt the biofilm. NT images, on the other hand, were still too noisy to allow quantitative measurements. Therefore, X-ray microtomography (provided it uses non-disruptive contrast agents) seems to provide more reliable microstructural descriptors.
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Edwards, T., Nowicki, S., Marzeion, B., Hock, R., Goelzer, H., Seroussi, H., et al. (2021). Projected land ice contributions to twenty-first-century sea level rise. Nature, 593(7857), 74–+.
Abstract: Efficient statistical emulation of melting land ice under various climate scenarios to 2100 indicates a contribution from melting land ice to sea level increase of at least 13 centimetres sea level equivalent. The land ice contribution to global mean sea level rise has not yet been predicted(1) using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models(2-8), but primarily used previous-generation scenarios(9) and climate models(10), and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios(11,12) using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.
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El-Alem, A., Chokmani, K., Venkatesan, A., Rachid, L., Agili, H., & Dedieu, J. (2021). How Accurate Is an Unmanned Aerial Vehicle Data-Based Model Applied on Satellite Imagery for Chlorophyll-a Estimation in Freshwater Bodies? Remote Sensing, 13(6).
Abstract: Optical sensors are increasingly sought to estimate the amount of chlorophyll a (chla) in freshwater bodies. Most, whether empirical or semi-empirical, are data-oriented. Two main limitations are often encountered in the development of such models. The availability of data needed for model calibration, validation, and testing and the locality of the model developed-the majority need a re-parameterization from lake to lake. An Unmanned aerial vehicle (UAV) data-based model for chla estimation is developed in this work and tested on Sentinel-2 imagery without any re-parametrization. The Ensemble-based system (EBS) algorithm was used to train the model. The leave-one-out cross validation technique was applied to evaluate the EBS, at a local scale, where results were satisfactory (R-2 = Nash = 0.94 and RMSE = 5.6 μg chla L-1). A blind database (collected over 89 lakes) was used to challenge the EBS' Sentine-2-derived chla estimates at a regional scale. Results were relatively less good, yet satisfactory (R-2 = 0.85, RMSE= 2.4 μg chla L-1, and Nash = 0.79). However, the EBS has shown some failure to correctly retrieve chla concentration in highly turbid waterbodies. This particularity nonetheless does not affect EBS performance, since turbid waters can easily be pre-recognized and masked before the chl_a modeling.
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Evangeliou, N., Platt, S., Eckhardt, S., Myhre, C., Laj, P., Alados-Arboledas, L., et al. (2021). Changes in black carbon emissions over Europe due to COVID-19 lockdowns. Atmospheric Chemistry And Physics, 21(4), 2675–2692.
Abstract: Following the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for COVID-19 in December 2019 in Wuhan (China) and its spread to the rest of the world, the World Health Organization declared a global pandemic in March 2020. Without effective treatment in the initial pandemic phase, social distancing and mandatory quarantines were introduced as the only available preventative measure. In contrast to the detrimental societal impacts, air quality improved in all countries in which strict lockdowns were applied, due to lower pollutant emissions. Here we investigate the effects of the COVID-19 lockdowns in Europe on ambient black carbon (BC), which affects climate and damages health, using in situ observations from 17 European stations in a Bayesian inversion framework. BC emissions declined by 23 kt in Europe (20% in Italy, 40% in Germany, 34% in Spain, 22% in France) during lockdowns compared to the same period in the previous 5 years, which is partially attributed to COVID-19 measures. BC temporal variation in the countries enduring the most drastic restrictions showed the most distinct lockdown impacts. Increased particle light absorption in the beginning of the lockdown, confirmed by assimilated satellite and remote sensing data, suggests residential combustion was the dominant BC source. Accordingly, in central and Eastern Europe, which experienced lower than average temperatures, BC was elevated compared to the previous 5 years. Nevertheless, an average decrease of 11% was seen for the whole of Europe compared to the start of the lockdown period, with the highest peaks in France (42 %), Germany (21 %), UK (13 %), Spain (11 %) and Italy (8 %). Such a decrease was not seen in the previous years, which also confirms the impact of COVID-19 on the European emissions of BC.
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Evin, G., Somot, S., & Hingray, B. (2021). Balanced estimate and uncertainty assessment of European climate change using the large EURO-CORDEX regional climate model ensemble. Earth System Dynamics, 12(4), 1543–1569.
Abstract: Large multiscenario multimodel ensembles (MMEs) of regional climate model (RCM) experiments driven by global climate models (GCMs) are made available worldwide and aim at providing robust estimates of climate changes and associated uncertainties. Due to many missing combinations of emission scenarios and climate models leading to sparse scenario-GCM-RCM matrices, these large ensembles, however, are very unbalanced, which makes uncertainty analyses impossible with standard approaches. In this paper, the uncertainty assessment is carried out by applying an advanced statistical approach, called QUALYPSO, to a very large ensemble of 87 EURO-CORDEX climate projections, the largest MME based on regional climate models ever produced in Europe. This analysis provides a detailed description of this MME, including (i) balanced estimates of mean changes for near-surface temperature and precipitation in Europe, (ii) the total uncertainty of projections and its partition as a function of time, and (iii) the list of the most important contributors to the model uncertainty. For changes in total precipitation and mean temperature in winter (DJF) and summer (JJA), the uncertainty due to RCMs can be as large as the uncertainty due to GCMs at the end of the century (2071-2099). Both uncertainty sources are mainly due to a small number of individual models clearly identified. Due to the highly unbalanced character of the MME, mean estimated changes can drastically differ from standard average estimates based on the raw ensemble of opportunity. For the RCP4.5 emission scenario in central-eastern Europe for instance, the difference between balanced and direct estimates is up to 0.8 degrees C for summer temperature changes and up to 20 % for summer precipitation changes at the end of the century.
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Ezersky, M., Eppelbaum, L., Legchenko, A., Al-Zoubi, A., & Abueladas, A. (2021). Salt layer characteristics in the Ghor Al-Haditha area, Jordan: comprehensive combined reprocessing of geophysical data. Environmental Earth Sciences, 80(4).
Abstract: The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole hazard. Numerous geophysical methods such as seismic refraction (SRFR), reflection (SRFL), seismic tomography, multichannel analysis of surface waves (MASW) were developed earlier for the salt layer identification. Geophysical criteria of salt parameters (such as longitudinal V-p and shear V-s wave velocities) were established to identify salt layers. This paper presents new geophysical results proving the salt extension in the Dead Sea (DS) coastal area in its eastern shore potentially representing a sinkhole hazard. The reprocessing technique of MASW data using the synthetic modeling enabled us to detect salt layer characteristics such as depth to its top, the thickness of the layer, and its V-s velocity. It was established that a salt layer with 7-10 m thick is located at a depth of 37-41 m and is characterized by shear-wave velocity (V-s) of 850-1200 m/s. Similar results were obtained by the Transient Electromagnetic (TEM) resistivity method, which detected a comparatively resistive salt layer at a background of very low resistivity. The resolution of the TEM method allows detecting a salt layer of 3 m thick and more at a depth of 39-40 m. Seismic refraction data processing has shown the presence of a salt layer with a velocity of more than 2900 m/s at approximately or the same depths. Analysis of seismic tomography data also confirms the parameters of the discovered target. Analysis of results of geophysical studies in the western and eastern DS shores, comparison of geological conditions in shores, and sinkhole development, enabled us to conclude with a high probability that salt layers exist in both shores and sinkhole development is determined here by similar mechanisms.
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Fall, C., Lavaysse, C., Drame, M., Panthou, G., & Gaye, A. (2021). Wet and dry spells in Senegal: comparison of detection based on satellite products, reanalysis, and in situ estimates. Natural Hazards And Earth System Sciences, 21(3), 1051–1069.
Abstract: In this study, the detection and characteristics of dry/wet spells (defined as episodes when precipitation is abnormally low or high compared to usual climatology) drawn from several datasets are compared for Senegal. Here, four datasets are based on satellite data (TRMM-3B42 V7, CMORPH V1.0, TAMSAT V3, and CHIRPS V2. 0), two on reanalysis products (NCEP-CFSR and ERAS), and three on rain gauge observations (CPC Unified V1.0/RT and a 65-rain-gauge network regridded by using two kriging methods, namely ordinary kriging, OK, and block kriging, BK). All datasets were converted to the same spatio-temporal resolution: daily cumulative rainfall on a regular 0.25 degrees grid. The BK dataset was used as a reference. Despite strong agreement between the datasets on the spatial variability in cumulative seasonal rainfall (correlations ranging from 0.94 to 0.99), there were significant disparities in dry/wet spells. The occurrence of dry spells is less in products using infrared measurement techniques than in products coupling infrared and microwave, pointing to more frequent dry spell events. All datasets show that dry spells appear to be more frequent at the start and end of rainy seasons. Thus, dry spell occurrences have a major influence on the duration of the rainy season, in particular through the “false onset” or “early cessation” of seasons. The amplitude of wet spells shows the greatest variation between datasets. Indeed, these major wet spells appear more intense in the OK and Tropical Rainfall Measuring Mission (TRMM) datasets than in the others. Lastly, the products indicate a similar wet spell frequency occurring at the height of the West African monsoon. Our findings provide guidance in choosing the most suitable datasets for implementing early warning systems (EWSs) using a multi-risk approach and integrating effective dry/wet spell indicators for monitoring and detecting extreme events.
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Fall, C., Lavaysse, C., Kerdiles, H., Drame, M., Roudier, P., & Gaye, A. (2021). Performance of dry and wet spells combined with remote sensing indicators for crop yield prediction in Senegal. Climate Risk Management, 33.
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Farinotti, D., Brinkerhoff, D., Furst, J., Gantayat, P., Gillet-Chaulet, F., Huss, M., et al. (2021). Results from the Ice Thickness Models Intercomparison eXperiment Phase 2 (ITMIX2). Frontiers In Earth Science, 8.
Abstract: Knowing the ice thickness distribution of a glacier is of fundamental importance for a number of applications, ranging from the planning of glaciological fieldwork to the assessments of future sea-level change. Across spatial scales, however, this knowledge is limited by the paucity and discrete character of available thickness observations. To obtain a spatially coherent distribution of the glacier ice thickness, interpolation or numerical models have to be used. Whilst the first phase of the Ice Thickness Models Intercomparison eXperiment (ITMIX) focused on approaches that estimate such spatial information from characteristics of the glacier surface alone, ITMIX2 sought insights for the capability of the models to extract information from a limited number of thickness observations. The analyses were designed around 23 test cases comprising both real-world and synthetic glaciers, with each test case comprising a set of 16 different experiments mimicking possible scenarios of data availability. A total of 13 models participated in the experiments. The results show that the inter-model variability in the calculated local thickness is high, and that for unmeasured locations, deviations of 16% of the mean glacier thickness are typical (median estimate, three-quarters of the deviations within 37% of the mean glacier thickness). This notwithstanding, limited sets of ice thickness observations are shown to be effective in constraining the mean glacier thickness, demonstrating the value of even partial surveys. Whilst the results are only weakly affected by the spatial distribution of the observations, surveys that preferentially sample the lowest glacier elevations are found to cause a systematic underestimation of the thickness in several models. Conversely, a preferential sampling of the thickest glacier parts proves effective in reducing the deviations. The response to the availability of ice thickness observations is characteristic to each approach and varies across models. On average across models, the deviation between modeled and observed thickness increase by 8.5% of the mean ice thickness every time the distance to the closest observation increases by a factor of 10. No single best model emerges from the analyses, confirming the added value of using model ensembles.
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Fassoni-Andrade, A., Fleischmann, A., Papa, F., Paiva, R., Wongchuig, S., Melack, J., et al. (2021). Amazon Hydrology From Space: Scientific Advances and Future Challenges. Reviews Of Geophysics, 59(4).
Abstract: As the largest river basin on Earth, the Amazon is of major importance to the world's climate and water resources. Over the past decades, advances in satellite-based remote sensing (RS) have brought our understanding of its terrestrial water cycle and the associated hydrological processes to a new era. Here, we review major studies and the various techniques using satellite RS in the Amazon. We show how RS played a major role in supporting new research and key findings regarding the Amazon water cycle, and how the region became a laboratory for groundbreaking investigations of new satellite retrievals and analyses. At the basin-scale, the understanding of several hydrological processes was only possible with the advent of RS observations, such as the characterization of “rainfall hotspots” in the Andes-Amazon transition, evapotranspiration rates, and variations of surface waters and groundwater storage. These results strongly contribute to the recent advances of hydrological models and to our new understanding of the Amazon water budget and aquatic environments. In the context of upcoming hydrology-oriented satellite missions, which will offer the opportunity for new synergies and new observations with finer space-time resolution, this review aims to guide future research agenda toward integrated monitoring and understanding of the Amazon water from space. Integrated multidisciplinary studies, fostered by international collaborations, set up future directions to tackle the great challenges the Amazon is currently facing, from climate change to increased anthropogenic pressure.
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Favez, O., Weber, S., Petit, J., Alleman, L., Albinet, A., Riffault, V., et al. (2021). Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program). Atmosphere, 12(2).
Abstract: The CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge-at a national level-on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (delta N-15) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively.
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Fayjaloun, R., Dabaghi, M., Cornou, C., Causse, M., Lu, Y., Stehly, L., et al. (2021). Hybrid Simulation of Near-Fault Ground Motion for a Potential M-w 7 Earthquake in Lebanon. Bulletin Of The Seismological Society Of America, 111(5), 2441–2462.
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Fayjaloun, R., Dabaghi, M., Cornou, C., Causse, M., Lu, Y., Stehly, L., et al. (2021). Hybrid Simulation of Near-Fault Ground Motion for a Potential M-w 7 Earthquake in Lebanon (vol 111, pg 2441, 2021). Bulletin Of The Seismological Society Of America, 111(6), 3498–3499.
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Fettweis, X., Hofer, S., Seferian, R., Amory, C., Delhasse, A., Doutreloup, S., et al. (2021). Brief communication: Reduction in the future Greenland ice sheet surface melt with the help of solar geoengineering. Cryosphere, 15(6), 3013–3019.
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Fleischmann, A., Breda, J., Passaia, O., Wongchuig, S., Fan, F., Paiva, R., et al. (2021). Regional scale hydrodynamic modeling of the river-floodplain-reservoir continuum. Journal Of Hydrology, 596.
Abstract: River floodplains and reservoirs interact throughout a basin drainage network, defining a coupled human-water system with multiple feedbacks. Recent modeling developments have aimed to improve the representation of such processes at regional to continental scales. However, most large-scale hydrological models adopt simplified lumped reservoir schemes, where an offline routine is run with inflows estimated by the model, with limited consideration of the complementarity between floodplains and reservoirs on altering the hydrological regime at regional scale. This paper presents a novel approach that fully couples river-floodplain-reservoir hydrodynamic and hydrological models, significantly improving the representation of reservoir dynamics and operation in the river-floodplain-reservoir continuum at large scale and across multiple dam cascades. The model is applied to the Parana River Basin with explicit simulation of 31 large dams and river hydraulic variables at basin scale. Three types of reservoir bathymetry representation are compared, from lumped to distributed methods, combined with three reservoir operation schemes and varying degrees of input data requirement within two parameterization scenarios (global and regional setups). The operation schemes were more relevant than the reservoir bathymetry representation to estimate downstream flows and water levels. While the data-driven operation scheme, based on linear regressions between observed water levels and dam outflows, provided the best estimates of both active storage and discharges, the more generic operation reasonably estimated discharges and peak attenuation, albeit not as accurately for active storage. The global parameterization of reservoir operation resulted in poorer performance compared to the regional-based one, but it satisfactorily modeled discharge and peak attenuation. Regarding the reservoir bathymetry representation, a basin scale comparison of the lumped and distributed schemes indicated the inability of the former to represent backwater effects. This was further corroborated by validating the longitudinal water level profile of Itaipu dam with ICESat satellite altimetry data. Finally, the model was used to show the complementarity between floodplains and reservoirs on attenuating floods at regional scale. Large scale models should move beyond offline coupling strategies, and include regional-based, data-driven reservoir operation schemes together with a distributed representation of reservoir bathymetry into river-floodplain hydraulic schemes. This will largely improve the estimation of river discharges, water levels and flood storage, and thus the model ability to represent the regional scale river-floodplain-reservoir continuum.
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Fleurbaey, H., Grilli, R., Mondelain, D., Kassi, S., Yachmenev, A., Yurchenko, S., et al. (2021). Electric-quadrupole and magnetic-dipole contributions to the v(2) + v(3) band of carbon dioxide near 3.3 μm. Journal Of Quantitative Spectroscopy & Radiative Transfer, 266.
Abstract: The recent detections of electric-quadrupole (E2) transitions in water vapor and magnetic-dipole (M1) transitions in carbon dioxide have opened a new field in molecular spectroscopy. While in their present status, the spectroscopic databases provide only electric-dipole (E1) transitions for polyatomic molecules (H2O, CO2, N2O, CH4, O-3 ...), the possible impact of weak E2 and M1 bands to the modeling of the Earth and planetary atmospheres has to be addressed. This is especially important in the case of carbon dioxide for which E2 and M1 bands may be located in spectral windows of weak E1 absorption. In the present work, a high sensitivity absorption spectrum of CO2 is recorded by Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OFCEAS) in the 3.3 μm transparency window of carbon dioxide. The studied spectral interval corresponds to the region where M1 transitions of the v(2) + v(3) band of carbon dioxide were recently identified in the spectrum of the Martian atmosphere. Here, both M1 and E2 transitions of the v2 + v3 band are detected by OFCEAS. Using recent ab initio calculations of the E2 spectrum of (CO2,)-C-12-O-16 intensity measurements of five M1 lines and three E2 lines allow us to disentangle the M-1 and E-2 con-tributions. Indeed, E2 intensity values (on the order of a few 10(-29) cm/molecule) are found in reasonable agreement with ab initio calculations while the intensity of the M1 lines (including an E2 contribution) agree very well with recent very long path measurements by Fourier Transform spectroscopy. We thus conclude that both E2 and M1 transitions should be systematically incorporated in the CO2 line list pro-vided by spectroscopic databases. (C) 2021 Elsevier Ltd. All rights reserved.
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Forquin, P., Blasone, M., Georges, D., & Dargaud, M. (2021). Continuous and discrete methods based on X-ray computed-tomography to model the fragmentation process in brittle solids over a wide range of strain-rates-application to three brittle materials. Journal Of The Mechanics And Physics Of Solids, 152.
Abstract: In the present work, two methods, named “continuous” and “discrete”, are proposed to model the fragmentation process in brittle solids. Both methods rely on a preliminary analysis of the existing flaws population in scanned samples with X-ray micro-Computed Tomography (microCT). By converting the size of defects into critical stresses, the density of critical defects versus the applied stress level is deduced and used as an input of both a continuum and a discrete method. To do so, the concept of critical defects obscuration is implemented. Introduced in the DFH (DenoualForquin-Hild) micromechanics model, this concept consists in describing how cracks propagating from triggered flaws prevent neighbouring flaws from being activated. This obscuration phenomenon is implemented in the present work by using the flaws population determined via microCT analysis as an input. In the continuous method, the differential equation of the obscuration probability provided in the DFH model is integrated. In the discrete method, a cubic subvolume of the scanned volume is considered and the growth of obscuration volumes is numerically simulated considering the real location of each critical defect and their stress of activation. Both methods provide predictions for the material dynamic strength and final cracking density according to the applied strain-rate. These two methods are applied to three types of brittle materials: an Ultra-High Performance Concrete (UHPC), a porous polycrystalline ice and a silicon carbide with spherical “fuse-flaws”. Finally, the obtained predictions are compared to the closedform solution of the DFH model, which is based on a Weibull distribution of the critical flaws identified from bending tests. Whereas the three approaches match very well at low strain-rates, the continuous and discrete methods diverge from the DFH closed-form solution at high strainrates, due to the activation of smaller and more numerous defects that could not be activated in the quasi-static bending tests.
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Fovet, O., Belemtougri, A., Boithias, L., Braud, I., Charlier, J., Cottet, M., et al. (2021). Intermittent rivers and ephemeral streams: Perspectives for critical zone science and research on socio-ecosystems. Wiley Interdisciplinary Reviews-Water, .
Abstract: Intermittent rivers and ephemeral streams (IRES) are now recognized to support specific freshwater biodiversity and ecosystem services and represent approximately half of the global river network, a fraction that is likely to increase in the context of global changes. Despite large research efforts on IRES during the past few decades, there is a need for developing a systemic approach to IRES that considers their hydrological, hydrogeological, hydraulic, ecological, and biogeochemical properties and processes, as well as their interactions with human societies. Thus, we assert that the interdisciplinary approach to ecosystem research promoted by critical zone sciences and socio-ecology is relevant. These approaches rely on infrastructure-Critical Zone Observatories (CZO) and Long-Term Socio-Ecological Research (LTSER) platforms-that are representative of the diversity of IRES (e.g., among climates or types of geology. We illustrate this within the French CZO and LTSER, including their diversity as socio-ecosystems, and detail human interactions with IRES. These networks are also specialized in the long-term observations required to detect and measure ecosystem responses of IRES to climate and human forcings despite the delay and buffering effects within ecosystems. The CZO and LTSER platforms also support development of innovative techniques and data analysis methods that can improve characterization of IRES, in particular for monitoring flow regimes, groundwater-surface water flow, or water biogeochemistry during rewetting. We provide scientific and methodological perspectives for which this interdisciplinary approach and its associated infrastructure would provide relevant and original insights that would help fill knowledge gaps about IRES. This article is categorized under: Water and Life > Conservation, Management, and Awareness
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Funatsu, B., Le Roux, R., Arvor, D., Espinoza, J., Claud, C., Ronchail, J., et al. (2021). Assessing precipitation extremes (1981-2018) and deep convective activity (2002-2018) in the Amazon region with CHIRPS and AMSU data. Climate Dynamics, .
Abstract: The frequency and spatial distributions of precipitation extremes (PEs) and deep convective clouds (DCC) across the Amazon region were assessed using satellite-derived data. For PEs, CHIRPS dataset for the period 1981-2018 were used to calculate a set of absolute, threshold, duration, and percentile-based threshold indices defined by the Expert Team on Climate Change Detection and Indices. DCC occurrence was assessed based on the Advanced Microwave Sounding Unit data for the period 2002-2018. In northern Amazon (north of 5 degrees S) PEs and DCC are more frequent (>= 60% frequency) during February-June. Averaged trends over these months have shown increase in daily rainfall above 20 mm of near 3 days over the 1981-2018 period, and an increase of 2 consecutive wet days (P >= 1 mm) in the same period. South of 5.S prevalence of PEs and DCC is largely observed during November-March (>= 60% frequency), whereas the longest persistence of dry days is observed during June-August. Though all PE trends point to an intensification of rainfall in November-March, only consecutive dry days in winter (JJA) and spring (SON) show significant trends, pointing to an increase of 7 days over the 38-yr winters. Rainfall extremes over the entire Amazon region were found to be moderate to strongly correlated with the mean vertically integrated moisture divergence, and in southern Amazon also to upper level divergence and upward vertical velocity. Increased frequency of DCC were found over the whole basin (similar to 18% yr(-1)), in contrast to decreased convective overshooting (up to similar to 15.4% yr(-1)).
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Genthon, C., Veron, D., Vignon, E., Six, D., Dufresne, J., Madeleine, J., et al. (2021). 10 years of temperature and wind observation on a 45 m tower at Dome C, East Antarctic plateau. Earth System Science Data, 13(12), 5731–5746.
Abstract: Long-term, continuous in situ observations of the near-surface atmospheric boundary layer are critical for many weather and climate applications. Although there is a proliferation of surface stations globally, especially in and around populous areas, there are notably fewer tall meteorological towers with multiple instrumented levels. This is particularly true in remote and extreme environments such as the East Antarctic plateau. In the article, we present and analyze 10 years of data from six levels of meteorological instrumentation mounted on a 42m tower located at Dome C, East Antarctica, near the Concordia research station, producing a unique climatology of the near-surface atmospheric environment (Genthon et al., 2021a, b). Monthly temperature and wind data demonstrate the large seasonal differences in the near-surface boundary layer dynamics, depending on the presence or absence of solar surface forcing. Strong vertical temperature gradients (inversions) frequently develop in calm, winter conditions, while vertical convective mixing occurs in the summer, leading to nearuniform temperatures along the tower. Seasonal variation in wind speed is much less notable at this location than the temperature variation as the winds are less influenced by the solar cycle; there are no katabatic winds as Dome C is quite flat. Harmonic analysis confirms that most of the energy in the power spectrum is at diurnal, annual and semi-annual timescales. Analysis of observational uncertainty and comparison to reanalysis data from the latest generation of ECMWF (European Centre for Medium-Range Weather Forecasts) reanalyses (ERA5) indicate that wind speed is particularly difficult to measure at this location. Data are distributed on the PANGAEA data repository at https://doi.org/10.1594/PANGAEA.932512 (Genthon et al., 2021a) and https://doi.org/10.1594/PANGAEA.932513 (Genthon et al., 2021b).
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Georges, D., Saletti, D., Montagnat, M., Forquin, P., & Hagenmuller, P. (2021). Influence of Porosity on Ice Dynamic Tensile Behavior as Assessed by Spalling Tests. Journal Of Dynamic Behavior Of Materials, .
Abstract: The impact of ice on structures is a strong concern, in particular for aeronautical or space crafts that are strongly damaged by the impact of atmospheric ice, and more specifically by hailstones during hailstorms. During the impact, the hailstone is submitted to a complex loading including a strong dynamic tensile component that is responsible for its fragmentation and influences the mechanical loading transmitted to the impacted structure. However, up to now, very limited work were conducted on the tensile strength of ice under dynamic loading and the microstructure influence was out the scope of most studies. In particular the presence of porosity in ice as observed in hailstones is thought to significantly affect the ice mechanical response. The aim of this paper is to investigate the role of porosity on the tensile behavior of polycrystalline ice at high strain rates. To do so, spalling tests with a Hopkinson bar apparatus were conducted on microstructures characterized by porosities with two different pore size distributions. The dynamic tensile strength was computed by the use of the so-called Novikov formula and several indicators were used to assess the quality of each test. A whole set of high porosity samples was tested and additional tests were performed on low porosity ice, expanding the existing results in the literature. The fragmentation processes occuring during the spalling tests were observed by means of an ultra high speed camera and the influence of porosity on the main fracture planes was investigated by analysing post-spalling samples with an automatic ice texture analyser and X-ray tomography. Tensile strength is shown to increase with strain rate over the range 24 s(-1) to 120 s(-1) and to decrease with increasing porosity. The presence of large porosities in the high porosity samples appear to contribute preferentially to this strength decrease. Relevant observations concerning the detected cracks, the tortuosity of crack paths and the presence of porosities on the crack surfaces seem to validate the hypothesis of porosities playing a key role for crack initiation and propagation during ice fragmentation.
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Giese, A., Arcone, S., Hawley, R., Lewis, G., & Wagnon, P. (2021). Detecting supraglacial debris thickness with GPR under suboptimal conditions. Journal Of Glaciology, 67(266), 1108–1120.
Abstract: The thickness of a supraglacial layer is critical to the magnitude and time frame of glacier melt. Field-based, short pulse, ground-penetrating radar (GPR) has successfully measured debris thickness during a glacier's melt season, when there is a strong return from the ice-debris interface, but profiling with GPR in the absence of a highly reflective ice interface has not been explored. We investigated the performance of 960 MHz signals over 2 km of transects on Changri Nup Glacier, Nepal, during the post-monsoon. We also performed laboratory experiments to interpret the field data and investigate electromagnetic wave propagation into dry rocky debris. Laboratory tests confirmed wave penetration into the glacier ice and suggest that the ice-debris interface return was missing in field data because of a weak dielectric contrast between solid ice and porous dry debris. We developed a new method to estimate debris thicknesses by applying a statistical approach to volumetric backscatter, and our backscatter-based calculated thickness retrievals gave reasonable agreement with debris depths measured manually in the field (10-40 cm). We conclude that, when melt season profiling is not an option, a remote system near 1 GHz could allow dry debris thickness to be estimated based on volumetric backscatter.
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Gimbert, F., Gilbert, A., Gagliardini, O., Vincent, C., & Moreau, L. (2021). Do Existing Theories Explain Seasonal to Multi-Decadal Changes in Glacier Basal Sliding Speed? Geophysical Research Letters, 48(15).
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Gimbert, F., Nanni, U., Roux, P., Helmstetter, A., Garambois, S., Lecointre, A., et al. (2021). A Multi-Physics Experiment with a Temporary Dense Seismic Array on the Argentiere Glacier, French Alps: The RESOLVE Project. Seismological Research Letters, 92(2), 1185–1201.
Abstract: Recent work in the field of cryo-seismology demonstrates that high-frequency (> 1 Hz) seismic waves provide key constraints on a wide range of glacier processes, such as basal friction, surface crevassing, or subglacial water flow. Establishing quantitative links between the seismic signal and the processes of interest, however, requires detailed characterization of the wavefield, which, at high frequencies, necessitates the deployment of large and dense seismic arrays. Although dense seismic array monitoring has recently become increasingly common in geophysics, its application to glaciated environments remains limited. Here, we present a dense seismic array experiment made of 98 three-component seismic stations continuously recording during 35 days in early spring 2018 on the Argentiere Glacier, French Alps. The seismic dataset is supplemented with a wide range of complementary observations obtained from ground-penetrating radar, drone imagery, Global Navigation Satellite Systems positioning, and in situ measurements of basal glacier sliding velocities and subglacial water discharge. We present first results through conducting spectral analysis, template matching, matched-field processing, and eikonal-wave tomography. We report enhanced spatial resolution on basal stick slip and englacial fracturing sources as well as novel constraints on the heterogeneous nature of the noise field generated by subglacial water flow and on the link between crevasse properties and englacial seismic velocities. We outline in which ways further work using this dataset could help tackle key remaining questions in the field.
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Gkinis, V., Vinther, B., Popp, T., Quistgaard, T., Faber, A., Holme, C., et al. (2021). A 120,000-year long climate record from a NW-Greenland deep ice core at ultra-high resolution. Scientific Data, 8(1).
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Gliss, J., Mortier, A., Schulz, M., Andrews, E., Balkanski, Y., Bauer, S., et al. (2021). AeroCom phase III multi-model evaluation of the aerosol life cycle and optical properties using ground- and space-based remote sensing as well as surface in situ observations. Atmospheric Chemistry And Physics, 21(1), 87–128.
Abstract: Within the framework of the AeroCom (Aerosol Comparisons between Observations and Models) initiative, the state-of-the-art modelling of aerosol optical properties is assessed from 14 global models participating in the phase III control experiment (AP3). The models are similar to CMIP6/AerChemMIP Earth System Models (ESMs) and provide a robust multi-model ensemble. Inter-model spread of aerosol species lifetimes and emissions appears to be similar to that of mass extinction coefficients (MECs), suggesting that aerosol optical depth (AOD) uncertainties are associated with a broad spectrum of parameterised aerosol processes. Total AOD is approximately the same as in AeroCom phase I (AP1) simulations. However, we find a 50% decrease in the optical depth (OD) of black carbon (BC), attributable to a combination of decreased emissions and lifetimes. Relative contributions from sea salt (SS) and dust (DU) have shifted from being approximately equal in AP1 to SS contributing about 2/3 of the natural AOD in AP3. This shift is linked with a decrease in DU mass burden, a lower DU MEC, and a slight decrease in DU lifetime, suggesting coarser DU particle sizes in AP3 compared to AP1. Relative to observations, the AP3 ensemble median and most of the participating models underestimate all aerosol optical properties investigated, that is, total AOD as well as fine and coarse AOD (AOD(f), AOD(c)), Angstrom exponent (AE), dry surface scattering (SCdry), and absorption (AC(dry)) coefficients. Compared to AERONET, the models underestimate total AOD by ca. 21% +/- 20% (as inferred from the ensemble median and interquartile range). Against satellite data, the ensemble AOD biases range from -37% (MODIS-Terra) to -16% (MERGED-FMI, a multi-satellite AOD product), which we explain by differences between individual satellites and AERONET measurements themselves. Correlation coefficients (R) between model and observation AOD records are generally high (R > 0.75), suggesting that the models are capable of capturing spatiotemporal variations in AOD. We find a much larger underestimate in coarse AOD(c) (similar to-45% +/- 25 %) than in fine AOD(f) (similar to-15% +/- 25 %) with slightly increased inter-model spread compared to total AOD. These results indicate problems in the modelling of DU and SS. The AOD(c) bias is likely due to missing DU over continental land masses (particularly over the United States, SE Asia, and S. America), while marine AERONET sites and the AATSR SU satellite data suggest more moderate oceanic biases in AOD(c). Column AEs are underestimated by about 10% +/- 16 %. For situations in which measurements show AE > 2, models underestimate AERONET AE by ca. 35 %. In contrast, all models (but one) exhibit large overestimates in AE when coarse aerosol dominates (bias ca. +140% if observed AE < 0.5). Simulated AE does not span the observed AE variability. These results indicate that models overestimate particle size (or underestimate the fine-mode fraction) for fine-dominated aerosol and underestimate size (or overestimate the fine-mode fraction) for coarse-dominated aerosol. This must have implications for lifetime, water uptake, scattering enhancement, and the aerosol radiative effect, which we can not quantify at this moment. Comparison against Global Atmosphere Watch (GAW) in situ data results in mean bias and inter-model variations of -35% +/- 25% and -20% +/- 18% for SCdry and AC(dry), respectively. The larger underestimate of SCdry than AC(dry) suggests the models will simulate an aerosol single scattering albedo that is too low. The larger underestimate of SCdry than ambient air AOD is consistent with recent findings that models overestimate scattering enhancement due to hygroscopic growth. The broadly consistent negative bias in AOD and surface scattering suggests an underestimate of aerosol radiative effects in current global aerosol models. Considerable inter-model diversity in the simulated optical properties is often found in regions that are, unfortunately, not or only sparsely covered by ground-based observations. This includes, for instance, the Sahara, Amazonia, central Australia, and the South Pacific. This highlights the need for a better site coverage in the observations, which would enable us to better assess the models, but also the performance of satellite products in these regions. Using fine-mode AOD as a proxy for present-day aerosol forcing estimates, our results suggest that models underestimate aerosol forcing by ca. -15 %, however, with a considerably large interquartile range, suggesting a spread between -35% and +10 %.
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Goni, I., Taylor, R., Favreau, G., Shamsudduha, M., Nazoumou, Y., & Ngatcha, B. (2021). Groundwater recharge from heavy rainfall in the southwestern Lake Chad Basin: evidence from isotopic observations. Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, 66(8), 1359–1371.
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Gonzalez, J., Comte, J., Legchenko, A., Ofterdinger, U., & Healy, D. (2021). Quantification of groundwater storage heterogeneity in weathered/fractured basement rock aquifers using electrical resistivity tomography: Sensitivity and uncertainty associated with petrophysical modelling. Journal Of Hydrology, 593.
Abstract: Quantifying groundwater storage in weathered/fractured basement rock aquifers can be challenging owing to both their high degree of heterogeneity and their overall low storage capacity. Therefore, in these aquifers, the use of direct borehole hydraulic data is usually insufficient. Here we assessed the popular method of electrical resistivity tomography (ERT), combined with borehole data and including associated uncertainties, to resolve the spatial variability of groundwater storage properties at high resolution within a fractured mica schist aquifer in Ireland. Porosity distributions across both the saturated and unsaturated zones were calculated from two-dimensional (2D) ERT resistivities using two standard petrophysical models, Archie and Waxman & Smits (WS), the latter accounting for the influence of clay minerals on resistivity data. Our results demonstrated the importance of the hydrogeological conceptual constraints provided by ERT when parametrizing the 2D petrophysical models from borehole point data. They also confirmed the importance of accounting for clay minerals (the products of bedrock weathering processes) in the WS model, whereas predictions from Archie's model produced unrealistically high porosity values of over an order of magnitude higher than the WS model. The WS model predicted porosities decreasing exponentially with depth, with values ranging from a few % in the shallowest, most-weathered part of the bedrock (upper 5 m on average) and deep fractured zones (to about 20 m deep), to <1% in the underlying fissured aquifer, and possibly down another order of magnitude in the deep massive bedrock. WS-derived porosities were in agreement with independent vertical water content profiles derived from magnetic resonance sounding (MRS), as well as point storativity values estimated from borehole hydraulic testing at the study site, with particularly good matches in the upper weathered/fractured bedrock and deeply weathered/fractured zones associated with regional faults. Detailed comparison suggested that WS provides an upper-bound estimate of groundwater storage in this environment. In the deep massive, un-weathered, and poorly fractured bedrock, however, discrepancies between groundwater storage estimate obtained from the three methods (ERT, MRS, and hydraulic) prevented reliable storage quantification, owing to the methods' inherent technical limitations in such low porosity rocks. Our results demonstrated the suitability of resistivity tomography to quantify groundwater storage heterogeneity in weathered/fractured basement rock aquifers at high resolution and with reasonable overall uncertainty given the relative high uncertainties in petrophysical parameters at the kilometric scale. The results are promising for better characterization of groundwater storage variations in these hydrogeological systems, which are crucial to predict their response to climate variability and human exploitation.
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Grange, S., Fischer, A., Zellweger, C., Alastuey, A., Querol, X., Jaffrezo, J., et al. (2021). Switzerland's PM10 and PM2.5 environmental increments show the importance of non-exhaust emissions. Atmospheric Environment-X, 12.
Abstract: Atmospheric particulate matter (PM) is a priority pollutant for urban air pollution management because of its negative effects on human health and visibility. Emissions from road traffic have been a major focus of management over the past few decades, but non-exhaust emissions i.e., emissions from brake, tyre, road wear, and the resuspension of dust have emerged to become a major source of unregulated PM in many locations. Here, a filter-based sampling campaign was conducted between 2018 and 2019 where a large number of PM constituents were quantified for five sites in Switzerland for both PM10 and PM2.5. This had the objective of investigating urban and urban-traffic PM increments in Switzerland. The results show that PM concentrations increased as the sampling locations moved along a rural to urban-traffic gradient. However, source apportionment analysis showed that sulfate-rich, nitrate-rich, and biogenic sources were not enhanced in urban environments, but road traffic and mineral dust sources were. The total mass enhancement for PM10 and PM 2.5 were 2.4 μg m(-3) and 2.0 μg m(-3) for the urban environment while the corresponding urban-traffic enhancements were 5.7 μg m(-3) and 2.8 μg m(-3). Emissions from road traffic were estimated to contribute more than 75% to the urban increments and non-exhaust emissions contributed 48% (PM10) and 25% (PM2.5) to the total road traffic related increment at an urban background site and 62% (PM10) and 49% (PM2.5) at an urban-traffic site. Analysis of the composition of Switzerland's PM showed that elements associated with non-exhaust emissions, specifically the brake wear tracers of antimony, barium, copper, and iron were the metals with the greatest urban and urban-traffic enhancements. Critically, the urban increment of these elements was enhanced for both PM10 and PM2.5 by about the same magnitude as the urban-traffic increment (by 2-3 times), demonstrating non-exhaust emissions are encountered across urban areas, not just the urban-traffic environment. Therefore, non-exhaust emissions were an important contributor to the urban and urban-traffic PM10 and PM2.5 increments in Switzerland's urban areas. The relative contributions of non-exhaust emissions to the urban and urban-traffic increments could be expected to increase due to the introduction of further exhaust after-treatment technologies (such as gasoline particulate filters; GPFs) and the transition to a more electrified vehicle fleet. A management pivot will be required to control these non-exhaust emission pathways and although this work exclusively uses data from Switzerland, the conclusions are likely relevant to many other European urban areas.
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Grosinger, J., Vallet, A., Palomo, I., Buclet, N., & Lavorel, S. (2021). Collective capabilities shape the co-production of nature's contributions to people in the alpine agricultural system of the Maurienne valley, France. Regional Environmental Change, 21(4).
Abstract: Nature's contributions to people (NCP) do not flow automatically from ecosystems to society, but they result from a co-production process of interactions between societal and ecological systems. In this study, we used the collective capabilities approach to address the social dimensions of co-production of the material NCP of cheese. These are the benefits collective structures retrieve from social-ecological interactions that individuals could not have achieved on their own and which frequently exceed pure instrumental values. Collective structures mobilise different types of social capitals in order to generate these collective capabilities. Here, we specifically investigated linkages between collective capabilities and their contributions to common perceptions and local identities. We conducted 44 semi-structured interviews with two distinct different actors' groups in a French Alpine agricultural system surrounding the production of the quality labelled Beaufort cow cheese. We analysed the interviews qualitatively and conducted quantitative analyses as well as content and sentiment analysis to identify the different levels and types of collective investment mobilised by actors to generate collective capabilities. We found that collective capabilities involved in NCP co-production contributed to common perceptions and to specific dimensions of local identities. These can be viewed as the results of relational value construction. Further, the analysis suggests that collective capability relies on dense social interactions between actors that contribute to a good quality of life in itself. This study advances previous attempts to further investigate the role of intra-societal relations for NCP co-production.
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Gualco, L., Campozano, L., Maisincho, L., Robaina, L., Munoz, L., Ruiz-Hernandez, J., et al. (2021). Corrections of Precipitation Particle Size Distribution Measured by a Parsivel OTT2 Disdrometer under Windy Conditions in the Antisana Massif, Ecuador. Water, 13(18).
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Guillet, G., Preunkert, S., Ravanel, L., Montagnat, M., & Friedrich, R. (2021). Investigation of a cold-based ice apron on a high-mountain permafrost rock wall using ice texture analysis and micro-C-14 dating: a case study of the Triangle du Tacul ice apron (Mont Blanc massif, France). Journal Of Glaciology, 67(266), 1205–1212.
Abstract: The current paper studies the dynamics and age of the Triangle du Tacul (TDT) ice apron, a massive ice volume lying on a steep high-mountain rock wall in the French side of the Mont-Blanc massif at an altitude close to 3640 m a.s.l. Three 60 cm long ice cores were drilled to bedrock (i.e. the rock wall) in 2018 and 2019 at the TDT ice apron. Texture (microstructure and lattice-preferred orientation, LPO) analyses were performed on one core. The two remaining cores were used for radiocarbon dating of the particulate organic carbon fraction (three samples in total). Microstructure and LPO do not substantially vary with along the axis of the ice core. Throughout the core, irregularly shaped grains, associated with strain-induced grain boundary migration and strong single maximum LPO, were observed. Measurements indicate that at the TDT ice deforms under a low strain-rate simple shear regime, with a shear plane parallel to the surface slope of the ice apron. Dynamic recrystallization stands out as the major mechanism for grain growth. Micro-radiocarbon dating indicates that the TDT ice becomes older with depth perpendicular to the ice surface. We observed ice ages older than 600 year BP and at the base of the lowest 30 cm older than 3000 years.
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Guillou, F., Metref, S., Cosme, E., Ubelmann, C., Ballarotta, M., Sommer, J., et al. (2021). Mapping Altimetry in the Forthcoming SWOT Era by Back-and-Forth Nudging a One-Layer Quasigeostrophic Model. Journal Of Atmospheric And Oceanic Technology, 38(4), 697–710.
Abstract: During the past 25 years, altimetric observations of the ocean surface from space have been mapped to provide two dimensional sea surface height (SSH) fields that are crucial for scientific research and operational applications. The SSH fields can be reconstructed from conventional altimetric data using temporal and spatial interpolation. For instance, the standard Developing Use of Altimetry for Climate Studies (DUACS) products are created with an optimal interpolation method that is effective for both low temporal and low spatial resolution. However, the upcoming next-generation SWOT mission will provide very high spatial resolution but with low temporal resolution. The present paper makes the case that this temporal-spatial discrepancy induces the need for new advanced mapping techniques involving information on the ocean dynamics. An algorithm is introduced, dubbed the BFN-QG, that uses a simple data assimilation method, the back-and-forth nudging (BNF), to interpolate altimetric data while respecting quasigeostrophic (QG) dynamics. The BFN-QG is tested in an observing system simulation experiments and compared to the DUACS products. The experiments consider as reference the high-resolution numerical model simulation NATL60 from which are produced realistic data: four conventional altimetric nadirs and SWOT data. In a combined nadirs and SWOT scenario, the BFN-QG substantially improves the mapping by reducing the root-mean-square errors and increasing the spectral effective resolution by 40 km. Also, the BFN-QG method can be adapted to combine large-scale corrections from nadir data and small-scale corrections from SWOT data so as to reduce the impact of SWOT correlated noises and still provide accurate SSH maps.
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Gutierrez, S., Segura Cajachagua, H., Huanca, M., Rojas, J., Vidal, Y., & Cuxart, J. (2021). Seasonal variability of daily evapotranspiration and energy fluxes in the Central Andes of Peru using eddy covariance techniques and empirical methods. Atmospheric Research, 261.
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Gutierrez-Cori, O., Espinoza, J., Li, L., Wongchuig, S., Arias, P., Ronchail, J., et al. (2021). On the Hydroclimate-Vegetation Relationship in the Southwestern Amazon During the 2000-2019 Period. Frontiers In Water, 3.
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Haalck, I., Loffler, P., Baduel, C., Wiberg, K., Ahrens, L., & Lai, F. (2021). Mining chemical information in Swedish wastewaters for simultaneous assessment of population consumption, treatment efficiency and environmental discharge of illicit drugs. Scientific Reports, 11(1).
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Haq, M., Azam, M., & Vincent, C. (2021). Efficiency of artificial neural networks for glacier ice-thickness estimation: a case study in western Himalaya, India. Journal Of Glaciology, 67(264), 671–684.
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Hattori, S., Iizuka, Y., Alexander, B., Ishino, S., Fujita, K., Zhai, S., et al. (2021). Isotopic evidence for acidity-driven enhancement of sulfate formation after SO2 emission control. Science Advances, 7(19).
Abstract: After the 1980s, atmospheric sulfate reduction is slower than the dramatic reductions in sulfur dioxide (SO2) emissions. However, a lack of observational evidence has hindered the identification of causal feedback mechanisms. Here, we report an increase in the oxygen isotopic composition of sulfate (Delta O-17(SO4)2-) in a Greenland ice core, implying an enhanced role of acidity-dependent in-cloud oxidation by ozone (up to 17 to 27%) in sulfate production since the 1960s. A global chemical transport model reproduces the magnitude of the increase in observed Delta O-17(SO4)2- with a 10 to 15% enhancement in the conversion efficiency from SO2 to sulfate in Eastern North America and Western Europe. With an expected continued decrease in atmospheric acidity, this feedback will continue in the future and partially hinder air quality improvements.
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Herzog, A., Hector, B., Cohard, J., Vouillamoz, J., Lawson, F., Peugeot, C., et al. (2021). A parametric sensitivity analysis for prioritizing regolith knowledge needs for modeling water transfers in the West African critical zone. Vadose Zone Journal, 20(6).
Abstract: Hard rock aquifers (HRAs) in West Africa (WA) are located within a thick regolith layer. The representation of thick tropical regolith in integrated hydrological models lacks consensus on aquifer geometries and parameter ranges. Our main objective was to determine the knowledge requirements on saturated hydraulic conductivity (K-s) to model the critical zone (CZ) of HRAs in WA. A parametric sensitivity analysis with a focus on the representation of the K-s heterogeneity of the regolith was conducted with a critical zone model (Parflow-CLM [Community Land Model]) of the Upper Oueme catchment in Benin (14,000 km(2)) at a 1- x 1-km(2) resolution. The impact of parameter changes in the near subsurface (0.3-to-5-m depth) and in the deeper regolith aquifer (24- and 48-m maximum depth) was assessed in five modeling experiments. Streamflow was largely dependent on K-s and on clay distribution in the near subsurface and less on the properties of the deeper subsurface. Groundwater table depths and amplitudes were controlled by vegetation and topography as observed on instrumented hillslopes and for K-s within the literature range. Experiments with higher K-s suggested a K-s threshold where dynamics become less determined by one-dimensional vertical and more determined by lateral processes. Such heterogeneity impacts from smaller scales need to be accounted for when hydrological models are upscaled to larger domains (1- x 1-km(2) resolution or coarser). Our findings highlight the need for a new conceptual approach to represent clay distribution in order to develop catchment-scale CZ models of HRAs in WA that capture the observed processes.
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Hippert-Ferrer, A., Yan, Y., Bolon, P., & Millan, R. (2021). Spatiotemporal Filling of Missing Data in Remotely Sensed Displacement Measurement Time Series. Ieee Geoscience And Remote Sensing Letters, 18(12), 2157–2161.
Abstract: Missing data is a critical pitfall in the investigation of remotely sensed displacement measurement because it prevents from a full understanding of the physical phenomenon under observation. In the sight of reconstructing incomplete displacement data, this letter presents a data-driven spatiotemporal gap-filling method, which is an extension of the expectation-maximization-empirical orthogonal function (EM-EOF) method. The presented method decomposes an augmented spatiotemporal covariance of a displacement time series into EOF modes and then selects the optimal set of EOF modes to reconstruct the time series. This selection is based on the cross-validation root-mean-square error and a confidence index associated with each eigenvalue. The estimated missing values are then iteratively updated until convergence. Results on displacement time series derived from cross correlation of Sentinel-2 optical images over Fox Glacier in New-Zealand's Alps show that the reconstruction accuracy is improved compared with the EM-EOF method. The proposed extension can tackle challenging cases, i.e., short time series with heterogeneous displacement behaviors corrupted by a large amount of missing data and noise.
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Hofer, S., Amory, C., Kittel, C., Carlsen, T., Le Toumelin, L., & Storelvmo, T. (2021). The Contribution of Drifting Snow to Cloud Properties and the Atmospheric Radiative Budget Over Antarctica. Geophysical Research Letters, 48(22).
Abstract: The Antarctic Ice Sheet experiences perpetual katabatic winds, transporting snow, and moisture from the interior towards the periphery. However, the impacts of Antarctic moisture and drifting snow on cloud structure and surface energy fluxes have not been widely investigated. Here, we use a regional climate model with a newly developed drifting snow scheme to show that accounting for drifting snow notably alters the spatial distribution, vertical structure and radiative effect of clouds over Antarctica. Overall, we find that accounting for drifting snow leads to a greater cloud cover providing an increase of +2.74 Wm(-2) in the surface radiative energy budget. Additionally, a comparison with 20 weather stations reveals a 2.17 Wm(-2) improvement in representing the radiative energy fluxes. Our results highlight the need to study the impact of drifting snow processes on the future evolution of clouds, the surface energy budget and the vertical atmospheric structure over Antarctica.
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Hugoni, M., Nunan, N., Thioulouse, J., Dubost, A., Abrouk, D., Martins, J., et al. (2021). Small-Scale Variability in Bacterial Community Structure in Different Soil Types. Microbial Ecology, .
Abstract: Microbial spatial distribution has mostly been studied at field to global scales (i.e., ecosystem scales). However, the spatial organization at small scales (i.e., centimeter to millimeter scales), which can help improve our understanding of the impacts of spatial communities structure on microbial functioning, has received comparatively little attention. Previous work has shown that small-scale spatial structure exists in soil microbial communities, but these studies have not compared soils from geographically distant locations, nor have they utilized community ecology approaches, such as the core and satellite hypothesis and/or abundance-occupancy relationships, often used in macro-ecology, to improve the description of the spatial organization of communities. In the present work, we focused on bacterial diversity (i.e., 16S rRNA gene sequencing) occurring in micro-samples from a variety of locations with different pedo-climatic histories (i.e., from semi-arid, alpine, and temperate climates) and physicochemical properties. The forms of ecological spatial relationships in bacterial communities (i.e., occupancy-frequency and abundance-occupancy) and taxa distributions (i.e., habitat generalists and specialists) were investigated. The results showed that bacterial composition differed in the four soils at the small scale. Moreover, one soil presented a satellite mode distribution, whereas the three others presented bimodal distributions. Interestingly, numerous core taxa were present in the four soils among which 8 OTUs were common to the four sites. These results confirm that analyses of the small-scale spatial distribution are necessary to understand consequent functional processes taking place in soils, affecting thus ecosystem functioning.
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Hugonnet, R., Mcnabb, R., Berthier, E., Menounos, B., Nuth, C., Girod, L., et al. (2021). Accelerated global glacier mass loss in the early twenty-first century. Nature, 592(7856), 726–+.
Abstract: Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology(1), raising global sea level(2) and elevating natural hazards(3). Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork(4,5). Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000-2019, glaciers lost a mass of 267 +/- 16 gigatonnes per year, equivalent to 21 +/- 3 per cent of the observed sea-level rise(6). We identify a mass loss acceleration of 48 +/- 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately(7-9). By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain(10). We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise. Analysis of satellite stereo imagery uncovers two decades of mass change for all of Earth's glaciers, revealing accelerated glacier shrinkage and regionally contrasting changes consistent with decadal climate variability.
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Huot, P., Fichefet, T., Jourdain, N., Mathiot, P., Rousset, C., Kittel, C., et al. (2021). Influence of ocean tides and ice shelves on ocean & ndash;ice interactions and dense shelf water formation in the D & rsquo;Urville Sea, Antarctica. Ocean Modelling, 162.
Abstract: The D'Urville Sea, East Antarctica, is a major source of Dense Shelf Water (DSW), a precursor of Antarctic Bottom Water (AABW). AABW is a key water mass involved in the worldwide ocean circulation and long-term climate variability. The properties of AABW in global climate models suffer from several biases, making climate projections uncertain. These models are potentially omitting or misrepresenting important mechanisms involved in the formation of DSW, such as tides and ocean-ice shelf interactions. Recent studies pointed out that tides and ice shelves significantly influence the coastal seas of Antarctica, where AABW originates from. Yet, the implications of these two processes in the formation and evolution of DSW are poorly understood, in particular in the D'Urville Sea. Using a series of NEMO-LIM numerical simulations, we assess the sensitivity of dense water formation in the D'Urville Sea to the representation of tides and ocean-ice shelf interactions during the years 2010-2015. We show that the ice shelves off Adelie Land are highly sensitive to tidal forcing, with a significant basal melt increase in the presence of tides. Ice shelf basal melt freshens and cools the ocean over significant portions of the coastal seas at the depth of the ice shelf draft. An opposite warming and increase in salinity are found in the upper layers. The influence of ice shelf basal melt on the ocean is largely increased in the presence of tides. However, the production of sea ice is found to be mostly unaffected by these two processes. Water mass transport out of polynyas and ice shelf cavities are then investigated, together with their sensitivity to tides and ocean-ice shelf interactions. Ice shelf basal melt impacts the volume of dense waters in two ways: (1) Dense Shelf Water and Modified Shelf Water are consumed to form water masses of intermediate density inside the ice shelf cavities, and (2) the freshening of the ocean subsurface makes its transformation into dense water by sea ice formation more difficult. These results suggest that ice shelf basal melt variability can explain part of the observed changes of dense water properties, and may also affect the production of dense water in a future climate.
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Huot, P., Kittel, C., Fichefet, T., Jourdain, N., Sterlin, J., & Fettweis, X. (2021). Effects of the atmospheric forcing resolution on simulated sea ice and polynyas off Adelie Land, East Antarctica. Ocean Modelling, 168.
Abstract: Coastal polynyas of the Southern Ocean play a central role in the ventilation of the deep ocean and affect the stability of ice shelves. It appears crucial to incorporate them into climate models, but it is unclear how to adequately simulate them. In particular, there is no consensus on the atmospheric forcing resolution needed to appropriately model the sea ice in coastal Antarctica. A high resolution might be required to represent the local winds such as katabatic winds which are key drivers of coastal polynyas. To fill in this gap, we have tested the sensitivity of sea ice and air-sea-ice interactions to the resolution of the atmospheric forcing in a high-resolution ocean-sea ice model. A set of regional atmospheric simulations at horizontal resolutions of 20, 10, and 5 km are performed with an atmospheric regional model and used to force three ocean-sea ice simulations in the Adelie Land sector, East Antarctica. Due to the better representation of topography with a refined grid, the offshore component of coastal winds becomes stronger at increased resolution. The wind intensification is particularly strong down valleys channelizing the katabatic flow, with increase in wind speed ranging between 1 and 3 m/s. Under a higher resolution forcing, polynyas open more frequently and are wider. This fosters the growth rate of sea ice in polynyas, while landfast ice and pack ice are weakly affected. In polynyas, the production of sea ice is increased by up to 30% at 5 km resolution compared to 20 km resolution. Polynyas downstream of the katabatic wind pathway are more affected than the ones driven by easterly winds, highlighting the importance of the local wind conditions. Brine rejection associated with these higher sea ice production rates affects the salinity budget of the ocean and enhances both the volume and density of the dense Shelf Water produced off Adelie Land. These results underpin the need to better account for local coastal winds and polynyas in ocean and climate models.
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Ishino, S., Hattori, S., Legrand, M., Chen, Q., Alexander, B., Shao, J., et al. (2021). Regional Characteristics of Atmospheric Sulfate Formation in East Antarctica Imprinted on O-17-Excess Signature. Journal Of Geophysical Research-Atmospheres, 126(6).
Abstract: O-17-excess (Delta O-17 = delta O-17 – 0.52 x delta O-18) of sulfate trapped in Antarctic ice cores has been proposed as a potential tool for assessing past oxidant chemistry, while insufficient understanding of atmospheric sulfate formation around Antarctica hampers its interpretation. To probe influences of regional specific chemistry, we compared year-round observations of Delta O-17 of non-sea-salt sulfate in aerosols (Delta O-17(SO42-)(nss)) at Dome C and Dumont d'Urville, inland and coastal sites in East Antarctica, throughout the year 2011. Although Delta O-17(SO42-)(nss) at both sites showed consistent seasonality with summer minima (similar to 1.0 parts per thousand) and winter maxima (similar to 2.5 parts per thousand) owing to sunlight-driven changes in the relative importance of O-3 oxidation to OH and H2O2 oxidation, significant intersite differences were observed in austral spring-summer and autumn. The cooccurrence of higher Delta O-17(SO42-)(nss) at inland (2.0 parts per thousand +/- 0.1 parts per thousand) than the coastal site (1.2 parts per thousand +/- 0.1 parts per thousand) and chemical destruction of methanesulfonate (MS-) in aerosols at inland during spring-summer (October-December), combined with the first estimated Delta O-17(MS-) of similar to 16 parts per thousand, implies that MS- destruction produces sulfate with high Delta O-17(SO42-)(nss) of similar to 12 parts per thousand. If contributing to the known postdepositional decrease of MS- in snow, this process should also cause a significant postdepositional increase in Delta O-17(SO42-)(nss) over 1 parts per thousand, that can reconcile the discrepancy between Delta O-17(SO42-)(nss) in the atmosphere and ice. The higher Delta O-17(SO42-)(nss) at the coastal site than inland during autumn (March-May) may be associated with oxidation process involving reactive bromine and/or sea-salt particles around the coastal region.
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Jamet, Q., Deremble, B., Wienders, N., Uchida, T., & Dewar, W. (2021). On Wind-Driven Energetics of Subtropical Gyres. Journal Of Advances In Modeling Earth Systems, 13(4).
Abstract: The flow of energy in the wind-driven circulation is examined in a combined theoretical and numerical study. Based on a multiple-scale analysis, we find the mesoscale field in the ocean interior is strongly affected by, but does not feed back onto, the ventilated thermocline. In the western boundary region, the associated currents first appear as coastal jets, conserving mean energy, and later as separated jet extensions where the mesoscale is energized by the mean field. It is in the separated jet zone where the primary loss of general circulation energy to the mesoscale occurs. These ideas are tested by an analysis of a regional 1/12 degrees primitive equation numerical model of the North Atlantic. The predictions of the theory are generally supported by the numerical results. The one exception is that topographic irregularities in the coastal jet spawn eddies, although these eddies contribute modestly to the energy budget. We therefore conclude the primary sink of wind input into the mean circulation is in the separated jet, and not the interior. The analysis also shows wind energy input to be much smaller than the interior energy fluxes; thus, the general circulation largely recirculates energy.
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Jiang, Z., Alexander, B., Savarino, J., Erbland, J., & Geng, L. (2021). Impacts of the photo-driven post-depositional processing on snow nitrate and its isotopes at Summit, Greenland: a model-based study. Cryosphere, 15(9), 4207–4220.
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Kaab, A., Jacquemart, M., Gilbert, A., Leinss, S., Girod, L., Huggel, C., et al. (2021). Sudden large-volume detachments of low-angle mountain glaciers more frequent than thought? Cryosphere, 15(4), 1751–1785.
Abstract: The detachment of large parts of low-angle mountain glaciers resulting in massive ice-rock avalanches have so far been believed to be a unique type of event, made known to the global scientific community first for the 2002 Kolka Glacier detachment, Caucasus Mountains, and then for the 2016 collapses of two glaciers in the Aru range, Tibet. Since 2016, several so-far unrecognized low-angle glacier detachments have been recognized and described, and new ones have occurred. In the current contribution, we compile, compare, and discuss 20 actual or suspected large-volume detachments of low-angle mountain glaciers at 10 different sites in the Caucasus, the Pamirs, Tibet, Altai, the North American Cordillera, and the Southern Andes. Many of the detachments reached volumes in the order of 10-100 millionm(3). The similarities and differences between the presented cases indicate that glacier detachments often involve a coincidental combination of factors related to the lowering of basal friction, high or increasing driving stresses, concentration of shear stress, or low resistance to exceed stability thresholds. Particularly soft glacier beds seem to be a common condition among the observed events as they offer smooth contact areas between the glacier and the underlying substrate and are prone to till-strength weakening and eventually basal failure under high pore-water pressure. Partially or fully thawed glacier bed conditions and the presence of liquid water could thus play an important role in the detachments. Surface slopes of the detached glaciers range between around 10 degrees and 20 degrees. This may be low enough to enable the development of thick and thus large-volume glaciers while also being steep enough to allow critical driving stresses to build up. We construct a simple slab model to estimate ranges of glacier slope and width above which a glacier may be able to detach when extensively losing basal resistance. From this model we estimate that all the detachments described in this study occurred due to a basal shear stress reduction of more than 50 %. Most of the ice-rock avalanches resulting from the detachments in this study have a particularly low angle of reach, down to around 5 degrees, likely due to their high ice content and connected liquefaction potential, the availability of soft basal slurries, and large amounts of basal water, as well as the smooth topographic setting typical for glacial valleys. Low-angle glacier detachments combine elements and likely also physical processes of glacier surges and ice break-offs from steep glaciers. The surge-like temporal evolution ahead of several detachments and their geographic proximity to other surge-type glaciers indicate the glacier detachments investigated can be interpreted as endmembers of the continuum of surge-like glacier instabilities. Though rare, glacier detachments appear to be more frequent than commonly thought and disclose, despite local differences in conditions and precursory evolutions, the fundamental and critical potential of low-angle soft glacier beds to fail catastrophically.
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Karlsson, N., Solgaard, A., Mankoff, K., Gillet-Chaulet, F., Macgregor, J., Box, J., et al. (2021). A first constraint on basal melt-water production of the Greenland ice sheet. Nature Communications, 12(1).
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Khadka, A., Matthews, T., Perry, L., Koch, I., Wagnon, P., Shrestha, D., et al. (2021). Weather on Mount Everest during the 2019 summer monsoon. Weather, .
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Khatri, H., Griffies, S., Uchida, T., Wang, H., & Menemenlis, D. (2021). Role of Mixed-Layer Instabilities in the Seasonal Evolution of Eddy Kinetic Energy Spectra in a Global Submesoscale Permitting Simulation. Geophysical Research Letters, 48(18).
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Khedim, N., Cecillon, L., Poulenard, J., Barre, P., Baudin, F., Marta, S., et al. (2021). Topsoil organic matter build-up in glacier forelands around the world. Global Change Biology, .
Abstract: Since the last glacial maximum, soil formation related to ice-cover shrinkage has been one major sink of carbon accumulating as soil organic matter (SOM), a phenomenon accelerated by the ongoing global warming. In recently deglacierized forelands, processes of SOM accumulation, including those that control carbon and nitrogen sequestration rates and biogeochemical stability of newly sequestered carbon, remain poorly understood. Here, we investigate the build-up of SOM during the initial stages (up to 410 years) of topsoil development in 10 glacier forelands distributed on four continents. We test whether the net accumulation of SOM on glacier forelands (i) depends on the time since deglacierization and local climatic conditions (temperature and precipitation); (ii) is accompanied by a decrease in its stability and (iii) is mostly due to an increasing contribution of organic matter from plant origin. We measured total SOM concentration (carbon, nitrogen), its relative hydrogen/oxygen enrichment, stable isotopic (C-13, N-15) and carbon functional groups (C-H, C=O, C=C) compositions, and its distribution in carbon pools of different thermal stability. We show that SOM content increases with time and is faster on forelands experiencing warmer climates. The build-up of SOM pools shows consistent trends across the studied soil chronosequences. During the first decades of soil development, the low amount of SOM is dominated by a thermally stable carbon pool with a small and highly thermolabile pool. The stability of SOM decreases with soil age at all sites, indicating that SOM storage is dominated by the accumulation of labile SOM during the first centuries of soil development, and suggesting plant carbon inputs to soil (SOM depleted in nitrogen, enriched in hydrogen and in aromatic carbon). Our findings highlight the potential vulnerability of SOM stocks from proglacial areas to decomposition and suggest that their durability largely depends on the relative contribution of carbon inputs from plants.
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Kittel, C., Amory, C., Agosta, C., Jourdain, N., Hofer, S., Delhasse, A., et al. (2021). Diverging future surface mass balance between the Antarctic ice shelves and grounded ice sheet. Cryosphere, 15(3), 1215–1236.
Abstract: The future surface mass balance (SMB) will influence the ice dynamics and the contribution of the Antarctic ice sheet (AIS) to the sea level rise. Most of recent Antarctic SMB projections were based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). However, new CMIP6 results have revealed a C1:3 degrees C higher mean Antarctic near-surface temperature than in CMIP5 at the end of the 21st century, enabling estimations of future SMB in warmer climates. Here, we investigate the AIS sensitivity to different warmings with an ensemble of four simulations performed with the polar regional climate model Modele Atmospherique Regional (MAR) forced by two CMIP5 and two CMIP6 models over 1981-2100. Statistical extrapolation enables us to expand our results to the whole CMIP5 and CMIP6 ensembles. Our results highlight a contrasting effect on the future grounded ice sheet and the ice shelves. The SMB over grounded ice is projected to increase as a response to stronger snowfall, only partly offset by enhanced meltwater run-off. This leads to a cumulated sealevel-rise mitigation (i.e. an increase in surface mass) of the grounded Antarctic surface by 5.1 +/- 1.9 cm sea level equivalent (SLE) in CMIP5-RCP8.5 (Relative Concentration Pathway 8.5) and 6.3 +/- 2.0 cm SLE in CMIP6-ssp585 (Shared Socioeconomic Pathways 585). Additionally, the CMIP6 low-emission ssp126 and intermediate-emission ssp245 scenarios project a stabilized surface mass gain, resulting in a lower mitigation to sea level rise than in ssp585. Over the ice shelves, the strong run-off increase associated with higher temperature is projected to decrease the SMB (more strongly in CMIP6-ssp585 compared to CMIP5-RCP8.5). Ice shelves are however predicted to have a close-to-present-equilibrium stable SMB under CMIP6 ssp126 and ssp245 scenarios. Future uncertainties are mainly due to the sensitivity to anthropogenic forcing and the timing of the projected warming. While ice shelves should remain at a close-to-equilibrium stable SMB under the Paris Agreement, MAR projects strong SMB decrease for an Antarctic near-surface warming above C2:5 degrees C compared to 1981-2010 mean temperature, limiting the warming range before potential irreversible damages on the ice shelves. Finally, our results reveal the existence of a potential threshold (C7:5 degrees C) that leads to a lower groundedSMB increase. This however has to be confirmed in following studies using more extreme or longer future scenarios.
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Klein, C., Jackson, L., Parker, D., Marsham, J., Taylor, C., Rowell, D., et al. (2021). Combining CMIP data with a regional convection-permitting model and observations to project extreme rainfall under climate change. Environmental Research Letters, 16(10).
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Kleinherenbrink, M., Korosov, A., Newman, T., Theodosiou, A., Komarov, A., Li, Y., et al. (2021). Estimating instantaneous sea-ice dynamics from space using the bi-static radar measurements of Earth Explorer 10 candidate Harmony. Cryosphere, 15(7), 3101–3118.
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Koenig, A., Magand, O., Laj, P., Andrade, M., Moreno, I., Velarde, F., et al. (2021). Seasonal patterns of atmospheric mercury in tropical South America as inferred by a continuous total gaseous mercury record at Chacaltaya station (5240 m) in Bolivia. Atmospheric Chemistry And Physics, 21(5), 3447–3472.
Abstract: High-quality atmospheric mercury (Hg) data are rare for South America, especially for its tropical region. As a consequence, mercury dynamics are still highly uncertain in this region. This is a significant deficiency, as South America appears to play a major role in the global budget of this toxic pollutant. To address this issue, we performed nearly 2 years (July 2014-February 2016) of continuous high-resolution total gaseous mercury (TGM) measurements at the Chacaltaya (CHC) mountain site in the Bolivian Andes, which is subject to a diverse mix of air masses coming predominantly from the Altiplano and the Amazon rainforest. For the first 11 months of measurements, we obtained a mean TGM concentration of 0 :89 +/- 0 :01 ngm(-3), which is in good agreement with the sparse amount of data available from the continent. For the remaining 9 months, we obtained a significantly higher TGM concentration of 1 :34 +/- 0 :01 ngm(-3), a difference which we tentatively attribute to the strong El Nino event of 2015-2016. Based on HYSPLIT (Hybrid SingleParticle Lagrangian Integrated Trajectory) back trajectories and clustering techniques, we show that lower mean TGM concentrations were linked to either westerly Altiplanic air masses or those originating from the lowlands to the southeast of CHC. Elevated TGM concentrations were related to northerly air masses of Amazonian or southerly air masses of Altiplanic origin, with the former possibly linked to artisanal and small-scale gold mining (ASGM), whereas the latter might be explained by volcanic activity. We observed a marked seasonal pattern, with low TGM concentrations in the dry season (austral winter), rising concentrations during the biomass burning (BB) season, and the highest concentrations at the beginning of the wet season (austral summer). With the help of simultaneously sampled equivalent black carbon (eBC) and carbon monoxide (CO) data, we use the clearly BB-influenced signal during the BB season (August to October) to derive a mean TGM = CO emission ratio of (2.3 +/- 0.6 x 10(-7) ppbvTGM ppbv (-1)(CO), which could be used to constrain South American BB emissions. Through the link with CO2 measured in situ and remotely sensed solarinduced fluorescence (SIF) as proxies for vegetation activity, we detect signs of a vegetation sink effect in Amazonian air
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Kokhanovsky, A., Gascoin, S., Arnaud, L., & Picard, G. (2021). Retrieval of Snow Albedo and Total Ozone Column from Single-View MSI/S-2 Spectral Reflectance Measurements over Antarctica. Remote Sensing, 13(21).
Abstract: We proposed a simple algorithm to retrieve the total ozone column and snow properties (spectral albedo and effective light absorption path) using the high spatial resolution single-view MSI/S-2 measurements over Antarctica. In addition, the algorithm allows the retrieval of the snow grain size on a scale of 10-20 m. This algorithm should be useful for the understanding of intra-pixel total ozone and snow albedo variability in complement to satellite observations performed on a much coarser spatial resolution scale (0.3-1 km and even larger spatial scales).
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Lagarde, S., Dietze, M., Gimbert, F., Laronne, J., Turowski, J., & Halfi, E. (2021). Grain-Size Distribution and Propagation Effects on Seismic Signals Generated by Bedload Transport. Water Resources Research, 57(4).
Abstract: Bedload transport is a key process in fluvial morphodynamics, but difficult to measure. The advent of seismic monitoring techniques has provided an alternative to in-stream monitoring, which is often costly and cannot be utilized during large floods. Seismic monitoring is a method requiring several steps to convert seismic data into bedload flux data. State-of-the-art conversion approaches exploit physical models predicting the seismic signal generated by bedload transport. However, due to a lack of well-constrained validation data, the accuracy of the resulting inversions is unknown. We use field experiments to constrain a seismic bedload model and compare the results to high-quality independent bedload measurements. Constraining the Green's function (i.e., seismic ground properties) with an active seismic survey resulted in an average absolute difference between modeled and empirically measured seismic bedload power of 11 dB in the relevant frequency band. Using generically estimated Green's function parameters resulted in a difference of 20 dB, thus highlighting the importance of using actual field parameters. Water turbulence and grain hiding are unlikely to be the cause of differences between field observations and our analysis. Rather, they may be either due to the inverted model being particularly sensitive to the coarse tail of the grain-size distribution, which is least well constrained from field observations, or due to the seismic model underestimating effects of the largest grains.
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Lalande, M., Menegoz, M., Krinner, G., Naegeli, K., & Wunderle, S. (2021). Climate change in the High Mountain Asia in CMIP6. Earth System Dynamics, 12(4), 1061–1098.
Abstract: Climate change over High Mountain Asia (HMA, including the Tibetan Plateau) is investigated over the period 1979-2014 and in future projections following the four Shared Socioeconomic Pathways: SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5. The skill of 26 Coupled Model Intercomparison Project phase 6 (CMIP6) models is estimated for near-surface air temperature, snow cover extent and total precipitation, and 10 of them are used to describe their projections until 2100. Similarly to previous CMIP models, this new generation of general circulation models (GCMs) shows a mean cold bias over this area reaching -1.9 [ -8.2 to 2.9] degrees C (90 % confidence interval) in comparison with the Climate Research Unit (CRU) observational dataset, associated with a snow cover mean overestimation of 12 % [ -13 % to 43 %], corresponding to a relative bias of 52 % [ -53 % to 183 %] in comparison with the NOAA Climate Data Record (CDR) satellite dataset. The temperature and snow cover model biases are more pronounced in winter. Simulated precipitation rates are overestimated by 1.5 [0.3 to 2 9] mm d(-1), corresponding to a relative bias of 143 % [31 % to 281 %], but this might be an apparent bias caused by the undercatch of solid precipitation in the APHRODI1E (Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation of Water Resources) observational reference. For most models, the cold surface bias is associated with an overestimation of snow cover extent, but this relationship does not hold for all models, suggesting that the processes of the origin of the biases can differ from one model to another. A significant correlation between snow cover bias and surface elevation is found, and to a lesser extent between temperature bias and surface elevation, highlighting the model weaknesses at high elevation. The models with the best performance for temperature are not necessarily the most skillful for the other variables, and there is no clear relationship between model resolution and model skill. This highlights the need for a better understanding of the physical processes driving the climate in this complex topographic area, as well as for further parameterization developments adapted to such areas. A dependency of the simulated past trends on the model biases is found for some variables and seasons; however, some highly biased models fall within the range of observed trends, suggesting that model bias is not a robust criterion to discard models in trend analysis. The HMA median warming simulated over 2081-2100 with respect to 1995-2014 ranges from 1.9 [1.2 to 2.7] degrees C for SSP1-2.6 to 6.5 [4.9 to 9.0] degrees C for SSP5-8.5. This general warming is associated with a relative median snow cover extent decrease from -9.4 % [ – 16.4 % to -5.0 %] to -32.2 % [ -49.1 % to -25.0 %] and a relative median precipitation increase from 8.5 % [4.8 % to 18.2 %] to 24.9 % [14.4 % to 48.1 %] by the end of the century in these respective scenarios. The warming is 11 % higher over HMA than over the other Northern Hemisphere continental surfaces, excluding the Arctic area. Seasonal temperature, snow cover and precipitation changes over HMA show a linear relationship with the global surface air temperature (GSAT), except for summer snow cover which shows a slower decrease at strong levels of GSAT.
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Larue, F., Picard, G., Aublanc, J., Arnaud, L., Robledano-Perez, A., Le Meur, E., et al. (2021). Radar altimeter waveform simulations in Antarctica with the Snow Microwave Radiative Transfer Model (SMRT). Remote Sensing Of Environment, 263.
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Lavaysse, C., Roudier, P., Venkatachalam, V., Van'T Klooster, J., & Clerici, M. (2021). On the Use of the eStation Developed in the GMES & Africa EU Project: Results from the User Survey. Atmosphere, 12(2).
Abstract: In 2007, at the 2nd Africa-EU Summit, the development and implementation of earth observation based services to support sustainable development in Africa was agreed. A joint Africa-EU strategy created a framework for cooperation to this end called GMES & Africa. This cooperation aims to produce products and services relevant to the needs of Africans and implemented by African institutions. It is based in particular on the European Copernicus program. The themes covered by the cooperation include natural resource management, marine and coastal areas, water resource management, climate variability and change, disaster risk reduction and food security. Building on its early involvement in the previous projects, the Joint Research Centre has developed an operational and distributable open-source data processing tool, called eStation. One year before the end of the first phase of the project, a full survey of eStation users was conducted. The objective of the survey was to get a full overview of the use, strength, weakness and way to improve the eStation in an operational context. This study presents the main results of the survey. It identifies who are the users, what their operational tasks are and how they communicate the information to decision makers. In addition, the use of the station is described, its strengths and weaknesses are identified as well as the technical and thematic difficulties encountered. The survey underlines the importance of maintaining a constant dialogue between users and developers in order to offer technical and thematic supports to improve the efficiency of the use of the tools. This can be done by organising training and workshops and is essential for the proper use of the tools and products.
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Le Guillou, F., Lahaye, N., Ubelmann, C., Metref, S., Cosme, E., Ponte, A., et al. (2021). Joint Estimation of Balanced Motions and Internal Tides From Future Wide-Swath Altimetry. Journal Of Advances In Modeling Earth Systems, 13(12).
Abstract: Wide-swath altimetry, for example, the Surface Water and Ocean Topography mission is expected to provide Sea Surface Height (SSH) measurements resolving scales of a few tens of kilometers. Over a large fraction of the globe, the SSH signal at these scales is essentially a superposition of a component due to balanced motions (BMs) and another component due to internal tides (ITs). Several oceanographic applications require the separation of these components and their mapping on regular grids. For that purpose, the paper introduces an alternating minimization algorithm that iteratively implements two data assimilation techniques, each specific to the mapping of one component: a quasi-geostrophic model with Back-and-Forth Nudging for BMs, and a linear shallow-water model with 4-Dimensional Variational assimilation for ITs. The algorithm is tested with Observation System Simulation Experiments where the truth is provided by a primitive-equation ocean model in an idealized configuration simulating a turbulent jet and mode-one ITs. The algorithm reconstructs almost 80% of the variance of BMs and ITs, the remaining 20% being mostly due to dynamics that cannot be described by the simple models used. Importantly, in addition to the reconstruction of stationary ITs, the amplitude and phase of nonstationary ITs are reconstructed. Sensitivity experiments show that the quality of reconstruction significantly depends upon the timing of observations. Although idealized, this study represents a step forward towards the disentanglement of BMs and ITs signals from real wide-swath altimetry data.
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Le Roux, E., Evin, G., Eckert, N., Blanchet, J., & Morin, S. (2021). Elevation-dependent trends in extreme snowfall in the French Alps from 1959 to 2019. Cryosphere, 15(9), 4335–4356.
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Le Toumelin, L., Amory, C., Favier, V., Kittel, C., Hofer, S., Fettweis, X., et al. (2021). Sensitivity of the surface energy budget to drifting snow as simulated by MAR in coastal Adelie Land, Antarctica. Cryosphere, 15(8), 3595–3614.
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Legout, C., Freche, G., Biron, R., Esteves, M., Navratil, O., Nord, G., et al. (2021). A critical zone observatory dedicated to suspended sediment transport: The meso-scale Galabre catchment (southern French Alps). Hydrological Processes, 35(3).
Abstract: The 20 km(2) Galabre catchment belongs to the French network of critical zone observatories (OZCAR; Gaillardet et al., Vadose Zone Journal, 2018, 17(1), 1-24). It is representative of the sedimentary lithology and meteorological forcing found in Mediterranean and mountainous areas. Due to the presence of highly erodible and sloping badlands on various lithologies, the site was instrumented in 2007 to understand the dynamics of suspended sediments (SS) in such areas. Two meteorological stations including measurements of air temperature, wind speed and direction, air moisture, rainfall intensity, raindrop size and velocity distribution were installed both in the upper and lower part of the catchment. At the catchment outlet, a gauging station records the water level, temperature and turbidity (10 min time-step). Stream water samples are collected automatically to estimate SS concentration-turbidity relationships, allowing quantification of SS fluxes with known uncertainty. The sediment samples are further characterized by measuring their particle size distributions and by applying a low-cost sediment fingerprinting approach using spectrocolorimetric tracers. Thus, the contributions of badlands located on different lithologies to total SS flux are quantified at a high temporal resolution, providing the opportunity to better analyse the links between meteorological forcing variability and watershed hydrosedimentary response. The set of measurements was extended to the dissolved phase in 2017. Both stream water electrical conductivity and major ion concentrations are measured each week and every 3 h during storm events. This extension of measurements to the dissolved phase will allow progress in understanding both the origin of the water during the events and the partitioning between particulate and dissolved fluxes of solutes in the critical zone. All data sets are available at .
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Legrand, M., Mcconnell, J., Preunkert, S., Chellman, N., & Arienzo, M. (2021). Causes of Enhanced Bromine Levels in Alpine Ice Cores During the 20th Century: Implications for Bromine in the Free European Troposphere. Journal Of Geophysical Research-Atmospheres, 126(8).
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Legrand, M., Weller, R., Preunkert, S., & Jourdain, B. (2021). Ammonium in Antarctic Aerosol: Marine Biological Activity Versus Long-Range Transport of Biomass Burning. Geophysical Research Letters, 48(11).
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Lei, Y., Yao, T., Tian, L., Sheng, Y., Liao, J., Zhao, H., et al. (2021). Response of downstream lakes to Aru glacier collapses on the western Tibetan Plateau. Cryosphere, 15(1), 199–214.
Abstract: The lower parts of two glaciers in the Am range on the western Tibetan Plateau (TP) collapsed on 17 July and 21 September 2016, respectively, causing fatal damage to local people and their livestock. The giant ice avalanches, with a total volume of 150 x 10(6) m(3), had almost melted by September 2019 (about 30 % of the second ice avalanche remained). The impact of these extreme disasters on downstream lakes has not been investigated yet. Based on in situ observation, bathymetry survey and satellite data, we explore the impact of the ice avalanches on the two downstream lakes (i.e., Am Co and Memar Co) in terms of lake morphology, water level and water temperature in the subsequent 4 years (2016-2019). After the first glacier collapse, the ice avalanche slid into Aru Co along with a large amount of debris, which generated great impact waves in Aru Co and significantly modified the lake's shoreline and underwater topography. An ice volume of at least 7.1 x 10(6) m(3 )was discharged into Aru Co, spread over the lake surface and considerably lowered its surface temperature by 2-4 degrees C in the first 2 weeks after the first glacier collapse. Due to the large amount of meltwater input, Memar Co exhibited more rapid expansion after the glacier collapses (2016-2019) than before (2003-2014), in particular during the warm season. The melting of ice avalanches was found to contribute to about 23 % of the increase in lake storage between 2016 and 2019. Our results indicate that the Am glacier collapses had both short-term and long-term impacts on the downstream lakes and provide a baseline in understanding the future lake response to glacier melting on the TP under a warming climate.
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Lemaitre-Basset, T., Collet, L., Thirel, G., Parajka, J., Evin, G., & Hingray, B. (2021). Climate change impact and uncertainty analysis on hydrological extremes in a French Mediterranean catchment. Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, .
Abstract: The Mediterranean region is a climate change hotspot for water resources. However, uncertainty analyses of hydrological projections are rarely quantified. In this study, an in-depth analysis of projections and uncertainties for high and low flows is performed. Climatic projections derived from a recent downscaling method were used, for two representative concentration pathway scenarios (RCPs), five general circulation model/regional climate model (GCM/RCM) couples, three hydrological models (HMs), and 29 calibration schemes. A quasi-ergodic analysis of variance was used to evaluate the contribution of each impact modelling step to the total uncertainty. For high flows, the results show a mean increase of 30% by 2085, and RCPs make the highest contribution to the total uncertainty, followed by GCMs. For low flows, 50% of projections indicate a decrease of 7% or more by 2085, and HM structures, hydrological model parameters, and GCMs are the most important uncertainty sources. These results contribute to raise awareness among water managers regarding future hydrological extreme events.
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Levin, I., Hammer, S., Kromer, B., Preunkert, S., Weller, R., & Worthy, D. (2021). Radiocarbon In Global Tropospheric Carbon Dioxide. Radiocarbon, .
Abstract: Since the 1950s, observations of radiocarbon (C-14) in tropospheric carbon dioxide (CO2) have been conducted in both hemispheres, documenting the so-called nuclear “bomb spike” and its transfer into the oceans and the terrestrial biosphere, the two compartments permanently exchanging carbon with the atmosphere. Results from the Heidelberg global network of Delta C-14-CO2 observations are revisited here with respect to the insights and quantitative constraints they provided on these carbon exchange fluxes. The recent development of global and hemispheric trends of Delta C-14-CO2 are further discussed in regard to their suitability to continue providing constraints for C-14-free fossil CO2 emission changes on the global and regional scale.
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Lilien, D., Steinhage, D., Taylor, D., Parrenin, F., Ritz, C., Mulvaney, R., et al. (2021). Brief communication: New radar constraints support presence of ice older than 1.5 Myr at Little Dome C. Cryosphere, 15(4), 1881–1888.
Abstract: The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The European Beyond EPICA consortium has selected Little Dome C (LDC), an area similar to 35 km southeast of Concordia Station, to attempt to recover such a record. Here, we present the results of the final ice-penetrating radar survey used to refine the exact drill site. These data were acquired during the 2019-2020 austral summer using a new, multi-channel high-resolution very high frequency (VHF) radar operating in the frequency range of 170-230 MHz. This new instrument is able to detect reflectors in the near-basal region, where previous surveys were largely unable to detect horizons. The radar stratigraphy is used to transfer the timescale of the EPICA Dome C ice core (EDC) to the area of Little Dome C, using radar isochrones dating back past 600 ka. We use these data to derive the expected depth-age relationship through the ice column at the now-chosen drill site, termed BELDC (Beyond EPICA LDC). These new data indicate that the ice at BELDC is considerably older than that at EDC at the same depth and that there is about 375m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, similar to 93% of the ice thickness, below which there is a basal unit with unknown properties. An ice-flow model tuned to the isochrones suggests ages likely reach 1.5 Myr near 2500 m, similar to 65m above the basal unit and similar to 265m above the bed, with sufficient resolution (19 +/- 2 kyrm(-1)) to resolve 41 kyr glacial cycles.
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Lindau, F., Simoes, J., Delmonte, B., Ginot, P., Baccolo, G., Paleari, C., et al. (2021). Giant dust particles at Nevado Illimani: a proxy of summertime deep convection over the Bolivian Altiplano. Cryosphere, 15(3), 1383–1397.
Abstract: A deeper understanding of past atmospheric circulation variability in the Central Andes is a high-priority topic in paleoclimatology mainly because of the necessity to validate climate models used to predict future precipitation trends and to develop mitigation and/or adaptation strategies for future climate change scenarios in this region. Within this context, we here investigate an 18-year firn core drilled at Nevado Illimani in order to interpret its mineral dust record in relation to seasonal processes, in particular atmospheric circulation and deep convection. The core was dated by annual layer counting based on seasonal oscillations of dust, calcium, and stable isotopes. Geochemical and mineralogical data show that dust is regionally sourced in winter and summer. During austral summer (wet season), an increase in the relative proportion of giant dust particles (empty set > 20 μm) is observed, in association with oscillations of stable isotope records (delta D, delta O-18). It seems that at Nevado Illimani both the deposition of dust and the isotopic signature of precipitation are influenced by atmospheric deep convection, which is also related to the total amount of precipitation in the area. This hypothesis is corroborated by regional meteorological data. The interpretation of giant particle and stable isotope records suggests that downdrafts due to convective activity promote turbulent conditions capable of suspending giant particles in the vicinity of Nevado Illimani. Giant particles and stable isotopes, when considered together, can be therefore used as a new proxy for obtaining information about deep convective activity in the past.
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Lipscomb, W., Leguy, G., Jourdain, N., Asay-Davis, X., Seroussi, H., & Nowicki, S. (2021). ISMIP6-based projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model. Cryosphere, 15(2), 633–661.
Abstract: The future retreat rate for marine-based regions of the Antarctic Ice Sheet is one of the largest uncertainties in sea-level projections. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) aims to improve projections and quantify uncertainties by running an ensemble of ice sheet models with atmosphere and ocean forcing derived from global climate models. Here, the Community Ice Sheet Model (CISM) is used to run ISMIP6-based projections of ocean-forced Antarctic Ice Sheet evolution. Using multiple combinations of sub-ice-shelf melt parameterizations and calibrations, CISM is spun up to steady state over many millennia. During the spin-up, basal friction parameters and basin-scale thermal forcing corrections are adjusted to optimize agreement with the observed ice thickness. The model is then run forward for 550 years, from 1950-2500, applying ocean thermal forcing anomalies from six climate models. In all simulations, the ocean forcing triggers long-term retreat of the West Antarctic Ice Sheet, especially in the Filchner-Ronne and Ross sectors. Mass loss accelerates late in the 21st century and then rises steadily for several centuries without leveling off. The resulting ocean-forced sea-level rise at year 2500 varies from about 150 to 1300 mm, depending on the melt scheme and ocean forcing. Further experiments show relatively high sensitivity to the basal friction law, moderate sensitivity to grid resolution and the prescribed collapse of small ice shelves, and low sensitivity to the stress-balance approximation. The Amundsen sector exhibits threshold behavior, with modest retreat under many parameter settings but complete collapse under some combinations of low basal friction and high thermal forcing anomalies. Large uncertainties remain, as a result of parameterized sub-shelf melt rates, simplified treatments of calving and basal friction, and the lack of ice-ocean coupling.
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Macdonald, A., Lark, R., Taylor, R., Abiye, T., Fallas, H., Favreau, G., et al. (2021). Mapping groundwater recharge in Africa from ground observations and implications for water security. Environmental Research Letters, 16(3).
Abstract: Groundwater forms the basis of water supplies across much of Africa and its development is rising as demand for secure water increases. Recharge rates are a key component for assessing groundwater development potential, but have not been mapped across Africa, other than from global models. Here we quantify long-term average (LTA) distributed groundwater recharge rates across Africa for the period 1970-2019 from 134 ground-based estimates and upscaled statistically. Natural diffuse and local focussed recharge, where this mechanism is widespread, are included but discrete leakage from large rivers, lakes or from irrigation are excluded. We find that measurable LTA recharge is found in most environments with average decadal recharge depths in arid and semi-arid areas of 60 mm (30-140 mm) and 200 mm (90-430 mm) respectively. A linear mixed model shows that at the scale of the African continent only LTA rainfall is related to LTA recharge-the inclusion of other climate and terrestrial factors do not improve the model. Kriging methods indicate spatial dependency to 900 km suggesting that factors other than LTA rainfall are important at local scales. We estimate that average decadal recharge in Africa is 15 000 km(3) (4900-45 000 km(3)), approximately 2% of estimated groundwater storage across the continent, but is characterised by stark variability between high-storage/low-recharge sedimentary aquifers in North Africa, and low-storage/high-recharge weathered crystalline-rock aquifers across much of tropical Africa. African water security is greatly enhanced by this distribution, as many countries with low recharge possess substantial groundwater storage, whereas countries with low storage experience high, regular recharge. The dataset provides a first, ground-based approximation of the renewability of groundwater storage in Africa and can be used to refine and validate global and continental hydrological models while also providing a baseline against future change.
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Maier, N., Gimbert, F., Gillet-Chaulet, F., & Gilbert, A. (2021). Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland. Cryosphere, 15(3), 1435–1451.
Abstract: On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that controls ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight major drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr-Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry of the grounded regions in Greenland is mainly dictated by Weertman-type hard-bed physics up to velocities of approximately 450m yr(-1), except within the Northeast Greenland Ice Stream and areas near floatation. Depending on the catchment, behavior of the fastest-flowing ice (similar to 1000 m yr(-1)) directly inland from marine-terminating outlets exhibits Weertman-type rate strengthening, Mohr-Coulomb-like behavior, or is not confidently resolved given our methodology. Given the complex basal boundary across Greenland, the relationships are captured reasonably well by simple traction laws which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a first constraint on the physics of basal motion over the grounded regions of Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.
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Marelle, L., Thomas, J., Ahmed, S., Tuite, K., Stutz, J., Dommergue, A., et al. (2021). Implementation and Impacts of Surface and Blowing Snow Sources of Arctic Bromine Activation Within WRF-Chem 4.1.1. Journal Of Advances In Modeling Earth Systems, 13(8).
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Marta, S., Azzoni, R., Fugazza, D., Tielidze, L., Chand, P., Sieron, K., et al. (2021). The Retreat of Mountain Glaciers since the Little Ice Age: A Spatially Explicit Database. Data, 6(10).
Abstract: Most of the world's mountain glaciers have been retreating for more than a century in response to climate change. Glacier retreat is evident on all continents, and the rate of retreat has accelerated during recent decades. Accurate, spatially explicit information on the position of glacier margins over time is useful for analyzing patterns of glacier retreat and measuring reductions in glacier surface area. This information is also essential for evaluating how mountain ecosystems are evolving due to climate warming and the attendant glacier retreat. Here, we present a non-comprehensive spatially explicit dataset showing multiple positions of glacier fronts since the Little Ice Age (LIA) maxima, including many data from the pre-satellite era. The dataset is based on multiple historical archival records including topographical maps; repeated photographs, paintings, and aerial or satellite images with a supplement of geochronology; and own field data. We provide ESRI shapefiles showing 728 past positions of 94 glacier fronts from all continents, except Antarctica, covering the period between the Little Ice Age maxima and the present. On average, the time series span the past 190 years. From 2 to 46 past positions per glacier are depicted (on average: 7.8).</p> Dataset 10.6084/m9.figshare.13700215</p> Dataset License CC-BY-4.0</p>
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Martinez-Carvajal, G., Oxarango, L., Adrien, J., Molle, P., & Forquet, N. (2021). Structural Changes in French VF Treatment Wetland Porous Media during the Rest Period: An Ex Situ Study Using X-ray Tomography. Water, 13(3).
Abstract: Clogging constitutes a major operational issue for treatment wetlands. The rest period is a key feature of French Vertical Flow (VF) treatment wetlands and serves to mitigate clogging. An ex-situ drying experiment was performed to mimic the rest period and record structural changes in the porous media using X-ray Computed Tomography (CT). Samples containing the deposit and gravel layers of a first stage French VF treatment wetland were extracted and left to dry in a control environment. Based on CT scans, three phases were identified (voids, biosolids, and gravels). The impact of the rest period was assessed by means of different pore-scale variables. Ultimately, the volume of biosolids had reduced to 58% of its initial value, the deposit layer thickness dropped to 68% of its initial value, and the void/biosolid specific surface area ratio increased from a minimum value of 1.1 to a maximum of 4.2. Cracks greater than 3 mm developed at the uppermost part of the deposit layer, while, in the gravel layer, the rise in void volume corresponds to pores smaller than 2 mm in diameter. Lastly, the air-filled microporosity is estimated to have increased by 0.11 v/v.
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Massazza, G., Bacci, M., Descroix, L., Ibrahim, M., Fiorillo, E., Katiellou, G., et al. (2021). Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger). Water, 13(12).
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Matsuoka, K., Skoglund, A., Roth, G., De Pomereu, J., Griffiths, H., Headland, R., et al. (2021). Quantarctica, an integrated mapping environment for Antarctica, the Southern Ocean, and sub-Antarctic islands. Environmental Modelling & Software, 140.
Abstract: Quantarctica (https://www.npolar.no/quantarctica) is a geospatial data package, analysis environment, and visualization platform for the Antarctic Continent, Southern Ocean (>40oS), and sub-Antarctic islands. Quantarctica works with the free, cross-platform Geographical Information System (GIS) software QGIS and can run without an Internet connection, making it a viable tool for fieldwork in remote areas. The data package includes basemaps, satellite imagery, terrain models, and scientific data in nine disciplines, including physical and biological sciences, environmental management, and social science. To provide a clear and responsive user experience, cartography and rendering settings are carefully prepared using colour sets that work well for typical data combinations and with consideration of users with common colour vision deficiencies. Metadata included in each dataset provides brief abstracts for non-specialists and references to the original data sources. Thus, Quantarctica provides an integrated environment to view and analyse multiple Antarctic datasets together conveniently and with a low entry barrier.
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Matthews, T., Perry, L., Aryal, D., Elmore, A., Khadka, A., Pelto, M., et al. (2021). Weather on K2 during historic first winter ascent. Weather, .
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Menard, C., Essery, R., Krinner, G., Arduini, G., Bartlett, P., Boone, A., et al. (2021). Scientific and Human Errors in a Snow Model Intercomparison. Bulletin Of The American Meteorological Society, 102(1), E61–E79.
Abstract: Twenty-seven models participated in the Earth System Model-Snow Model Intercomparison Project (ESM-SnowMIP), the most data-rich MIP dedicated to snow modeling. Our findings do not support the hypothesis advanced by previous snow MIPs: evaluating models against more variables and providing evaluation datasets extended temporally and spatially does not facilitate identification of key new processes requiring improvement to model snow mass and energy budgets, even at point scales. In fact, the same modeling issues identified by previous snow MIPs arose: albedo is a major source of uncertainty, surface exchange parameterizations are problematic, and individual model performance is inconsistent. This lack of progress is attributed partly to the large number of human errors that led to anomalous model behavior and to numerous resubmissions. It is unclear how widespread such errors are in our field and others; dedicated time and resources will be needed to tackle this issue to prevent highly sophisticated models and their research outputs from being vulnerable because of avoidable human mistakes. The design of and the data available to successive snow MIPs were also questioned. Evaluation of models against bulk snow properties was found to be sufficient for some but inappropriate for more complex snow models whose skills at simulating internal snow properties remained untested. Discussions between the authors of this paper on the purpose of MIPs revealed varied, and sometimes contradictory, motivations behind their participation. These findings started a collaborative effort to adapt future snow MIPs to respond to the diverse needs of the community.
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Michoud, V., Hallemans, E., Chiappini, L., Leoz-Garziandia, E., Colomb, A., Dusanter, S., et al. (2021). Molecular characterization of gaseous and particulate oxygenated compounds at a remote site in Cape Corsica in the western Mediterranean Basin. Atmospheric Chemistry And Physics, 21(10), 8067–8088.
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Misset, C., Recking, A., Legout, C., Bakker, M., Gimbert, F., Geay, T., et al. (2021). Using Continuous Turbidity and Seismic Measurements to Unravel Sediment Provenance and Interaction Between Suspended and Bedload Transport in an Alpine Catchment. Geophysical Research Letters, 48(4).
Abstract: Fine sediment transport results from the complexity of the interactions between the different modes of transport and the variety of possible sediment sources, from the river bed stocks remobilization to hillslopes erosion. From a 2-year period in an Alpine catchment, we show how the combined use of continuous turbidity and seismic measurements can help to address these issues. In the studied catchment, the signals are more strongly correlated during the high flows of the snowmelt period than during the summer period when the river bed is stable and the hillslopes are no longer protected by a snow cover during storms. This sheds light on the seasonal control exerted by the river bed mobility and the snow cover on suspended sediment dynamics in mountainous catchments. It also questions the potential shift of this dynamics from river bed to hillslope dominated in a context of global warming.
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Misset, C., Recking, A., Legout, C., Viana-Bandeira, B., & Poirel, A. (2021). Assessment of fine sediment river bed stocks in seven Alpine catchments. Catena, 196.
Abstract: While the finest fraction of suspension has long been considered to have limited interactions with the river bed, several recent studies based on flume and field observations raise questions about this hypothesis which is fundamental for suspended load modeling and river management. In this study, we report a large field campaign in which we quantify the river bed stocks of fine particles in 7 contrasted Alpine catchments. Using a simple protocol, we performed more than 300 riverbed measurements of the local surface and subsurface stocks. Results indicate that even when the river bed surface contains no fine particles, significant quantities can be found in the subsurface layer which is in most cases the layer having the higher stocks. We also observed that stocks highly depend on the facies considered suggesting that storage processes are strongly driven by the local hydraulics and river bed characteristics. By integrating these local stocks at the catchment scale, we estimated that they could represent more than 50% of the mean annual suspended load in catchments having large alluvial braided sections. On the opposite, these stocks could be as small as 1% in highly eroded head water catchments. This suggests that the bed of large alluvial Alpine rivers can be considered as a significant source of fine particles. These observations were confirmed by using a simplified vertical scouring model to estimate conditions for these stocks to be released in the flow. However, the use of this model suggests that other bed reworking processes (channel widening and migration) have to be considered. Finally, these observations suggest that interactions between particles transported as suspension and gravel beds are far from being negligible processes in catchments having large alluvial sections typically found in Alpine environments.
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Montagnat, M., Bourcier, M., Philip, A., Bons, P., Bauer, C., Deconinck, P., et al. (2021). Texture characterization of some large hailstones with an automated technique. Journal Of Glaciology, 67(266), 1190–1204.
Abstract: Hailstone structures have been studied for over a century, but so far mainly by manual optical means. This paper presents new texture and microstructure data (i.e. crystal lattice orientations, grain sizes and shapes) measured with an Automatic Ice Texture Analyzer, which gives access to high spatial and angular resolutions. The hailstones show two main characteristics: (1) they are structured with several concentric layers composed of alternating fine equiaxed grains and coarse elongated and radially oriented grains, and (2) they show two texture types with c-axes oriented either parallel or perpendicular to the radial direction. Such textures are compared with the ones observed in lake S1 and S2 ices, respectively. The S1 texture type (with c-axes parallel to the columnar crystals that grew in the radial direction) may result from epitaxial growth from a polycrystalline embryo, while the S2 texture (c-axes in the plane perpendicular to the column direction) may result from the growth from an embryo made of a few crystals with mainly one crystallographic orientation. Our novel high-resolution maps and measurements of both microstructure and texture may help to shed new light on the long-term discussion on the growth mechanisms of large hailstones.
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Nagaraj, P., Subbarayappa, M., Vouillamoz, J., & Hoareau, J. (2021). Estimation of anisotropic hydraulic conductivity using geophysical data in a coastal aquifer of Karnataka, India. Hydrological Processes, 35(10).
Abstract: Estimation of hydraulic parameters is essential to understand the interaction between groundwater flow and seawater intrusion. Though several studies have addressed hydraulic parameter estimation, based on pumping tests as well as geophysical methods, not many studies have addressed the problem with clayey formations being present. In this study, a methodology is proposed to estimate anisotropic hydraulic conductivity and porosity values for the coastal aquifer with unconsolidated formations. For this purpose, the one-dimensional resistivity of the aquifer and the groundwater conductivity data are used to estimate porosity at discrete points. The hydraulic conductivity values are estimated by its mutual dependence with porosity and petrophysical parameters. From these estimated values, the bilinear relationship between hydraulic conductivity and aquifer resistivity is established based on the clay content of the sampled formation. The methodology is applied on a coastal aquifer along with the coastal Karnataka, India, which has significant clayey formations embedded in unconsolidated rock. The estimation of hydraulic conductivity values from the established correlations has a correlation coefficient of 0.83 with pumping test data, indicating good reliability of the methodology. The established correlations also enable the estimation of horizontal hydraulic conductivity on two-dimensional resistivity sections, which was not addressed by earlier studies. The inventive approach of using the established bilinear correlations at one-dimensional to two-dimensional resistivity sections is verified by the comparison method. The horizontal hydraulic conductivity agrees with previous findings from inverse modelling. Additionally, this study provides critical insights into the estimation of vertical hydraulic conductivity and an equation is formulated which relates vertical hydraulic conductivity with horizontal. Based on the approach presented, the anisotropic hydraulic conductivity of any type aquifer with embedded clayey formations can be estimated. The anisotropic hydraulic conductivity has the potential to be used as an important input to the groundwater models.
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Nakhle, P., Ribolzi, O., Boithias, L., Rattanavong, S., Auda, Y., Sayavong, S., et al. (2021). Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR. Scientific Reports, 11(1).
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Nanni, U., Gimbert, F., Roux, P., & Lecointre, A. (2021). Observing the subglacial hydrology network and its dynamics with a dense seismic array. Proceedings Of The National Academy Of Sciences Of The United States Of America, 118(28).
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Nguyen, A., Nemery, J., Gratiot, N., Garnier, J., Dao, T., Thieu, V., et al. (2021). Biogeochemical functioning of an urbanized tropical estuary: Implementing the generic C-GEM (reactive transport) model. Science Of The Total Environment, 784.
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Nguyen, T., Bui, X., Ngo, H., Nguyen, T., Nguyen, K., Nguyen, H., et al. (2021). Nutrient recovery and microalgae biomass production from urine by membrane photobioreactor at low biomass retention times. Science Of The Total Environment, 785.
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Noblet, C., Besombes, J., Lemire, M., Pin, M., Jaffrezo, J., Favez, O., et al. (2021). Emission factors and chemical characterization of particulate emissions from garden green waste burning. Science Of The Total Environment, 798.
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Obahoundje, S., Ta, M., Diedhiou, A., Amoussou, E., & Kouadio, K. (2021). Sensitivity of Hydropower Generation to Changes in Climate and Land Use in the Mono Basin (West Africa) using CORDEX Dataset and WEAP Model. Environmental Processes-An International Journal, .
Abstract: The availability of water resources in a reservoir for electricity generation is strongly linked to climate and weather conditions. Also, the use of these water resources is influenced by the population size as well as anthropogenic activities. This research attempts to assess the combined effects of (i) climate change (CC), (ii) land use/land cover change (LULCC), and (iii) development (Dev) conditions on water resources and hydropower generation (HPGen) using Regional Climate Models (RCMs) from Coordinated Regional Downscaling Experiment (CORDEX) under the Representative Concentrated Pathways (RCP): RCP4.5 and RCP8.5. The RCMs considered are: CanRCM, CCLM, and WRF being drived by CanESM2, CNRM-CERFACS, and NorESM1, respectively. The Water Evaluation and Planning model (WEAP) tool is used to simulate the water availability and HPGen in the Mono basin under present and future conditions. The ensemble mean of the three-climate dataset analysis reveals that the temperature is projected to increase significantly while the precipitation change is uncertain under both RCPs in the near (2020-2050) and the far (2070-2090) futures. These changes in climate variables consequently affected simulated water availability for different water consumption sectors especially the HPGen in the near and far futures. Moreover, the Dev was found to exacerbate the burden that constitutes the CC for water availability and HPGen. Nevertheless, LULCC associated with either CC or both CC and Dev were projected by all the RCMs and their ensemble mean to reduce this burden. However, its side effects namely reservoir siltation and sedimentation need to be deeply investigated.
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Obahoundje, S., Ta, M., Diedhiou, A., Amoussou, E., & Kouadio, K. (2021). Sensitivity of Hydropower Generation to Changes in Climate and Land Use in the Mono Basin (West Africa) using CORDEX Dataset and WEAP Model. Environmental Processes-An International Journal, .
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Olmi, R., Bittelli, M., Picard, G., Arnaud, L., Mialon, A., & Priori, S. (2021). Investigating the influence of the grain size and distribution on the macroscopic dielectric properties of Antarctic firn. Cold Regions Science And Technology, 185.
Abstract: This study is based on the analysis of detailed measurements of firn dielectric properties performed in Antarctica through coring down to 106 m. Dielectric measurements in the frequency band (0.4-2.5 GHz) have been carried out using an open-resonator probe. Density was also measured for the same samples. The experimental results confirmed the well-known dependence of the real part of permittivity epsilon' on depth and density, showing an increase of epsilon' with density. The imaginary part also increases with depth with a rather complex dependence on frequency, probably due to the presence of salts or impurities. The analysis of the experimental data was performed by implementing 3D and 2D full wave numerical models, to simulate a mixture of firn crystals at prescribed densities, corresponding to the measured densities on the ice cores. The numerical analysis of the ensemble of inclusions showed that the usual symmetric formulae used for modeling ice dielectric properties agree with the average results of the simulation, but they are not able to explain the spreading of the measured data at given density. A dielectric model was then developed allowing for quantification of the dependence of dielectric properties on density, by combining two models: one consisting in firn crystals into an air host, the other assuming the presence of air inclusions into a homogeneous firn host. The weighted equation is based on the volume fraction. A simple geometric shape (ellipsoidal) is assumed for both ice crystals and air inclusions. This kind of shape is reasonable for the purpose of the dielectric study. The result is a mixture, smoothly changing from firn particles in air (low density) to air bubbles in an ice matrix (high density). A statistical analysis has been accomplished to investigate the dependence of the dielectric properties on the geometrical arrangement of the inclusions. For that purpose, a large number of simulations with different arrangements (micro-states) giving rise to the same average density (macro-states) has been carried out. The permittivity change due to micro-state variability appears to be at least two-three times the model variation due to density alone, and comparable to the measured variability at a given depth, suggesting that firn structure has a significant effect on the dielectric properties.
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Ortega-Ramirez, M., & Oxarango, L. (2021). Effect of X-ray μCT Resolution on the Computation of Permeability and Dispersion Coefficient for Granular Soils. Transport In Porous Media, .
Abstract: X-ray micro-computed tomography (mu CT) can produce realistic 3D-images of the pore structure of a material. Extracting its geometry enables the computation of effective properties of the material-such as the permeability (k) and the hydrodynamic dispersion coefficient (D-h)-, through the solutions of the Stokes equation (SE) and Advection-Diffusion equation (ADE), respectively. In this study, the effect of the image resolution on these properties is discussed. For such purpose, four different resolutions are evaluated for both a real sample of Fontainebleau sand and a numerically generated sample created by degrading the Fontainebleau image with highest resolution. The SE was computed using the commercial software GeoDict. To solve the ADE, a Finite Volume software was developed which includes a high order total variation diminishing scheme for advection. The analysis of dispersion was based on numerical breakthrough curves. Our model was tested in a large range of Peclet numbers (Pe) and travel distances, accurately describing the transition between diffusion and advection dominated regimes of dispersion. The D-h exhibits a linear increase with travel distance for Pe > 10. This classical effect increases with increasing Pe. The percentage change on k and D-h increases with decreasing resolution in agreement with the corresponding behavior of porosity, specific surface and pore size distributions. The images directly scaled with the μCT showed more discrepancy than the numerically scaled images. The criteria to estimate the quality of permeability from the pore size distribution proposed on our previous study remains valid. The D-h is less sensitive to resolution than k.
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Osterwalder, S., Dunham-Cheatham, S., Araujo, B., Magand, O., Thomas, J., Baladima, F., et al. (2021). Fate of Springtime Atmospheric Reactive Mercury: Concentrations and Deposition at Zeppelin, Svalbard. Acs Earth And Space Chemistry, 5(11), 3234–3246.
Abstract: Mid-latitude atmospheric elemental mercury (Hg) emissions undergo extensive oxidation to reactive Hg (RM) compounds during Arctic polar sunrise, resulting in enhanced atmospheric deposition that impacts Arctic marine wildlife and humans. It has been difficult to estimate RM dry deposition, because RM concentrations, compounds, and their deposition velocities are ill-defined. Here, we investigate RM concentrations sampled with membrane-based methods and find these to exceed denuder-based RM detection by 5 times at the Zeppelin Observatory on Svalbard (March 26-July 24, 2019). Measured dry deposition of gaseous oxidized Hg was about half of the modeled RM deposition, demonstrating that particulate-bound Hg was an important component of dry deposition. Using thermal membrane desorption, RM chemistry was found to be dominated by Hg-Cl/Br (51%) and Hg-N (45%) compounds. Back-trajectory analysis indicated that Hg-Br/Cl compounds were predominantly advected from within the marine boundary layer (sea ice exposure), while Hg-N originated from the free troposphere. Weekly average RM compound-specific dry deposition velocities ranged from 0.12 to 0.49 cm s(-1), with a net RM dry deposition of 1.9 μg m(-2) (1.5-2.5 μg m(-2); 95% confidence interval) that exceeds the mean annual Hg wet deposition flux in Svalbard. Overall, we find that springtime atmospheric RM deposition has been underestimated in the Arctic marine environment.
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Osterwalder, S., Nerentorp, M., Zhu, W., Jiskra, M., Nilsson, E., Nilsson, M., et al. (2021). Critical Observations of Gaseous Elemental Mercury Air-Sea Exchange. Global Biogeochemical Cycles, 35(8).
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Payne, A., Nowicki, S., Abe-Ouchi, A., Agosta, C., Alexander, P., Albrecht, T., et al. (2021). Future Sea Level Change Under Coupled Model Intercomparison Project Phase 5 and Phase 6 Scenarios From the Greenland and Antarctic Ice Sheets. Geophysical Research Letters, 48(16).
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Piantini, M., Gimbert, F., Bellot, H., & Recking, A. (2021). Triggering and propagation of exogenous sediment pulses in mountain channels: insights from flume experiments with seismic monitoring. Earth Surface Dynamics, 9(6), 1423–1439.
Abstract: the upper part of mountain river catchments, large amounts of loose debris produced by mass-wasting processes can accumulate at the base of slopes and cliffs. Sudden destabilizations of these deposits are thought to trigger energetic sediment pulses that may travel in downstream rivers with little exchange with the local bed. The dynamics of these exogenous sediment pulses remain poorly known because direct field observations are lacking, and the processes that control their formation and propagation have rarely been explored. Here we carry out flume experiments with the aims of investigating (i) the role of sediment accumulation zones in the generation of sediment pulses, (ii) their propagation dynamics in low-order mountain channels, and (iii) the capability of seismic methods to unravel their physical properties. We use an original setup wherein we supply liquid and solid discharge to a low-slope storage zone acting like a natural sediment accumulation zone that is connected to a downstream 18% steep channel equipped with geophones. We show that the ability of the self-formed deposit to generate sediment pulses is controlled by the fine fraction of the mixture. In particular, when coarse grains coexist with a high content of finer particles, the storage area experiences alternating phases of aggradation and erosion strongly impacted by grain sorting. The upstream processes also influence the composition of the sediment pulses, which are formed by a front made of the coarsest fraction of the sediment mixture, a body composed of a high concentration of sand corresponding to the peak of solid discharge, and a diluted tail that exhibits a wide grain size distribution. Seismic measurements reveal that the front dominates the overall seismic noise, but we observe a complex dependency between seismic power and sediment pulse transport characteristics, which questions the applicability of existing seismic theories in such a context. These findings challenge the classical approach for which the sediment budget of mountain catchments is merely reduced to an available volume, since not only hydrological but also granular conditions should be considered to predict the occurrence and propagation of such sediment pulses.
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Pietri, A., Capet, X., D'Ovidio, F., Levy, M., Le Sommer, J., Molines, J., et al. (2021). Skills and Limitations of the Adiabatic Omega Equation: How Effective Is It to Retrieve Oceanic Vertical Circulation at Mesoscale and Submesoscale? Journal Of Physical Oceanography, 51(3), 931–954.
Abstract: The quasigeostrophic and the generalized omega equations are the most widely used methods to reconstruct vertical velocity w from in situ data. As observational networks with much higher spatial and temporal resolutions are being designed, the question arises of identifying the approximations and scales at which an accurate estimation of w through the omega equation can be achieved and what critical scales and observables are needed. In this paper we test different adiabatic omega reconstructions of w over several regions representative of main oceanic regimes of the global ocean in a fully eddy-resolving numerical simulation with a 1/60 degrees horizontal resolution. We find that the best reconstructions are observed in conditions characterized by energetic turbulence and/or weak stratification where near-surface frontal processes are felt deep into the ocean interior. The quasigeostrophic omega equation gives satisfactory results for scales larger than similar to 10 km horizontally while the improvements using a generalized formulation are substantial only in conditions where frontal turbulent processes are important (providing improvements with satisfactory reconstruction skill down to similar to 5 km in scale). The main sources of uncertainties that could be identified are related to processes responsible for ocean thermal wind imbalance (TWI), which is particularly difficult to account for (especially in observation-based studies) and to the deep flow that is generally improperly accounted for in omega reconstructions through the bottom boundary condition. Nevertheless, the reconstruction of mesoscale vertical velocities may be sufficient to estimate vertical fluxes of oceanic properties in many cases of practical interest.
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Pignede, E., Roudier, P., Diedhiou, A., Bi, V., Kobea, A., Konate, D., et al. (2021). Sugarcane Yield Forecast in Ivory Coast (West Africa) Based on Weather and Vegetation Index Data. Atmosphere, 12(11).
Abstract: One way to use climate services in the case of sugarcane is to develop models that forecast yields to help the sector to be better prepared against climate risks. In this study, several models for forecasting sugarcane yields were developed and compared in the north of Ivory Coast (West Africa). These models were based on statistical methods, ranging from linear regression to machine learning algorithms such as the random forest method, fed by climate data (rainfall, temperature); satellite products (NDVI, EVI from MODIS Vegetation Index product) and information on cropping practices. The results show that the forecasting of sugarcane yield depended on the area considered. At the plot level, the noise due to cultivation practices can hide the effects of climate on yields and leads to poor forecasting performance. However, models using satellite variables are more efficient and those with EVI alone may explain 43% of yield variations. Moreover, taking into account cultural practices in the model improves the score and enables one to forecast 3 months before harvest in 50% and 69% of cases whether yields will be high or low, respectively, with errors of only 10% and 2%, respectively. These results on the predictive potential of sugarcane yields are useful for planning and climate risk management in this sector.
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Pohl, B., Favier, V., Wille, J., Udy, D., Vance, T., Pergaud, J., et al. (2021). Relationship Between Weather Regimes and Atmospheric Rivers in East Antarctica. Journal Of Geophysical Research-Atmospheres, 126(24).
Abstract: Here, we define weather regimes in the East Antarctica-Southern Ocean sector based on daily anomalies of 700 hPa geopotential height derived from ERA5 reanalysis during 1979-2018. Most regimes and their preferred transitions depict synoptic-scale disturbances propagating eastwards off the Antarctic coastline. While regime sequences are generally short, their interannual variability is strongly driven by the polarity of the Southern Annular Mode (SAM). Regime occurrences are then intersected with atmospheric rivers (ARs) detected over the same region and period. ARs are equiprobable throughout the year, but clearly concentrate during regimes associated with a strong atmospheric ridges/blockings on the eastern part of the domain, which act to channel meridional advection of heat and moisture from the lower latitudes towards Antarctica. Both regimes and ARs significantly shape climate variability in Antarctica. Regimes favorable to AR occurrences are associated with anomalously warm and humid conditions in coastal Antarctica and, to a lesser extent, the hinterland parts of the Antarctic plateau. These anomalies are strongly enhanced during AR events, with warmer anomalies and dramatically amplified snowfall amounts. Large-scale conditions favoring AR development are finally explored. They show weak dependency to the SAM, but particularly strong atmospheric ridges/blockings over the Southern Ocean appear as the most favorable pattern, in which ARs can be embedded, and to which they contribute.
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Pohl, B., Saucede, T., Favier, V., Pergaud, J., Verfaillie, D., Feral, J., et al. (2021). Recent Climate Variability around the Kerguelen Islands (Southern Ocean) Seen through Weather Regimes. Journal Of Applied Meteorology And Climatology, 60(5), 711–731.
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Potter, E., Orr, A., Willis, I., Bannister, D., & Wagnon, P. (2021). Meteorological impacts of a novel debris-covered glacier category in a regional climate model across a Himalayan catchment. Atmospheric Science Letters, .
Abstract: Many of the glaciers in the Nepalese Himalaya are partially covered in a layer of loose rock known as debris cover. In the Dudh Koshi River Basin, Nepal, approximately 25% of glaciers are debris-covered. Debris-covered glaciers have been shown to have a substantial impact on near-surface meteorological variables and the surface energy balance, in comparison to clean-ice glaciers. The Weather Research and Forecasting (WRF) model is often used for high-resolution weather and climate modelling, however representation of debris-covered glaciers is not included in the standard land cover and soil categories. Here we include a simple representation of thick debris-covered glaciers in the WRF model, and investigate the impact on the near-surface atmosphere over the Dudh Koshi River Basin for July 2013. Inclusion of this new category is found to improve the model representation of near-surface temperature and relative humidity, in comparison with a simulation using the default category of clean-ice glaciers, when compared to observations. The addition of the new debris-cover category in the model warms the near-surface air over the debris-covered portion of the glacier, and the wind continues further up the valley, compared to the simulation using clean-ice. This has consequent effects on water vapour and column-integrated total water path, over both the portions of the glacier with and without debris cover. Correctly simulating meteorological variables such as these is vital for accurate precipitation forecasts over glacierized regions, and therefore estimating future glacier melt and river runoff in the Himalaya. These results highlight the need for debris cover to be included in high-resolution regional climate models over debris-covered glaciers.
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Quiquet, A., Dumas, C., Paillard, D., Ramstein, G., Ritz, C., & Roche, D. (2021). Deglacial Ice Sheet Instabilities Induced by Proglacial Lakes. Geophysical Research Letters, 48(9).
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Rahimi, J., Ago, E. E., Ayantunde, A., Berger, S., Bogaert, J., Butterbach-Bahl, K., et al. (2021). Modeling gas exchange and biomass production in West African Sahelian and Sudanian ecological zones. Geoscientific Model Development, 14(6), 3789–3812.
Abstract: West African Sahelian and Sudanian ecosystems provide essential services to people and also play a significant role within the global carbon cycle. However, climate and land use are dynamically changing, and uncertainty remains with respect to how these changes will affect the potential of these regions to provide food and fodder resources or how they will affect the biosphere–atmosphere exchange of CO2. In this study, we investigate the capacity of a process-based biogeochemical model, LandscapeDNDC, to simulate net ecosystem exchange (NEE) and aboveground biomass of typical managed and natural Sahelian and Sudanian savanna ecosystems. In order to improve the simulation of phenology, we introduced soil-water availability as a common driver of foliage development and productivity for all of these systems. The new approach was tested by using a sample of sites (calibration sites) that provided NEE from flux tower observations as well as leaf area index data from satellite images (MODIS, MODerate resolution Imaging Spectroradiometer). For assessing the simulation accuracy, we applied the calibrated model to 42 additional sites (validation sites) across West Africa for which measured aboveground biomass data were available. The model showed good performance regarding biomass of crops, grass, or trees, yielding correlation coefficients of 0.82, 0.94, and 0.77 and root-mean-square errors of 0.15, 0.22, and 0.12 kg m−2, respectively. The simulations indicate aboveground carbon stocks of up to 0.17, 0.33, and 0.54 kg C ha−1 m−2 for agricultural, savanna grasslands, and savanna mixed tree–grassland sites, respectively. Carbon stocks and exchange rates were particularly correlated with the abundance of trees, and grass biomass and crop yields were higher under more humid climatic conditions. Our study shows the capability of LandscapeDNDC to accurately simulate carbon balances in natural and agricultural ecosystems in semiarid West Africa under a wide range of conditions; thus, the model could be used to assess the impact of land-use and climate change on the regional biomass productivity.
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Reveillet, M., Vincent, C., Six, D., Rabatel, A., Sanchez, O., Piard, L., et al. (2021). Spatio-temporal variability of surface mass balance in the accumulation zone of the Mer de Glace, French Alps, from multitemporal terrestrial LiDAR measurements. Journal Of Glaciology, 67(261), 137–146.
Abstract: Spatio-temporal variability of the winter surface mass balance is a major uncertainty in the modelling of annual surface mass balance. Moreover, its measurement at high spatio-temporal resolution (sub-200 m) is very useful to force, calibrate or validate models. This study presents the results of year-round field campaigns to study the evolution of the surface mass balance in a 2 km(2) portion of the accumulation zone of the Mer de Glace (France). It is based on repeated LiDAR acquisitions, submergence-velocity measurements and meteorological records. The two methods used to quantify submergence velocities show good agreement. They present a linear temporal evolution without significant seasonal changes but display significant spatial variability. We conclude that a dense network of submergence velocity measurements is required to reduce the uncertainties when computing winter and annual surface mass balance from digital elevation model differencing. Finally, a hight spatio-temporal variability of the winter surface mass balance is highlighted (e.g., a std dev. of 0.92 m in April) even though the topography is homogeneous (std dev. of 25 m). Attempts to relate this variability to different morpho-topographic variables and wind-related indexes show the need for studies conducted at the snowfall event scale to obtain a better understanding of the variability in mass balance at the glacier scale.
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Revuelto, J., Cluzet, B., Duran, N., Fructus, M., Lafaysse, M., Cosme, E., et al. (2021). Assimilation of surface reflectance in snow simulations: Impact on bulk snow variables. Journal Of Hydrology, 603.
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Rignot, E., An, L., Chauche, N., Morlighem, M., Jeong, S., Wood, M., et al. (2021). Retreat of Humboldt Gletscher, North Greenland, Driven by Undercutting From a Warmer Ocean. Geophysical Research Letters, 48(6).
Abstract: Humboldt Gletscher is a 100-km wide, slow-moving glacier in north Greenland which holds a 19-cm global sea level equivalent. Humboldt has been the fourth largest contributor to sea level rise since 1972 but the cause of its mass loss has not been elucidated. Multi-beam echo sounding data collected in 2019 indicate a seabed 200 m deeper than previously known. Conductivity temperature depth data reveal the presence of warm water of Atlantic origin at 0 degrees C at the glacier front and a warming of the ocean waters by 0.9 +/- 0.1 degrees C since 1962. Using an ocean model, we reconstruct grounded ice undercutting by the ocean, combine it with calculated retreat caused by ice thinning to floatation, and are able to fully explain the observed retreat. Two thirds of the retreat are caused by undercutting of grounded ice, which is a physical process not included in most ice sheet models.
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Rivera, I., Molina-Carpio, J., Espinoza, J., Gutierrez-Cori, O., Ceron, W., Frappart, F., et al. (2021). The Role of the Rainfall Variability in the Decline of the Surface Suspended Sediment in the Upper Madeira Basin (2003-2017). Frontiers In Water, 3.
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Rose, C., Coen, M., Andrews, E., Lin, Y., Bossert, I., Myhre, C., et al. (2021). Seasonality of the particle number concentration and size distribution: a global analysis retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories. Atmospheric Chemistry And Physics, 21(22), 17185–17223.
Abstract: Aerosol particles are a complex component of the atmospheric system which influence climate directly by interacting with solar radiation, and indirectly by contributing to cloud formation. The variety of their sources, as well as the multiple transformations they may undergo during their transport (including wet and dry deposition), result in significant spatial and temporal variability of their properties. Documenting this variability is essential to provide a proper representation of aerosols and cloud condensation nuclei (CCN) in climate models. Using measurements conducted in 2016 or 2017 at 62 ground-based stations around the world, this study provides the most up-to-date picture of the spatial distribution of particle number concentration (N-tot) and number size distribution (PNSD, from 39 sites). A sensitivity study was first performed to assess the impact of data availability on N-tot's annual and seasonal statistics, as well as on the analysis of its diel cycle. Thresholds of 50% and 60% were set at the seasonal and annual scale, respectively, for the study of the corresponding statistics, and a slightly higher coverage (75 %) was required to document the diel cycle. Although some observations are common to a majority of sites, the variety of environments characterizing these stations made it possible to highlight contrasting findings, which, among other factors, seem to be significantly related to the level of anthropogenic influence. The concentrations measured at polar sites are the lowest (similar to 10(2) cm(-3)) and show a clear seasonality, which is also visible in the shape of the PNSD, while diel cycles are in general less evident, due notably to the absence of a regular day-night cycle in some seasons. In contrast, the concentrations characteristic of urban environments are the highest (similar to 10(3)-10(4) cm(-3)) and do not show pronounced seasonal variations, whereas diel cycles tend to be very regular over the year at these stations. The remaining sites, including mountain and non-urban continental and coastal stations, do not exhibit as obvious common behaviour as polar and urban sites and display, on average, intermediate N-tot (similar to 10(2)-10(3) cm(-3)). Particle concentrations measured at mountain sites, however, are generally lower compared to nearby lowland sites, and tend to exhibit somewhat more pronounced seasonal variations as a likely result of the strong impact of the atmospheric boundary layer (ABL) influence in connection with the topography of the sites. ABL dynamics also likely contribute to the diel cycle of N-tot observed at these stations. Based on available PNSD measurements, CCN-sized particles (considered here as either >50 nm or >100 nm) can represent from a few percent to almost all of N-tot, corresponding to seasonal medians on the order of similar to 10 to 1000 cm(-3), with seasonal patterns and a hierarchy of the site types broadly similar to those observed for N-tot. Overall, this work illustrates the importance of in situ measurements, in particular for the study of aerosol physical properties, and thus strongly supports the development of a broad global network of near surface observatories to increase and homogenize the spatial coverage of the measurements, and guarantee as well data availability and quality. The results of this study also provide a valuable, freely available and easy to use support for model comparison and validation, with the ultimate goal of contributing to improvement of the representation of aerosol-cloud interactions in models, and, therefore, of the evaluation of the impact of aerosol particles on climate.
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Rosero, P., Crespo-Perez, V., Espinosa, R., Andino, P., Barragan, A., Moret, P., et al. (2021). Multi-taxa colonisation along the foreland of a vanishing equatorial glacier. Ecography, 44(7), 1010–1021.
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Rounce, D., Hock, R., Mcnabb, R., Millan, R., Sommer, C., Braun, M., et al. (2021). Distributed Global Debris Thickness Estimates Reveal Debris Significantly Impacts Glacier Mass Balance. Geophysical Research Letters, 48(8).
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Rowan, A., Nicholson, L., Quincey, D., Gibson, M., Irvine-Fynn, T., Watson, C., et al. (2021). Seasonally stable temperature gradients through supraglacial debris in the Everest region of Nepal, Central Himalaya. Journal Of Glaciology, 67(261), 170–181.
Abstract: Rock debris covers similar to 30% of glacier ablation areas in the Central Himalaya and modifies the impact of atmospheric conditions on mass balance. The thermal properties of supraglacial debris are diurnally variable but remain poorly constrained for monsoon-influenced glaciers over the timescale of the ablation season. We measured vertical debris profile temperatures at 12 sites on four glaciers in the Everest region with debris thickness ranging from 0.08 to 2.8 m. Typically, the length of the ice ablation season beneath supraglacial debris was 160 days (15 May to 22 October)-a month longer than the monsoon season. Debris temperature gradients were approximately linear (r(2) > 0.83), measured as -40 degrees C m(-1) where debris was up to 0.1 m thick, -20 degrees C m(-1) for debris 0.1-0.5 m thick, and -4 degrees C m(-1) for debris greater than 0.5 m thick. Our results demonstrate that the influence of supraglacial debris on the temperature of the underlying ice surface, and therefore melt, is stable at a seasonal timescale and can be estimated from near-surface temperature. These results have the potential to greatly improve the representation of ablation in calculations of debris-covered glacier mass balance and projections of their response to climate change.
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Royer, A., Picard, G., Vargel, C., Langlois, A., Gouttevin, I., & Dumont, M. (2021). Improved Simulation of Arctic Circumpolar Land Area Snow Properties and Soil Temperatures. Frontiers In Earth Science, 9.
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Ruiz-Hernandez, J., Condom, T., Ribstein, P., Le Moine, N., Espinoza, J., Junquas, C., et al. (2021). Spatial variability of diurnal to seasonal cycles of precipitation from a high-altitude equatorial Andean valley to the Amazon Basin. Journal Of Hydrology-Regional Studies, 38.
Abstract: Study region: The upper part of the Guayllabamba and Napo basins (78.2 degrees W, 0.3 degrees S; 18,500 km(2)) in the equatorial Andes, which are vulnerable to stress on the ecosystem services. Study focus: This paper analyses the diurnal cycle of precipitation over a transect from the Andes to the Amazon. The diurnal cycle is estimated as the diurnal distribution of precipitation for 2014-2019 using records from 80 stations. Cluster analysis performed on the diurnal cycle estimates depicts the spatial association between the diurnal and seasonal cycles of precipitation. New hydrological insights: A northwest-southeast spatial variation in the diurnal and seasonal cycles is identified with four groups of stations. In the western part, the seasonal cycles of Groups 1 and 2 are bimodal with precipitation maxima in the March-April and October-November seasons and a short drier season in July-August. In the eastern part, Group 3 also presents bimodality, but a weaker seasonal cycle. Conversely, Group 4 is unimodal with a peak in June. Distinct diurnal cycles are observed in both drier and wetter seasons of Groups 1-3; no marked diurnal cycle is observed in Group 4. Groups 3 and 4 are the most spatially heterogeneous, with an exceptional horizontal variation of 330 mm/yr/km. The analysis of these variations provides insight into the atmospheric dynamics driving precipitation in this zone, and may help to better optimize the water supply system.
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Rull, V., Vegas-Vilarrubia, T., Corella, J., & Valero-Garces, B. (2021). Bronze Age to Medieval vegetation dynamics and landscape anthropization in the southern-central Pyrenees. Palaeogeography Palaeoclimatology Palaeoecology, 571.
Abstract: The varved sediments of Lake Montcort`es (central pre-Pyrenees) have provided a continuous high-resolution record of the last ca. 3000 years. Previous chronological and sedimentological studies of this record have furnished detailed paleoenvironmental reconstructions. However, palynological studies are only available for the last millennium, when the landscape around the lake had already been transformed by humans. Therefore, the earlier vegetation of Montcortes and the history of its anthropogenic transformations remain unknown. This paper presents a palynological analysis of the interval between the Late Bronze Age and the Early Medieval period, aimed at recording preanthropic conditions, anthropization onset and the further landscape transformations. During the Late Bronze Age (ca. 1100 BCE to 770 BCE), the vegetation did not show any evidence of human impact. The decisive anthropogenic transformation of the Montcort`es catchment vegetation and landscape started at the beginning of the Iron Age (770 BCE) and continued during Roman and Medieval times in the form of recurrent burning, grazing, cultivation, silviculture and hemp retting. Some intervals of lower human pressure were recorded, but the original vegetation never returned. The anthropization that took place during the Iron Age did not cause notable changes in the sediment yield to the lake, but a significant limnological shift occurred, as manifested in the initiation of varve formation, a process that has been continuous until today. Climatic shifts seem to have played a secondary role in influencing vegetation and landscape changes. These results contrast with previous inferences of low anthropogenic impact until the Medieval Period, at a regional level. Similar studies may be developed on other mountain ranges to verify whether landscape anthropization occurred earlier than previously thought, and to verify the potential occurrence of elevational gradients in the anthropization of mountain landscapes.
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Samake, A., Martins, J., Bonin, A., Uzu, G., Taberlet, P., Conil, S., et al. (2021). Variability of the Atmospheric PM10 Microbiome in Three Climatic Regions of France. Frontiers In Microbiology, 11.
Abstract: Primary Biogenic Organic Aerosols (PBOA) were recently shown to be produced by only a few types of microorganisms, emitted by the surrounding vegetation in the case of a regionally homogeneous field site. This study presents the first comprehensive description of the structure and main sources of airborne microbial communities associated with temporal trends in Sugar Compounds (SC) concentrations of PM10 in 3 sites under a climatic gradient in France. By combining sugar chemistry and DNA Metabarcoding approaches, we intended to identify PM10-associated microbial communities and their main sources at three sampling-sites in France, under different climates, during the summer of 2018. This study accounted also for the interannual variability in summer airborne microbial community structure (bacteria and fungi only) associated with PM10-SC concentrations during a 2 consecutive years' survey at one site. Our results showed that temporal changes in PM10-SC in the three sites are associated with the abundance of only a few specific taxa of airborne fungi and bacterial. These taxa differ significantly between the 3 climatic regions studied. The microbial communities structure associated with SC concentrations of PM10 during a consecutive 2-year study remained stable in the rural area. Atmospheric concentration levels of PM10-SC species varied significantly between the 3 study sites, but with no clear difference according to site typology (rural vs. urban), suggesting that SC emissions are related to regional rather than local climatic characteristics. The overall microbial beta diversity in PM10 samples is significantly different from that of the main vegetation around the urban sites studied. This indicates that the airborne microorganisms at these urban sites are not solely from the immediate surrounding vegetation, which contrasts with observations at the scale of a regionally homogeneous rural site in 2017. These results improve our understanding of the spatial behavior of tracers of PBOA emission sources, which need to be better characterized to further implement this important mass fraction of Organic Matter (OM) in Chemical Transport models (CTM).
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Sandells, M., Lowe, H., Picard, G., Dumont, M., Essery, R., Floury, N., et al. (2021). X-Ray Tomography-Based Microstructure Representation in the Snow Microwave Radiative Transfer Model. Ieee Transactions On Geoscience And Remote Sensing, .
Abstract: The modular Snow Microwave Radiative Transfer (SMRT) model simulates microwave scattering behavior in snow via different selectable theories and snow microstructure representations, which is well suited to intercomparisons analyses. Here, five microstructure models were parameterized from X-ray tomography and thin-section images of snow samples and evaluated with SMRT. Three field experiments provided observations of scattering and absorption coefficients, brightness temperature, and/or backscatter with the increasing complexity of snowpack. These took place in Sodankyla, Finland, and Weissfluhjoch, Switzerland. Simulations of scattering and absorption coefficients agreed well with observations, with higher errors for snow with predominantly vertical structures. For simulation of brightness temperature, difficulty in retrieving stickiness with the Sticky Hard Sphere microstructure model resulted in relatively poor performance for two experiments, but good agreement for the third. Exponential microstructure gave generally good results, near to the best performing models for two field experiments. The Independent Sphere model gave intermediate results. New Teubner-Strey and Gaussian Random Field models demonstrated the advantages of SMRT over microwave models with restricted microstructural geometry. Relative model performance is assessed by the quality of the microstructure model fit to micro-computed tomography (CT) data and further improvements may be possible with different fitting techniques. Careful consideration of simulation stratigraphy is required in this new era of high-resolution microstructure measurement as layers thinner than the wavelength introduce artificial scattering boundaries not seen by the instrument.
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Santos-Gonzalez, J., Gomez-Villar, A., Gonzalez-Gutierrez, R., Corella, J., Benito, G., Redondo-Vega, J., et al. (2021). Geomorphological impact, hydraulics and watershed- lake connectivity during extreme floods in mountain areas: The 1959 Vega de Tera dam failure, NW Spain. Geomorphology, 375.
Abstract: Dam-failure floods typically involve greater peak discharge than the largest meteorological flood at a basin. Determining the geomorphic effectiveness of extreme flooding caused by a breach mechanism provides insight into the role of flood scale on the resulting processes and landforms. Here, we present a geomorphological and hydraulic analysis of the 1959 Vega de Tera (NW Spain) dam-break flood, a worldwide notable dam-failure incident that released a flow of 7.8106 m(3) that caused the death of 144 people at Ribadelago before reaching Lake Sanabria (9 km down valley). This watershed-lake connection provides a comprehensive analysis of an extreme sediment delivery event in the context of a millennial long lake depositional record. One-dimensional unsteady flow computation shows a peak flow hydrograph attenuating from 13,000 m(3) s(-1) to 5150 m(3) s(-1), that reached a maximum flow depth of 34 m and velocity of 30 ms(-1). Spatial variation of erosional and depositional landforms are related with local flow hydraulics: i) in steep sectors flow regime was supercritical (shear value up to 11,200 Pa) and produced up to 30 m deep bedrock channel erosion; ii) at the boundary of steep and flatten sectors, transition to subcritical regime generated large plunge pools (up to 6000 m(2) and 15.2 min depth); iii) in low-gradient sectors low shear stress gave rise to depositional landforms, namely gravel bars with dam boulders up to 3 m long, and a debris cone with coarse gravel and expansion sand bars. The depositional landforms amount for a total volume of ca 2.11 . 106 m(3) in the Tera valley (37% in the gorge and 63% in the floodplain). The dense, energetic sediment-laden flow reached Lake Sanabria forming a debris cone close to the mouth and caused an underwater hyperpycnal current, depositing a similar to 10 cm-thick sandy-silt layer all over the two distal subbasins. The estimated volume of the deposited fine sediments in the lake ranges between 200,000 and 368,000 m(3). The lake record shows that this was the largest flood in the basin during the Holocene. Previous to the dam break, the sediment connectivity between the Sanabria watershed and the lake was limited because of the “staircase” topography and the presence of small glacial depressions filled with sediments since deglaciation. Even during the flood, the great majority of the sediments were deposited along the flood pathway, and only a small percentage (10-20%) reached the lake. Although the hydraulics of the Tera River were not changed after the flood, the newly formed pools in the watershed could diminish the connectivity between the river and the lake in the future, as some new sedimentation areas (pools) were generated acting as natural dams and thus decreasing sediment input to the lake. (C) 2020 Elsevier B.V. All rights reserved.
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Schmidely, L., Nehrbass-Ahles, C., Schmitt, J., Han, J., Silva, L., Shin, J., et al. (2021). CH4 and N2O fluctuations during the penultimate deglaciation. Climate Of The Past, 17(4), 1627–1643.
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Scholzen, C., Schuler, T., & Gilbert, A. (2021). Sensitivity of subglacial drainage to water supply distribution at the Kongsfjord basin, Svalbard. Cryosphere, 15(6), 2719–2738.
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Sellier, V., Navratil, O., Laceby, J., Legout, C., Foucher, A., Allenbach, M., et al. (2021). Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands). Soil, 7(2), 743–766.
Abstract: Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km(2)). Source (n = 24) and river sediment (n = 19) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365-735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1% of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6% of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour + geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 +/- 25% for the 2015 flood event, whereas the colour + geochemistry model (3) estimated that the mining tributaries contributed 65 +/- 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 +/- 8% by the geochemistry model (2) versus 88 +/- 8% by the colour C geochemistry model (3) for the 2017 flood event. Therefore, the use of these approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.
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Senior, C., Marsham, J., Berthou, S., Burgin, L., Folwell, S., Kendon, E., et al. (2021). Convection-Permitting Regional Climate Change Simulations for Understanding Future Climate and Informing Decision-Making in Africa. Bulletin Of The American Meteorological Society, 102(6), E1206–E1223.
Abstract: Pan-Africa convection-permitting regional climate model simulations have been performed to study the impact of high resolution and the explicit representation of atmospheric moist convection on the present and future climate of Africa. These unique simulations have allowed European and African climate scientists to understand the critical role that the representation of convection plays in the ability of a contemporary climate model to capture climate and climate change, including many impact-relevant aspects such as rainfall variability and extremes. There are significant improvements in not only the small-scale characteristics of rainfall such as its intensity and diurnal cycle, but also in the large-scale circulation. Similarly, effects of explicit convection affect not only projected changes in rainfall extremes, dry spells, and high winds, but also continental-scale circulation and regional rainfall accumulations. The physics underlying such differences are in many cases expected to be relevant to all models that use parameterized convection. In some cases physical understanding of small-scale change means that we can provide regional decision-makers with new scales of information across a range of sectors. We demonstrate the potential value of these simulations both as scientific tools to increase climate process understanding and, when used with other models, for direct user applications. We describe how these ground-breaking simulations have been achieved under the U.K. Government's Future Climate for Africa Programme. We anticipate a growing number of such simulations, which we advocate should become a routine component of climate projection, and encourage international coordination of such computationally and human-resource expensive simulations as effectively as possible.
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Serazin, G., Di Luca, A., Sen Gupta, A., Roge, M., Jourdain, N., Argueso, D., et al. (2021). East Australian Cyclones and Air-Sea Feedbacks. Journal Of Geophysical Research-Atmospheres, 126(20).
Abstract: The importance of resolving mesoscale air-sea interactions to represent cyclones impacting the East Coast of Australia, the so-called East Coast Lows (ECLs), is investigated using the Australian Regional Coupled Model based on NEMO-OASIS-WRF (NOW) at 1/4 degrees resolution. The fully coupled model is shown to be capable of reproducing correctly relevant features such as the seasonality, spatial distribution and intensity of ECLs while it partially resolves mesoscale processes, such as air-sea feedbacks over ocean eddies and fronts. The mesoscale thermal feedback (TFB) and the current feedback (CFB) are shown to influence the intensity of northern ECLs (north of 30 degrees S), with the TFB modulating the pre-storm sea surface temperature (SST) by shifting ECL locations eastwards and the CFB modulating the wind stress. By fully uncoupling the atmospheric model of NOW, the intensity of northern ECLs is increased due to the absence of the cold wake that provides a negative feedback to the cyclone. The number of ECLs might also be affected by the air-sea feedbacks but large interannual variability hampers significant results with short-term simulations. The TFB and CFB modify the climatology of SST (mean and variability) but no direct link is found between these changes and those noticed in ECL properties. These results show that the representation of ECLs, mainly north of 30 degrees S, depend on how air-sea feedbacks are simulated. This is particularly important for atmospheric downscaling of climate projections as small-scale SST interactions and the effects of ocean currents are not accounted for.
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Seyedhashemi, H., Hingray, B., Lavaysse, C., & Chamarande, T. (2021). The Impact of Low-Resource Periods on the Reliability of Wind Power Systems for Rural Electrification in Africa. Energies, 14(11).
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Shangguan, Y., Zhuang, X., Querol, X., Li, B., Li, J., Moreno, N., et al. (2021). Mineralogical and geochemical variations from coal to deposited dust and toxicity of size-segregated respirable dust in a blasting mining underground coal mine in Hunan Province, South China. International Journal Of Coal Geology, 248.
Abstract: This study systematically investigates the mineralogical and geochemical variations in parent coal, coal gangue (roof, parting, and floor), deposited coal mine dust (DD), and respirable fractions of DD (RD) in an underground coal mine using the blasting mining method in China to evaluate the major sources of DD. The emission of dust in this study is affected by coal gangue sources during the mining process, which causes different geochemical patterns in the DD samples. Moreover, weathering of the cement gunite walls plays an important role in the enrichment of specific elements in the DD from air uptake and air out galleries. Furthermore, the spatial variation in RD characteristics, including mineralogy, geochemistry, and oxidative potential (OP), is discussed, with emphasis on the major health-relevant species and elements. Organic species from coal dust seem to be the essential components contributing to OP rather than metals, although some metals (e.g., Cr, Co, Ge, Se, Zn, Ba, Rb, Cs, Sn, and Pb) influence OP to some degree.
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Sierra, J., Arias, P., Duran-Quesada, A., Tapias, K., Vieira, S., & Martinez, J. (2021). The Choco low-level jet: past, present and future. Climate Dynamics, .
Abstract: The Choco low-level jet is among the main regional circulation mechanisms related to the advection of water vapor from the eastern Pacific to northwestern South America. Variations in the intensity of position of the jet core are identified as determinant for regional moisture transport and associated rainfall. This paper analyzes the annual cycle of intensity and latitudinal location of this jet according to different reanalysis and observational datasets. Moreover, we compare possible changes in the Choco jet occurred during past climates, like the little ice age (LIA), with those associated with future scenarios of greenhouse gas concentrations (RCP8.5), using simulations from the Paleoclimate Modelling Intercomparison Project Phase 3 (PMIP3) and the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our results suggest that according to reanalysis/observational data, as well as the CMIP5 models with the best representation of the Choco jet in present climate, there is a positive correlation between the jet intensity and its latitudinal location, and such relationship is associated with the sea level pressure (SLP) difference between the eastern tropical Pacific and the northwestern South American landmass. Hence, stronger (weaker) SLP differences favor a stronger (weaker) intensity and a northward (southward) location of the Choco jet. PMIP3 simulations suggest a stronger and northward Choco jet during LIA due to a stronger SLP difference in comparison to present climate. However, under the RCP8.5 scenario, there is not robust agreement among CMIP5 models although the best models suggest a southward jet at the end of the 21st century. This suggests that the mechanisms influencing the Choco jet may play different roles during past natural climate changes with respect to anthropogenically-forced climate changes.
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Sierra, J., Junquas, C., Espinoza, J., Segura, H., Condom, T., Andrade, M., et al. (2021). Deforestation impacts on Amazon-Andes hydroclimatic connectivity. Climate Dynamics, .
Abstract: Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation on the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-years high-resolution simulations (2001-2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (similar to 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (similar to 20-30%) due to a strong reduction in the humidity transport from the Amazon plains towards the Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.
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Simonin, M., Martins, J., Uzu, G., Spadini, L., Navel, A., & Richaume, A. (2021). Low mobility of CuO and TiO2 nanoparticles in agricultural soils of contrasting texture and organic matter content. Science Of The Total Environment, 783.
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Simu, S., Miyazaki, Y., Tachibana, E., Finkenzeller, H., Brioude, J., Colomb, A., et al. (2021). Origin of water-soluble organic aerosols at the Maido high-altitude observatory, Reunion Island, in the tropical Indian Ocean. Atmospheric Chemistry And Physics, 21(22), 17017–17029.
Abstract: The tropical and subtropical Indian Ocean (IO) is expected to be a significant source of water-soluble organic aerosols (WSOAs), which are important factors relevant to cloud formation of aerosol particles. Current atmospheric numerical models significantly underestimate the budget of organic aerosols and their precursors, especially over tropical oceans. This is primarily due to poor knowledge of sources and the paucity of observations of these parameters considering spatial and temporal variation over the tropical open ocean. To evaluate the contribution of sources to WSOA as well as their formation processes, submicrometer aerosol sampling was conducted at the high-altitude Maido observatory (21.1 degrees S, 55.4 degrees E; 2160ma.s.l.), located on the remote island of La Reunion in the southwest IO. The aerosol samples were continuously collected during local daytime and nighttime, which corresponded to the ambient conditions of the marine boundary layer (MBL) and free troposphere (FT), respectively, from 15 March to 24 May 2018. Chemical analysis showed that organic matter was the dominant component of submicrometer water-soluble aerosol (similar to 45 +/- 17 %) during the wet season (15 March-23 April). On the other hand, sulfate dominated (similar to 77 +/- 17 %) during the dry season (24 April-24 May), most of which was attributable to the effect of volcanic eruption. Measurements of the stable carbon isotope ratio of water-soluble organic carbon (WSOC) suggested that marine sources contributed significantly to the observed WSOC mass in both the MBL and the FT in the wet season, whereas a mixture of marine and terrestrial sources contributed to WSOC in the dry season. The distinct seasonal changes in the dominant source of WSOC were also supported by Lagrangian trajectory analysis. Positive matrix factorization analysis suggested that marine secondary organic aerosol (OA) dominantly contributed to the observed WSOC mass (similar to 70 %) during the wet season, whereas mixtures of marine and terrestrial sources contributed during the dry season in both MBL and FT. Overall, this study demonstrates that the effect of marine secondary sources is likely important up to the FT in the wet season, which may affect cloud formation as well as direct radiative forcing over oceanic regions.
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Svensson, J., Strom, J., Honkanen, H., Asmi, E., Dkhar, N., Tayal, S., et al. (2021). Deposition of light-absorbing particles in glacier snow of the Sunderdhunga Valley, the southern forefront of the central Himalayas. Atmospheric Chemistry And Physics, 21(4), 2931–2943.
Abstract: Anthropogenic activities on the Indo-Gangetic Plain emit vast amounts of light-absorbing particles (LAPs) into the atmosphere, modifying the atmospheric radiation state. With transport to the nearby Himalayas and deposition to its surfaces the particles contribute to glacier melt and snowmelt via darkening of the highly reflective snow. The central Himalayas have been identified as a region where LAPs are especially pronounced in glacier snow but still remain a region where measurements of LAPs in the snow are scarce. Here we study the deposition of LAPs in five snow pits sampled in 2016 (and one from 2015) within 1 km from each other from two glaciers in the Sunderdhunga Valley, in the state of Uttarakhand, India, in the central Himalayas. The snow pits display a distinct enriched LAP layer interleaved by younger snow above and older snow below. The LAPs exhibit a distinct vertical distribution in these different snow layers. For the analyzed elemental carbon (EC), the younger snow layers in the different pits show similarities, which can be characterized by a deposition constant of about 50 μg m(-2) mm(-1) snow water equivalent (SWE), while the old-snow layers also indicate similar values, described by a deposition constant of roughly 150 μg m(-2) mm(-1) SWE. The enriched LAP layer, contrarily, displays no similar trends between the pits. Instead, it is characterized by very high amounts of LAPs and differ in orders of magnitude for concentration between the pits. The enriched LAP layer is likely a result of strong melting that took place during the summers of 2015 and 2016, as well as possible lateral transport of LAPs. The mineral dust fractional absorption is slightly below 50% for the young- and old-snow layers, whereas it is the dominating light-absorbing constituent in the enriched LAP layer, thus, highlighting the importance of dust in the region. Our results indicate the problems with complex topography in the Himalayas but, nonetheless, can be useful in large-scale assessments of LAPs in Himalayan snow.
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Thollet, F., Rousseau, C., Camenen, B., Boubkraoui, S., Branger, F., Lauters, F., et al. (2021). Long term high frequency sediment observatory in an alpine catchment: The Arc-Isere rivers, France. Hydrological Processes, 35(2).
Abstract: We present a dataset on to the Arc-Isere long-term environmental research observatory, which is part of the Rhone Basin Long Term Environmental Research Observatory. This alpine catchment located in the French Alps is characterized by high Suspended Particulate Matter (SPM) in anthropogenized valleys. Suspended Sediment Concentrations (SSC) naturally observed in the river are very high, ranging from a few tens of milligrams per litre at low flow to tens of grams per litre during major natural hydrological events (floods, debris flows) or river dam hydraulic flushes. One research objective related to this site is to better understanding the SSC dynamics along the river using a system of nested catchments (Arvan, Arc, and Isere) in order to assess both temporal and spatial dynamics. The data allow the quantification of fine sediment yields and also the evaluation of possible morphological changes due to fine sediment deposition or resuspension. Additionally, the observatory database support studies on contaminants (either dissolved or particulate contaminants). Our monitoring includes six stations with high frequency (2-30 min) streamflow, SSC measurement using turbidity sensors, and associated automatic sampling. Discharge is measured via water level measurements and a rating curve. The oldest station (Grenoble-campus) started recording discharge and concentration data from April 2006 while others stations were built between 2009 and 2011. Data are available in an online data website called 'Base de Donnees des Observatoires en Hydrologie' (Hydrological observatory database, ) with a DOI reference for the dataset. The hydrological and sediment transport time series are stored, managed and made available to a wide community with unfettered access in order to be used at their full extent. This database is used as a data exchange tool for both scientists and operational end-users and there is an associated online tool to compute integrated fluxes.
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Thomas, M., Laube, J., Kaiser, J., Allin, S., Martinerie, P., Mulvaney, R., et al. (2021). Stratospheric carbon isotope fractionation and tropospheric histories of CFC-11, CFC-12, and CFC-113 isotopologues. Atmospheric Chemistry And Physics, 21(9), 6857–6873.
Abstract: We present novel measurements of the carbon isotope composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CF2ClCFCl2), three atmospheric trace gases that are important for both stratospheric ozone depletion and global warming. These measurements were carried out on air samples collected in the stratosphere – the main sink region for these gases – and on air extracted from deep polar firn snow. We quantify, for the first time, the apparent isotopic fractionation, epsilon(app)(C-13), for these gases as they are destroyed in the high- and mid-latitude stratosphere: epsilon(app)(CFC-12, high-latitude) = (-20.2 +/- 4.4) parts per thousand, and epsilon(app)(CFC-113, high-latitude) = (-9.4 +/- 4.4) parts per thousand, epsilon(app)(CFC-12, mid-latitude) = (30.3 +/- 10.7) parts per thousand, and epsilon(app)(CFC-113, mid-latitude) = (34.4 +/- 9.8) parts per thousand. Our CFC-11 measurements were not sufficient to calculate epsilon(app)(CFC-11), so we instead used previously reported photolytic fractionation for CFC-11 and CFC-12 to scale our epsilon(app)(CFC-12), resulting in epsilon(app)(CFC-11, high-latitude) = (-7.8 +/- 1.7) parts per thousand and epsilon(app)(CFC-11, mid-latitude) = (-11.7 +/- 4.2) parts per thousand. Measurements of firn air were used to construct histories of the tropospheric isotopic composition, delta(T)(C-13), for CFC-11 (1950s to 2009), CFC-12 (1950s to 2009), and CFC-113 (1970s to 2009), with delta(T)(C-13) increasing for each gas. We used epsilon(app)(high-latitude), which was derived from more data, and a constant isotopic composition of emissions, delta(E)(C-13), to model delta(T)(C-13, CFC-11), delta(T)(C-13, CFC-12), and delta(T)(C-13, CFC-113). For CFC-11 and CFC-12, modelled delta(T)(C-13) was consistent with measured delta(T)(C-13) for the entire period covered by the measurements, suggesting that no dramatic change in delta(E)(C-13, CFC-11) or delta(E)(C-13, CFC-12) has occurred since the 1950s. For CFC-113, our modelled delta(T)(C-13, CFC-113) did not agree with our measurements earlier than 1980. This discrepancy may be indicative of a change in delta(E)(C-13, CFC-113). However, this conclusion is based largely on a single sample and only just significant outside the 95% confidence interval. Therefore more work is needed to independently verify this temporal trend in the global tropospheric C-13 isotopic composition of CFC-113. Our modelling predicts increasing delta(T)(C-13, CFC-11), delta(T)(C-13, CFC-12), and delta(T)(C-13, CFC-113) into the future. We investigated the effect of recently reported new CFC-11 emissions on background delta(T)(C-13, CFC-11) by fixing model emissions after 2012 and comparing delta(T)(C-13, CFC-11) in this scenario to the model base case. The difference in delta(T)(C-13, CFC-11) between these scenarios was 1.4 parts per thousand in 2050. This difference is smaller than our model uncertainty envelope and would therefore require improved modelling and measurement precision as well as better quantified isotopic source compositions to detect.
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Trechera, P., Moreno, T., Cordoba, P., Moreno, N., Amato, F., Cortes, J., et al. (2021). Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals. Science Of The Total Environment, 800.
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Troger, R., Ren, H., Yin, D., Postigo, C., Nguyen, P., Baduel, C., et al. (2021). What 's in the water? – Target and suspect screening of contaminants of emerging concern in raw water and drinking water from Europe and Asia. Water Research, 198.
Abstract: There is growing worry that drinking water can be affected by contaminants of emerging concern (CECs), potentially threatening human health. In this study, a wide range of CECs ( n = 177), including pharmaceuticals, pesticides, perfluoroalkyl substances (PFASs) and other compounds, were analysed in raw water and in drinking water collected from drinking water treatment plants (DWTPs) in Europe and Asia ( n = 13). The impact of human activities was reflected in large numbers of compounds detected ( n = 115) and high variation in concentrations in the raw water (range 15-7995 ng L & minus;1 for E177 CECs). The variation was less pronounced in drinking water, with total concentration ranging from 35 to 919 ng L & minus;1 . Treatment efficiency was on average 65 +/- 28%, with wide variation between different DWTPs. The DWTP with the highest ECEC concentrations in raw water had the most efficient treatment procedure (average treatment efficiency 89%), whereas the DWTP with the lowest E177 CEC concentration in the raw water had the lowest average treatment efficiency (2.3%). Suspect screening was performed for 500 compounds ranked high as chemicals of concern for drinking water, using a prioritisation tool (SusTool). Overall, 208 features of interest were discovered and three were confirmed with reference standards. There was co-variation between removal efficiency in DWTPs for the target compounds and the suspected features detected using suspect screening, implying that removal of known contaminants can be used to predict overall removal of potential CECs for drinking water production. Our results can be of high value for DWTPs around the globe in their planning for future treatment strategies to meet the increasing concern about human ex-posure to unknown CECs present in their drinking water. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
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Tuite, K., Thomas, J., Veres, P., Roberts, J., Stevens, P., Griffith, S., et al. (2021). Quantifying Nitrous Acid Formation Mechanisms Using Measured Vertical Profiles During the CalNex 2010 Campaign and 1D Column Modeling. Journal Of Geophysical Research-Atmospheres, 126(13).
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Uber, M., Nord, G., Legout, C., & Cea, L. (2021). How do modeling choices and erosion zone locations impact the representation of connectivity and the dynamics of suspended sediments in a multi-source soil erosion model? Earth Surface Dynamics, 9(1), 123–144.
Abstract: Soil erosion and suspended sediment transport understanding is an important issue in terms of soil and water resources management in the critical zone. In mesoscale watersheds (> 10 km(2)) the spatial distribution of potential sediment sources within the catchment associated with rainfall dynamics is considered to be the main factor in the observed suspended sediment flux variability within and between runoff events. Given the high spatial heterogeneity that can exist for such scales of interest, distributed physically based models of soil erosion and sediment transport are powerful tools to distinguish the specific effect of structural and functional connectivity on suspended sediment flux dynamics. As the spatial discretization of a model and its parameterization can crucially influence how the structural connectivity of the catchment is represented in the model, this study analyzed the impact of modeling choices in terms of the contributing drainage area (CDA) threshold to define the river network and of Manning's roughness parameter (n) on the sediment flux variability at the outlet of two geomorphologically distinct watersheds. While the modeled liquid and solid discharges were found to be sensitive to these choices, the patterns of the modeled source contributions remained relatively similar when the CDA threshold was restricted to the range of 15 to 50 ha, with n restricted to the range 0.4-0.8 on the hill-slopes and to 0.025-0.075 in the river. The comparison of the two catchments showed that the actual location of sediment sources was more important than the choices made during discretization and parameterization of the model. Among the various structural connectivity indicators used to describe the geological sources, the mean distance to the stream was the most relevant proxy for the temporal characteristics of the modeled sedigraphs.
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Uchida, T., Deremble, B., & Penduff, T. (2021). The Seasonal Variability of the Ocean Energy Cycle from a Quasi-Geostrophic Double Gyre Ensemble. Fluids, 6(6).
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Veillon, F., Dumont, M., Amory, C., & Fructus, M. (2021). A versatile method for computing optimized snow albedo from spectrally fixed radiative variables: VALHALLA v1.0. Geoscientific Model Development, 14(12), 7329–7343.
Abstract: In climate models, the snow albedo scheme generally calculates only a narrowband or broad-band albedo, which leads to significant uncertainties. Here, we present the Versatile ALbedo calculation metHod based on spectrALLy fixed radiative vAriables (VALHALLA version 1.0) to optimize spectral snow albedo calculation. For this optimization, the energy absorbed by the snowpack is calculated by the spectral albedo model Two-streAm Radiative TransfEr in Snow (TARIES) and the spectral irradiance model Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART). This calculation takes into account the spectral characteristics of the incident radiation and the optical properties of the snow based on an analytical approximation of the radiative transfer of snow. For this method, 30 wavelengths, called tie points (TPs), and 16 reference irradiance profiles are calculated to incorporate the absorbed energy and the reference irradiance. The absorbed energy is then interpolated for each wavelength between two TPs with adequate kernel functions derived from radiative transfer theory for snow and the atmosphere. We show that the accuracy of the absorbed energy calculation primarily depends on the adaptation of the irradiance of the reference profile to that of the simulation (absolute difference < 1 W m(-2) for broadband absorbed energy and absolute difference < 0.005 for broadband albedo). In addition to the performance in terms of accuracy and calculation time, the method is adaptable to any atmospheric input (broadband, narrowband) and is easily adaptable for integration into a radiative scheme of a global or regional climate model.
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Verfaillie, D., Charton, J., Schimmelpfennig, I., Stroebele, Z., Jomelli, V., Betard, F., et al. (2021). Evolution of the Cook Ice Cap (Kerguelen Islands) between the last centuries and 2100 ce based on cosmogenic dating and glacio-climatic modelling. Antarctic Science, 33(3), 301–317.
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Verjans, V., Leeson, A., Mcmillan, M., Stevens, C., Van Wessem, J., Van De Berg, W., et al. (2021). Uncertainty in East Antarctic Firn Thickness Constrained Using a Model Ensemble Approach. Geophysical Research Letters, 48(7).
Abstract: Mass balance assessments of the East Antarctic ice sheet (EAIS) are highly sensitive to changes in firn thickness, causing substantial disagreement in estimates of its contribution to sea-level. To better constrain the uncertainty in recent firn thickness changes, we develop an ensemble of 54 model scenarios of firn evolution between 1992 and 2017. Using statistical emulation of firn-densification models, we quantify the impact of firn compaction formulation, differing climatic forcing, and surface snow density on firn thickness evolution. At basin scales, the ensemble uncertainty in firn thickness change ranges between 0.2 and 1.0 cm yr(-1) (15%-300% relative uncertainty), with the choice of climate forcing having the largest influence on the spread. Our results show the regions of the ice sheet where unexplained discrepancies exist between observed elevation changes and an extensive set of modeled firn thickness changes estimates, marking an important step toward more accurately constraining ice sheet mass balance.
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Verron, J., Bonnefond, P., Andersen, O., Ardhuin, F., Berge-Nguyen, M., Bhowmick, S., et al. (2021). The SARAL/AltiKa mission: A step forward to the future of altimetry. Advances In Space Research, 68(2), 808–828.
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Vincent, C., Cusicanqui, D., Jourdain, B., Laarman, O., Six, D., Gilbert, A., et al. (2021). Geodetic point surface mass balances: a new approach to determine point surface mass balances on glaciers from remote sensing measurements. Cryosphere, 15(3), 1259–1276.
Abstract: Mass balance observations are very useful to assess climate change in different regions of the world. As opposed to glacier-wide mass balances which are influenced by the dynamic response of each glacier, point mass balances provide a direct climatic signal that depends on surface accumulation and ablation only. Unfortunately, major efforts are required to conduct in situ measurements on glaciers. Here, we propose a new approach that determines point surface mass balances from remote sensing observations. We call this balance the geodetic point surface mass balance. From observations and modelling performed on the Argentiere and Mer de Glace glaciers over the last decade, we show that the vertical ice flow velocity changes are small in areas of low bedrock slope. Therefore, assuming constant vertical velocities in time for such areas and provided that the vertical velocities have been measured for at least 1 year in the past, our method can be used to reconstruct annual point surface mass balances from surface elevations and horizontal velocities alone. We demonstrate that the annual point surface mass balances can be reconstructed with an accuracy of about 0.3?m of water equivalent per year (mw.e. a(-1)) using the vertical velocities observed over the previous years and data from unmanned aerial vehicle images. Given the recent improvements of satellite sensors, it should be possible to apply this method to high-spatial-resolution satellite images as well.
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Wagnon, P., Brun, F., Khadka, A., Berthier, E., Shrestha, D., Vincent, C., et al. (2021). Reanalysing the 2007-19 glaciological mass-balance series of Mera Glacier, Nepal, Central Himalaya, using geodetic mass balance. Journal Of Glaciology, 67(261), 117–125.
Abstract: The 2007-19 glaciological mass-balance series of Mera Glacier in the Everest Region, East Nepal, is reanalysed using the geodetic mass balance assessed by differencing two DEMs obtained from Pleiades stereo-images acquired in November 2012 and in October 2018. The glaciological glacier-wide annual mass balance of Mera Glacier has to be systematically decreased by 0.11 m w.e. a(-1) to match the geodetic mass balance. We attribute part of the positive bias of the glaciological mass balance to an over-estimation of the accumulation above 5520 m a.s.l., likely due to a measurement network unable to capture its spatial variability. Over the period 2007-19, Mera Glacier has lost mass at a rate of -0.41 +/- 0.20 m w.e. a(-1), in general agreement with regional averages for the central Himalaya. We observe a succession of negative mass-balance years since 2013.
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Weber, S., Uzu, G., Favez, O., Borlaza, L., Calas, A., Salameh, D., et al. (2021). Source apportionment of atmospheric PM10 oxidative potential: synthesis of 15 year-round urban datasets in France. Atmospheric Chemistry And Physics, 21(14), 11353–11378.
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Weyrich, P., Ruin, I., Terti, G., & Scolobig, A. (2021). Using serious games to evaluate the potential of social media information in early warning disaster management. International Journal Of Disaster Risk Reduction, 56.
Abstract: In recent years, the sharp increase in the use of social media by the public during major natural disasters has attracted the attention of various public agencies and safety organizations. Social media present a potential alternative communication system not only for disseminating information to the public, but also for receiving information from the individuals at risk. However, there is limited research on how emergency managers would use such information and whether it would make warning decision-making more effective or not. To address this gap, we used an existing serious game to accommodate informational and communication complexities in early warning disaster management. We played 4 game sessions with practitioners and PhD students involved in disaster risk management to simulate and test how public information from social media is used in emergency operation centres to make (protective and communicative) decisions. This includes how information is perceived in terms of levels of trust, usefulness and completeness depending on its type, source, quality/content and channel. Overall, we observe that information from the crowd disseminated on social media leads to better decisions and increases associated confidence levels. More precisely, we find that information from weather spotters, i.e. people trained in meteorology, is more trusted than information from the general public independent of the information quality. Ultimately, we demonstrate the usefulness of public social media information in warning decision-making, as well as the potential of serious games to evaluate warning communication, for instance by increasing warning communication literacy and enhancing collaborative capacity.
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Wilcox, C., Aly, C., Vischel, T., Panthou, G., Blanchet, J., Quantin, G., et al. (2021). Stochastorm: A Stochastic Rainfall Simulator for Convective Storms. Journal Of Hydrometeorology, 22(2), 387–404.
Abstract: Stochastic rainfall generators aim to reproduce the main statistical features of rainfall at small spatial and temporal scales. The simulated synthetic rainfall series are recognized as suitable for use with impact analysis in water, agricultural, and ecological management. Convection-driven precipitation, dominant in certain regions of the world such as the intertropical belt regions, presents properties that require specific consideration when modeling: (i) strong rainfall intermittency, (ii) high variability of intensities within storms, (iii) strong spatiotemporal correlation of intensities, and (iv) marked seasonality of storm properties. In this article, improvements for an existing stochastic generator of rainfall fields that models convective storms are presented. Notable novelties include (i) the ability to model precipitation event timing, (ii) an improved temporal disaggregation scheme representing the rainfall distribution at subevent scales, and (iii) using covariates to reflect seasonal changes in precipitation occurrence and marginal distribution parameters. Extreme values are explicitly considered in the distribution of storm event intensities. The simulator is calibrated and validated using 28 years of 5-min precipitation data from the 30-rain-gauge AMMA-CATCH network in the Sahelian region of southwest Niger. Both large propagative systems and smaller local convective precipitation are generated. Results show that simulator improvements coherently represent the local climatology. The simulator can generate scenarios for impact studies with accurate representation of convective precipitation characteristics.
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Wongchuig, S., Espinoza, J., Condom, T., Segura, H., Ronchail, J., Arias, P., et al. (2021). A regional view of the linkages between hydro-climatic changes and deforestation in the Southern Amazon. International Journal Of Climatology, .
Abstract: In the last four decades, the Southern Amazon (south of 8 degrees S) has shown changes in the spatial and temporal patterns of its hydro-climatic components, leading to drier conditions. Due to climate and land-use changes, this region is considered as a zone under biophysical transition processes. Previous studies have documented a complex interaction between climate and deforestation either on a large-scale or based on limited in situ data, typically covering the Brazilian Amazon. In this study, we analyse the relationships between hydro-climate, the surface water-energy partitioning and an index of regional forest cover change for the period 1981-2018. Additionally, we discretized three regions covering the Bolivian Amazon and the southern portions of the Peruvian and Brazilian Amazon due to their differences in the evolution of land use. In the Bolivian region, a high ratio of forest cover change, exceeding 40-50%, is related to a significant tendency to become water-limited. This change is associated with decreased rainfall, increased potential evapotranspiration and decreased actual evapotranspiration. Regardless of the region analysed, those that are characterized by a high ratio of forest cover change (>40-50%) show growing imbalance between increasing potential and decreasing actual evapotranspiration. However, in the Peruvian and Brazilian regions, hydro-climatic conditions remain energy-limited due to minor rainfall changes. The observed differences in surface water-energy partitioning behaviour evidence a complex dependence of both sub-regional (i.e., land cover changes) and large-scale (i.e., strengthening of the Walker and Hadley circulations) conditions. Our findings indicate a clear link between hydro-climatic changes and deforestation, providing a new perspective on their spatial variability on a sub-regional scale.
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Wood, M., Rignot, E., Fenty, I., An, L., Bjork, A., Van Den Broeke, M., et al. (2021). Ocean forcing drives glacier retreat in Greenland. Science Advances, 7(1).
Abstract: The retreat and acceleration of Greenland glaciers since the mid-1990s have been attributed to the enhanced intrusion of warm Atlantic Waters (AW) into fjords, but this assertion has not been quantitatively tested on a Greenland-wide basis or included in models. Here, we investigate how AW influenced retreat at 226 marine-terminating glaciers using ocean modeling, remote sensing, and in situ observations. We identify 74 glaciers in deep fjords with AW controlling 49% of the mass loss that retreated when warming increased undercutting by 48%. Conversely, 27 glaciers calving on shallow ridges and 24 in cold, shallow waters retreated little, contributing 15% of the loss, while 10 glaciers retreated substantially following the collapse of several ice shelves. The retreat mechanisms remain undiagnosed at 87 glaciers without ocean and bathymetry data, which controlled 19% of the loss. Ice sheet projections that exclude ocean-induced undercutting may underestimate mass loss by at least a factor of 2.
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Xiao, C., Du, Z., Handley, M., Mayewski, P., Cao, J., Schupbach, S., et al. (2021). Iron in the NEEM ice core relative to Asian loess records over the last glacial-interglacial cycle. National Science Review, 8(7).
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Zhai, S., Wang, X., Mcconnell, J., Geng, L., Cole-Dai, J., Sigl, M., et al. (2021). Anthropogenic Impacts on Tropospheric Reactive Chlorine Since the Preindustrial. Geophysical Research Letters, 48(14).
Abstract: Tropospheric reactive gaseous chlorine (Cl-y) impacts the atmosphere's oxidation capacity with implications for chemically reduced gases such as methane. Here we use Greenland ice-core records of chlorine, sodium, and acidity, and global model simulations to show how tropospheric Cl-y has been impacted by anthropogenic emissions since the 1940s. We show that anthropogenic contribution of nonsea-salt chlorine significantly influenced total chlorine and its trends after the 1940s. The modeled regional 170% Cl-y increase from preindustrial to the 1970s was driven by acid displacement from sea-salt-aerosol, direct emission of hydrochloric acid (HCl) from combustion, and chemical reactions driven by anthropogenic nitrogen oxide (NOx) emissions. Since the 1970s, the modeled 6% Cl-y decrease was caused mainly by reduced anthropogenic HCl emissions from air pollution mitigation policies. Our findings suggest that anthropogenic emissions of acidic gases and their emission control strategies have substantial impacts on Cl-y with implications for tropospheric oxidants, methane, and mercury.
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Zhang, T., Wang, T., Feng, Y., Li, X., & Krinner, G. (2021). An emerging impact of Eurasian spring snow cover on summer rainfall in Eastern China. Environmental Research Letters, 16(5).
Abstract: Eurasian spring snow cover is widely considered as an important predictor of Asian summer monsoon rainfall, but its possible role in the formation of the north-south dipole structure of rainfall anomalies (NSDR)-a major mode of the eastern China summer rainfall variability-remains elusive. Here, we show that, there is a close connection between the western Eurasian spring snow cover (WESS) and NSDR during our research period 1967-2018, with less WESS tends to be accompanied by a wetter south-drier north pattern over eastern China, and vice versa. However, this relationship was not significant before the late 1990s, but has since become significant. Further analyses demonstrate that the shift in the WESS-NSDR relationship could be attributed to the modulation of summer North Atlantic Oscillation (SNAO). After the late 1990s, the WESS-related anomalous atmospheric circulations during summer are largely reinforced by the constructive superposition of those with same signs induced by SNAO, which in turn would intensify the impact of WESS and hence lead to a strong WESS-NSDR connection. In contrast, the influences of WESS are counteracted by those with opposite signs associated with SNAO before the late 1990s and thereby result in a weak snow-rainfall relationship. Our findings, along with the decline in Eurasian spring snow cover, provide a potential explanation for the recent 'South Flood-North Drought' pattern observed over eastern China.
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Zhao, M., Ponte, R., Penduff, T., Close, S., Llovel, W., & Molines, J. (2021). Imprints of Ocean Chaotic Intrinsic Variability on Bottom Pressure and Implications for Data and Model Analyses. Geophysical Research Letters, 48(24).
Abstract: Variations in ocean bottom pressure are important for understanding ocean circulation and climate. While most studies have focused on atmospherically driven variability, here we use eddy-permitting large ensemble simulation output from the OceaniC Chaos-ImPacts, strUcture, predicTability (OCCIPUT) project to isolate chaotic intrinsic variability generated by nonlinear oceanic processes. Analyzing separately the mean seasonal cycle and remainder variability in intra-annual (60-365 days) and subseasonal (2-60 days) bands, we find intrinsic variations larger than atmospherically driven ones over eddy-active regions across all timescales, particularly in the intra-annual range, where intrinsic variations dominate in almost 25% of the oceans. At scales larger than mesoscale, intrinsic variability is still considerable, supporting the process of energy inverse cascade toward lower frequency and larger scales. Results highlight the importance of intrinsic variability over a range of spatiotemporal scales and provide new insights on the interpretation of GRACE-like observations and their de-aliasing procedures.
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Zogheib, C., Ochoa-Tocachi, B., Moulds, S., Ossa-Moreno, J., Villacis, M., Verano, C., et al. (2021). A methodology to downscale water demand data with application to the Andean region (Ecuador, Peru, Bolivia, Chile). Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, .
Abstract: Mountainous regions are a hotspot for water scarcity and anthropogenic pressure on water resources. Substantial uncertainty surrounds projections of future climate and water availability. Furthermore, quantitative and distributed data on water demand are generally scarce, dispersed, and highly heterogeneous. This forms a major bottleneck to studying water resources issues and developing strategies to improve water resource management. Here we present a methodology to produce and evaluate high-resolution gridded maps of anthropogenic surface water demand with application to the Andean region. These data are disaggregated according to the major types of water demand: domestic users, irrigated area, and hydropower. This dataset was built by homogenizing, integrating, and interpolating data obtained from various national institutions in charge of water resource management as well as relevant global datasets. The maps can be used to research anthropogenic impacts on water resources, and to guide regional decision-making in regions such as the Andes.
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2020 |
Aires, F., Venot, J., Massuel, S., Gratiot, N., Pham-Duc, B., & Prigent, C. (2020). Surface Water Evolution (2001-2017) at the Cambodia/Vietnam Border in the Upper Mekong Delta Using Satellite MODIS Observations. Remote Sensing, 12(5).
Abstract: Studying the spatial and temporal distribution of surface water resources is critical, especially in highly populated areas and in regions under climate change pressure. There is an increasing number of satellite Earth observations that can provide information to monitor surface water at global scale. However, mapping surface waters at local and regional scales is still a challenge for numerous reasons (insufficient spatial resolution, vegetation or cloud opacity, limited time-frequency or time-record, information content of the instrument, lack in global retrieval method, interpretability of results, etc.). In this paper, we use 17 years of the MODIS (MODerate-resolution Imaging Spectro-radiometer) observations at a 8-day resolution. This satellite dataset is combined with ground expertise to analyse the evolution of surface waters at the Cambodia/Vietnam border in the Upper Mekong Delta. The trends and evolution of surface waters are very significant and contrasted, illustrating the impact of agriculture practices and dykes construction. In most of the study area in Cambodia. surface water areas show a decreasing trend but with a strong inter-annual variability. In specific areas, an increase of the wet surfaces is even observed. Ground expertise and historical knowledge of the development of the territory enable to link the decrease to ongoing excavation of drainage canals and the increase of deforestation and land reclamation, exposing flooded surfaces previously hidden by vegetation cover. By contrast, in Vietnam, the decreasing trend in wet surfaces is very clear and can be explained by the development of dykes dating back to the 1990s with an acceleration in the late 2000s as part of a national strategy of agriculture intensification. This study shows that coupling satellite data with ground-expertise allows to monitor surface waters at mesoscale (<100 x 100 km(2)), demonstrating the potential of interdisciplinary approaches for water ressource management and planning.
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Ajayi, A., Le Sommer, J., Chassignet, E., Molines, J., Xu, X., Albert, A., et al. (2020). Spatial and Temporal Variability of the North Atlantic Eddy Field From Two Kilometric-Resolution Ocean Models. Journal Of Geophysical Research-Oceans, 125(5).
Abstract: Ocean circulation is dominated by turbulent geostrophic eddy fields with typical scales ranging from 10 to 300 km. At mesoscales (>50 km), the size of eddy structures varies regionally following the Rossby radius of deformation. The variability of the scale of smaller eddies is not well known due to the limitations in existing numerical simulations and satellite capability. Nevertheless, it is well established that oceanic flows (<50 km) generally exhibit strong seasonality. In this study, we present a basin-scale analysis of coherent structures down to 10km in the North Atlantic Ocean using two submesoscale-permitting ocean models, a NEMO-based North Atlantic simulation with a horizontal resolution of 1/60 (NATL60) and an HYCOM-based Atlantic simulation with a horizontal resolution of 1/50 (HYCOM50). We investigate the spatial and temporal variability of the scale of eddy structures with a particular focus on eddies with scales of 10 to 100km, and examine the impact of the seasonality of submesoscale energy on the seasonality and distribution of coherent structures in the North Atlantic. Our results show an overall good agreement between the two models in terms of surface wave number spectra and seasonal variability. The key findings of the paper are that (i) the mean size of ocean eddies show strong seasonality; (ii) this seasonality is associated with an increased population of submesoscale eddies (10-50km) in winter; and (iii) the net release of available potential energy associated with mixed layer instability is responsible for the emergence of the increased population of submesoscale eddies in wintertime. Plain Language Summary The ocean is dominated by circular currents of water in swirling motion called oceanic eddies. This class of motion is by far the largest reservoir of oceanic kinetic energy. Much is known about this oceanic eddies at scale >50 km while we are yet to fully comprehend their distribution in terms of size and dynamics at scales <50 km. This is due to the lack of sufficient observational data sets at these scales in the ocean. In this study, we use two kilometric-resolving models of the North Atlantic ocean to investigate the spatial and temporal variability of oceanic eddies down to 10-km scale. Our results show that the distribution of oceanic eddies at spatial scale <100 km undergo strong seasonality and that this seasonality is as a result of an increased population of smaller eddies (10-50 km) often called submesoscales eddies in wintertime. We found that submesoscale turbulence (a class of oceanic turbulence at fine scale) is responsible for the increase in smaller-scale eddy distribution in winter. Key Points The scale of North Atlantic eddies with scale <100 km is studied using two kilometric-resolution ocean models The mean size of these eddies varies across the basin and shows a strong seasonality This seasonality is driven by mixed layer instability and is associated with an increased population of submesoscale eddies in winter
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Allan, R., Barlow, M., Byrne, M., Cherchi, A., Douville, H., Fowler, H., et al. (2020). Advances in understanding large-scale responses of the water cycle to climate change. Annals Of The New York Academy Of Sciences, .
Abstract: Globally, thermodynamics explains an increase in atmospheric water vapor with warming of around 7%/degrees C near to the surface. In contrast, global precipitation and evaporation are constrained by the Earth's energy balance to increase at similar to 2-3%/degrees C. However, this rate of increase is suppressed by rapid atmospheric adjustments in response to greenhouse gases and absorbing aerosols that directly alter the atmospheric energy budget. Rapid adjustments to forcings, cooling effects from scattering aerosol, and observational uncertainty can explain why observed global precipitation responses are currently difficult to detect but are expected to emerge and accelerate as warming increases and aerosol forcing diminishes. Precipitation increases with warming are expected to be smaller over land than ocean due to limitations on moisture convergence, exacerbated by feedbacks and affected by rapid adjustments. Thermodynamic increases in atmospheric moisture fluxes amplify wet and dry events, driving an intensification of precipitation extremes. The rate of intensification can deviate from a simple thermodynamic response due to in-storm and larger-scale feedback processes, while changes in large-scale dynamics and catchment characteristics further modulate the frequency of flooding in response to precipitation increases. Changes in atmospheric circulation in response to radiative forcing and evolving surface temperature patterns are capable of dominating water cycle changes in some regions. Moreover, the direct impact of human activities on the water cycle through water abstraction, irrigation, and land use change is already a significant component of regional water cycle change and is expected to further increase in importance as water demand grows with global population.
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Amoussou, E., Awoye, H., Vodounon, H., Obahoundje, S., Camberlin, P., Diedhiou, A., et al. (2020). Climate and Extreme Rainfall Events in the Mono River Basin (West Africa): Investigating Future Changes with Regional Climate Models. Water, 12(3).
Abstract: This study characterizes the future changes in extreme rainfall and air temperature in the Mono river basin where the main economic activity is weather dependent and local populations are highly vulnerable to natural hazards, including flood inundations. Daily precipitation and temperature from observational datasets and Regional Climate Models (RCMs) output from REMO, RegCM, HadRM3, and RCA were used to analyze climatic variations in space and time, and fit a GEV model to investigate the extreme rainfalls and their return periods. The results indicate that the realism of the simulated climate in this domain is mainly controlled by the choice of the RCMs. These RCMs projected a 1 to 1.5 degrees C temperature increase by 2050 while the projected trends for cumulated precipitation are null or very moderate and diverge among models. Contrasting results were obtained for the intense rainfall events, with RegCM and HadRM3 pointing to a significant increase in the intensity of extreme rainfall events. The GEV model is well suited for the prediction of heavy rainfall events although there are uncertainties beyond the 90th percentile. The annual maxima of daily precipitation will also increase by 2050 and could be of benefit to the ecosystem services and socioeconomic activities in the Mono river basin but could also be a threat.
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Amoussou, E., Awoye, H., Vodounon, H., Obahoundje, S., Camberlin, P., Diedhiou, A., et al. (2020). Climate and Extreme Rainfall Events in the Mono River Basin (West Africa): Investigating Future Changes with Regional Climate Models. Water, 12(3).
Abstract: This study characterizes the future changes in extreme rainfall and air temperature in the Mono river basin where the main economic activity is weather dependent and local populations are highly vulnerable to natural hazards, including flood inundations. Daily precipitation and temperature from observational datasets and Regional Climate Models (RCMs) output from REMO, RegCM, HadRM3, and RCA were used to analyze climatic variations in space and time, and fit a GEV model to investigate the extreme rainfalls and their return periods. The results indicate that the realism of the simulated climate in this domain is mainly controlled by the choice of the RCMs. These RCMs projected a 1 to 1.5 degrees C temperature increase by 2050 while the projected trends for cumulated precipitation are null or very moderate and diverge among models. Contrasting results were obtained for the intense rainfall events, with RegCM and HadRM3 pointing to a significant increase in the intensity of extreme rainfall events. The GEV model is well suited for the prediction of heavy rainfall events although there are uncertainties beyond the 90th percentile. The annual maxima of daily precipitation will also increase by 2050 and could be of benefit to the ecosystem services and socioeconomic activities in the Mono river basin but could also be a threat.
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Ampuero, A., Strikis, N., Apaestegui, J., Vuille, M., Novello, V., Espinoza, J., et al. (2020). The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin. Journal Of Geophysical Research-Atmospheres, 125(4).
Abstract: In the Amazon basin, intense precipitation recycling across the forest significantly modifies the isotopic composition of rainfall (delta O-18, delta D). In the tropical hydrologic cycle, such an effect can be identified through deuterium excess (dxs), yet it remains unclear what environmental factors control dxs, increasing the uncertainty of dxs-based paleoclimate reconstructions. Here we present a 4-year record of the isotopic composition of rainfall, monitored in the northwestern Amazon basin. We analyze the isotopic variations as a function of the air mass history, based on atmospheric back trajectory analyses, satellite observations of precipitation upstream, leaf area index, and simulated moisture recycling along the transport pathway. We show that the precipitation recycling in the forest exerts a significant control on the isotopic composition of precipitation in the northwestern Amazon basin, especially on dxs during the dry season (r = 0.71). Applying these observations to existing speleothem and pollen paleorecords, we conclude that winter precipitation increased after the mid-Holocene, as the expansion of the forest allowed for more moisture recycling. Therefore, forest effects should be considered when interpreting paleorecords of past precipitation changes.
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Andresen, C., Lawrence, D., Wilson, C., Mcguire, A., Koven, C., Schaefer, K., et al. (2020). Soil moisture and hydrology projections of the permafrost region a model intercomparison. Cryosphere, 14(2), 445–459.
Abstract: This study investigates and compares soil moisture and hydrology projections of broadly used land models with permafrost processes and highlights the causes and impacts of permafrost zone soil moisture projections. Climate models project warmer temperatures and increases in precipitation (P) which will intensify evapotranspiration (ET) and runoff in land models. However, this study shows that most models project a long-term drying of the surface soil (0-20 cm) for the permafrost region despite increases in the net air-surface water flux (P-ET). Drying is generally explained by infiltration of moisture to deeper soil layers as the active layer deepens or permafrost thaws completely. Although most models agree on drying, the projections vary strongly in magnitude and spatial pattern. Land models tend to agree with decadal runoff trends but underestimate runoff volume when compared to gauge data across the major Arctic river basins, potentially indicating model structural limitations. Coordinated efforts to address the ongoing challenges presented in this study will help reduce uncertainty in our capability to predict the future Arctic hydrological state and associated land-atmosphere biogeochemical processes across spatial and temporal scales.
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Antoine, G., Camenen, B., Jodeau, M., Nemery, J., & Esteves, M. (2020). Downstream erosion and deposition dynamics of fine suspended sediments due to dam flushing. Journal Of Hydrology, 585.
Abstract: Fine sediment dynamics downstream dams is a key issue when dealing with environmental impact of hydraulic flushing. This paper presents an analysis of six field campaigns carried out during dam flushing events (in June 2006, 2007, 2009, 2010, 2011, and 2012) in the Arc- Isere river system in the Northern French Alps. Suspended sediment concentrations (SSC) and discharges were evaluated using direct measurements or/and 1D hydraulic modelling at up to 14 locations along the 120 kilometres-long river channel. The total suspended sediment flux (SSF) is analysed along the Arc and Isere rivers for each Arc dam flushing event. Uncertainties were quantified based on a propagation method of both measurement and modelling errors. The resulting confidence interval provides elements of discussion on the significance of the sediment mass balance between two consecutive measurement sites. Whereas the discharge time-series of each flushing event is roughly the same, the quantity of fine sediments removed from the reservoirs varied from 10,000 tons in 2007 to 40,000 tons in 2006. Also, a significant erosion is observed in the river system for some events (20,000 tons in 2007) while the SSF barely varied for other events (in 2009 and 2011). This detailed data set allows to identify specific locations in the river network where deposition or erosion occurred. This dynamics is closely related to both the hydrology in the upper Isere River and the morphology of the Arc and Isere rivers, which have been affected by the 2008 and 2010 floods.
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Arias, P., Martinez, J., Mejia, J., Pazos, M., Espinoza, J., & Wongchuig-Correa, S. (2020). Changes in Normalized Difference Vegetation Index in the Orinoco and Amazon River Basins: Links to Tropical Atlantic Surface Temperatures. Journal Of Climate, 33(19), 8537–8559.
Abstract: We analyze the observed relationship between sea surface temperatures (SSTs) over the Atlantic Ocean and the normalized difference vegetation index (NDVI) in the Orinoco and Amazon basins. Monthly correlations between anomalies of NDVI and SSTs are computed for different regions of the Atlantic Ocean. We also use a mixture of observations and reanalysis products to analyze lagged correlations. Our results show that during August-September (i.e., the dry-to-wet transition season), changes in NDVI in the central Amazon and the so-called Arc of Deforestation are associated with precedent changes in the SSTs of the tropical North Atlantic (TNA) and the Caribbean (CABN) during March-June. Anomalous warming of the CABN and TNA generates changes in surface winds and atmospheric moisture transport in the region, decreasing precipitation, with consequent decreases of soil moisture, moisture recycling, and NDVI. An increase in TNA and CABN SSTs during March-June is also associated with an increase of NDVI over the northern Orinoco during June (i.e., the wet season). Unlike in the southern Amazon, precipitation and soil moisture in the Orinoco basin do not exhibit significant changes associated with SSTs. By contrast, atmospheric moisture recycling and transport increase with warmer SSTs in the TNA. Therefore, for the Orinoco, the link between SSTs and NDVI appears to be related not to changes in precipitation but to changes in moisture recycling. However, the causality between these changes needs to be further explored. These findings highlight the contrasting responses of the Amazon and Orinoco basins to Atlantic temperatures and the dominant role of atmospheric moisture transport linking these responses.
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Armijos, E., Crave, A., Espinoza, J., Filizola, N., Espinoza-Villar, R., Ayes, I., et al. (2020). Rainfall control on Amazon sediment flux: synthesis from 20 years of monitoring. Environmental Research Communications, 2(5).
Abstract: The biodiversity and productivity of the Amazon floodplain depend on nutrients and organic matter transported with suspended sediments. Nevertheless, there are still fundamental unknowns about how hydrological and rainfall variability influence sediment flux in the Amazon River. To address this gap, we analyzed 3069 sediment samples collected every 10 days during 1995-2014 at five gauging stations located in the main rivers. We have two distinct fractions of suspended sediments, fine (clay and silt) and coarse (sand), which followed contrasting seasonal and long-term patterns. By taking these dynamics into account, it was estimated, for first time, in the Amazon plain, that the suspended sediment flux separately measured approximately 60% fine and 40% coarse sediment. We find that the fine suspended sediments flux is linked to rainfall and higher coarse suspended sediment flux is related with discharge. Additionally this work presents the time lag between rainfall and discharge, which is related to the upstream area of the gauging. This result is an important contribution to knowledge of biological and geomorphological issues in Amazon basin.
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Attard, G., Bayer, P., Rossier, Y., Blum, P., & Eisenlohr, L. (2020). A novel concept for managing thermal interference between geothermal systems in cities. Renewable Energy, 145, 914–924.
Abstract: The growing interest in shallow geothermal resources leads to dense installation areas, where interference and decrease in efficiency might occur. To optimize geothermal use in cities which prevents interference between neighbouring and future installations, we present a novel concept relying on the definition of thermal protection perimeters (TPP) around geothermal installations. These perimeters are determined by quantifying the thermal probability of capture around closed- and open-loop geothermal systems. Then, the maximal acceptable power that can be exploited in the vicinity of the installations can be continuously mapped. Existing analytical heat transport models are adapted to calculate these thermal capture probabilities. Two applications are illustrated in Lyon (France). The first application shows that adapted analytical models can help to manage multiple geothermal installations already in place in sectors of few square kilometres. In the second application, a numerical deterministic model is used to determine the TPP of one open-loop system at a local scale. The numerical approach applied for this case allows to account for flow disturbances caused by underground constructions, and thus offers a refined representativeness of the probability of capture. The presented methodology facilitates compatibility assessments between existing and planned new geothermal installations, which is otherwise not feasible by only mapping thermal plumes caused by existing installations, as done in common practice. (C) 2019 Elsevier Ltd. All rights reserved.
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Aviles, G., Descloitres, M., Duwig, C., Rossier, Y., Spadini, L., Legchenko, A., et al. (2020). Insight into the Katari-Lago Menor Basin aquifer, Lake Titicaca-Bolivia, inferred from geophysical (TDEM), hydrogeological and geochemical data. Journal Of South American Earth Sciences, 99.
Abstract: The increasing demand for water and irrigation in the semi-arid Bolivian Altiplano requires a better knowledge of the available resources, particularly groundwater. The aim of this study is to provide a first insight into the hydrogeological structure (0-200 m deep) and groundwater dynamics of the Katari-Lago Menor Basin aquifer located between the Eastern Cordillera and Lake Titicaca, Bolivia. This aquifer is studied using geophysical data (a total of 187 Time Domain Electromagnetic (TDEM) soundings), piezometric data (97 groundwater level measurements) and geochemical data (52 groundwater samples), combined with geological, lithological and topographical information. The results allowed identifying stratigraphic models consistent with the Quaternary sediments being hydraulically connected and behaving as a single regional basin-aquifer. This basin-aquifer is delimited by the most ancient lake invasions towards the southern, western and northern sides and by the lower limit of rock glaciers towards the eastern side. A large portion of the aquifer presents an unconfined behaviour varying from 50 to 150 m while the confined portion varies from 100 to 150 m. Groundwater flow within the Katari and Lago Menor Basin aquifer is composed of several interconnected groundwater flow systems. The main groundwater flow system starts in the high mountain ranges of the Eastern Cordillera, follows the topographic Piedmont gradient (NE to SW) and discharges in a series of wetlands. This multidisciplinary approach proved to be an appropriate method to derive a consistent picture of the hydrogeological functioning of the Katari-Lago Menor Basin aquifer.
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Ayar, P., Blanchet, J., Paquet, E., & Penot, D. (2020). Space-time simulation of precipitation based on weather pattern sub-sampling and meta-Gaussian model. Journal Of Hydrology, 581.
Abstract: Simulation methods for design flood estimations in dam safety studies require fine scale precipitation data to provide quality input for hydrological models, especially for extrapolation to extreme events. This leads to use statistical models such as stochastic weather generators. The aim here is to develop a stochastic model adaptable on mountainous catchments in France and accounting for spatial and temporal dependencies in daily precipitation fields. To achieve this goal, the framework of spatial random processes is adopted here. The novelty of the model developed in this study resides in the combination of an autoregressive meta-Gaussian process accounting for the spatio-temporal dependencies and weather pattern sub-sampling discriminating the different rainfall intensity classes. The model is tested from rain gauges in the Ardeche catchment located in South of France. The model estimation is performed in four steps, dealing respectively with: (i) the at-site marginal distribution, (ii) the mapping of the marginal distribution parameters at the target resolution, (iii) the at-site temporal correlation and (iv) the spatial covariance function. The model simulations are evaluated in terms of marginal distribution, inter-site dependence and areal rainfall properties and compared to the observations at calibration stations and also on a set of independent validation stations. Regarding all these aspects, the model shows good abilities to reproduce the observed statistics and presents really small discrepancies compared to the stations data. The sub-sampling is particularly efficient to reproduce the seasonal variations and the marginal mapping procedure induces very small differences in terms of daily rain amounts and daily occurrence probabilities.
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Bakker, M., Gimbert, F., Geay, T., Misset, C., Zanker, S., & Recking, A. (2020). Field Application and Validation of a Seismic Bedload Transport Model. Journal Of Geophysical Research-Earth Surface, 125(5).
Abstract: Bedload transport drives morphological changes in gravel-bed streams and sediment transfer in catchments. The large impact forces associated with bedload motion and its highly dynamic spatiotemporal nature make it difficult to monitor bedload transport in the field. In this study, we revise a physically-based model of bedload-induced seismic ground motion proposed by Tsai et al. (2012, ) and apply it to invert bedload flux from seismic measurements alongside an Alpine stream. First, we constrain the seismic response of a braided river reach with a simple active experiment using a series of large-rock impacts. This allows the characterization of surface wave propagation and attenuation with distance from the impact source. Second, we distinguish bedload-generated ground vibrations from those caused by turbulent flow using frequency-based scaling relationships between seismic power and discharge. Finally, absolute bedload transport rates are quantified from seismic measurements using inverse modeling based on a simplified formulation of bedload particle motion. The results are verified with a large data set of bedload samples, demonstrating that seismic measurements can provide an indirect measure for bedload flux with uncertainties within a factor of 5(+/- 1) for instantaneous measurements (between 0.01 and 1 kg/m/s). Larger deviations may be caused by uncertainties in the contribution of turbulent flow effects, particle impact velocity, and especially particle size that may vary with sediment supply and flow conditions. When constraining these uncertainties, instream sediment transport measurements are no longer necessarily required and seismic monitoring may provide an accurate and continuous means to investigate bedload dynamics in gravel-bed streams.
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Baray, J., Deguillaume, L., Colomb, A., Sellegri, K., Freney, E., Rose, C., et al. (2020). Cezeaux-Aulnat-Opme-Puy De Dome: a multi-site for the long-term survey of the tropospheric composition and climate change. Atmospheric Measurement Techniques, 13(6), 3413–3445.
Abstract: For the last 25 years, CO-PDD (Cezeaux-Aulnat-Opme-puy de Dome) has evolved to become a full instrumented platform for atmospheric research. It has received credentials as a national observing platform in France and is internationally recognized as a global station in the GAW (Global Atmosphere Watch) network. It is a reference site of European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on top of the puy de Dome mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cezeaux (410 m), and Aulnat (330 m). The integration of different sites offers a unique combination of in situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical, and physical properties of aerosol particles, clouds, and precipitations. Given its location far away from any major emission sources, its altitude, and the mountain orography, the puy de Dome station is ideally located to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in fall and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at the puy de Dome strongly contribute to improving knowledge in atmospheric sciences, including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical), and the provision of reference information for climate/chemistry models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid and ice cloud probes in natural conditions, or in situ systems to collect aerosol and cloud. This paper reviews 25 years (1995-2020) of atmospheric observation at the station and related scientific research contributing to atmospheric and climate science.
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Barbero, A., Blouzon, C., Savarino, J., Caillon, N., Dommergue, A., & Grilli, R. (2020). A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications. Atmospheric Measurement Techniques, 13(8), 4317–4331.
Abstract: We present a compact, affordable and robust instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous detection of NOx, IO, CHOCHO and O-3 in the 400-475 nm wavelength region. The instrument relies on the injection of a high-power LED source in a high-finesse cavity (F similar to 33100), with the transmission signal being detected by a compact spectrometer based on a high-order diffraction grating and a charge-coupled device (CCD) camera. A minimum detectable absorption of 2.0 x 10(-10) cm(-1) was achieved within similar to 22 min of total acquisition, corresponding to a figure of merit of 1.8 x 10(-10) cm(-1) Hz(-1/2) per spectral element. Due to the multiplexing broadband feature of the setup, multi-species detection can be performed with simultaneous detection of NO2, IO, CHOCHO and O-3 achieving detection limits of 11, 0.3, 10 ppt (parts per trillion) and 47 ppb (parts per billion) (1 sigma) within 22 min of measurement, respectively (half of the time is spent on the acquisition of the reference spectrum in the absence of the absorber, and the other half is spent on the absorption spectrum). The implementation on the inlet gas line of a compact ozone generator based on electrolysis of water allows for the measurement of NOx (NO + NO2) and therefore an indirect detection of NO with detection limits for NOx and NO of 10 and 21 ppt (1 sigma), respectively. The device has been designed to fit in a 19 in., 3U (5.25 in.) rack-mount case; weighs 15 kg; and has a total electrical power consumption of < 300 W. The instrument can be employed to address different scientific objectives such as better constraining the oxidative capacity of the atmosphere, studying the chemistry of highly reactive species in atmospheric chambers as well as in the field and looking at the sources of glyoxal in the marine boundary layer to study possible implications on the formation of secondary aerosol particles.
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Barnier, B., Domina, A., Gulev, S., Molines, J., Maitre, T., Penduff, T., et al. (2020). Modelling the impact of flow-driven turbine power plants on great wind-driven ocean currents and the assessment of their energy potential. Nature Energy, 5(3), 240–249.
Abstract: The persistence in the strength and direction of western boundary great ocean currents suggests that flow-driven turbines implemented in these currents have great potential for energy exploitation. However, technological developments in the design and installation of power-generating plants in the ocean are tied to our capacity to accurately identify the most favourable sites and provide practical assessments of the potentially recoverable energy. Here we use a global eddy-resolving ocean model to demonstrate that large ocean power plants may exert feedback on oceanic circulation that results in highly unpredictable changes in ocean currents. Regionally, these changes can drastically modify the path of the current. In extreme cases this corresponds to a decrease in the available power by more than 80% from initial expectations. Ocean currents offer a potential source of power, but identification of the best sites requires a detailed understanding of their variability. Barnier et al. undertake global eddy-resolving ocean modelling to gain insight into the feedback from ocean power plants on currents and the changes they can induce.
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Barraza, F., Uzu, G., Jaffrezo, J., Schreck, E., Budzinski, H., Le Menach, K., et al. (2020). Contrasts in chemical composition and oxidative potential in PM10 near flares in oil extraction and refining areas in Ecuador. Atmospheric Environment, 223.
Abstract: For decades, oil extraction in rural sites in the North Amazon Region (NAR) in Ecuador, have generated mixtures of potentially toxic compounds, such as polycyclic aromatic hydrocarbons (PAHs) and metal(loid)s. The main national refinery and the thermal power plant located in Esmeraldas, on the North Pacific Coast (NPC), are also considered as important sources of air contamination. Particulate matter (PM10) emitted at both sites could induce the formation of reactive oxygen species (ROS) in the lungs upon inhalation and could be associated with respiratory diseases. In this study, PM10 mass composition was monitored over a two-year period in both regions: NAR (close to oil platforms and open flares) and NPC (in a public school close to the refinery). PM10 composition was assessed in terms of metal(loid)s, organic and elementary carbon (OC, EC), monosaccharides (levoglucosan, mannosan, galactosan), glucose, polyols (sorbitol, mannitol, arabitol), water soluble ions and polycyclic aromatic compounds (PAHs, oxy-PAHs and nitro-PAHs). Additionally, three complementary biochemical and acellular tests were performed to evaluate the oxidative potential (OP). Results show that the PM10 mass and elemental concentrations were higher in NPC than in NAR. Barium and Mo concentrations, commonly used in oil operations, were up to 1000-fold higher than values recorded in other regions of Ecuador. OC/EC ratios and polyols concentrations were higher in NAR than in NPC, indicating a larger biogenic contribution to the PM mass in this region. In NAR, the main sources associated with ROS burden were biogenic emissions and oil production, as indicated by positive correlations between OP, sugars, Ba, some PAHs and oxy-PAHs. On the other hand, in NPC, associations between NH4+, Ba, As and Ni imply that oil refining and industrial activities are the main contributors to the OP of PM10.
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Barthel, A., Agosta, C., Little, C., Hattermann, T., Jourdain, N., Goelzer, H., et al. (2020). CMIP5 model selection for ISMIP6 ice sheet model forcing: Greenland and Antarctica. Cryosphere, 14(3), 855–879.
Abstract: The ice sheet model intercomparison project for CMIP6 (ISMIP6) effort brings together the ice sheet and climate modeling communities to gain understanding of the ice sheet contribution to sea level rise. ISMIP6 conducts stand-alone ice sheet experiments that use space- and time-varying forcing derived from atmosphere-ocean coupled global climate models (AOGCMs) to reflect plausible trajectories for climate projections. The goal of this study is to recommend a subset of CMIP5 AOGCMs (three core and three targeted) to produce forcing for ISMIP6 stand-alone ice sheet simulations, based on (i) their representation of current climate near Antarctica and Greenland relative to observations and (ii) their ability to sample a diversity of projected atmosphere and ocean changes over the 21st century. The selection is performed separately for Greenland and Antarctica. Model evaluation over the historical period focuses on variables used to generate ice sheet forcing. For stage (i), we combine metrics of atmosphere and surface ocean state (annual- and seasonal-mean variables over large spatial domains) with metrics of time-mean subsurface ocean temperature biases averaged over sectors of the continental shelf. For stage (ii), we maximize the diversity of climate projections among the best-performing models. Model selection is also constrained by technical limitations, such as availability of required data from RCP2.6 and RCP8.5 projections. The selected top three CMIP5 climate models are CCSM4, MIROC-ESM-CHEM, and NorESM1-M for Antarctica and HadGEM2-ES, MIROC5, and NorESM1-M for Greenland. This model selection was designed specifically for ISMIP6 but can be adapted for other applications.
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Belis, C., Pernigotti, D., Pirovano, G., Favez, O., Jaffrezo, J., Kuenen, J., et al. (2020). Evaluation of receptor and chemical transport models for PM10 source apportionment. Atmospheric Environment-X, 5.
Abstract: In this study, the performance of two types of source apportionment models was evaluated by assessing the results provided by 40 different groups in the framework of an intercomparison organised by FAIRMODE WG3 (Forum for air quality modelling in Europe, Working Group 3). The evaluation was based on two performance indicators: z-scores and the root mean square error weighted by the reference uncertainty (RMSEu), with pre-established acceptability criteria. By involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), the intercomparison provided a unique opportunity for their cross-validation. In addition, comparing the CTM chemical profiles with those measured directly at the source contributed to corroborate the consistency of the tested model results. The most commonly used RM was the US EPA- PMF version 5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) while more difficulties were observed with the source contribution time series (72% of RMSEu accepted). Industrial activities proved to be the most difficult sources to be quantified by RMs, with high variability in the estimated contributions. In the CTMs, the sum of computed source contributions was lower than the measured gravimetric PM10 mass concentrations. The performance tests pointed out the differences between the two CTM approaches used for source apportionment in this study: brute force (or emission reduction impact) and tagged species methods. The sources meeting the z-score and RMSEu acceptability criteria tests were 50% and 86%, respectively. The CTM source contributions to PM10 were in the majority of cases lower than the RM averages for the corresponding source. The CTMs and RMs source contributions for the overall dataset were more comparable (83% of the z-scores accepted) than their time series (successful RMSEu in the range 25% – 34%). The comparability between CTMs and RMs varied depending on the source: traffic/exhaust and industry were the source categories with the best results in the RMSEu tests while the most critical ones were soil dust and road dust. The differences between RMs and CTMs source reconstructions confirmed the importance of cross validating the results of these two families of models.
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Belke-Brea, M., Domine, F., Barrere, M., Picard, G., & Arnaud, L. (2020). Impact of Shrubs on Winter Surface Albedo and Snow Specific Surface Area at a Low Arctic Site: In Situ Measurements and Simulations. Journal Of Climate, 33(2), 597–609.
Abstract: Erect shrubs in the Arctic reduce surface albedo when branches protrude above the snow and modify snow properties, in particular specific surface area (SSA). Important consequences are changes in the land surface-atmosphere energy exchange and the increase of snow melting in autumn, possibly inducing reduced soil thermal insulation and in turn permafrost cooling. Near Umiujaq (56.5 degrees N, 76.5 degrees W) in the Canadian low Arctic where dwarf birches (Betula glandulosa) are expanding, spectral albedo (400-1080 nm) under diffuse light and vertical profiles of SSA were measured in November and December 2015 at four sites: three with protruding branches and one with only snow. At the beginning of the snow season (8 November), shrub-induced albedo reductions were found to be wavelength dependent and as high as 55% at 500 nm and 18% at 1000 nm, which, integrated over the measurement range (400-1080 nm), corresponds to 70 W m(-2) of additional absorbed energy. The impact of shrubs is not just snow darkening. They also affect snow SSA in multiple ways, by accumulating snow with high SSA during cold windy precipitation and favoring SSA decrease by inducing melting during warm spells. However, the impact on the radiation budget of direct darkening from shrubs likely dominates over the indirect change in SSA. Spectral albedo was simulated with a linear mixing equation (LME), which fitted well with observed spectra. The average root-mean-square error was 0.009. We conclude that LMEs are a suitable tool to parameterize mixed surface albedo in snow and climate models.
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Belke-Brea, M., Domine, F., Boudreau, S., Picard, G., Barrere, M., Arnaud, L., et al. (2020). New Allometric Equations for Arctic Shrubs and Their Application for Calculating the Albedo of Surfaces with Snow and Protruding Branches. Journal Of Hydrometeorology, 21(11), 2581–2594.
Abstract: Arctic shrubs reduce surface albedo in winter when branches protrude above the snow. To calculate the albedo of those mixed surfaces, the branch area index (BAI) of Arctic shrubs needs to be known. Moreover, an exposed-vegetation function is required to determine the BAI for protruding branches only. This study used a structural analysis of 30 Betula glandulosa shrubs, sampled near Umiujaq, northern Quebec, to (i) establish an allometric relationship between shrub height and BAI and (ii) determine a specific exposed-vegetation function for Arctic shrubs. The spectral albedo (4001080 nm) of mixed surfaces was then simulated with the equations derived from this study and validated with in situ measured spectra. Shrubs were sampled from two sites, one along the coast and the other in a nearby valley. The shrub height-BAI relationship varied between both sites. BAI values of shrubs growing in the wind-sheltered valley were 30%50% lower. The exposed-vegetation function obtained here differed from the linear functions found in the literature. The linear functions strongly overestimated the BAI of exposed branches. Albedo was well simulated with an accuracy of 3% when using an allometric relationship adapted to the environmental conditions of our study site. However, simulated albedo values were consistently higher than field measurements, probably because radiation absorbed by impurities and buried branches was neglected in the model. We conclude that specific exposed-vegetation and allometric equations need to be implemented in models to accurately simulate the albedo of mixed snow-shrub surfaces.
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Bessagnet, B., Menut, L., Lapere, R., Couvidat, F., Jaffrezo, J., Mailler, S., et al. (2020). High Resolution Chemistry Transport Modeling with the On-Line CHIMERE-WRF Model over the French Alps-Analysis of a Feedback of Surface Particulate Matter Concentrations on Mountain Meteorology. Atmosphere, 11(6).
Abstract: Air pollution is of major concern throughout the world and the use of modeling tools to analyze and forecast the pollutant concentrations in complex orographic areas remains challenging. This work proposes an exhaustive framework to analyze the ability of models to simulate the air quality over the French Alps up to 1.2 km resolution over Grenoble and the Arve Valley. The on-line coupled suite of models CHIMERE-WRF is used in its recent version to analyze a 1 month episode in November-December 2013. As expected, an improved resolution increases the concentrations close to the emission areas and reduced the negative bias for Particulate Matter that is the usual weakness of air quality models. However, the nitrate concentrations seem overestimated with at the same time an overestimation of surface temperature in the morning by WRF. Different WRF settings found in the literature are tested to improve the results, particularly the ability of the meteorological model to simulate the strong thermal inversions in the morning. Wood burning is one of the main contributor of air pollution during the period ranging from 80 to 90% of the Organic Matter. The activation of the on-line coupling has a moderate impact on the background concentrations but surprisingly a change of Particulate Matter (PM) concentrations in the valley will affect more the meteorology nearby high altitude areas than in the valley. This phenomenon is the result of a chain of processes involving the radiative effects and the water vapor column gradients in complex orographic areas. At last, the model confirms that the surrounding glaciers are largely impacted by long range transport of desert dust. However, in wintertime some outbreaks of anthropogenic pollution from the valley when the synoptic situation changes can be advected up to the nearby high altitude areas, then deposited.
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Bichet, A., Diedhiou, A., Hingray, B., Evin, G., Toure, N., Browne, K., et al. (2020). Assessing uncertainties in the regional projections of precipitation in CORDEX-AFRICA. Climatic Change, .
Abstract: Over the past decades, large variations of precipitation were observed in Africa, which often led to dramatic consequences for local society and economy. To avoid such disasters in the future, it is crucial to better anticipate the expected changes, especially in the current context of climate change and population growth. To this date, however, projections of precipitation over Africa are still associated with very large uncertainties. To better understand how this uncertainty can be reduced, this study uses an advanced Bayesian analysis of variance (ANOVA) method to characterize, for the first time in the regional climate projections of CORDEX-AFRICA, the different sources of uncertainty associated with the projections of precipitation over Africa. By 2090, the ensemble mean precipitation is projected to increase over the Horn of Africa from September to May and over the eastern Sahel and Guinea Coast from June to November. It is projected to decrease over the northern coast and southern Africa all year long, over western Sahel from March to August, and over the Sahel and Guinea Coast from March to May. Most of these projections however are not robust, i.e., the magnitude of change is smaller than the associated uncertainty. Over time, the relative contribution of internal variability (excluding interannual variability) to total uncertainty is moderate and quickly falls below 10%. By 2090, it is found that over the Horn of Africa, northern coast, southern Africa, and Sahel, most of the uncertainty results from a large dispersion across the driving Global Climate Models (in particular MIROC, CSIRO, CCCma, and IPSL), whereas over the tropics and parts of eastern Africa, most of the uncertainty results from a large dispersion across Regional Climate Models (in particular CLMcom).
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Bishop, K., Shanley, J., Riscassi, A., De Wit, H., Eklof, K., Meng, B., et al. (2020). Recent advances in understanding and measurement of mercury in the environment: Terrestrial Hg cycling. Science Of The Total Environment, 721.
Abstract: This review documents recent advances in terrestrial mercury cycling. Terrestrial mercury (Hg) research has matured in some areas, and is developing rapidly in others. We summarize the state of the science circa 2010 as a starting point, and then present the advances during the last decade in three areas: land use, sulfate deposition, and climate change. The advances are presented in the framework of three Hg “gateways” to the terrestrial environment: inputs from the atmosphere, uptake in food, and run off with surface water. Among the most notable advances: The Arctic has emerged as a hotbed of Hg cycling, with high stream fluxes and large stores of Hg poised for release from permafrost with rapid high-latitude warming. The bi-directional exchange of Hg between the atmosphere and terrestrial surfaces is better understood, thanks largely to interpretation from Hg isotopes; the latest estimates place land surface Hg re-emission lower than previously thought. Artisanal gold mining is now thought responsible for over half the global stream flux of Hg. There is evidence that decreasing inputs ofHg to ecosystems may bring recovery sooner than expected, despite large ecosystem stores of legacy Hg. Freshly deposited Hg is more likely than stored Hg to methylate and be incorporated in rice. Topography and hydrological connectivity have emerged as master variables for explaining the disparate response of THg and MeHg to forest harvest and other land disturbance. These and other advances reported here are of value in evaluating the effectiveness of theMinamata Convention on reducing environmental Hg exposure to humans and wildlife. (C) 2020 The Authors. Published by Elsevier B.V.
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Blanchet, J., & Creutin, J. (2020). Explaining Rainfall Accumulations over Several Days in the French Alps Using Low-Dimensional Atmospheric Predictors Based on Analogy. Journal Of Applied Meteorology And Climatology, 59(2), 237–250.
Abstract: We propose a new approach to explain multiday rainfall accumulation over a French Alpine watershed using large-scale atmospheric predictors based on analogy. The classical analogy framework associates a rainfall cumulative distribution function (CDF) with a given atmospheric situation from the precipitation accumulations yielded by the closest situations. The analogy may apply to single-day or multiday sequences of pressure fields. The proposed approach represents a paradigm shift in analogy. It relies on the similarity of the local topology mapping the pressure field sequences, somehow forgetting the pressure fields per se. This topology is summarized by the way the sequences of pressure fields resemble their neighbors (dimensional predictors) and how fast they evolve in time (dynamical predictors). Although some information-and hence predictability-is expected to be lost when compared with classical analogy, this approach provides new insight on the atmospheric features generating rainfall CDFs. We apply both approaches to geopotential heights over western Europe in view of assessing 3-day rainfall accumulations over the Isere River catchment at Grenoble, France. Results show that dimensional predictors are the most skillful features for predicting 3-day rainfall-bringing alone 60% of the predictability of the classical analogy approach-whereas the dynamical predictors are less explicative. These results open new directions of research that the classical analogy approach cannot handle. They show, for instance, that both dry sequences and strong rainfall sequences are associated with singular 500-hPa geopotential shapes acting as local attractors-a way of explaining the change in rainfall CDFs in a changing climate.
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Blanchet, J., & Melese, V. (2020). A Bayesian Framework for the Multiscale Assessment of Storm Severity and Related Uncertainties. Journal Of Hydrometeorology, 21(1), 109–122.
Abstract: This article proposes a statistical framework for assessing the multiscale severity of a given storm at a given location. By severity we refer to the rareness of the storm event, as measured by the return period. Rather than focusing on predetermined spatiotemporal scales, we consider a model assessing the return period of a storm event observed across the continuum of durations and areas around a focus location. We develop a Bayesian intensity-duration-area-frequency model based on extreme value distribution and space-time scale invariance hypotheses. The model allows us to derive an analytical expression of the return period for any duration and area, while the Bayesian framework allows us by construction to assess the related uncertainties. We apply this framework to high-resolution radar-rain gauge reanalysis data covering a mountainous region of southern France during the autumns 2008-15 and comprising 50 rain events. We estimate the model at two grid points located a few kilometers apart on either side of the mountain crest, considering spatiotemporal scales ranging over 3-48 h and 1-2025 km(2). We show that at all scales and for all significant events, the return period uncertainties are skewed to the right, evidencing the need of considering uncertainty to avoid systematic risk underestimation. We also reveal the large variability of the storm severity both at short distance and across scales, due to both the natural variability of rainfall and the mask effect induced by the mountain crest.
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Bodian, A., Diop, L., Panthou, G., Dacosta, H., Deme, A., Dezetter, A., et al. (2020). Recent Trend in Hydroclimatic Conditions in the Senegal River Basin. Water, 12(2).
Abstract: Analyzing trends of annual rainfall and assessing the impacts of these trends on the hydrological regime are crucial in the context of climate change and increasing water use. This research investigates the recent trend of hydroclimatic variables in the Senegal River basin based on 36 rain gauge stations and three hydrometric stations not influenced by hydraulic structures. The Man Kendall and Pettitt's tests were applied for the annual rainfall time series from 1940 to 2013 to detect the shift and the general trend of the annual rainfall. In addition, trends of average annual flow rate (AAFR), maximum daily flow (MADF), and low flow rate (LFR) were evaluated before and after annual rainfall shift. The results show that the first shift is situated on average at 1969 whereas the second one is at 1994. While the first shift is very consistent between stations (between 1966 and 1972), there is a significant dispersion of the second change-point between 1984 and 2002. After the second shift (1994), an increase of annual rainfall is noticed compared to the previous period (1969-1994) which indicates a not significant, partial rainfall recovery at the basin level. The relative changes of hydrologic variables differ based on the variables and the sub-basin. Relative changes before and after first change-point are significantly negative for all variables. The highest relative changes are observed for the AAFR. Considering the periods before and second shifts, the relative changes are mainly significantly positive except for the LFR.
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Bolibar, J., Rabatel, A., Gouttevin, I., & Galiez, C. (2020). A deep learning reconstruction of mass balance series for all glaciers in the French Alps: 1967-2015. Earth System Science Data, 12(3), 1973–1983.
Abstract: Glacier mass balance (MB) data are crucial to understanding and quantifying the regional effects of climate on glaciers and the high-mountain water cycle, yet observations cover only a small fraction of glaciers in the world. We present a dataset of annual glacier-wide mass balance of all the glaciers in the French Alps for the 1967-2015 period. This dataset has been reconstructed using deep learning (i.e. a deep artificial neural network) based on direct MB observations and remote -sensing annual estimates, meteorological reanalyses and topographical data from glacier inventories. The method's validity was assessed previously through an extensive cross -validation against a dataset of 32 glaciers, with an estimated average error (RMSE) of 0.55 mw.e. a(-1), an explained variance (r(2)) of 75 % and an average bias of -0.021 m w.e. a(-1.) We estimate an average regional area-weighted glacier-wide MB of -0.69 +/- 0.21 (1 sigma) mw.e. a(-1) for the 1967-2015 period with negative mass balances in the 1970s (-0.44 m w.e. a-1), moderately negative in the 1980s (-0.16 m w.e. a(-1)) and an increasing negative trend from the 1990s onwards, up to -1.26 m w.e. a(-1) in the 2010s. Following a topographical and regional analysis, we estimate that the massifs with the highest mass losses for the 1967-2015 period are the Chablais (-0.93 mw.e. a(-1)), Champsaur (-0.86 m w.e. a(-1)), and Haute-Maurienne and Ubaye ranges (-0.84 mw.e. a(-1) each), and the ones presenting the lowest mass losses are the Mont-Blanc (-0.68 mw.e. a1), Oisans and Haute-Tarentaise ranges (-0.75 m w.e. a(-1) each). This dataset available at https://doi.org/10.5281/zenodo.3925378 (Bolibar et al., 2020a) provides relevant and timely data for studies in the fields of glaciology, hydrology and ecology in the French Alps in need of regional or glacier-specific annual net glacier mass changes in glacierized catchments.
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Bolibar, J., Rabatel, A., Gouttevin, I., Galiez, C., Condom, T., & Sauquet, E. (2020). Deep learning applied to glacier evolution modelling. Cryosphere, 14(2), 565–584.
Abstract: We present a novel approach to simulate and reconstruct annual glacier-wide surface mass balance (SMB) series based on a deep artificial neural network (ANN; i.e. deep learning). This method has been included as the SMB component of an open-source regional glacier evolution model. While most glacier models tend to incorporate more and more physical processes, here we take an alternative approach by creating a parameterized model based on data science. Annual glacier-wide SMBs can be simulated from topo-climatic predictors using either deep learning or Lasso (least absolute shrinkage and selection operator; regularized multilinear regression), whereas the glacier geometry is updated using a glacier-specific parameterization. We compare and cross-validate our nonlinear deep learning SMB model against other standard linear statistical methods on a dataset of 32 French Alpine glaciers. Deep learning is found to outperform linear methods, with improved explained variance (up to + 64% in space and +108% in time) and accuracy (up to +47% in space and +58% in time), resulting in an estimated r(2) of 0.77 and a root-mean-square error (RMSE) of 0.51 m w.e. Substantial nonlinear structures are captured by deep learning, with around 35% of nonlinear behaviour in the temporal dimension. For the glacier geometry evolution, the main uncertainties come from the ice thickness data used to initialize the model. These results should encourage the use of deep learning in glacier modelling as a powerful nonlinear tool, capable of capturing the nonlinearities of the climate and glacier systems, that can serve to reconstruct or simulate SMB time series for individual glaciers in a whole region for past and future climates.
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Boucher, O., Servonnat, J., Albright, A., Aumont, O., Balkanski, Y., Bastrikov, V., et al. (2020). Presentation and Evaluation of the IPSL-CM6A-LR Climate Model. Journal Of Advances In Modeling Earth Systems, 12(7).
Abstract: This study presents the global climate model IPSL-CM6A-LR developed at Institut Pierre-Simon Laplace (IPSL) to study natural climate variability and climate response to natural and anthropogenic forcings as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). This article describes the different model components, their coupling, and the simulated climate in comparison to previous model versions. We focus here on the representation of the physical climate along with the main characteristics of the global carbon cycle. The model's climatology, as assessed from a range of metrics (related in particular to radiation, temperature, precipitation, and wind), is strongly improved in comparison to previous model versions. Although they are reduced, a number of known biases and shortcomings (e.g., double Intertropical Convergence Zone [ITCZ], frequency of midlatitude wintertime blockings, and El Nino-Southern Oscillation [ENSO] dynamics) persist. The equilibrium climate sensitivity and transient climate response have both increased from the previous climate model IPSL-CM5A-LR used in CMIP5. A large ensemble of more than 30 members for the historical period (1850-2018) and a smaller ensemble for a range of emissions scenarios (until 2100 and 2300) are also presented and discussed.
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Bracegirdle, T., Krinner, G., Tonelli, M., Haumann, F., Naughten, K., Rackow, T., et al. (2020). Twenty first century changes in Antarctic and Southern Ocean surface climate in CMIP6. Atmospheric Science Letters, 21, e984.
Abstract: Two decades into the 21st century there is growing evidence for global impacts of Antarctic and Southern Ocean climate change. Reliable estimates of how the Antarctic climate system would behave under a range of scenarios of future external climate forcing are thus a high priority. Output from new model simulations coordinated as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) provides an opportunity for a comprehensive analysis of the latest generation of state-of-the-art climate models following a wider range of experiment types and scenarios than previous CMIP phases. Here the main broad-scale 21st century Antarctic projections provided by the CMIP6 models are shown across four forcing scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5. End-of-century Antarctic surface-air temperature change across these scenarios (relative to 1995-2014) is 1.3, 2.5, 3.7 and 4.8 degrees C. The corresponding proportional precipitation rate changes are 8, 16, 24 and 31%. In addition to these end-of-century changes, an assessment of scenario dependence of pathways of absolute and global-relative 21st century projections is conducted. Potential differences in regional response are of particular relevance to coastal Antarctica, where, for example, ecosystems and ice shelves are highly sensitive to the timing of crossing of key thresholds in both atmospheric and oceanic conditions. Overall, it is found that the projected changes over coastal Antarctica do not scale linearly with global forcing. We identify two factors that appear to contribute: (a) a stronger global-relative Southern Ocean warming in stabilisation (SSP2-4.5) and aggressive mitigation (SSP1-2.6) scenarios as the Southern Ocean continues to warm and (b) projected recovery of Southern Hemisphere stratospheric ozone and its effect on the mid-latitude westerlies. The major implication is that over coastal Antarctica, the surface warming by 2100 is stronger relative to the global mean surface warming for the low forcing compared to high forcing future scenarios.
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Brancato, V., Rignot, E., Milillo, P., Morlighem, M., Mouginot, J., An, L., et al. (2020). Grounding Line Retreat of Denman Glacier, East Antarctica, Measured With COSMO-SkyMed Radar Interferometry Data. Geophysical Research Letters, 47(7).
Abstract: Denman Glacier, East Antarctica, holds an ice volume equivalent to a 1.5 m rise in global sea level. Using satellite radar interferometry from the COSMO-SkyMed constellation, we detect a 5.4 0.3 km grounding line retreat between 1996 and 2017-2018. A novel reconstruction of the glacier bed topography indicates that the retreat proceeds on the western flank along a previously unknown 5 km wide, 1,800 m deep trough, deepening to 3,400 m below sea level. On the eastern flank, the grounding line is stabilized by a 10 km wide ridge. At tidal frequencies, the grounding line extends over a several kilometer-wide grounding zone, enabling warm ocean water to melt ice at critical locations for glacier stability. If warm, modified Circumpolar Deep Water reaches the sub-ice-shelf cavity and continues to melt ice at a rate exceeding balance conditions, the potential exists for Denman Glacier to retreat irreversibly into the deepest, marine-based basin in Antarctica. Plain Language Summary Using satellite radar data from the Italian COSMO-SkyMed constellation, we document the grounding line retreat of Denman Glacier, a major glacier in East Antarctica that holds an ice volume equivalent to a 1.5 m global sea level rise. The grounding line is retreating asymmetrically. On the eastern flank, the glacier is protected by a subglacial ridge. On the western flank, we find a deep and steep trough with a bed slope that makes the glacier conducive to rapid retreat. If warm water continues to induce high rates of ice melt near the glacier grounding zone, the potential exists for Denman Glacier to undergo a rapid and irreversible retreat, with major consequences for sea level rise.
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Braud, I., Chaffard, V., Coussot, C., Galle, S., Juen, P., Alexandre, H., et al. (2020). Building the information system of the French Critical Zone Observatories network: Theia/OZCAR-IS. Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, .
Abstract: The French Critical Zone research infrastructure, OZCAR-RI, gathers 20 observatories sampling various compartments of the critical zone, each having developed their own data management and distribution systems. A common information system (Theia/OZCAR IS) was built to make theirin situobservation FAIR (findable, accessible, interoperable, reusable). The IS architecture was designed after consultation of the users, data producers and IT teams involved in data management. A common data model based on various metadata standards was defined to create information fluxes between observatories' ISs and the Theia/OZCAR IS. Controlled vocabularies were defined to develop a data discovery web portal offering a faceted search with various criteria, including variables names and categories that were harmonized in a thesaurus published on the web. This paper describes the IS architecture, the pivot data model and open-source solutions used to implement data discovery, and future steps to implement data downloading and interoperability services.
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Bricaud, C., Le Sommer, J., Madec, G., Calone, C., Deshayes, J., Ethe, C., et al. (2020). Multi-grid algorithm for passive tracer transport in the NEMO ocean circulation model: a case study with the NEMO OGCM (version 3.6). Geoscientific Model Development, 13(11), 5465–5483.
Abstract: Ocean biogeochemical models are key tools for both scientific and operational applications. Nevertheless the cost of these models is often expensive because of the large number of biogeochemical tracers. This has motivated the development of multi-grid approaches where ocean dynamics and tracer transport are computed on grids of different spatial resolution. However, existing multi-grid approaches to tracer transport in ocean modelling do not allow the computation of ocean dynamics and tracer transport simultaneously. This paper describes a new multi-grid approach developed for accelerating the computation of passive tracer transport in the Nucleus for European Modelling of the Ocean (NEMO) ocean circulation model. In practice, passive tracer transport is computed at runtime on a grid with coarser spatial resolution than the hydrodynamics, which reduces the CPU cost of computing the evolution of tracers. We describe the multi-grid algorithm, its practical implementation in the NEMO ocean model, and discuss its performance on the basis of a series of sensitivity experiments with global ocean model configurations. Our experiments confirm that the spatial resolution of hydrodynamical fields can be coarsened by a factor of 3 in both horizontal directions without significantly affecting the resolved passive tracer fields. Overall, the proposed algorithm yields a reduction by a factor of 7 of the overhead associated with running a full biogeochemical model like PISCES (with 24 passive tracers). Propositions for further reducing this cost without affecting the resolved solution are discussed.
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Brocca, L., Massari, C., Pellarin, T., Filippucci, P., Ciabatta, L., Camici, S., et al. (2020). River flow prediction in data scarce regions: soil moisture integrated satellite rainfall products outperform rain gauge observations in West Africa. Scientific Reports, 10(1).
Abstract: Satellite precipitation products have been largely improved in the recent years particularly with the launch of the global precipitation measurement (GPM) core satellite. Moreover, the development of techniques for exploiting the information provided by satellite soil moisture to complement/enhance precipitation products have improved the accuracy of accumulated rainfall estimates over land. Such satellite enhanced precipitation products, available with a short latency (<1 day), represent an important and new source of information for river flow prediction and water resources management, particularly in developing countries in which ground observations are scarcely available and the access to such data is not always ensured. In this study, three recently developed rainfall products obtained from the integration of GPM rainfall and satellite soil moisture products have been used; namely GPM+SM2RAIN, PRISM-SMOS, and PRISM-SMAP. The prediction of observed daily river discharge at 10 basins located in Europe (4), West Africa (3) and South Africa (3) is carried out. For comparison, we have also considered three rainfall products based on: (1) GPM only, i.e., the Early Run version of the Integrated Multi-Satellite Retrievals for GPM (GPM-ER), (2) rain gauges, i.e., the Global Precipitation Climatology Centre, and (3) the latest European Centre for Medium-Range Weather Forecasts reanalysis, ERA5. Three different conceptual and lumped rainfall-runoff models are employed to obtain robust and reliable results over the 3-year data period 2015-2017. Results indicate that, particularly over scarcely gauged areas (West Africa), the integrated products outperform both ground- and reanalysis-based rainfall estimates. For all basins, the GPM+SM2RAIN product is performing the best among the short latency products with mean Kling-Gupta Efficiency (KGE) equal to 0.87, and significantly better than GPM-ER (mean KGE=0.77). The integrated products are found to reproduce particularly well the high flows. These results highlight the strong need to disseminate such integrated satellite rainfall products for hydrological (and agricultural) applications in poorly gauged areas such as Africa and South America.
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Brondex, J., Gagliardini, O., Gillet-Chaulet, F., & Chekki, M. (2020). Comparing the long-term fate of a snow cave and a rigid container buried at Dome C, Antarctica. Cold Regions Science And Technology, 180.
Abstract: Ice Memory is an international project aiming at creating a global ice archive sanctuary in Antarctica. The design of a perennial subsurface storage space for the cores is a cornerstone of this project. Here, we use an ice/firn flow model to investigate possible storage solutions that would meet the specific requirements of the project. To this end, we consider two extreme cases in terms of rigidity of the facility: an ice cave excavated into the firn and a perfectly rigid container buried within it. We focus on the rate of sinking of the facility as well as on the rate of closure of the cave and the evolution of the normal stresses supported by the container. Our results show that the lifetime of a cave is highly affected by the initial density of snow in its surrounding. On the other hand, the presence of the rigid container within the domain perturbs the flow of snow, creating patches of high density in its surrounding and leading to significant normal stresses on its walls. In particular, strong stress concentrations are obtained at the container angles. These results prove that unreinforced shipping containers are unsuited for this task.
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Brun, F., Treichler, D., Shean, D., & Immerzeel, W. (2020). Limited Contribution of Glacier Mass Loss to the Recent Increase in Tibetan Plateau Lake Volume. Frontiers In Earth Science, 8.
Abstract: The Tibetan plateau plays an essential role in the water supply to Asia's large river systems and, as the largest and highest mountain plateau in the world, it drives the Asian monsoon and influences global atmospheric circulation patterns. The increase in the Tibetan plateau lake volume since the mid-1990s is well documented, however the drivers of lake growth remain largely unexplained. In this study we investigate changes in lake and glacier volumes, together with changes in precipitation and evapotranspiration at basin scale. We calculate the contribution of glacier mass loss to the lake volume increase for the period 1994-2015. We demonstrate that glacier mass loss does have a limited contribution to the lake volume increase (19 +/- 21% for the whole Tibetan plateau). Glacier mass loss is thus insufficient to explain all of the lake volume gain, and despite large spread in various products that estimate precipitation and evaporation, we suggest that an increase in precipitation excess (precipitation – evapotranspiration) may be sufficient to explain the lake volume gain.
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Buckingham, C., Lucas, N., Belcher, S., Rippeth, T., Grant, A., Le Sommer, J., et al. (2020). The Contribution of Surface and Submesoscale Processes to Turbulence in the Open Ocean Surface Boundary Layer. Journal Of Advances In Modeling Earth Systems, .
Abstract: The ocean surface boundary layer is a critical interface across which momentum, heat, and trace gases are exchanged between the oceans and atmosphere. Surface processes (winds, waves, and buoyancy forcing) are known to contribute significantly to fluxes within this layer. Recently, studies have suggested that submesoscale processes, which occur at small scales (0.1-10 km, hours to days) and therefore are not yet represented in most ocean models, may play critical roles in these turbulent exchanges. While observational support for such phenomena has been demonstrated in the vicinity of strong current systems and littoral regions, relatively few observations exist in the open-ocean environment to warrant representation in Earth system models. We use novel observations and simulations to quantify the contributions of surface and submesoscale processes to turbulent kinetic energy (TKE) dissipation in the open-ocean surface boundary layer. Our observations are derived from moorings in the North Atlantic, December 2012 to April 2013, and are complemented by atmospheric reanalysis. We develop a conceptual framework for dissipation rates due to surface and submesoscale processes. Using this framework and comparing with observed dissipation rates, we find that surface processes dominate TKE dissipation. A parameterization for symmetric instability is consistent with this result. We next employ simulations from an ocean front-resolving model to reestablish that dissipation due to surface processes exceeds that of submesoscale processes by 1-2 orders of magnitude. Together, these results suggest submesoscale processes do not dramatically modify vertical TKE budgets, though such dynamics may be climatically important owing to their ability to remove energy from the ocean.
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Bull, C., Kiss, A., Sen Gupta, A., Jourdain, N., Argueso, D., Di Luca, A., et al. (2020). Regional Versus Remote Atmosphere-Ocean Drivers of the Rapid Projected Intensification of the East Australian Current. Journal Of Geophysical Research-Oceans, 125(7).
Abstract: Like many western boundary currents, the East Australian Current (EAC) extension is projected to get stronger and warmer in the future. The CMIP5 multimodel mean (MMM) projection suggests up to 5 degrees C of warming under an RCP85 scenario by 2100. Previous studies employed Sverdrup balance to associate a trend in basin wide zonally integrated wind stress curl (resulting from the multidecadal poleward intensification in the westerly winds over the Southern Ocean) with enhanced transport in the EAC extension. Possible regional drivers are yet to be considered. Here we introduce the NEMO-OASIS-WRF coupled regional climate model as a framework to improve our understanding of CMIP5 projections. We analyze a hierarchy of simulations in which the regional atmosphere and ocean circulations are allowed to freely evolve subject to boundary conditions that represent present-day and CMIP5 RCP8.5 climate change anomalies. Evaluation of the historical simulation shows an EAC extension that is stronger than similar ocean-only models and observations. This bias is not explained by a linear response to differences in wind stress. The climate change simulations show that regional atmospheric CMIP5 MMM anomalies drive 73% of the projected 12 Sv increase in EAC extension transport whereas the remote ocean boundary conditions and regional radiative forcing (greenhouse gases within the domain) play a smaller role. The importance of regional changes in wind stress curl in driving the enhanced EAC extension is consistent with linear theory where the NEMO-OASIS-WRF response is closer to linear transport estimates compared to the CMIP5 MMM.
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Burke, E., Zhang, Y., & Krinner, G. (2020). Evaluating permafrost physics in the Coupled Model Intercomparison Project 6 (CMIP6) models and their sensitivity to climate change. Cryosphere, 14(9), 3155–3174.
Abstract: Permafrost is a ubiquitous phenomenon in the Arctic. Its future evolution is likely to control changes in northern high-latitude hydrology and biogeochemistry. Here we evaluate the permafrost dynamics in the global models participating in the Coupled Model Intercomparison Project (present generation – CMIP6; previous generation – CMIP5) along with the sensitivity of permafrost to climate change. Whilst the northern high-latitude air temperatures are relatively well simulated by the climate models, they do introduce a bias into any subsequent model estimate of permafrost. Therefore evaluation metrics are defined in relation to the air temperature. This paper shows that the climate, snow and permafrost physics of the CMIP6 multi-model ensemble is very similar to that of the CMIP5 multi-model ensemble. The main differences are that a small number of models have demonstrably better snow insulation in CMIP6 than in CMIP5 and a small number have a deeper soil profile. These changes lead to a small overall improvement in the representation of the permafrost extent. There is little improvement in the simulation of maximum summer thaw depth between CMIP5 and CMIP6. We suggest that more models should include a better-resolved and deeper soil profile as a first step towards addressing this. We use the annual mean thawed volume of the top 2 m of the soil defined from the model soil profiles for the permafrost region to quantify changes in permafrost dynamics. The CMIP6 models project that the annual mean frozen volume in the top 2 m of the soil could decrease by 10 %-40% degrees C-1 of global mean surface air temperature increase.
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Cappelaere, B., Feurer, D., Vischel, T., Ottle, C., Issoufou, H., Saux-Picart, S., et al. (2020). Modeling Land Surface Fluxes from Uncertain Rainfall: A Case Study in the Sahel with Field-Driven Stochastic Rainfields. Atmosphere, 11(5).
Abstract: In distributed land surface modeling (LSM) studies, uncertainty in the rainfields that are used to force models is a major source of error in predicted land surface response variables. This is particularly true for applications in the African Sahel region, where weak knowledge of highly time/space-variable convective rainfall in a poorly monitored region is a considerable obstacle to such developments. In this study, we used a field-based stochastic rainfield generator to analyze the propagation of the rainfall uncertainty through a distributed land surface model simulating water and energy fluxes in Sahelian ecosystems. Ensemble time/space rainfields were generated from field observations of the local AMMA-CATCH-Niger recording raingauge network. The rainfields were then used to force the SEtHyS-Savannah LSM, yielding an ensemble of time/space simulated fluxes. Through informative graphical representations and innovative diagnosis metrics, these outputs were analyzed to separate the different components of flux variability, among which was the uncertainty represented by ensemble-wise variability. Scale dependence was analyzed for each flux type in the water and energy budgets, producing a comprehensive picture of uncertainty propagation for the various flux types, with its relationship to intrinsic space/time flux variability. The study was performed over a 2530 km(2)domain over six months, covering an entire monsoon season and the subsequent dry-down, using a kilometer/daily base resolution of analysis. The newly introduced dimensionless uncertainty measure, called the uncertainty coefficient, proved to be more effective in describing uncertainty patterns and relationships than a more classical measure based on variance fractions. Results show a clear scaling relationship in uncertainty coefficients between rainfall and the dependent fluxes, specific to each flux type. These results suggest a higher sensitivity to rainfall uncertainty for hydrological than for agro-ecological or meteorological applications, even though eddy fluxes do receive a substantial part of that source uncertainty.
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Chagnaud, G., Gallee, H., Lebel, T., Panthou, G., & Vischel, T. (2020). A Boundary Forcing Sensitivity Analysis of the West African Monsoon Simulated by the Modele Atmospherique Regional. Atmosphere, 11(2).
Abstract: The rainfall regime of West Africa is highly variable over a large range of space and time scales. With rainfall agriculture being predominent in the region, the local population is extremely vulnerable to intraseasonal dry spells and multi-year droughts as well as to intense rainfall over small time steps. Were this variability to increase, it might render the area close from becoming unhabitable. Anticipating any change is thus crucial from both a societal and a scientific perspective. Despite continuous efforts in Global Climate Model (GCM) development, there is still no agreement on the sign of the future rainfall regime change in the region. Regional Climate Models (RCMs) are used for more accurate projections of future changes as well as end-user-oriented impact studies. In this study, the sensitivity of the Modele Atmospherique Regional (MAR) to homogeneous perturbations in boundary forcing air temperature and/or SST is assessed with the aim to better understand (i) the thermodynamical imprint of the recent rainfall regime changes and (ii) the impact of errors in driving data on the West African rainfall regime simulated by an RCM. After an evaluation step where the model is proved to satisfactorily simulate the West African Monsoon (WAM), sensitivity experiments display contrasted, sizable and robust responses of the simulated rainfall regime. The rainfall responses to the boundary forcing perturbations compare in magnitude with the intrinsic model bias, giving support for such an analysis. A physical interpretation of the rainfall anomalies provides confidence in the model response consistency and shows the potential of such an experimental protocol for future climate change downscalling over this region.
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Charrondiere, C., Brun, C., Sicart, J., Cohard, J., Biron, R., & Blein, S. (2020). Buoyancy Effects in the Turbulence Kinetic Energy Budget and Reynolds Stress Budget for a Katabatic Jet over a Steep Alpine Slope. Boundary-Layer Meteorology, 177(1), 97–122.
Abstract: Katabatic winds are very frequent but poorly understood or simulated over steep slopes. This study focuses on a katabatic jet above a steep alpine slope. We assess the buoyancy terms in both the turbulence kinetic energy (TKE) and the Reynolds shear-stress budget equations. We specifically focus on the contribution of the slope-normal and along-slope turbulent sensible heat fluxes to these terms. Four levels of measurements below and above the maximum wind-speed height enable analysis of the buoyancy effect along the vertical profile as follow: (i) buoyancy tends to destroy TKE, as expected in stable conditions, and the turbulent momentum flux in the inner-layer region of the jet below the maximum wind-speed height z(j); (ii) results also suggest buoyancy contributes to the production of TKE in the outer-layer shear region of the jet (well above z(j)) while consumption of the turbulent momentum flux is observed in the same region; (iii) In the region around the maximum wind speed where mechanical shear production is marginal, buoyancy tends to destroy TKE and our results suggest it tends to increase the momentum flux. The present study also provides an analytical condition for the limit between production and consumption of the turbulent momentum flux due to buoyancy as a function of the slope angle, similar to the condition already proposed for TKE. We reintroduce the stress Richardson number, which is the equivalent of the flux Richardson number for the Reynolds shear-stress budget. We point out that the flux Richardson number and the stress Richardson number are complementary stability parameters for characterizing the katabatic flow apart from the region around the maximum wind-speed height.
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Cheruy, F., Ducharne, A., Hourdin, F., Musat, I., Vignon, E., Gastineau, G., et al. (2020). Improved Near-Surface Continental Climate in IPSL-CM6A-LR by Combined Evolutions of Atmospheric and Land Surface Physics. Journal Of Advances In Modeling Earth Systems, 12(10).
Abstract: This work is motivated by the identification of the land-atmosphere interactions as one of the key sources of uncertainty in climate change simulations. It documents new developments in related processes, namely, boundary layer/convection/clouds parameterizations and land surface parameterization in the Earth System Model of the Institut Pierre Simon Laplace (IPSL). Simulations forced by prescribed oceanic conditions are produced with different combinations of atmospheric and land surface parameterizations. They are used to explore the sensitivity to the atmospheric physics and/or soil physics of major biases in the near surface variables over continents, the energy and moisture coupling established at the soil/atmosphere interface in not too wet (energy limited) and not too dry (moisture limited) soil moisture regions also known as transition or “hot-spot” regions, the river runoff at the outlet of major rivers. The package implemented in the IPSL-Climate Model for the Phase 6 of the Coupled Models Intercomparison Project (CMIP6) allows us to reduce several biases in the surface albedo, the snow cover, and the continental surface air temperature in summer as well as in the temperature profile in the surface layer of the polar regions. The interactions between soil moisture and atmosphere in hotspot regions are in better agreement with the observations. Rainfall is also significantly improved in volume and seasonality in several major river basins leading to an overall improvement in river discharge. However, the lack of consideration of floodplains and human influences in the model, for example, dams and irrigation, impacts the realism of simulated discharge.
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Close, S., Penduff, T., Speich, S., & Molines, J. (2020). A means of estimating the intrinsic and atmospherically-forced contributions to sea surface height variability applied to altimetric observations. Progress In Oceanography, 184.
Abstract: Drawing on a 50-member ocean ensemble hindcast, the magnitude and characteristic temporal and spatial scales of intrinsic and forced sea surface height (SSH) variability are evaluated over a 37-year period. The intrinsic and forced contributions derived from the ensemble are found to have similar temporal spectra, but different characteristic spatial scales. These results suggest that, with an appropriate choice of cutoff scales, simple spatial filtering can be used to estimate the forced and intrinsic contributions given either a single model run, or an observational data set. The method is tested using a single member drawn from the ensemble, before being applied to the observed altimetric record. Two sample applications with relevance to large-scale climate are used to illustrate the method's potential utility. Firstly, the long-term trends calculated from the total and recreated forced components using the altimetric record are compared and local differences highlighted. Second, the recreated forced SSH is shown to covary with the North Atlantic Oscillation at seasonal time scales in regions where no such influence can be found using the original SSH signal. Some limitations and uses for which the method may prove unsuitable are also briefly considered.
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Cluzet, B., Revuelto, J., Lafaysse, M., Tuzet, F., Cosme, E., Picard, G., et al. (2020). Towards the assimilation of satellite reflectance into semi-distributed ensemble snowpack simulations. Cold Regions Science And Technology, 170.
Abstract: Uncertainties of snowpack models and of their meteorological forcings limit their use by avalanche hazard forecasters, or for glaciological and hydrological studies. The spatialized simulations currently available for avalanche hazard forecasting are only assimilating sparse meteorological observations. As suggested by recent studies, their forecasting skills could be significantly improved by assimilating satellite data such as snow reflectances from satellites in the visible and the near-infrared spectra. Indeed, these data can help constrain the microstructural properties of surface snow and light absorbing impurities content, which in turn affect the surface energy and mass budgets. This paper investigates the prerequisites of satellite data assimilation into a detailed snowpack model. An ensemble version of Meteo-France operational snowpack forecasting system (named S2M) was built for this study. This operational system runs on topographic classes instead of grid points, so-called 'semi-distributed' approach. Each class corresponds to one of the 23 mountain massifs of the French Alps (about 1000 km(2) each), an altitudinal range (by step of 300 m) and aspect (by step of 45 degrees). We assess the feasability of satellite data assimilation in such a semi-distributed geometry. Ensemble simulations are compared with satellite observations from MODIS and Sentinel-2, and with in-situ reflectance observations. The study focuses on the 2013-2014 and 2016-2017 winters in the Grandes-Rousses massif. Substantial Pearson R-2 correlations (0.75-0.90) of MODIS observations with simulations are found over the domain. This suggests that assimilating it could have an impact on the spatialized snowpack forecasting system. However, observations contain significant biases (0.1-0.2 in reflectance) which prevent their direct assimilation. MODIS spectral band ratios seem to be much less biased. This may open the way to an operational assimilation of MODIS reflectances into the Meteo-France snowpack modelling system.
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Coen, M., Andrews, E., Alastuey, A., Arsov, T., Backman, J., Brem, B., et al. (2020). Multidecadal trend analysis of in situ aerosol radiative properties around the world. Atmospheric Chemistry And Physics, 20(14), 8867–8908.
Abstract: In order to assess the evolution of aerosol parameters affecting climate change, a long-term trend analysis of aerosol optical properties was performed on time series from 52 stations situated across five continents. The time series of measured scattering, backscattering and absorption coefficients as well as the derived single scattering albedo, backscattering fraction, scattering and absorption Angstrom exponents covered at least 10 years and up to 40 years for some stations. The non-parametric seasonal Mann-Kendall (MK) statistical test associated with several pre-whitening methods and with Sen's slope was used as the main trend analysis method. Comparisons with general least mean square associated with autoregressive bootstrap (GLS/ARB) and with standard least mean square analysis (LMS) enabled confirmation of the detected MK statistically significant trends and the assessment of advantages and limitations of each method. Currently, scattering and backscattering coefficient trends are mostly decreasing in Europe and North America and are not statistically significant in Asia, while polar stations exhibit a mix of increasing and decreasing trends. A few increasing trends are also found at some stations in North America and Australia. Absorption coefficient time series also exhibit primarily decreasing trends. For single scattering albedo, 52 % of the sites exhibit statistically significant positive trends, mostly in Asia, eastern/northern Europe and the Arctic, 22 % of sites exhibit statistically significant negative trends, mostly in central Europe and central North America, while the remaining 26 % of sites have trends which are not statistically significant. In addition to evaluating trends for the overall time series, the evolution of the trends in sequential 10-year segments was also analyzed. For scattering and backscattering, statistically significant increasing 10-year trends are primarily found for earlier periods (10-year trends ending in 2010-2015) for polar stations and Mauna Loa. For most of the stations, the present-day statistically significant decreasing 10-year trends of the single scattering albedo were preceded by not statistically significant and statistically significant increasing 10-year trends. The effect of air pollution abatement policies in continental North America is very obvious in the 10-year trends of the scattering coefficient – there is a shift to statistically significant negative trends in 2009-2012 for all stations in the eastern and central USA. This long-term trend analysis of aerosol radiative properties with a broad spatial coverage provides insight into potential aerosol effects on climate changes.
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Colombo, P., Barnier, B., Penduff, T., Chanut, J., Deshayes, J., Molines, J., et al. (2020). Representation of the Denmark Strait overflow in a z-coordinate eddying configuration of the NEMO (v3.6) ocean model: resolution and parameter impacts. Geoscientific Model Development, 13(7), 3347–3371.
Abstract: We investigate in this paper the sensitivity of the representation of the Denmark Strait overflow produced by a regional z-coordinate configuration of NEMO (version 3.6) to the horizontal and vertical grid resolutions and to various numerical and physical parameters. Three different horizontal resolutions, 1/12, 1/36, and 1/60 degrees, are respectively used with 46, 75, 150, and 300 vertical levels. In the given numerical set-up, the increase in the vertical resolution did not bring improvement at eddy-permitting resolution (1/12 degrees). We find a greater dilution of the overflow as the number of vertical level increases, and the worst solution is the one with 300 vertical levels. It is found that when the local slope of the grid is weaker than the slope of the topography the result is a more diluted vein. Such a grid enhances the dilution of the plume in the ambient fluid and produces its thickening. Although the greater number of levels allows for a better resolution of the ageostrophic Ekman flow in the bottom layer, the final result also depends on how the local grid slope matches the topographic slope. We also find that for a fixed number of levels, the representation of the overflow is improved when horizontal resolution is increased to 1/36 and 1/60 degrees, with the most drastic improvements being obtained with 150 levels. With such a number of vertical levels, the enhanced vertical mixing associated with the step-like representation of the topography remains limited to a thin bottom layer representing a minor portion of the overflow. Two major additional players contribute to the sinking of the overflow: the breaking of the overflow into boluses of dense water which contribute to spreading the overflow waters along the Greenland shelf and within the Irminger Basin, and the resolved vertical shear that results from the resolution of the bottom Ekman boundary layer dynamics. This improves the accuracy of the calculation of the entrainment by the turbulent kinetic energy mixing scheme (as it depends on the local shear) and improves the properties of the overflow waters such that they more favourably compare with observations. At 300 vertical levels the dilution is again increased for all horizontal resolutions. The impact on the overflow representation of many other numerical parameters was tested (momentum advection scheme, lateral friction, bottom boundary layer parameterization, closure parameterization, etc.), but none had a significant impact on the overflow representation.
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Condom, T., Martinez, R., Pabon, J., Costa, F., Pineda, L., Nieto, J., et al. (2020). Climatological and Hydrological Observations for the South American Andes: In situ Stations, Satellite, and Reanalysis Data Sets. Frontiers In Earth Science, 8.
Abstract: Modern hydrology relies on multiple sources of information combined with climatological, hydrological and glaciological data. These data can be collected through various sources such as private initiatives by companies, research programs, and both national and international organisms. They also vary by types, e.g., in situ measurements, satellite, reanalysis and simulated data. Recently the ANDEX research project, as a GEWEX regional program, was created to understand the processes related to the hydrological cycle and energy fluxes in the Andean region from Colombia to Patagonia. It is quite challenging to carry out this program given the complex orography and diversity of climates from tropical to sub-polar climates. This review article is a compilation of the various databases that are useful for hydrometeorological research in the South American Andes. The National Meteorological and Hydrological Services in Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela and Argentina provide a large amount of data however the high-elevation areas are poorly instrumented and the number of stations varies greatly between the countries. National databases are only partially shared with the international bodies responsible for summarizing the existing data; this causes problems in term of data product assimilation. Across the entire continent, too few radiosondes are being used despite the fact that these data are crucial for validating and identifying problems in the atmospheric models. An increasing number of satellite data are available but it is difficult to assimilate them into the hydroclimatological models suited to the adjusted spatial and temporal resolutions. Specifically, for precipitation, we recommend merged products that account for the high spatial and temporal variability across the Andes. Finally, the international ANDEX program could be an excellent opportunity to increase the knowledge of the hydrological processes in the Andes.
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Cornford, S., Seroussi, H., Asay-Davis, X., Gudmundsson, G., Arthern, R., Borstad, C., et al. (2020). Results of the third Marine Ice Sheet Model Intercomparison Project (MISMIP plus ). Cryosphere, 14(7), 2283–2301.
Abstract: We present the result of the third Marine Ice Sheet Model Intercomparison Project, MISMIP+. MISMIP+ is intended to be a benchmark for ice-flow models which include fast sliding marine ice streams and floating ice shelves and in particular a treatment of viscous stress that is sufficient to model buttressing, where upstream ice flow is restrained by a downstream ice shelf. A set of idealized experiments first tests that models are able to maintain a steady state with the grounding line located on a retrograde slope due to buttressing and then explore scenarios where a reduction in that buttressing causes ice stream acceleration, thinning, and grounding line retreat. The majority of participating models passed the first test and then produced similar responses to the loss of buttressing. We find that the most important distinction between models in this particular type of simulation is in the treatment of sliding at the bed, with other distinctions – notably the difference between the simpler and more complete treatments of englacial stress but also the differences between numerical methods – taking a secondary role.
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Couvreux, F., Bazile, E., Rodier, Q., Maronga, B., Matheou, G., Chinita, M., et al. (2020). Intercomparison of Large-Eddy Simulations of the Antarctic Boundary Layer for Very Stable Stratification. Boundary-Layer Meteorology, 176(3), 369–400.
Abstract: In polar regions, where the boundary layer is often stably stratified, atmospheric models produce large biases depending on the boundary-layer parametrizations and the parametrization of the exchange of energy at the surface. This model intercomparison focuses on the very stable stratification encountered over the Antarctic Plateau in 2009. Here, we analyze results from 10 large-eddy-simulation (LES) codes for different spatial resolutions over 24 consecutive hours, and compare them with observations acquired at the Concordia Research Station during summer. This is a challenging exercise for such simulations since they need to reproduce both the 300-m-deep convective boundary layer and the very thin stable boundary layer characterized by a strong vertical temperature gradient (10 K difference over the lowest 20 m) when the sun is low over the horizon. A large variability in surface fluxes among the different models is highlighted. The LES models correctly reproduce the convective boundary layer in terms of mean profiles and turbulent characteristics but display more spread during stable conditions, which is largely reduced by increasing the horizontal and vertical resolutions in additional simulations focusing only on the stable period. This highlights the fact that very fine resolution is needed to represent such conditions. Complementary sensitivity studies are conducted regarding the roughness length, the subgrid-scale turbulence closure as well as the resolution and domain size. While we find little dependence on the surface-flux parametrization, the results indicate a pronounced sensitivity to both the roughness length and the turbulence closure.
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Cushing, E., Hollender, F., Moiriat, D., Guyonnet-Benaize, C., Theodoulidis, N., Pons-Branchu, E., et al. (2020). Building a three dimensional model of the active Plio-Quaternary basin of Argostoli (Cephalonia Island, Greece): An integrated geophysical and geological approach. Engineering Geology, 265.
Abstract: This work is a multidisciplinary approach from geological and geophysical surveys to build a 3D geological model of Argostoli Basin (Cephalonia Island, Greece) aiming to be used for computational 3D simulation of seismic motion. Cephalonia Island is located at the north-western end of the Aegean subduction frontal thrust that is linked to the dextral Cephalonia Transform Fault (west of Cephalonia) where the seismic hazard is high in terms of earthquake frequency and magnitude. The Plio-Quaternary Koutavos-Argostoli basin site was selected within the French Research Agency PIA SINAPS@ project (www.institut-seism.fr/projets/sinaps/ – last accessed on November 25th 2019) to host a vertical accelerometer array. The long-term goal is to validate three-dimensional nonlinear numerical simulation codes to assess the site-specific amplification and nonlinearity. Herein the geological and geophysical surveys carried out from 2011 to 2017 are presented and in particular the complementary investigations that led to the identification of the main stratigraphic units and their structures. In addition, coral debris sampled from the vertical array deep borehole cores were used for Th-230/U-234 measurements, which confirmed the Pleistocene age of the Koutavos basin. The characterization of the three-dimensional structure of the stratigraphic units was achieved by coupling geological cross-sections (i.e., depth geometry) and geophysical surveys based of surface wave analysis.
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Cuthbert, M., Taylor, R., Favreau, G., Todd, M., Shamsudduha, M., Villholth, K., et al. (2020). Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa (vol 572, pg 230, 2019). Nature, 588(7838), E25.
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Daellenbach, K., Uzu, G., Jiang, J., Cassagnes, L., Leni, Z., Vlachou, A., et al. (2020). Sources of particulate-matter air pollution and its oxidative potential in Europe. Nature, 587(7834), 414–+.
Abstract: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally(1-3). Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concentration, with particle size and composition also thought to play a part(4). Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain(5-8). Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results(7). In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concentration(7). Here we use field observations and air-quality modelling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorganic components, crustal material and secondary biogenic organic aerosols control the mass concentration of particulate matter. By contrast, oxidative potential concentration is associated mostly with anthropogenic sources, in particular with fine-mode secondary organic aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concentrations of particulate matter alone may not reduce the oxidative potential concentration. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass. Observations and air-quality modelling reveal that the sources of particulate matter and oxidative potential in Europe are different, implying that reducing mass concentrations of particulate matter alone may not reduce oxidative potential.
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Danso, D., Anquetin, S., Diedhiou, A., & Adamou, R. (2020). Cloudiness Information Services for Solar Energy Management in West Africa. Atmosphere, 11(8).
Abstract: In West Africa (WA), interest in solar energy development has risen in recent years with many planned and ongoing projects currently in the region. However, a major drawback to this development in the region is the intense cloud cover that reduces the incoming solar radiation when present and causes fluctuations in solar power production. Therefore, understanding the occurrence of clouds and their link to the surface solar radiation in the region is important for making plans to manage future solar energy production. In this study, we use the state-of-the-art European Centre for Medium-range Weather Forecasts ReAnalysis (ERA5) dataset to examine the occurrence and persistence of cloudy and clear-sky conditions in the region. Then, we investigate the effects of cloud cover on the quantity and variability of the incoming solar radiation. The cloud shortwave radiation attenuation (CRASW down arrow) is used to quantify the amount of incoming solar radiation that is lost due to clouds. The results showed that the attenuation of incoming solar radiation is stronger in all months over the southern part of WA near the Guinea Coast. Across the whole region, the maximum attenuation occurs in August, with a meanCRASW down arrow of about 55% over southern WA and between 20% and 35% in the Sahelian region. Southern WA is characterized by a higher occurrence of persistent cloudy conditions, while the Sahel region and northern WA are associated with frequent clear-sky conditions. Nonetheless, continuous periods with extremely low surface solar radiation were found to be few over the whole region. The analysis also showed that the surface solar radiation received from November to April only varies marginally from one year to the other. However, there is a higher uncertainty during the core of the monsoon season (June to October) with regard to the quantity of incoming solar radiation. The results obtained show the need for robust management plans to ensure the long-term success of solar energy projects in the region.
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Danso, D., Anquetin, S., Diedhiou, A., Kouadio, K., & Kobea, A. (2020). Daytime low-level clouds in West Africa – occurrence, associated drivers, and shortwave radiation attenuation. Earth System Dynamics, 11(4), 1133–1152.
Abstract: This study focuses on daytime low-level clouds (LLCs) that occur within the first 2 km of the atmosphere over West Africa (WA). These daytime LLCs play a major role in the earth's radiative balance, yet their understanding is still relatively low in WA. We use the state-of-the-art ERA5 dataset to understand their occurrence and associated drivers as well as their impact on the incoming surface solar radiation in the two contrasting Guinean and Sahelian regions of WA. The diurnal cycle of the daytime occurrence of three LLC classes namely No LCC, LLC Class-1 (LLCs with lower fraction), and LLC Class-2 (LLCs with higher fraction) is first studied. The monthly evolutions of hourly and long-lasting LLC (for at least 6 consecutive hours) events are then analyzed as well as the synoptic-scale moisture flux associated with the long-lasting LLC events. Finally, the impact of LLC on the surface heat fluxes and the incoming solar irradiance is investigated. During the summer months in the Guinean region, LLC Class-1 occurrence is low, while LLC Class-2 is frequent (occurrence frequency around 75 % in August). In the Sahel, LLC Class-1 is dominant in the summer months (occurrence frequency more than 80 % from June to October); however the peak occurrence frequency of Class-2 is also in the summer. In both regions, events with No LLC do not present any specific correlation with the time of the day. However, a diurnal evolution that appears to be strongly different from one region to the other is noted for the occurrence of LLC Class-2. LLC occurrence in both regions is associated with high moisture flux driven by strong southwesterly winds from the Gulf of Guinea and significant background moisture levels. LLC Class-2 in particular leads to a significant reduction in the upward transfer of energy and a net downward energy transfer caused by the release of large amounts of energy in the atmosphere during the cloud formation. In July, August, and September (JAS), most of the LLC Class-2 events may likely be the low-level stratiform clouds that occur frequently over the Guinean region, while they may be deep convective clouds in the Sahel. Additionally, LLC Class-2 causes high attenuation of the incoming solar radiation, especially during JAS, where about 49 % and 44 % of the downwelling surface shortwave radiation is lost on average in Guinea and the Sahel, respectively.
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Davaze, L., Rabatel, A., Dufour, A., Hugonnet, R., & Arnaud, Y. (2020). Region-Wide Annual Glacier Surface Mass Balance for the European Alps From 2000 to 2016. Frontiers In Earth Science, 8.
Abstract: Studying glacier mass changes at regional scale provides critical insights into the impact of climate change on glacierized regions, but is impractical usingin situestimates alone due to logistical and human constraints. We present annual mass-balance time series for 239 glaciers in the European Alps, using optical satellite images for the period of 2000 to 2016. Our approach, called the SLA-method, is based on the estimation of the glacier snowline altitude (SLA) for each year combined with the geodetic mass balance over the study period to derive the annual mass balance.In situannual mass-balances from 23 glaciers were used to validate our approach and underline its robustness to generate annual mass-balance time series. Such temporally-resolved observations provide a unique potential to investigate the behavior of glaciers in regions where few or no data are available. At the European Alps scale, our geodetic estimate was performed for 361 glaciers (75% of the glacierized area) and indicates a mean annual mass loss of -0.74 +/- 0.20 m w.e. yr(-1)from 2000 to 2016. The spatial variability in the average glacier mass loss is significantly correlated to three morpho-topographic variables (mean glacier slope, median, and maximum altitudes), altogether explaining 36% of the observed variance. Comparing the mass losses fromin situand SLA-method estimates and taking into account the glacier slope and maximum elevation, we show that steeper glaciers and glaciers with higher maximum elevation experienced less mass loss. Because steeper glaciers (>20 degrees) are poorly represented byin situestimates, we suggest that region-wide extrapolation of field measurements could be improved by including a morpho-topographic dependency. The analysis of the annual mass changes with regard to a global atmospheric dataset (ERA5) showed that: (i) extreme climate events are registered by all glaciers across the European Alps, and we identified opposite weather regimes favorable or detrimental to the mass change; (ii) the interannual variability of glacier mass balances in the “central European Alps” is lower; and (iii) current strong imbalance of glaciers in the European Alps is likely mainly the consequence of the multi-decadal increasing trend in atmospheric temperature, clearly documented from ERA5 data.
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Delrieu, G., Khanal, A., Yu, N., Cazenave, F., Boudevillain, B., & Gaussiat, N. (2020). Preliminary investigation of the relationship between differential phase shift and path-integrated attenuation at the X band frequency in an Alpine environment. Atmospheric Measurement Techniques, 13(7), 3731–3749.
Abstract: The RadAlp experiment aims at developing advanced methods for rainfall and snowfall estimation using weather radar remote sensing techniques in high mountain regions for improved water resource assessment and hydrological risk mitigation. A unique observation system has been deployed since 2016 in the Grenoble region of France. It is composed of an X-band radar operated by Meteo-France on top of the Moucherotte mountain (1901m above sea level; hereinafter MOUC radar). In the Grenoble valley (220m above sea level; hereinafter a.s.l.), we operate a research X-band radar called XPORT and in situ sensors (weather station, rain gauge and disdrometer). In this paper we present a methodology for studying the relationship between the differential phase shift due to propagation in precipitation (Phi(dp)) and path-integrated attenuation (PIA) at X band. This relationship is critical for quantitative precipitation estimation (QPE) based on polarimetry due to severe attenuation effects in rain at the considered frequency. Furthermore, this relationship is still poorly documented in the melting layer (ML) due to the complexity of the hydrometeors' distributions in terms of size, shape and density. The available observation system offers promising features to improve this understanding and to subsequently better process the radar observations in the ML. We use the mountain reference technique (MRT) for direct PIA estimations associated with the decrease in returns from mountain targets during precipitation events. The polarimetric PIA estimations are based on the regularization of the profiles of the total differential phase shift (Psi(dp)) from which the profiles of the specific differential phase shift on propagation (K-dp) are derived. This is followed by the application of relationships between the specific attenuation (k) and the specific differential phase shift. Such k-K-dp relationships are estimated for rain by using drop size distribution (DSD) measurements available at ground level. Two sets of precipitation events are considered in this preliminary study, namely (i) nine convective cases with high rain rates which allow us to study the phi(dp)-PIA relationship in rain, and (ii) a stratiform case with moderate rain rates, for which the melting layer (ML) rose up from about 1000 up to 2500ma.s.l., where we were able to perform a horizontal scanning of the ML with the MOUC radar and a detailed analysis of the phi(dp)-PIA relationship in the various layers of the ML. A common methodology was developed for the two configurations with some specific parameterizations. The various sources of error affecting the two PIA estimators are discussed, namely the stability of the dry weather mountain reference targets, radome attenuation, noise of the total differential phase shift profiles, contamination due to the differential phase shift on backscatter and relevance of the k-K-dp relationship derived from DSD measurements, etc. In the end, the rain case study indicates that the relationship between MRT-derived PIAs and polarimetry-derived PIAs presents an overall coherence but quite a considerable dispersion (explained variance of 0.77). Interestingly, the nonlinear k-K-dp relationship derived from independent DSD measurements yields almost unbiased PIA estimates. For the stratiform case, clear signatures of the MRT-derived PIAs, the corresponding phi(dp) value and their ratio are evidenced within the ML. In particular, the averaged PIA/phi(dp) ratio, a proxy for the slope of a linear k-K-dp relationship in the ML, peaks at the level of the copolar correlation coefficient (rho(hv)) peak, just below the reflectivity peak, with a value of about 0.42 dB per degree. Its value in rain below the ML is 0.33 dB per degree, which is in rather good agreement with the slope of the linear k-K-dp relationship derived from DSD measurements at ground level. The PIA/phi(dp) ratio remains quite high in the upper part of the ML, between 0.32 and 0.38 dB per degree, before tending towards 0 above the ML.
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Derkacheva, A., Mouginot, J., Millan, R., Maier, N., & Gillet-Chaulet, F. (2020). Data Reduction Using Statistical and Regression Approaches for Ice Velocity Derived by Landsat-8, Sentinel-1 and Sentinel-2. Remote Sensing, 12(12).
Abstract: During the last decade, the number of available satellite observations has increased significantly, allowing for far more frequent measurements of the glacier speed. Appropriate methods of post-processing need to be developed to efficiently deal with the large volumes of data generated and relatively large intrinsic errors associated with the measurements. Here, we process and combine together measurements of ice velocity of Russell Gletscher in Greenland from three satellites-Sentinel-1, Sentinel-2, and Landsat-8, creating a multi-year velocity database with high temporal and spatial resolution. We then investigate post-processing methodologies with the aim of generating corrected, ordered, and simplified time series. We tested rolling mean and median, cubic spline regression, and linear non-parametric local regression (LOWESS) smoothing algorithms to reduce data noise, evaluated the results against ground-based GPS in one location, and compared the results between two locations with different characteristics. We found that LOWESS provides the best solution for noisy measurements that are unevenly distributed in time. Using this methodology with these sensors, we can robustly derive time series with temporal resolution of 2-3 weeks and improve the accuracy on the ice velocity to about 10 m/yr, or a factor of three compared to the initial measurements. The presented methodology could be applied to the entire Greenland ice sheet with an aim of reconstructing comprehensive sub-seasonal ice flow dynamics and mass balance.
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Descroix, L., Faty, B., Manga, S., Diedhiou, A., Lambert, L., Soumare, S., et al. (2020). Are the Fouta Djallon Highlands Still the Water Tower of West Africa? Water, 12(11).
Abstract: A large share of surface water resources in Sahelian countries originates from Guinea's Fouta Djallon highlands, earning the area the name of “the water tower of West Africa”. This paper aims to investigate the recent dynamics of the Fouta Djallon's hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover. The latter is described at three different space scales and with different methods. Twenty-five years after the end of the 1968-1993 major drought, annual discharges continue to slowly increase, nearly reaching a long-term average, as natural reservoirs which emptied to sustain streamflows during the drought have been replenishing since the 1990s, explaining the slow increase in discharges. However, another important trend has been detected since the beginning of the drought, i.e., the increase in the depletion coefficient of most of the Fouta Djallon upper basins, as a consequence of the reduction in the soil water-holding capacity. After confirming the pertinence and significance of this increase and subsequent decrease in the depletion coefficient, this paper identifies the factors possibly linked with the basins' storage capacity trends. The densely populated areas of the summit plateau are also shown to be the ones where vegetation cover is not threatened and where ecological intensification of rural activities is ancient.
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Descroix, L., Sane, Y., Thior, M., Manga, S., Ba, B., Mingou, J., et al. (2020). Inverse Estuaries in West Africa: Evidence of the Rainfall Recovery? Water, 12(3).
Abstract: In West Africa, as in many other estuaries, enormous volumes of marine water are entering the continent. Fresh water discharge is very low, and it is commonly strongly linked to rainfall level. Some of these estuaries are inverse estuaries. During the Great Sahelian Drought (1968-1993), their hyperhaline feature was exacerbated. This paper aims to describe the evolution of the two main West African inverse estuaries, those of the Saloum River and the Casamance River, since the end of the drought. Water salinity measurements were carried out over three to five years according to the sites in order to document this evolution and to compare data with the historical ones collected during the long dry period at the end of 20th century. The results show that in both estuaries, the mean water salinity values have markedly decreased since the end of the drought. However, the Saloum estuary remains a totally inverse estuary, while for the Casamance River, the estuarine turbidity maximum (ETM) is the location of the salinity maximum, and it moves according to the seasons from a location 1-10 km downwards from the upstream estuary entry, during the dry season, to a location 40-70 km downwards from this point, during the rainy season. These observations fit with the functioning of the mangrove, the West African mangrove being among the few in the world that are markedly increasing since the beginning of the 1990s and the end of the dry period, as mangrove growth is favored by the relative salinity reduction. Finally, one of the inverse estuary behavior factors is the low fresh water incoming from the continent. The small area of the Casamance and Saloum basins (20,150 and 26,500 km(2) respectively) is to be compared with the basins of their two main neighbor basins, the Gambia River and the Senegal River, which provide significant fresh water discharge to their estuary.
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Descroix, L., Sane, Y., Thior, M., Manga, S., Ba, B., Mingou, J., et al. (2020). Inverse Estuaries in West Africa: Evidence of the Rainfall Recovery? Water, 12(3).
Abstract: In West Africa, as in many other estuaries, enormous volumes of marine water are entering the continent. Fresh water discharge is very low, and it is commonly strongly linked to rainfall level. Some of these estuaries are inverse estuaries. During the Great Sahelian Drought (1968-1993), their hyperhaline feature was exacerbated. This paper aims to describe the evolution of the two main West African inverse estuaries, those of the Saloum River and the Casamance River, since the end of the drought. Water salinity measurements were carried out over three to five years according to the sites in order to document this evolution and to compare data with the historical ones collected during the long dry period at the end of 20th century. The results show that in both estuaries, the mean water salinity values have markedly decreased since the end of the drought. However, the Saloum estuary remains a totally inverse estuary, while for the Casamance River, the estuarine turbidity maximum (ETM) is the location of the salinity maximum, and it moves according to the seasons from a location 1-10 km downwards from the upstream estuary entry, during the dry season, to a location 40-70 km downwards from this point, during the rainy season. These observations fit with the functioning of the mangrove, the West African mangrove being among the few in the world that are markedly increasing since the beginning of the 1990s and the end of the dry period, as mangrove growth is favored by the relative salinity reduction. Finally, one of the inverse estuary behavior factors is the low fresh water incoming from the continent. The small area of the Casamance and Saloum basins (20,150 and 26,500 km(2) respectively) is to be compared with the basins of their two main neighbor basins, the Gambia River and the Senegal River, which provide significant fresh water discharge to their estuary.
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Didi S.R.M., Ly, M., Kouadio, K., Bichet, A., Diedhiou, A., Coulibaly, J. S. L., et al. (2020). Using the CHIRPS Dataset to Investigate Historical Changes in Precipitation Extremes in West Africa. Climate, 8(7).
Abstract: This study aims to provide improved knowledge and evidence on current (1986-2015) climate variation based on six rainfall indices over five West African countries (Senegal, Niger, Burkina Faso, Ivory Coast, and Benin) using the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) dataset. On average, precipitation has increased over the central Sahel and the western Sahel. This increase is associated with increase in the number of rainy days, longer wet spells and shorter dry spells. Over the Guinea Coast, the slight increase in precipitation is associated with an increase in the intensity of rainfall with a shorter duration of wet spells. However, these mean changes in precipitation are not all statistically significant and uniform within a country. While previous studies are focused on regional and sub-regional scales, this study contributes to deliver a climate information at a country level that is more relevant for decision making and for policy makers, and to document climate-related risks within a country to feed impact studies in key sectors of the development, such as agriculture and water resources.
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Donat-Magnin, M., Jourdain, N., Gallee, H., Amory, C., Kittel, C., Fettweis, X., et al. (2020). Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica. Cryosphere, 14(1), 229–249.
Abstract: Understanding the interannual variability of surface mass balance (SMB) and surface melting in Antarctica is key to quantify the signal-to-noise ratio in climate trends, identify opportunities for multi-year climate predictions and assess the ability of climate models to respond to climate variability. Here we simulate summer SMB and surface melting from 1979 to 2017 using the Regional Atmosphere Model (MAR) at 10 km resolution over the drainage basins of the Amundsen Sea glaciers in West Antarctica. Our simulations reproduce the mean present-day climate in terms of near-surface temperature (mean overestimation of 0.10 degrees C), near-surface wind speed (mean underestimation of 0.42 m s(-1)), and SMB (relative bias < 20 % over Thwaites glacier). The simulated interannual variability of SMB and melting is also close to observation-based estimates. For all the Amundsen glacial drainage basins, the interannual variability of summer SMB and surface melting is driven by two distinct mechanisms: high summer SMB tends to occur when the Amundsen Sea Low (ASL) is shifted southward and westward, while high summer melt rates tend to occur when ASL is shallower (i.e. anticyclonic anomaly). Both mechanisms create a northerly flow anomaly that increases moisture convergence and cloud cover over the Amundsen Sea and therefore favors snowfall and downward longwave radiation over the ice sheet. The part of interannual summer SMB variance explained by the ASL longitudinal migrations increases westward and reaches 40 % for Getz. Interannual variation in the ASL relative central pressure is the largest driver of melt rate variability, with 11 % to 21 % of explained variance (increasing westward). While high summer SMB and melt rates are both favored by positive phases of El Nino-Southern Oscillation (ENSO), the Southern Oscillation Index (SOI) only explains 5 % to 16 % of SMB or melt rate interannual variance in our simulations, with moderate statistical significance. However, the part explained by SOI in the previous austral winter is greater, suggesting that at least a part of the ENSO-SMB and ENSO-melt relationships in summer is inherited from the previous austral winter. Possible mechanisms involve sea ice advection from the Ross Sea and intrusions of circumpolar deep water combined with melt-induced ocean overturning circulation in ice shelf cavities. Finally, we do not find any correlation with the Southern Annular Mode (SAM) in summer.
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Dumont, M., Tuzet, F., Gascoin, S., Picard, G., Kutuzov, S., Lafaysse, M., et al. (2020). Accelerated Snow Melt in the Russian Caucasus Mountains After the Saharan Dust Outbreak in March 2018. Journal Of Geophysical Research-Earth Surface, 125(9).
Abstract: Light absorbing particles, such as mineral dust, are a potent climate forcing agent. Many snow-covered areas are subject to dust outbreak events originating from desert regions able to significantly decrease snow albedo. Here, using a combination of Sentinel-2 imagery, in situ measurements and ensemble detailed snowpack simulations, we study the impact on snow cover duration of a major dust deposition event that occurred in the Caucasus in March 2018. This is, to the best of our knowledge, the first study using ensemble approach and Sentinel-2 imagery to quantify the impact of a dust event on the snow cover evolution. We demonstrate that the calculation of the impact is strongly affected by the snow model uncertainties but that the March 2018 dust event systematically shortened the snow cover duration inWestern Caucasus. The shortening is higher for location with higher accumulation and higher elevation (median values of 23 +/- 7 days) than for location at lower elevation (median values of 15 +/- 3 days). This is because for sites with higher location and higher accumulation, melt occurs later in the season when more incoming solar energy is available. This highlights the huge impact of a single 1- day event on snow cover duration, and consequently, on the hydrology of a large region.
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Dunn, R., Alexander, L., Donat, M., Zhang, X., Bador, M., Herold, N., et al. (2020). Development of an Updated Global Land In Situ-Based Data Set of Temperature and Precipitation Extremes: HadEX3. Journal Of Geophysical Research-Atmospheres, 125(16).
Abstract: We present the second update to a data set of gridded land-based temperature and precipitation extremes indices: HadEX3. This consists of 17 temperature and 12 precipitation indices derived from daily, in situ observations and recommended by the World Meteorological Organization (WMO) Expert Team on Climate Change Detection and Indices (ETCCDI). These indices have been calculated at around 7,000 locations for temperature and 17,000 for precipitation. The annual (and monthly) indices have been interpolated on a1.875 degrees x1.25 degrees longitude-latitude grid, covering 1901-2018. We show changes in these indices by examining “global”-average time series in comparison with previous observational data sets and also estimating the uncertainty resulting from the nonuniform distribution of meteorological stations. Both the short and long time scale behavior of HadEX3 agrees well with existing products. Changes in the temperature indices are widespread and consistent with global-scale warming. The extremes related to daily minimum temperatures are changing faster than the maximum. Spatial changes in the linear trends of precipitation indices over 1950-2018 are less spatially coherent than those for temperature indices. Globally, there are more heavy precipitation events that are also more intense and contribute a greater fraction to the total. Some of the indices use a reference period for calculating exceedance thresholds. We present a comparison between using 1961-1990 and 1981-2010. The differences between the time series of the temperature indices observed over longer time scales are shown to be the result of the interaction of the reference period with a warming climate. The gridded netCDF files and, where possible, underlying station indices are available from and .
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Dussaillant, I., Berthier, E., Brun, F., Masiokas, M., Hugonnet, R., Favier, V., et al. (2020). Two decades of glacier mass loss along the Andes. Nature Geoscience, 13(9), 802–+.
Abstract: Andean glaciers are among the fastest shrinking and largest contributors to sea level rise on Earth. They also represent crucial water resources in many tropical and semi-arid mountain catchments. Yet the magnitude of the recent ice loss is still debated. Here we present Andean glacier mass changes (from 10 degrees N to 56 degrees S) between 2000 and 2018 using time series of digital elevation models derived from ASTER stereo images. The total mass change over this period was -22.9 +/- 5.9 Gt yr(-1) (-0.72 +/- 0.22 m w.e. yr(-1) (m w.e., metres of water equivalent)), with the most negative mass balances in the Patagonian Andes (-0.78 +/- 0.25 m w.e. yr(-1)) and the Tropical Andes (-0.42 +/- 0.24 m w.e. yr(-1)), compared to relatively moderate losses (-0.28 +/- 0.18 m w.e. yr(-1)) in the Dry Andes. Subperiod analysis (2000-2009 versus 2009-2018) revealed a steady mass loss in the tropics and south of 45 degrees S. Conversely, a shift from a slightly positive to a strongly negative mass balance was measured between 26 and 45 degrees S. In the latter region, the drastic glacier loss in recent years coincides with the extremely dry conditions since 2010 and partially helped to mitigate the negative hydrological impacts of this severe and sustained drought. These results provide a comprehensive, high-resolution and multidecadal data set of recent Andes-wide glacier mass changes that constitutes a relevant basis for the calibration and validation of hydrological and glaciological models intended to project future glacier changes and their hydrological impacts.
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Dutheil, C., Lengaigne, M., Bador, M., Vialard, J., Lefevre, J., Jourdain, N., et al. (2020). Impact of projected sea surface temperature biases on tropical cyclones projections in the South Pacific. Scientific Reports, 10(1).
Abstract: Climate model projections generally indicate fewer but more intense tropical cyclones (TCs) in response to increasing anthropogenic emissions. However these simulations suffer from long-standing biases in their Sea Surface Temperature (SST). While most studies investigating future changes in TC activity using high-resolution atmospheric models correct for the present-day SST bias, they do not consider the reliability of the projected SST changes from global climate models. The present study illustrates that future South Pacific TC activity changes are strongly sensitive to correcting the projected SST changes using an emergent constraint method. This additional correction indeed leads to a strong reduction of the cyclogenesis (-55%) over the South Pacific basin, while no statistically significant change arises in the uncorrected simulations. Cyclogenesis indices suggest that this strong reduction in the corrected experiment is caused by stronger vertical wind shear in response to a South Pacific Convergence Zone equatorward shift. We thus find that uncertainty in the projected SST patterns could strongly hamper the reliability of South Pacific TC projections. The strong sensitivity found in the current study will need to be investigated with other models, observational constraint methods and in other TC basins in order to assess the reliability of regional TC projections.
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Esmaeilirad, S., Lai, A., Abbaszade, G., Schnelle-Kreis, J., Zimmermann, R., Uzu, G., et al. (2020). Source apportionment of fine particulate matter in a Middle Eastern Metropolis, Tehran-Iran, using PMF with organic and inorganic markers. Science Of The Total Environment, 705.
Abstract: With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical analysis of filter samples. The dominant mass components were organic matter (OM), sulfate and EC. With a 20% water-soluble organic carbon (WSOC) fraction, the predominance of primary anthropogenic sources (i.e. fossil fuel combustion) was anticipated. A positive matrix factorization (PMF) analysis using the ME-2 (Multilinear Engine-2) solver was then applied to this dataset. 5 factors were identified by Marker-PMF, named as traffic exhaust (TE), biomass burning (BB), industries (Ind.), nitrate-rich and sulfate-rich. Another 4 factors were identified by Metal-PMF, including, dust, vehicles (traffic nonexhaust, TNE), industries (Ind.) and heavy fuel combustion (HFC). Traffic exhaust was the dominant source with 44.5% contribution to total quantified PM2.5 mass. Sulfate-rich (24.2%) and nitrate-rich (18.4%) factors were the next major contributing sources. Dust (4.4%) and biomass burning (6.7%) also had small contributions while the total share of all other factors was < 2%. Investigating the correlations of different factors between the two sampling sites showed that traffic emissions and biomass burning were local, whereas dust, heavy fuel combustion and industrial sources were regional. Results of this study indicate that gas- and particle-phase pollutants emitted from fossil fuel combustion (mobile and stationary) are the principal origin of both primary and secondary fine aerosols in Tehran. (C) 2019 Published by Elsevier B.V.
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Espinoza, J., Garreaud, R., Poveda, G., Arias, P., Molina-Carpio, J., Masiokas, M., et al. (2020). Hydroclimate of the Andes Part I: Main Climatic Features. Frontiers In Earth Science, 8.
Abstract: The Andes is the longest cordillera in the world and extends from northern South America to the southern extreme of the continent (from 11 degrees N to 53 degrees S). The Andes runs through seven countries and is characterized by a wide variety of ecosystems strongly related to the contrasting climate over its eastern and western sides, as well as along its latitudinal extension. This region faces very high potential impacts of climate change, which could affect food and water security for about 90 million people. In addition, climate change represents an important threat on biodiversity, particularly in the tropical Andes, which is the most biodiverse region on Earth. From a scientific and societal view, the Andes exhibits specific challenges because of its unique landscape and the fragile equilibrium between the growing population and its environment. In this manuscript, we provide an updated review of the most relevant scientific literature regarding the hydroclimate of the Andes with an integrated view of the entire Andes range. This review paper is presented in two parts. Part I is dedicated to summarize the scientific knowledge about the main climatic features of the Andes, with emphasis on mean large-scale atmospheric circulation, the Andes-Amazon hydroclimate interconnections and the most distinctive diurnal and annual cycles of precipitation. Part II, which is also included in the research topic “Connecting Mountain Hydroclimate Through the American Cordilleras,” focuses on the hydroclimate variability of the Andes at the sub-continental scale, including the effects of El Nino-Southern Oscillation.
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Essery, R., Kim, H., Wang, L., Bartlett, P., Boone, A., Brutel-Vuilmet, C., et al. (2020). Snow cover duration trends observed at sites and predicted by multiple models. Cryosphere, 14(12), 4687–4698.
Abstract: The 30-year simulations of seasonal snow cover in 22 physically based models driven with bias-corrected meteorological reanalyses are examined at four sites with long records of snow observations. Annual snow cover durations differ widely between models, but interannual variations are strongly correlated because of the common driving data. No significant trends are observed in starting dates for seasonal snow cover, but there are significant trends towards snow cover ending earlier at two of the sites in observations and most of the models. A simplified model with just two parameters controlling solar radiation and sensible heat contributions to snowmelt spans the ranges of snow cover durations and trends. This model predicts that sites where snow persists beyond annual peaks in solar radiation and air temperature will experience rapid decreases in snow cover duration with warming as snow begins to melt earlier and at times of year with more energy available for melting.
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Farah, A., Villani, P., Rose, C., Conil, S., Langrene, L., Laj, P., et al. (2020). Characterization of Aerosol Physical and Optical Properties at the Observatoire Perenne de l'Environnement (OPE) Site. Atmosphere, 11(2).
Abstract: The Observatoire Perenne de l'Environnement (OPE) station is a rural background site located in North-Eastern France. Besides emissions from agricultural activities, the site is located far from local emissions but at an even distance from the intense emission zones of Western Germany to the north-east and the Paris area to the south-west. In the paper, we report and analyze almost six years of measurements (1 May 2012 to 31 December 2018) of the optical and physical properties of aerosol particles. Based on aerosol optical and physical measurements combined with air mass back-trajectories, we investigate the dependence of these properties on air mass type. Two distinct equivalent black carbon (EBC) sources-origins-fossil fuel (FF) and biomass burning (BB)- were identified. FF was the dominant source of EBC (>70%) but showed a very marked seasonal variation. BB fraction is found higher during the cold seasons in the order of 35% (0.1 μg m(-3)) against 17% (0.05 μg m(-3)) during the warm seasons. The highest EBC and N0.54-1.15 (particles whose diameter ranged from 0.54 to 1.15 μm) median concentrations were observed during the night time and during the cold seasons compared to the warmer seasons, indicating primary sources trapped within a thin boundary layer (BL). A different behavior is found for N10-550 (particles whose diameter ranged from 10 to 550 nm) and coarse mode particles (N1.15-4.5, i.e., particles whose diameter ranged from 1.15 to 4.5 μm) median concentrations, which were observed during the warm seasons compared to the cold seasons, indicating rather biogenic secondary sources for the smaller particles, and potentially primary biogenic sources for the coarse mode particles. The scattering and absorption coefficients and single scattering albedo (SSA) show the same seasonal variations like the ones of N0.54-1.15 concentrations, indicating that particles larger than 500 nm seemed to contribute the most to the optical properties of the aerosol.
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Farias-Barahona, D., Wilson, R., Bravo, C., Vivero, S., Caro, A., Shaw, T., et al. (2020). A near 90-year record of the evolution of El Morado Glacier and its proglacial lake, Central Chilean Andes. Journal Of Glaciology, 66(259), 846–860.
Abstract: Using an ensemble of close- and long-range remote sensing, lake bathymetry and regional meteorological data, we present a detailed assessment of the geometric changes of El Morado Glacier in the Central Andes of Chile and its adjacent proglacial lake between 1932 and 2019. Overall, the results revealed a period of marked glacier down wasting, with a mean geodetic glacier mass balance of -0.39 +/- 0.15 m w.e.a(-1)observed for the entire glacier between 1955 and 2015 with an area loss of 40% between 1955 and 2019. We estimate an ice elevation change of -1.00 +/- 0.17 m a(-1)for the glacier tongue between 1932 and 2019. The increase in the ice thinning rates and area loss during the last decade is coincident with the severe drought in this region (2010-present), which our minimal surface mass-balance model is able to reproduce. As a result of the glacier changes observed, the proglacial lake increased in area substantially between 1955 and 2019, with bathymetry data suggesting a water volume of 3.6 million m(3)in 2017. This study highlights the need for further monitoring of glacierised areas in the Central Andes. Such efforts would facilitate a better understanding of the downstream impacts of glacier downwasting.
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Figueroa, M., Armijos, E., Espinoza, J., Ronchail, J., & Fraizy, P. (2020). On the relationship between reversal of the river stage (repiquetes), rainfall and low-level wind regimes over the western Amazon basin. Journal Of Hydrology-Regional Studies, 32.
Abstract: Study region: The Amazonas River and its tributaries (Peru), where riparian farmers face hydrological events that put their lowland crops at high risk of production loss during the flood recession period. Study focus: This paper analyzes the hydro-meteorological mechanisms over the Andes-Amazon basins that produce “repiquetes”, which are sudden reversals of the river stage. They are defined and characterized for the period 1996-2018 by using river stage data from three hydrological gauging stations for the Amazonas, Maranon and Ucayali Rivers. Daily rainfall and low-level winds depict the large-scale atmospheric patterns associated with repiquetes. New hydrological insights: Among 73 significant repiquetes (reversal >= 20 cm) observed in the Amazonas River, 64 % were preceded by repiquetes only in the Maranon River, 5 % by repiquetes only in the Ucayali River, 21 % by repiquetes in both rivers and 10 % was only registered in the Amazonas River without upstream precursor. These results show that repiquetes in the Maranon River are the primary precursors of repiquetes in the Amazonas River. Most repiquetes are associated with abundant rainfall over the Peruvian and Ecuadorian Andes-Amazon transition region related to a remarkable change in the direction of the meridional wind, from north to south, and an easterly flow five to three days before the beginning of a repiquete in the Amazonas River.
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Flechard, C., Ibrom, A., Skiba, U., De Vries, W., Van Oijen, M., Cameron, D., et al. (2020). Carbon-nitrogen interactions in European forests and semi-natural vegetation – Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling. Biogeosciences, 17(6), 1583–1620.
Abstract: The impact of atmospheric reactive nitrogen (N-r) deposition on carbon (C) sequestration in soils and biomass of unfertilized, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC/dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates of N-r deposition obtained from large-scale chemical transport models. This study and a companion paper (Flechard et al., 2020) strive to reduce uncertainties of N effects on C sequestration by linking multi-annual gross and net ecosystem productivity estimates from 40 eddy covariance flux towers across Europe to local measurement-based estimates of dry and wet N-r deposition from a dedicated collocated monitoring network. To identify possible ecological drivers and processes affecting the interplay between C and N-r inputs and losses, these data were also combined with in situ flux measurements of NO, N2O and CH4 fluxes; soil NO3- leaching sampling; and results of soil incubation experiments for N and greenhouse gas (GHG) emissions, as well as surveys of available data from online databases and from the literature, together with forest ecosystem (BAS-FOR) modelling. Multi-year averages of net ecosystem productivity (NEP) in forests ranged from -70 to 826 gCm(-2) yr(-1) at total wet + dry inorganic N-r deposition rates (N-dep) of 0.3 to 4.3 gNm(-2) yr(-1) and from -4 to 361 g Cm-2 yr(-1) at N-dep rates of 0.1 to 3.1 gNm(-2) yr(-1) in short semi-natural vegetation (moorlands, wetlands and unfertilized extensively managed grasslands). The GHG budgets of the forests were strongly dominated by CO2 exchange, while CH4 and N2O exchange comprised a larger proportion of the GHG balance in short semi-natural vegetation. Uncertainties in elemental budgets were much larger for nitrogen than carbon, especially at sites with elevated N-dep where N-r leaching losses were also very large, and compounded by the lack of reliable data on organic nitrogen and N-2 losses by denitrification. Nitrogen losses in the form of NO, N2O and especially NO3- were on average 27%(range 6 %-54 %) of N-dep at sites with N-dep < 1 gNm(-2) yr(-1) versus 65% (range 35 %-85 %) for N-dep > 3 gNm(-2) yr(-1). Such large levels of N-r loss likely indicate that different stages of N saturation occurred at a number of sites. The joint analysis of the C and N budgets provided further hints that N saturation could be detected in altered patterns of forest growth. Net ecosystem productivity increased with N-r deposition up to 2-2.5 gNm(-2) yr(-1), with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP/GPP ratio). At elevated N-dep levels (> 2.5 gNm(-2) yr(-1)), where inorganic N-r losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate N-dep levels was partly the result of geographical cross-correlations between N-dep and climate, indicating that the actual mean dC/dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. N-dep.
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Flechard, C., Van Oijen, M., Cameron, D., De Vries, W., Ibrom, A., Buchmann, N., et al. (2020). Carbon-nitrogen interactions in European forests and semi-natural vegetation – Part 2: Untangling climatic, edaphic, management and nitrogen deposition effects on carbon sequestration potentials. Biogeosciences, 17(6), 1621–1654.
Abstract: The effects of atmospheric nitrogen deposition (N-dep) on carbon (C) sequestration in forests have often been assessed by relating differences in productivity to spatial variations of N-dep across a large geographic domain. These correlations generally suffer from covariation of other confounding variables related to climate and other growth-limiting factors, as well as large uncertainties in total (dry + wet) reactive nitrogen (N-r) deposition. We propose a methodology for untangling the effects of N-dep from those of meteorological variables, soil water retention capacity and stand age, using a mechanistic forest growth model in combination with eddy covariance CO2 exchange fluxes from a Europe-wide network of 22 forest flux towers. Total N-r deposition rates were estimated from local measurements as far as possible. The forest data were compared with data from natural or semi-natural, non-woody vegetation sites. The response of forest net ecosystem productivity to nitrogen deposition (dNEP/dN(dep)) was estimated after accounting for the effects on gross primary productivity (GPP) of the co-correlates by means of a meta-modelling standardization procedure, which resulted in a reduction by a factor of about 2 of the uncorrected, apparent dGPP/dN(dep) value. This model-enhanced analysis of the C and N-dep flux observations at the scale of the European network suggests a mean overall dNEP/dN(dep) response of forest lifetime C sequestration to N-dep of the order of 40-50 g C per g N, which is slightly larger but not significantly different from the range of estimates published in the most recent reviews. Importantly, patterns of gross primary and net ecosystem productivity versus N-dep were non-linear, with no further growth responses at high N-dep levels (N-dep > 2.5-3 gNm(-2) yr(-1)) but accompanied by increasingly large ecosystem N losses by leaching and gaseous emissions. The reduced increase in productivity per unit N deposited at high N-dep levels implies that the forecast increased N-r emissions and increased N-dep levels in large areas of Asia may not positively impact the continent's forest CO2 sink. The large level of unexplained variability in observed carbon sequestration efficiency (CSE) across sites further adds to the uncertainty in the dC/dN response.
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Foucras, M., Zribi, M., Albergel, C., Baghdadi, N., Calvet, J., & Pellarin, T. (2020). Estimating 500-m Resolution Soil Moisture Using Sentinel-1 and Optical Data Synergy. Water, 12(3).
Abstract: The aim of this study is to estimate surface soil moisture at a spatial resolution of 500 m and a temporal resolution of at least 6 days, by combining remote sensing data from Sentinel-1 and optical data from Sentinel-2 and MODIS (Moderate-Resolution Imaging Spectroradiometer). The proposed methodology is based on the change detection technique, applied to a series of measurements over a three-year period (2015 to 2018). The algorithm described here as “Soil Moisture Estimations from the Synergy of Sentinel-1 and optical sensors (SMES)” proposes different options, allowing information from vegetation densities and seasonal conditions to be taken into account. The output from this algorithm is a moisture index ranging between 0 and 1, with 0 corresponding to the driest soils and 1 to the wettest soils. This methodology has been tested at different test sites (South of France, Central Tunisia, Western Benin and Southwestern Niger), characterized by a wide range of different climatic conditions. The resulting surface soil moisture estimations are compared with in situ measurements and already existing satellite-derived soil moisture ASCAT (Advanced SCATterometer) products. They are found to be well correlated, for the African regions in particular (RMSE below 6 vol.%). This outcome indicates that the proposed algorithm can be used with confidence to estimate the surface soil moisture of a wide range of climatically different sites.
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Fourteau, K., Arnaud, L., Fain, X., Martinerie, P., Etheridge, D., Lipenkov, V., et al. (2020). Historical porosity data in polar firn. Earth System Science Data, 12(2), 1171–1177.
Abstract: In the 1990s, closed and open porosity volumes of firn samples were measured by J.-M. Barnola using the technique of gas pycnometry, on firn from three different polar sites. They are the basis of a parameterization of closed porosity in polar firn, first introduced in Goujon et al. (2003) and used in several firn physics models (e.g., Buizert et al., 2012). However, these data and their processing have not been published in their own right yet. In this short article, we detail how they were processed by J.-M. Barnola and how the closed porosity parameterization was obtained. We show that the original data processing only partially accounts for the presence of reopened bubbles in the samples. Since the proper correction to apply for this effect is hard to estimate, we also processed the data without including a correction for reopened bubbles. Finally, we made these pycnometry data available in order to be used by the glaciology community, notably for the study of polar ice formation and of the composition of gas records in ice cores. They are hosted on the PANGAEA database: https://doi.org/10.1594/PANGAEA.907678 (Fourteau et al., 2019a).
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Fourteau, K., Gillet-Chaulet, F., Martinerie, P., & Fain, X. (2020). A Micro-Mechanical Model for the Transformation of Dry Polar Firn Into Ice Using the Level-Set Method. Frontiers In Earth Science, 8.
Abstract: Interpretation of greenhouse gas records in polar ice cores requires a good understanding of the mechanisms controlling gas trapping in polar ice, and therefore of the processes of densification and pore closure in firn (compacted snow). Current firn densification models are based on a macroscopic description of the firn and rely on empirical laws and/or idealized geometries to obtain the equations governing the densification and pore closure. Here, we propose a physically-based methodology explicitly representing the porous structure and its evolution over time. In order to handle the complex geometry and topological changes that occur during firn densification, we rely on a Level-Set representation of the interface between the ice and the pores. Two mechanisms are considered for the displacement of the interface: (i) mass surface diffusion driven by local pore curvature and (ii) ice dislocation creep. For the latter, ice is modeled as a viscous material and the flow velocities are solutions of the Stokes equations. First applications show that the model is able to densify firn and split pores. Using the model in cold and arid conditions of the Antarctic plateau, we show that gas trapping models do not have to consider the reduced compressibility of closed pores compared to open pores in the deepest part of firns. Our results also suggest that the mechanism of curvature-driven surface diffusion does not result in pore splitting, and that ice creep has to be taken into account for pores to close. Future applications of this type of model could help quantify the evolution and closure of firn porous networks for various accumulation and temperature conditions.
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Fourteau, K., Martinerie, P., Fain, X., Ekaykin, A., Chappellaz, J., & Lipenkov, V. (2020). Estimation of gas record alteration in very low-accumulation ice cores. Climate Of The Past, 16(2), 503–522.
Abstract: We measured the methane mixing ratios of enclosed air in five ice core sections drilled on the East Antarctic Plateau. Our work aims to study two effects that alter the recorded gas concentrations in ice cores: layered gas trapping artifacts and firn smoothing. Layered gas trapping artifacts are due to the heterogeneous nature of polar firn, where some strata might close early and trap abnormally old gases that appear as spurious values during measurements. The smoothing is due to the combined effects of diffusive mixing in the firn and the progressive closure of bubbles at the bottom of the firn. Consequently, the gases trapped in a given ice layer span a distribution of ages. This means that the gas concentration in an ice layer is the average value over a certain period of time, which removes the fast variability from the record. Here, we focus on the study of East Antarctic Plateau ice cores, as these low-accumulation ice cores are particularly affected by both layering and smoothing. We use high-resolution methane data to test a simple trapping model reproducing the layered gas trapping artifacts for different accumulation conditions typical of the East Antarctic Plateau. We also use the high-resolution methane measurements to estimate the gas age distributions of the enclosed air in the five newly measured ice core sections. It appears that for accumulations below 2 cm ice equivalent yr(-1) the gas records experience nearly the same degree of smoothing. We therefore propose to use a single gas age distribution to represent the firn smoothing observed in the glacial ice cores of the East Antarctic Plateau. Finally, we used the layered gas trapping model and the estimation of glacial firn smoothing to quantify their potential impacts on a hypothetical 1.5-million-year-old ice core from the East Antarctic Plateau. Our results indicate that layering artifacts are no longer individually resolved in the case of very thinned ice near the bedrock. They nonetheless contribute to slight biases of the measured signal (less than 10 ppbv and 0.5 ppmv in the case of methane using our currently established continuous CH4 analysis and carbon dioxide, respectively). However, these biases are small compared to the dampening experienced by the record due to firn smoothing.
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Gavrikov, A., Gulev, S., Markina, M., Tilinina, N., Verezemskaya, P., Barnier, B., et al. (2020). RAS-NAAD: 40-yr High-Resolution North Atlantic Atmospheric Hindcast for Multipurpose Applications (New Dataset for the Regional Mesoscale Studies in the Atmosphere and the Ocean). Journal Of Applied Meteorology And Climatology, 59(5), 793–817.
Abstract: We present in this paper the results of the Russian Academy of Sciences North Atlantic Atmospheric Downscaling (RAS-NAAD) project, which provides a 40-yr 3D hindcast of the North Atlantic (10 degrees-80 degrees N) atmosphere at 14-km spatial resolution with 50 levels in the vertical direction (up to 50 hPa), performed with a regional setting of theWRF-ARW3.8.1model for the period 1979-2018 and forced by ERA-Interim as a lateral boundary condition. The dataset provides a variety of surface and free-atmosphere parameters at sigma model levels and meets many demands of meteorologists, climate scientists, and oceanographers working in both research and operational domains. Three-dimensional model output at 3-hourly time resolution is freely available to the users. Our evaluation demonstrates a realistic representation of most characteristics in both datasets and also identifies biases mostly in the ice-covered regions. High-resolution and nonhydrostatic model settings in NAAD resolve mesoscale dynamics first of all in the subpolar latitudes. NAAD also provides a new view of the North Atlantic extratropical cyclone activity with a much larger number of cyclones as compared with most reanalyses. It also effectively captures highly localized mechanisms of atmospheric moisture transports. Applications of NAAD to ocean circulation and wave modeling are demonstrated.
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Gehlen, M., Berthet, S., Seferian, R., Ethe, C., & Penduff, T. (2020). Quantification of Chaotic Intrinsic Variability of Sea-Air CO2 Fluxes at Interannual Timescales. Geophysical Research Letters, 47(22).
Abstract: Chaotic intrinsic variability (CIV) emerges spontaneously from nonlinear ocean dynamics even without any atmospheric variability. Eddy-permitting numerical simulations suggest that CIV is a significant contributor to the interannual to decadal variability of physical properties. Here we show from an ensemble of global ocean eddy-permitting simulations that large-scale interannual CIV propagates from physical properties to sea-air CO2 fluxes in areas of high mesoscale eddy activity (e.g., Southern Ocean and western boundary currents). In these regions and at scales larger than 500 km (similar to 5 degrees), CIV contributes significantly to the interannual variability of sea-air CO2 fluxes. Between 35 degrees S and 45 degrees S (midlatitude Southern Ocean), CIV amounts to 23.76 TgC yr(-1) or one half of the atmospherically forced variability. Locally, its contribution to the total interannual variance of sea-air CO2 fluxes exceeds 76%. Outside eddy-active regions its contribution to total interannual variability is below 16%. Plain Language Summary Sea-air CO2 fluxes undergo substantial regional and interannual fluctuations. These fluctuations are mostly forced by changes in large-scale atmospheric patterns, but ocean internal dynamics could also contribute to them. This study quantifies these two sources of variability and their contributions to fluctuations of sea-air CO2 fluxes over large oceanic regions. It relies on the analyses of three ocean numerical simulations driven by the same atmospheric forcing but starting from small differences in initial conditions, and including a simplified representation of marine ecosystems. Simulations are run at a horizontal resolution allowing to model part of the effect of ocean mesoscale activity on physical and chemical tracers. We demonstrate that nonlinear oceanic processes drive fluctuations of sea-air CO2 fluxes at interannual timescales that are inherently random. The magnitude of these fluctuations is substantial over areas of high kinetic energy and locally exceeds 76% of the total interannual variance of sea-air CO2 fluxes.
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Giese, A., Boone, A., Wagnon, P., & Hawley, R. (2020). Incorporating moisture content in surface energy balance modeling of a debris-covered glacier. Cryosphere, 14(5), 1555–1577.
Abstract: Few surface energy balance models for debriscovered glaciers account for the presence of moisture in the debris, which invariably affects the debris layer's thermal properties and, in turn, the surface energy balance and subdebris melt of a debris-covered glacier. We adapted the interactions between soil, biosphere, and atmosphere (ISBA) land surface model within the SURFace EXternalisee (SURFEX) platform to represent glacier debris rather than soil (referred to hereafter as ISBA-DEB). The new ISBA-DEB model includes the varying content, transport, and state of moisture in debris with depth and through time. It robustly simulates not only the thermal evolution of the glacier-debris-snow column but also moisture transport and phase changes within the debris – and how these, in turn, affect conductive and latent heat fluxes. We discuss the key developments in the adapted ISBA-DEB and demonstrate the capabilities of the model, including how the time- and depth-varying thermal conductivity and specific heat capacity depend on evolving temperature and moisture. Sensitivity tests emphasize the importance of accurately constraining the roughness lengths and surface slope. Emissivity, in comparison to other tested parameters, has less of an effect on melt. ISBA-DEB builds on existing work to represent the energy balance of a supraglacial debris layer through time in its novel application of a land surface model to debris-covered glaciers. Comparison of measured and simulated debris temperatures suggests that ISBA-DEB includes some – but not all – processes relevant to melt under highly permeable debris. Future work, informed by further observations, should explore the importance of advection and vapor transfer in the energy balance.
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Gillet-Chaulet, F. (2020). Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter. Cryosphere, 14(3), 811–832.
Abstract: Marine-based sectors of the Antarctic Ice Sheet are increasingly contributing to sea level rise. The basal conditions exert an important control on the ice dynamics and can be propitious to instabilities in the grounding line position. Because the force balance is non-inertial, most ice flow models are now equipped with time-independent inverse methods to constrain the basal conditions from observed surface velocities. However, transient simulations starting from this initial state usually suffer from inconsistencies and are not able to reproduce observed trends. Here, using a synthetic flow line experiment, we assess the performance of an ensemble Kalman filter for the assimilation of transient observations of surface elevation and velocities in a marine ice sheet model. The model solves the shallow shelf equation for the force balance and the continuity equation for ice thickness evolution. The position of the grounding line is determined by the floatation criterion. The filter analysis estimates both the state of the model, represented by the surface elevation, and the basal conditions, with the simultaneous inversion of the basal friction and topography. The idealised experiment reproduces a marine ice sheet that is in the early stage of an unstable retreat. Using observation frequencies and uncertainties consistent with current observing systems, we find that the filter allows the accurate recovery of both the basal friction and topography after few assimilation cycles with relatively small ensemble sizes. In addition it is found that assimilating the surface observations has a positive impact on constraining the evolution of the grounding line during the assimilation window. Using the initialised state to perform century-scale forecast simulations, we show that grounding line retreat rates are in agreement with the reference; however remaining uncertainties in the basal conditions may lead to significant delays in the initiation of the unstable retreat. These results are encouraging for the application to real glacial systems.
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Gomez-Navarro, L., Cosme, E., Le Sommer, J., Papadakis, N., & Pascual, A. (2020). Development of an Image De-Noising Method in Preparation for the Surface Water and Ocean Topography Satellite Mission. Remote Sensing, 12(4).
Abstract: In the near future, the Surface Water Ocean Topography (SWOT) mission will provide images of altimetric data at kilometric resolution. This unprecedented 2-dimensional data structure will allow the estimation of geostrophy-related quantities that are essential for studying the ocean surface dynamics and for data assimilation uses. To estimate these quantities, i.e., to compute spatial derivatives of the Sea Surface Height (SSH) measurements, the uncorrelated, small-scale noise and errors expected to affect the SWOT data must be smoothed out while minimizing the loss of relevant, physical SSH information. This paper introduces a new technique for de-noising the future SWOT SSH images. The de-noising model is formulated as a regularized least-square problem with a Tikhonov regularization based on the first-, second-, and third-order derivatives of SSH. The method is implemented and compared to other, convolution-based filtering methods with boxcar and Gaussian kernels. This is performed using a large set of pseudo-SWOT data generated in the western Mediterranean Sea from a 1/60 simulation and the SWOT simulator. Based on root mean square error and spectral diagnostics, our de-noising method shows a better performance than the convolution-based methods. We find the optimal parametrization to be when only the second-order SSH derivative is penalized. This de-noising reduces the spatial scale resolved by SWOT by a factor of 2, and at 10 km wavelengths, the noise level is reduced by factors of for summer and winter, respectively. This is encouraging for the processing of the future SWOT data.
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Grilli, R., Darchambeau, F., Chappellaz, J., Mugisha, A., Triest, J., & Umutoni, A. (2020). Continuous in situ measurement of dissolved methane in Lake Kivu using a membrane inlet laser spectrometer. Geoscientific Instrumentation Methods And Data Systems, 9(1), 141–151.
Abstract: We report the first high-resolution continuous profile of dissolved methane in the shallow water of Lake Kivu, Rwanda. The measurements were performed using an in situ dissolved gas sensor, called Sub-Ocean, based on a patented membrane-based extraction technique coupled with a highly sensitive optical spectrometer. The sensor was originally designed for ocean settings, but both the spectrometer and the extraction system were modified to extend the dynamical range up to 6 orders of magnitude with respect to the original prototype (from nmol L-1 to mmol L-1 detection) to fit the range of concentrations at Lake Kivu. The accuracy of the instrument was estimated to +/- 22 % (2 sigma) from the standard deviation of eight profiles at 80 m depth, corresponding to +/- 0.112 mbar of CH4 in water or +/- 160 nmol L-1 at 25 degrees C and 1 atm. The instrument was able to continuously profile the top 150 m of the water column within only 25 min The maximum observed mixing ratio of CH4 in the gas phase concentration was 77 %, which at 150 m depth and under thermal conditions of the lake corresponds to 3.5 mmol L-1. Deeper down, dissolved CH4 concentrations were too large for the methane absorption spectrum to be correctly retrieved. Results are in good agreement with discrete in situ measurements conducted with the commercial HydroC (R) sensor. This fast-profiling feature is highly useful for studying the transport, production and consumption of CH4 and other dissolved gases in aquatic systems. While the sensor is well adapted for investigating most environments with a concentration of CH4 up to a few millimoles per liter, in the future the spectrometer could be replaced with a less sensitive analytical technique possibly including simultaneous detection of dissolved CO2 and total dissolved gas pressure, for exploring settings with very high concentrations of CH4 such as the bottom waters of Lake Kivu.
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Guedron, S., Audry, S., Acha, D., Bouchet, S., Point, D., Condom, T., et al. (2020). Diagenetic production, accumulation and sediment-water exchanges of methylmercury in contrasted sediment facies of Lake Titicaca (Bolivia). Science Of The Total Environment, 723.
Abstract: Monomethylmercury (MMHg) concentrations in aquatic biota from Lake Titicaca are elevated although the mercury (Hg) contamination level of the lake is low. The contribution of sediments to the lake MMHg pool remained however unclear. In this work, seven cores representative of the contrasted sediments and aquatic ecotopes of Lake Titicaca were sliced and analyzed for Hg and redox-sensitive elements (Mn, Fe, N and S) speciation in pore-water (PW) and sediment to document early diagenetic processes responsible for MMHg production and accumulation in PW during organic matter (OM) oxidation. The highest MMHg concentrations (up to 12.2 ng L-1 and 90% of THg) were found in subsurface PWs of the carbonate-rich sediments which cover 75% of the small basin and 20% of the large one. In other sediment facies, the larger content of OM restricted MMHg production and accumulation in PW by sequestering Hg in the solid phase and potentially also by decreasing its bioavailability in the PW. Diagenetically reduced S and Fe played a dual role either favoring or restricting the availability of Hg for biomethylation. The calculation of theoretical diffusive fluxes suggests that Lake Titicaca bottom sediments are a net source of MMHg, accounting for more than one third of the daily MMHg accumulated in the water column of the Lago Menor. We suggest that in the context of rising anthropogenic pressure, the enhancement of eutrophication in high altitude Altiplano lakes may increase these MMHg effluxes into the water column and favor its accumulation in water and biota. (C) 2020 Elsevier B.V. All rights reserved.
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Hanna, E., Pattyn, F., Navarro, F., Favier, V., Goelzer, H., Van Den Broeke, M., et al. (2020). Mass balance of the ice sheets and glaciers – Progress since AR5 and challenges. Earth-Science Reviews, 201.
Abstract: Recent research shows increasing decadal ice mass losses from the Greenland and Antarctic Ice Sheets and more generally from glaciers worldwide in the light of continued global warming. Here, in an update of our previous ISMASS paper (Hanna et al., 2013), we review recent observational estimates of ice sheet and glacier mass balance, and their related uncertainties, first briefly considering relevant monitoring methods. Focusing on the response to climate change during 1992-2018, and especially the post-IPCC AR5 period, we discuss recent changes in the relative contributions of ice sheets and glaciers to sea-level change. We assess recent advances in understanding of the relative importance of surface mass balance and ice dynamics in overall ice-sheet mass change. We also consider recent improvements in ice-sheet modelling, highlighting data-model linkages and the use of updated observational datasets in ice-sheet models. Finally, by identifying key deficiencies in the observations and models that hamper current understanding and limit reliability of future ice-sheet projections, we make recommendations to the research community for reducing these knowledge gaps. Our synthesis aims to provide a critical and timely review of the current state of the science in advance of the next Intergovernmental Panel on Climate Change Assessment Report that is due in 2021.
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Hausmann, U., Sallee, J., Jourdain, N., Mathiot, P., Rousset, C., Madec, G., et al. (2020). The Role of Tides in Ocean-Ice Shelf Interactions in the Southwestern Weddell Sea. Journal Of Geophysical Research-Oceans, 125(6).
Abstract: To investigate the role of tides in Weddell Sea ocean-ice shelf melt interactions, and resulting consequences for ocean properties and sea ice interactions, we develop a regional ocean-sea ice model configuration, with time-varying ocean boundary and atmospheric forcing, including the deep open ocean (at 2.5-4 km horizontal resolution), the southwestern continental shelf (approximate to 2.5 km), and the adjacent cavities of eastern Weddell, Larsen, and Filchner-Ronne ice shelves (FRIS, 1.5-2.5 km). Simulated circulation, water mass, and ice shelf melt properties compare overall well with available open ocean and cavity observational knowledge. Tides are shown to enhance the kinetic energy of the time-varying flow in contact with the ice shelves, thereby increasing melt. This dynamically driven impact of tides on net melting is to almost 90% compensated by cooling through the meltwater that is produced but not quickly exported from regions of melting in the Weddell Sea cold-cavity regime. The resulting systematic tide-driven enhancement of both produced meltwater and its refreezing on ascending branches of, especially the FRIS, cavity circulation acts to increase net ice shelf melting (by 50% in respect to the state without tides, approximate to 50 Gt yr(-1)). In addition, tides also increase the melt-induced FRIS cavity circulation, and the meltwater export by the FRIS outflow. Simulations suggest attendant changes on the open-ocean southwestern continental shelf, characterized by overall freshening and small year-round sea ice thickening, as well as in the deep southwestern Weddell Sea in the form of a marked freshening of newly formed bottom waters.
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Helanow, C., Iverson, N., Zoet, L., & Gagliardini, O. (2020). Sliding Relations for Glacier Slip With Cavities Over Three-Dimensional Beds. Geophysical Research Letters, 47(3).
Abstract: Results of glacier flow models and associated estimates of future sea level rise depend sensitively on the prescribed relation between shear stress and slip velocity at the glacier bed. Using a fully three-dimensional numerical model of ice flow, we compute steady-state sliding relations for where ice slips over a rock bed with three-dimensional, periodic topography. In agreement with studies of two-dimensional beds, water-filled cavities that form down-glacier from bedforms cause basal shear stress to peak at a threshold slip velocity and decrease at higher velocities (i.e., rate-weakening drag). However, the shear stress magnitude and extent of rate-weakening drag depend systematically on lateral topographic variations not considered previously. Moreover, steep up-glacier-facing slopes of bedforms can result in shear stress that increases monotonically over a wide range of slip velocity, helping to stabilize slip. These results highlight the potential variability of sliding relations and their likely sensitivity to the morphological diversity of glacier beds. Plain Language Summary Parts of ice sheets that flow into the oceans and affect sea level can flow unusually fast by slipping over their beds. We use a computer to solve for the first time in three dimensions the equations that describe the flow of ice as it slips over a bumpy rock bed. We include the important tendency for glaciers to separate from rock and form water-filled cavities down-glacier from bumps. These calculations indicate that resistance to slip depends sensitively on the bump shape and spacing. Cavities can cause the bed to become more slippery the faster the ice slides, with this destabilizing effect being more severe for bumps that are laterally narrow and widely spaced. However, bumps with steeply sloping up-glacier sides can reverse this effect and cause resistance to slip to increase over a wide range of increasing slip velocity. This diverse behavior highlights the need for estimates of glacier slip velocity to incorporate the actual topography of glacier beds.
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Helbig, N., Moeser, D., Teich, M., Vincent, L., Lejeune, Y., Sicart, J., et al. (2020). Snow processes in mountain forests: interception modeling for coarse-scale applications. Hydrology And Earth System Sciences, 24(5), 2545–2560.
Abstract: Snow interception by the forest canopy controls the spatial heterogeneity of subcanopy snow accumulation leading to significant differences between forested and non-forested areas at a variety of scales. Snow intercepted by the forest canopy can also drastically change the surface albedo. As such, accurately modeling snow interception is of importance for various model applications such as hydrological, weather, and climate predictions. Due to difficulties in the direct measurements of snow interception, previous empirical snow interception models were developed at just the point scale. The lack of spatially extensive data sets has hindered the validation of snow interception models in different snow climates, forest types, and at various spatial scales and has reduced the accurate representation of snow interception in coarse-scale models. We present two novel empirical models for the spatial mean and one for the standard deviation of snow interception derived from an extensive snow interception data set collected in an evergreen coniferous forest in the Swiss Alps. Besides open-site snowfall, subgrid model input parameters include the standard deviation of the DSM (digital surface model) and/or the sky view factor, both of which can be easily precomputed. Validation of both models was performed with snow interception data sets acquired in geographically different locations under disparate weather conditions. Snow interception data sets from the Rocky Mountains, US, and the French Alps compared well to the modeled snow interception with a normalized root mean square error (NRMSE) for the spatial mean of <= 10 % for both models and NRMSE of the standard deviation of <= 13 %. Compared to a previous model for the spatial mean interception of snow water equivalent, the presented models show improved model performances. Our results indicate that the proposed snow interception models can be applied in coarse land surface model grid cells provided that a sufficiently fine-scale DSM is available to derive subgrid forest parameters.
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Helmig, D., Liptzin, D., Hueber, J., & Savarino, J. (2020). Impact of exhaust emissions on chemical snowpack composition at Concordia Station, Antarctica. Cryosphere, 14(1), 199–209.
Abstract: The chemistry of reactive gases inside the snowpack and in the lower atmosphere was investigated at Concordia Station (Dome C), Antarctica, from December 2012 to January 2014. Measured species included ozone, nitrogen oxides, gaseous elemental mercury (GEM), and formaldehyde, for study of photochemical reactions, surface exchange, and the seasonal cycles and atmospheric chemistry of these gases. The experiment was installed approximate to 1 km from the station main infrastructure inside the station clean air sector and within the station electrical power grid boundary. Ambient air was sampled continuously from inlets mounted above the surface on a 10m meteorological tower. In addition, snowpack air was collected at 30 cm intervals to 1.2m depth from two manifolds that had both above- and below-surface sampling inlets. Despite being in the clean air sector, over the course of the 1.2-year study, we observed on the order of 50 occasions when exhaust plumes from the camp, most notably from the power generation system, were transported to the study site. Continuous monitoring of nitrogen oxides (NOx) provided a measurement of a chemical tracer for exhaust plumes. Highly elevated levels of NOx (up to 1000 x background) and lowered ozone (down to approximate to 50 %), most likely from reaction of ozone with nitric oxide, were measured in air from above and within the snowpack. Within 5-15 min from observing elevated pollutant levels above the snow, rapidly increasing and long-lasting concentration enhancements were measured in snowpack air. While pollution events typically lasted only a few minutes to an hour above the snow surface, elevated NOx levels were observed in the snowpack lasting from a few days to approximate to 1 week. GEM and formaldehyde measurements were less sensitive and covered a shorter measurement period; neither of these species' data showed noticeable concentration changes during these events that were above the normal variability seen in the data. Nonetheless, the clarity of the NOx and ozone observations adds important new insight into the discussion of if and how snow photochemical experiments within reach of the power grid of polar research sites are possibly compromised by the snowpack being chemically influenced (contaminated) by gaseous and particulate emissions from the research camp activities. This question is critical for evaluating if snowpack trace chemical measurements from within the camp boundaries are representative for the vast polar ice sheets.
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Hinderer, J., Hector, B., Riccardi, U., Rosat, S., Boy, J., Calvo, M., et al. (2020). A study of the monsoonal hydrology contribution using a 8-yr record (2010-2018) from superconducting gravimeter OSG-060 at Djougou (Benin, West Africa). Geophysical Journal International, 221(1), 431–439.
Abstract: We analyse a nearly 8-yr record (2010-2018) of the superconducting gravimeter OSG-060 located at Djougou (Benin, West Africa). After tidal analysis removing all solid Earth and ocean loading tidal contributions and correcting for the long-term instrumental drift and atmospheric loading, we obtain a gravity residual signal which is essentially a hydrological signal due to the monsoon. This signal is first compared to several global hydrology models (ERA, GLDAS and MERRA). Our superconducting gravimeter residual signal is also superimposed onto episodic absolute gravity measurements and to space gravimetry GRACE data. A further comparison is done using local hydrological data like soil moisture in the very superficial layer (0-1.2 m), water table depth and rainfall. The temporal evolution of the correlation coefficient between the gravity observation and both the soil moisture and the water table is well explained by the direct infiltration process of rain water together with the lateral transfer discharging the water table. Finally, we compute the water storage changes (WSC) using a simulation based on the physically based Parflow-CLM numerical model of the catchment, which solves the water and energy budget from the impermeable bedrock to the top of the canopy layer using the 3-D Richards equation for the water transfers in the ground, the kinematic wave equation for the surface runoff and a land surface model (CLM) for the energy budget and evapotranspiration calculation. This model forced by rain is in agreement with evapotranspiration and stream flow data and leads to simulated water storage changes that nicely fit to the observed gravity signal. This study points out the important role played by surface gravity changes in terms of a reliable proxy for water storage changes occurring in small catchments.
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Hinderer, J., Riccardi, U., Rosat, S., Boy, J., Hector, B., Calvo, M., et al. (2020). A study of the solid earth tides, ocean and atmospheric loadings using an 8-year record (2010-2018) from superconducting gravimeter OSG-060 at Djougou (Benin, West Africa). Journal Of Geodynamics, 134.
Abstract: We investigate a nearly 8-year record (2010-2018) of the superconducting gravimeter OSG-060 located at Djougou (Benin, West Africa). We first perform a tidal analysis with ET34-ANA v7.1 software that leads to the gravimetric amplitude and phase factors for all separable waves according to the available time duration. We test nine different ocean tide models for the main eleven tidal constituents (Ssa, Mm, Mf, Q1, O1, P1, K1, N2, M2, S2, K2). After correction for ocean tidal loading we obtain the real and imaginary parts of the residual vector. We also investigate atmospheric loading which is dominated in this equatorial location by the thermal waves S1 and S2 that are modulated in amplitude by annual and semi-annual components. After correction for ocean loading, we test different air pressure corrections on the tidal gravimetric factors for the waves Sa, Ssa, S1 and S2. We show the rather large discrepancy that exists between the classical single admittance pressure reduction and a hybrid model using global atmospheric models everywhere except in the local zone where the model pressure is replaced by the observed pressure.
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Hirschi, J., Barnier, B., Boning, C., Biastoch, A., Blaker, A., Coward, A., et al. (2020). The Atlantic Meridional Overturning Circulation in High-Resolution Models. Journal Of Geophysical Research-Oceans, 125(4).
Abstract: The Atlantic meridional overturning circulation (AMOC) represents the zonally integrated stream function of meridional volume transport in the Atlantic Basin. The AMOC plays an important role in transporting heat meridionally in the climate system. Observations suggest a heat transport by the AMOC of 1.3 PW at 26 degrees N-a latitude which is close to where the Atlantic northward heat transport is thought to reach its maximum. This shapes the climate of the North Atlantic region as we know it today. In recent years there has been significant progress both in our ability to observe the AMOC in nature and to simulate it in numerical models. Most previous modeling investigations of the AMOC and its impact on climate have relied on models with horizontal resolution that does not resolve ocean mesoscale eddies and the dynamics of the Gulf Stream/North Atlantic Current system. As a result of recent increases in computing power, models are now being run that are able to represent mesoscale ocean dynamics and the circulation features that rely on them. The aim of this review is to describe new insights into the AMOC provided by high-resolution models. Furthermore, we will describe how high-resolution model simulations can help resolve outstanding challenges in our understanding of the AMOC.
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Hmiel, B., Petrenko, V., Dyonisius, M., Buizert, C., Smith, A., Place, P., et al. (2020). Preindustrial (CH4)-C-14 indicates greater anthropogenic fossil CH4 emissions. Nature, 578(7795), 409–+.
Abstract: Atmospheric methane (CH4) is a potent greenhouse gas, and its mole fraction has more than doubled since the preindustrial era(1). Fossil fuel extraction and use are among the largest anthropogenic sources of CH4 emissions, but the precise magnitude of these contributions is a subject of debate(2,3). Carbon-14 in CH4 ((CH4)-C-14) can be used to distinguish between fossil (C-14-free) CH4 emissions and contemporaneous biogenic sources; however, poorly constrained direct (CH4)-C-14 emissions from nuclear reactors have complicated this approach since the middle of the 20th century(4,5). Moreover, the partitioning of total fossil CH4 emissions (presently 172 to 195 teragrams CH4 per year)(2,3) between anthropogenic and natural geological sources (such as seeps and mud volcanoes) is under debate; emission inventories suggest that the latter account for about 40 to 60 teragrams CH4 per year(6,7). Geological emissions were less than 15.4 teragrams CH4 per year at the end of the Pleistocene, about 11,600 years ago(8), but that period is an imperfect analogue for present-day emissions owing to the large terrestrial ice sheet cover, lower sea level and extensive permafrost. Here we use preindustrial-era ice core (CH4)-C-14 measurements to show that natural geological CH4 emissions to the atmosphere were about 1.6 teragrams CH4 per year, with a maximum of 5.4 teragrams CH4 per year (95 per cent confidence limit)-an order of magnitude lower than the currently used estimates. This result indicates that anthropogenic fossil CH4 emissions are underestimated by about 38 to 58 teragrams CH4 per year, or about 25 to 40 per cent of recent estimates. Our record highlights the human impact on the atmosphere and climate, provides a firm target for inventories of the global CH4 budget, and will help to inform strategies for targeted emission reductions(9,10). Isotopic evidence from ice cores indicates that preindustrial-era geological methane emissions were lower than previously thought, suggesting that present-day emissions of methane from fossil fuels are underestimated.
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Hollender, F., Roumelioti, Z., Maufroy, E., Traversa, P., & Mariscal, A. (2020). Can We Trust High-Frequency Content in Strong-Motion Database Signals? Impact of Housing, Coupling, and Installation Depth of Seismic Sensors. Seismological Research Letters, 91(4), 2192–2205.
Abstract: Seismic hazard studies provide indicators of seismic motion that are expressed for “free-field,” that is, representative of the ground motion exactly at the free surface, without disturbances due to interactions between soil and buildings or other structures. Most of these studies are based on ground-motion prediction equations, which are, themselves, formulated to predict free-field motion, as they are derived from similarly free data. However, is this really the case? In this study, we use several examples to illustrate how small structures hosting permanent strong-motion stations (often anchored on small concrete slabs) generate soilstructure interaction effects that can amplify the high-frequency part of the earthquake signal (10 Hz) by up to a factor of 2-3 for stations on soils. We also show that the installation depth of a station, even if very shallow (i.e., a few meters), can change the recorded response, mainly by deamplifying the signal in high frequencies (> 10 Hz) by a factor up to 0.3. Such effects imply that there are actual differences between recorded and true free-field signals. Depending on the housing conditions, these effects can have significant impact on response spectra at high frequencies, and on measurements of the kappa parameter. It is, thus, becoming clear that such effects should be taken into account in studies involving high-frequency seismic motion. To do so, scientists need a detailed description of the conditions of installation and housing of seismological and accelerometric stations, which often lacks from the metadata distributed through the various, commonly used web services. Increasing such information and facilitating the access to it would allow the identification of stations that are problematic and of those that are truly close to free-field recording conditions. In a subsequent step, it would be important to quantify the modification curve of the response of stations that experience such effects.
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Jakobsson, M., Mayer, L., Bringensparr, C., Castro, C., Mohammad, R., Johnson, P., et al. (2020). The International Bathymetric Chart of the Arctic Ocean Version 4.0. Scientific Data, 7(1).
Abstract: Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 x 200m versus 500 x 500m) and with individual depth soundings constraining three times more area of the Arctic Ocean (similar to 19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises similar to 14.3% in Ver. 4.0 compared to similar to 5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet. Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12369314
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Jamet, Q., Ajayi, A., Le Sommer, J., Penduff, T., Hogg, A., & Dewar, W. (2020). On Energy Cascades in General Flows: A Lagrangian Application. Journal Of Advances In Modeling Earth Systems, 12(12).
Abstract: An important characteristic of geophysically turbulent flows is the transfer of energy between scales. Balanced flows pass energy from smaller to larger scales as part of the well-known upscale cascade, while submesoscale and smaller scale flows can transfer energy eventually to smaller, dissipative scales. Much effort has been put into quantifying these transfers, but a complicating factor in realistic settings is that the underlying flows are often strongly spatially heterogeneous and anisotropic. Furthermore, the flows may be embedded in irregularly shaped domains that can be multiply connected. As a result, straightforward approaches like computing Fourier spatial spectra of nonlinear terms suffer from a number of conceptual issues. In this paper, we develop a method to compute cross-scale energy transfers in general settings, allowing for arbitrary flow structure, anisotropy, and inhomogeneity. We employ Green's function approach to the kinetic energy equation to relate kinetic energy at a point to its Lagrangian history. A spatial filtering of the resulting equation naturally decomposes kinetic energy into length-scale-dependent contributions and describes how the transfer of energy between those scalestakes place. The method is applied to a doubly periodic simulation of vortex merger, resulting in the demonstration of the expected upscale energy cascade. Somewhat novel results are that the energy transfers are dominated by pressure work, rather than kinetic energy exchange, and dissipation is a noticeable influence on the larger scale energy budgets. We also describe, but do not employ here, a technique for developing filters to use in complex domains.
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Jamet, Q., Dewar, W., Wienders, N., Deremble, B., Close, S., & Penduff, T. (2020). Locally and Remotely Forced Subtropical AMOC Variability: A Matter of Time Scales. Journal Of Climate, 33(12), 5155–5172.
Abstract: Mechanisms driving the North Atlantic meridional overturning circulation (AMOC) variability at low frequency are of central interest for accurate climate predictions. Although the subpolar gyre region has been identified as a preferred place for generating climate time-scale signals, their southward propagation remains under consideration, complicating the interpretation of the observed time series provided by the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array-Western Boundary Time Series (RAPID-MOCHA-WBTS) program. In this study, we aim at disentangling the respective contribution of the local atmospheric forcing from signals of remote origin for the subtropical low-frequency AMOC variability. We analyze for this a set of four ensembles of a regional (20 degrees S-55 degrees N), eddy-resolving (1/12 degrees) North Atlantic oceanic configuration, where surface forcing and open boundary conditions are alternatively permuted from fully varying (realistic) to yearly repeating signals. Their analysis reveals the predominance of local, atmospherically forced signal at interannual time scales (2-10 years), whereas signals imposed by the boundaries are responsible for the decadal (10-30 years) part of the spectrum. Due to this marked time-scale separation, we show that, although the intergyre region exhibits peculiarities, most of the subtropical AMOC variability can be understood as a linear superposition of these two signals. Finally, we find that the decadal-scale, boundary-forced AMOC variability has both northern and southern origins, although the former dominates over the latter, including at the site of the RAPID array (26.5 degrees N).
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Jordan, T., Porter, D., Tinto, K., Millan, R., Muto, A., Hogan, K., et al. (2020). New gravity-derived bathymetry for the Thwaites, Crosson, and Dotson ice shelves revealing two ice shelf populations. Cryosphere, 14(9), 2869–2882.
Abstract: Ice shelves play a critical role in the long-term stability of ice sheets through their buttressing effect. The underlying bathymetry and cavity thickness are key inputs for modelling future ice sheet evolution. However, direct observation of sub-ice-shelf bathymetry is time-consuming, logistically risky, and in some areas simply not possible. Here we use new compilations of airborne and marine gravity, radar depth sounding, and swath bathymetry to provide new estimates of sub-ice-shelf bathymetry outboard of the rapidly changing West Antarctic Thwaites Glacier and beneath the adjacent Dotson and Crosson ice shelves. This region is of special interest, as the low-lying inland reverse slope of the Thwaites Glacier system makes it vulnerable to marine ice sheet instability, with rapid grounding line retreat observed since 1993 suggesting this process may be underway. Our results confirm a major marine channel > 800m deep extends tens of kilometres to the front of Thwaites Glacier, while the adjacent ice shelves are underlain by more complex bathymetry. Comparison of our new bathymetry with ice shelf draft reveals that ice shelves formed since 1993 comprise a distinct population where the draft conforms closely to the underlying bathymetry, unlike the older ice shelves, which show a more uniform depth of the ice base. This indicates that despite rapid basal melting in some areas, these recently floated parts of the ice shelf are not yet in dynamic equilibrium with their retreated grounding line positions and the underlying ocean system, a factor which must be included in future models of this region's evolution.
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Jourdain, N., Asay-Davis, X., Hattermann, T., Straneo, F., Seroussi, H., Little, C., et al. (2020). A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections. Cryosphere, 14(9), 3111–3134.
Abstract: Climate model projections have previously been used to compute ice shelf basal melt rates in ice sheet models, but the strategies employed – e.g., ocean input, parameterization, calibration technique, and corrections – have varied widely and are often ad hoc. Here, a methodology is proposed for the calculation of circum-Antarctic basal melt rates for floating ice, based on climate models, that is suitable for ISMIP6, the Ice Sheet Model Intercomparison Project for CMIP6 (6th Coupled Model Intercomparison Project). The past and future evolution of ocean temperature and salinity is derived from a climate model by estimating anomalies with respect to the modern day, which are added to a present-day climatology constructed from existing observational datasets. Temperature and salinity are extrapolated to any position potentially occupied by a simulated ice shelf. A simple formulation is proposed for a basal melt parameterization in ISMIP6, constrained by the observed temperature climatology, with a quadratic dependency on either the nonlocal or local thermal forcing. Two calibration methods are proposed: (1) based on the mean Antarctic melt rate (MeanAnt) and (2) based on melt rates near Pine Island's deep grounding line (PIGL). Future Antarctic mean melt rates are an order of magnitude greater in PIGL than in MeanAnt. The PIGL calibration and the local parameterization result in more realistic melt rates near grounding lines. PIGL is also more consistent with observations of interannual melt rate variability underneath Pine Island and Dotson ice shelves. This work stresses the need for more physics and less calibration in the parameterizations and for more observations of hydrographic properties and melt rates at interannual and decadal timescales.
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Kane, E., Rignot, E., Mouginot, J., Millan, R., Li, X., Scheuchl, B., et al. (2020). Impact of Calving Dynamics on Kangilernata Sermia, Greenland. Geophysical Research Letters, 47(20).
Abstract: Iceberg calving is a major component of glacier mass ablation that is not well understood due to a lack of detailed temporal and spatial observations. Here, we measure glacier speed and surface elevation at 3 min intervals using a portable radar interferometer at Kangilernata Sermia, West Greenland, for a period of 2 weeks in July 2016. We detect a 20% diurnal variation in glacier speed in phase with tidal height propagating kilometers inland. We find no speedup from ice shedding off the calving face or the detachment of floating ice blocks but a 30% speedup within a few hundred meters of the ice front that persists for days when calving removes full-thickness grounded ice blocks. Within one ice thickness from the calving front, we detect maximum strain rates 2 to 3 times larger than observable from satellite data, which has implications for studying iceberg calving as a fracturing process.
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Kebe, I., Diallo, I., Sylla, M., De Sales, F., & Diedhiou, A. (2020). Late 21st Century Projected Changes in the Relationship between Precipitation, African Easterly Jet, and African Easterly Waves. Atmosphere, 11(4).
Abstract: The present study utilizes three high-resolution simulations from the Regional Climate Model version 4 (RegCM4) to examine the late 21st century changes (2080-2099) in the West African Monsoon (WAM) features. A set of three Earth System Models are utilized to provide initial and lateral boundary conditions to the RegCM4 experiments. Our analysis focuses on seasonal mean changes in WAM large-scale dynamical features, along with their connections with the summer monsoon precipitation. In the historical period, the simulation ensemble means mimic reasonably well the intensity and spatial distribution of the WAM rainfall as well as the WAM circulation patterns at different scales. The future projection of the WAM climate exhibits warming over the whole West Africa leading to precipitation reduction over the Sahel region, and a slight increase over some areas of the Guinea Coast. The position of the African Easterly Jet (AEJ) is shifted southward and the African Easterly Waves (AEWs) activities are reduced, which affect in turn the WAM rainbelt characteristics in terms of position and strength. Overall the changes in simulated AEJ and AEWs contribute substantially to reduce the seasonal summer mean precipitation in West Africa by the late 21st century, with prevailing negative changes in the Savanna-Sahel region. To further explore the robustness of the relationships revealed in this paper, future studies using different high-resolution regional climate models with large ensemble are recommended.
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Khan, S., Bjork, A., Bamber, J., Morlighem, M., Bevis, M., Kjor, K., et al. (2020). Centennial response of Greenland's three largest outlet glaciers. Nature Communications, 11(1).
Abstract: The Greenland Ice Sheet is the largest land ice contributor to sea level rise. This will continue in the future but at an uncertain rate and observational estimates are limited to the last few decades. Understanding the long-term glacier response to external forcing is key to improving projections. Here we use historical photographs to calculate ice loss from 1880-2012 for Jakobshavn, Helheim, and Kangerlussuaq glacier. We estimate ice loss corresponding to a sea level rise of 8.11.1 millimetres from these three glaciers. Projections of mass loss for these glaciers, using the worst-case scenario, Representative Concentration Pathways 8.5, suggest a sea level contribution of 9.1-14.9mm by 2100. RCP8.5 implies an additional global temperature increase of 3.7 degrees C by 2100, approximately four times larger than that which has taken place since 1880. We infer that projections forced by RCP8.5 underestimate glacier mass loss which could exceed this worst-case scenario. The Greenland Ice Sheet is the largest land ice contributor to sea level rise and understanding the long-term glacier response to external forcing is key to improved projections. Here the authors show Greenland's three largest outlet glaciers will likely exceed current worst-case scenario
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Khedhaouiria, D., Mailhot, A., & Favre, A. (2020). Regional modeling of daily precipitation fields across the Great Lakes region (Canada) using the CFSR reanalysis. Stochastic Environmental Research And Risk Assessment, 34(9), 1385–1405.
Abstract: High densities of local-scale daily precipitation series across relatively large domains are of special interest for a wide range of applications (e.g., hydrological modeling, agriculture). The focus of the present study is to post-process gridded precipitation from a single reanalysis to correct bias and scale mismatch with observations, and to extend the same post-processing at sites without historical data. A Stochastic Model Output Statistical approach combined with meta-Gaussian spatiotemporal random fields, calibrated at sites, is employed to post-process the Climate Forecast System Reanalysis (CFSR) precipitation. The post-processed data, characterized by local parameters, is then mapped across the Great Lakes region (Canada) using two different approaches: (1) kriging, and (2) Vector Generalized Additive Model (VGAM) with spatial covariates. The kriging enables the interpolation of these parameters, while the spatial VGAM helps to spatially post-process CFSR precipitation using a single model. Thek-fold cross-validation procedure is employed to assess the ability of the two approaches to predict selected characteristics and climate indices. The kriging and spatial VGAM approaches modeled effectively the distribution of the precipitation process to similar extents (e.g., mean daily precipitation, variability and the number of wet days). The kriging approach produces slightly better estimates of climate indices than the spatial VGAM models. Both approaches demonstrate significant improvement of the metric estimation compared to those of CFSR without post-processing.
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Kinnard, C., Ginot, P., Surazakov, A., Macdonell, S., Nicholson, L., Patris, N., et al. (2020). Mass Balance and Climate History of a High-Altitude Glacier, Desert Andes of Chile. Frontiers In Earth Science, 8.
Abstract: Glaciers in the dry Chilean Andes provide important ecological services, yet their mass balance response to past and ongoing climate change has been little studied. This study examines the recent (2002-2015), historical (1955-2005), and past (<1900) mass balance history of the high-altitude Guanaco Glacier (29.34 degrees S, >5000 m), using a combination of glaciological, geodetic, and ice core observations. Mass balance has been predominantly negative since 2002. Analysis of mass balance and meteorological data since 2002 suggests that mass balance is currently mostly sensitive to precipitation variations, while low temperatures, aridity and high solar radiation and wind speeds cause large sublimation losses and limited melting. Mass balance reconstructed by geodetic methods shows that Guanaco Glacier has been losing mass since at least 1955, and that mass loss has increased over time until present. An ice core recovered from the deepest part of the glacier in 2008 revealed that the glacier is cold-based with a -5.5 degrees C basal temperature and a warm reversal of the temperature profile above 60-m depth attributed to the recent atmospheric warming trend. Detailed stratigraphic and stable isotope analyses of the upper 20 m of the core revealed seasonal cycles in the delta O-18 and delta H-2 records with periods varying between 0.5 and 3 m. w.e. a(-1). Deuterium excess values larger than 10 parts per thousand suggest limited post-depositional sublimation, while the presence of numerous refrozen ice layers indicate significant summer melt. Tritium concentration in the upper 20 m of the core was very low, while Pb-210 was undetected, indicating that the glacier surface in 2008 was at least 100 years old. Taken together, these results suggest that Guanaco Glacier formed under drastically different climate conditions than today, with humid conditions causing high accumulation rates, reduced sublimation and increased melting. Reconstruction of mass balance based on correlations with precipitation and streamflow records show periods of sustained mass gain in the early 20th century and the 1980s, separated by periods of mass loss. The southern migration of the South Pacific Subtropical High over the course of the 20th and 21st centuries is proposed as the main mechanism explaining the progressive precipitation starvation of glaciers in this area.
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Kouadio, K., Amoussou, E., Coulibaly, T., Diedhiou, A., Coulibaly, H., Didi, R., et al. (2020). Analysis of hydrological dynamics and hydropower generation in a West African anthropized watershed in a context of climate change. Modeling Earth Systems And Environment, .
Abstract: This study was conducted in the Bandama watershed (BW) in Cote d'Ivoire (West Africa). The objective is to analyze hydrological dynamics and hydropower generation in BW in a context of climate change. The methodology is based on the Inverse Distance Weighted (IDW) used to interpolate rainfall and on statistical tests (Normality, Buishand, Pettitt and Hubert) applied on hydrometeorological and hydrometric data to analyze the hydrological functioning of BW. Hydropower generation at Kossou dam was analyzed with Pearson Chi square independence method according to Representative Concentration Pathways (RCP) 4.5 and 8.5 scenarios of CMIP5 (coupled model intercomparison project phase 5) and CORDEX-AFRICA (coordinated regional climate downscaling experiment). The results showed the variability of rainfall as well monthly, seasonal as annual from 1980 to 2013; the hydroclimatic variability in the basin characterized by the presence of breaks in stationarity in 1998 and 2008, and the variability of flow. The Buishand and Pettitt tests described these two ruptures. The segmentation of Hubert specified three sub-periods. The results also showed that there is an alternation of wet and dry periods followed by a slight resumption. The climate projection scenarios RCP 4.5 and 8.5 have shown that the change in the variability of rainfall and flow in the BW will have a negative impact on hydropower generation at Kossou from 2030 to 2050.
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Krinner, G., Kharin, V., Roehrig, R., Scinocca, J., & Codron, F. (2020). Historically-based run-time bias corrections substantially improve model projections of 100 years of future climate change. Communications Earth & Environment, 1(1), 29.
Abstract: Climate models and/or their output are usually bias-corrected for climate impact studies. The underlying assumption of these corrections is that climate biases are essentially stationary between historical and future climate states. Under very strong climate change, the validity of this assumption is uncertain, so the practical benefit of bias corrections remains an open question. Here, this issue is addressed in the context of bias correcting the climate models themselves. Employing the ARPEGE, LMDZ and CanAM4 atmospheric models, we undertook experiments in which one centre's atmospheric model takes another centre's coupled model as observations during the historical period, to define the bias correction, and as the reference under future projections of strong climate change, to evaluate its impact. This allows testing of the stationarity assumption directly from the historical through future periods for three different models. These experiments provide evidence for the validity of the new bias-corrected model approach. In particular, temperature, wind and pressure biases are reduced by 40-60% and, with few exceptions, more than 50% of the improvement obtained over the historical period is on average preserved after 100 years of strong climate change. Below 3 degrees C global average surface temperature increase, these corrections globally retain 80% of their benefit. Empirical bias corrections in climate models based on historical data improve future projections of climate change, even in strong change over 100 years, suggest experiments with three climate models.
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Laj, P., Bigi, A., Rose, C., Andrews, E., Myhre, C., Coen, M., et al. (2020). A global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories. Atmospheric Measurement Techniques, 13(8), 4353–4392.
Abstract: Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.
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Lamare, M., Dumont, M., Picard, G., Larue, F., Tuzet, F., Delcourt, C., et al. (2020). Simulating optical top-of-atmosphere radiance satellite images over snow-covered rugged terrain. Cryosphere, 14(11), 3995–4020.
Abstract: The monitoring of snow-covered surfaces on Earth is largely facilitated by the wealth of satellite data available, with increasing spatial resolution and temporal coverage over the last few years. Yet to date, retrievals of snow physical properties still remain complicated in mountainous areas, owing to the complex interactions of solar radiation with terrain features such as multiple scattering between slopes, exacerbated over bright surfaces. Existing physically based models of solar radiation across rough scenes are either too complex and resource-demanding for the implementation of systematic satellite image processing, not designed for highly reflective surfaces such as snow, or tied to a specific satellite sensor. This study proposes a new formulation, combining a forward model of solar radiation over rugged terrain with dedicated snow optics into a flexible multi-sensor tool that bridges a gap in the optical remote sensing of snow-covered surfaces in mountainous regions. The model presented here allows one to perform rapid calculations over large snow-covered areas. Good results are obtained even for extreme cases, such as steep shadowed slopes or, on the contrary, strongly illuminated sun-facing slopes. Simulations of Sentinel-3 OLCI (Ocean and Land Colour Instrument) scenes performed over a mountainous region in the French Alps allow us to reduce the bias by up to a factor of 6 in the visible wavelengths compared to methods that account for slope inclination only. Furthermore, the study underlines the contribution of the individual fluxes to the total top-of-atmosphere radiance, highlighting the importance of reflected radiation from surrounding slopes which, in midwinter after a recent snowfall (13 February 2018), accounts on average for 7% of the signal at 400 nm and 16% at 1020 nm (on 13 February 2018), as well as of coupled diffuse radiation scattered by the neighbourhood, which contributes to 18% at 400 nm and 4% at 1020 nm. Given the importance of these contributions, accounting for slopes and reflected radiation between terrain features is a requirement for improving the accuracy of satellite retrievals of snow properties over snow-covered rugged terrain. The forward formulation presented here is the first step towards this goal, paving the way for future retrievals.
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Largeron, C., Dumont, M., Morin, S., Boone, A., Lafaysse, M., Metref, S., et al. (2020). Toward Snow Cover Estimation in Mountainous Areas Using Modern Data Assimilation Methods: A Review. Frontiers In Earth Science, 8.
Abstract: The snow cover is a key component of land surface hydrology, especially in mountain areas where it governs the amount and timing of water availability in downstream areas. It is involved in relevant climate feedbacks and natural hazards such as avalanches and floods. Monitoring and forecasting snow cover characteristics is challenging. While snow cover extent is relatively easy to retrieve from satellite data, remote sensing retrievals of the snow water equivalent (SWE) is often inaccurate, particularly in complex mountainous terrain. Model-based snow cover estimates, driven by meteorological data, often bear significant uncertainties due to both input data and model errors. Data assimilation can combine both approaches to improve SWE estimates. In this paper, we review current state-of-the-art data assimilation methodologies used to optimally combine measurements with snow cover models in order to reduce uncertainties. The suitability of a given data assimilation method varies with the numerical complexity of snow models as well as the availability and the type of observations. This review describes the issues and challenges associated with data assimilation applied to the mountain snow cover, providing recommendations for existing and upcoming monitoring and prediction systems of snow hydrology in mountainous regions.
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Larue, F., Picard, G., Arnaud, L., Ollivier, I., Delcourt, C., Lamare, M., et al. (2020). Snow albedo sensitivity to macroscopic surface roughness using a new ray-tracing model. Cryosphere, 14(5), 1651–1672.
Abstract: Most models simulating snow albedo assume a flat and smooth surface, neglecting surface roughness. However, the presence of macroscopic roughness leads to a systematic decrease in albedo due to two effects: (1) photons are trapped in concavities (multiple reflection effect) and (2) when the sun is low, the roughness sides facing the sun experience an overall decrease in the local incidence angle relative to a smooth surface, promoting higher absorption, whilst the other sides have weak contributions because of the increased incidence angle or because they are shadowed (called the effective-angle effect here). This paper aims to quantify the impact of surface roughness on albedo and to assess the respective role of these two effects, with (1) observations over varying amounts of surface roughness and (2) simulations using the new rough surface ray-tracing (RSRT) model, based on a Monte Carlo method for photon transport calculation. The observations include spectral albedo (400-1050 nm) over manually created roughness surfaces with multiple geometrical characteristics. Measurements highlight that even a low fraction of surface roughness features (7% of the surface) causes an albedo decrease of 0.02 at 1000 nm when the solar zenith angle (theta(s)) is larger than 50 degrees. For higher fractions (13 %, 27% and 63 %), and when the roughness orientation is perpendicular to the sun, the decrease is of 0.03-0.04 at 700 nm and of 0.06-0.10 at 1000 nm. The impact is 20% lower when roughness orientation is parallel to the sun. The observations are subsequently compared to RSRT simulations. Accounting for surface roughness improves the model observation agreement by a factor of 2 at 700 and 1000 nm (errors of 0.03 and 0.04, respectively) compared to simulations considering a flat smooth surface. The model is used to explore the albedo sensitivity to surface roughness with varying snow properties and illumination conditions. Both multiple reflections and the effective-angle effect have a greater impact with low specific surface area (SSA; < 10m(2) kg(-1)). The effective-angle effect also increases rapidly with theta(s) at large theta(s). This latter effect is larger when the overall slope of the surface is facing away from the sun and has a roughness orientation perpendicular to the sun. For a snowpack where artificial surface roughness features were created, we showed that a broadband albedo decrease of 0.05 may cause an increase in the net shortwave radiation of 80% (from 15 to 27Wm(-2)). This paper highlights the necessity of considering surface roughness in the estimation of the surface energy budget and opens the way for considering natural rough surfaces in snow modelling.
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Lavaysse, C., Stockdale, T., Mccormick, N., & Vogt, J. (2020). Evaluation of a New Precipitation-Based Index for Global Seasonal Forecasting of Unusually Wet and Dry Periods. Weather And Forecasting, 35(4), 1189–1202.
Abstract: This paper describes the assessment of the performance of a method for providing early warnings of unusually wet and dry precipitation conditions globally. The indicator that is used for forecasting these conditions is computed from forecasted standardized precipitation index (SPI) values for accumulation periods of 1, 3, and 6 months. The SPI forecasts are derived from forecasted precipitation produced by the latest probabilistic seasonal forecast of ECMWF. Early warnings of unusual precipitation periods are shown only when and where the forecast is considered robust (i.e., with at least 40% of ensemble members associated with intense forecasts), and corresponding with significant SPI values (i.e., below 21 for dry, or above 11 for wet conditions). The intensity of the forecasted events is derived based on the extreme forecast index and associated shift of tails products developed by ECMWF. Different warning levels are then assessed, depending on the return period of the forecast intensity, and the coherence of the ensemble forecast members. The assessment of the indicators performance is based on the 25-member ensemble forecast system that is carried out everymonth during the 36 years of the hindcast period (1981-2016). The results showthat significant information is provided even for the longest lead time, albeit with a large variability across the globe with the highest scores over central Russia, SoutheastAsia, and the northern part of SouthAmerica orAustralia. Because of the loss of predictability, each SPI is based on the first lead time. Asensitivity test highlights the influence on the robustness of the forecasts of the warning levels used, as well as the effects of prior conditions and of seasonality.
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Le Roux, E., Evin, G., Eckert, N., Blanchet, J., & Morin, S. (2020). Non-stationary extreme value analysis of ground snow loads in the French Alps: a comparison with building standards. Natural Hazards And Earth System Sciences, 20(11), 2961–2977.
Abstract: In a context of climate change, trends in extreme snow loads need to be determined to minimize the risk of structure collapse. We study trends in 50-year return levels of ground snow load (GSL) using non-stationary extreme value models. These trends are assessed at a mountain massif scale from GSL data, provided for the French Alps from 1959 to 2019 by a meteorological reanalysis and a snowpack model. Our results indicate a temporal decrease in 50-year return levels from 900 to 4200 m, significant in the northwest of the French Alps up to 2100 m. We detect the most important decrease at 900m with an average of -30% for return levels between 1960 and 2010. Despite these decreases, in 2019 return levels still exceed return levels designed for French building standards under a stationary assumption. At worst (i.e. at 1800 m), return levels exceed standards by 15% on average, and half of the massifs exceed standards. We believe that these exceedances are due to questionable assumptions concerning the computation of standards. For example, these were devised with GSL, estimated from snow depth maxima and constant snow density set to 150 kg m(-3), which underestimate typical GSL values for the snowpack.
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Le, H., Gratiot, N., Santini, W., Ribolzi, O., Tran, D., Meriaux, X., et al. (2020). Suspended sediment properties in the Lower Mekong River, from fluvial to estuarine environments. Estuarine Coastal And Shelf Science, 233.
Abstract: The Mekong river is one of the largest rivers in the world, which flows through six countries of Southeast Asia (China, Myanmar, Laos, Thailand, Cambodia and Vietnam). Its hydro-sedimentary regime is changing rapidly, as a consequence of a regional shift of land use (agriculture, road, etc.), damming, sand mining and climate changes, among others. This study assesses the behavior of particles transported in suspension in the Lower Mekong River (LMR), along approximately 1700 km from fluvial to estuarine environments. Suspended sediment properties were estimated, simultaneously with hydrodynamic conditions, during three field campaigns. In addition, further investigations were performed in the laboratory to assess the structures of particles (flocculated or not), their capacity to flocculate (and the impacts on siltation), under a wide range of sediment concentration (20-30,000 mg.L-1). This study confirms that suspended sediment transported in the LMR are predominantly (75% by volume) flocculi (or freshly eroded soils aggregates), with median aggregated particle size in the range 10-20 μm and median settling velocity of the order of 0.01-0.1 μm s(-1). These flocculi are robust under the hydrodynamic conditions (turbulence and suspended sediment concentration – SSC) existing in the LMR. Laboratory investigations reveal the existence of a threshold sediment concentration (400 mg.L-1), beyond which flocculation and sedimentation increase of orders of magnitudes. Thus, concentration that exceeds this threshold might promote the formation of so-called fluid mud layers. Because of the nonlinear response of flocculation and sedimentation with SSC and considering the ongoing changes at a regional scale in the LMR, higher occurrence of fluid mud layers in the fluvial upstream waterbodies might be anticipated, and a lower occurrence in estuaries and alongshore where the concentration decrease. The geomorphology could be impacted, with an over-siltation in dams and an exacerbated erosion of the muddy-mangrove coast.
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Le, H., Lambrechts, J., Ortleb, S., Gratiot, N., Deleersnijder, E., & Soares-Frazao, S. (2020). An implicit wetting-drying algorithm for the discontinuous Galerkin method: application to the Tonle Sap, Mekong River Basin. Environmental Fluid Mechanics, 20(4), 923–951.
Abstract: The accurate simulation of wetting-drying processes in floodplains and coastal zones is a challenge for hydrodynamic modelling, especially for long time simulations. Indeed, dedicated numerical procedures are generally time-consuming, instabilities can occur at the wet/dry front, rapid transition of wet/dry interface and mass conservation are not always ensured. We present the extension of an existing wetting-drying algorithm in two space dimensions and its application to a real case. The wetting-drying algorithm is implemented in Second-generation Louvain-la-Neuve Ice-ocean Model (), a discontinuous Galerkin finite element model solving the shallow water equations in a fully implicit way. This algorithm consists in applying a threshold value of fluid depth for a thin layer and a blending parameter in order to guarantee positive values of the water depth, while preserving local mass conservation and the well balanced property at wet/dry interfaces. The technique is first validated against standard analytical test cases (Balzano 1, Balzano 3 and Thacker test cases) and is subsquently applied in a realistic domain, the Tonle Sap Lake in the Mekong River Basin, where the water level can vary by about 10 m between the dry and the wet season.
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Leduc-Leballeur, M., Picard, G., Macelloni, G., Mialon, A., & Kerr, Y. (2020). Melt in Antarctica derived from Soil Moisture and Ocean Salinity (SMOS) observations at L band. Cryosphere, 14(2), 539–548.
Abstract: Melt occurrence in Antarctica is derived from L-band observations from the Soil Moisture and Ocean Salinity (SMOS) satellite between the austral summer 2010-2011 and 2017-2018. The detection algorithm is adapted from a threshold method previously developed for 19 GHz passive microwave measurements from the special sensor microwave imager (SSM/I) and special sensor microwave imager sounder (SSMIS). The comparison of daily melt occurrence retrieved from 1.4 and 19 GHz observations shows an overall close agreement, but a lag of few days is usually observed by SMOS at the beginning of the melt season. To understand the difference, a theoretical analysis is performed using a microwave emission radiative transfer model. It shows that the sensitivity of 1.4 GHz signal to liquid water is significantly weaker than at 19 GHz if the water is only present in the uppermost tens of centimetres of the snowpack. Conversely, 1.4 GHz measurements are sensitive to water when spread over at least 1m and when present in depths up to hundreds of metres. This is explained by the large penetration depth in dry snow and by the long wavelength (21 cm). We conclude that SMOS and higher-frequency radiometers provide interesting complementary information on melt occurrence and on the location of the water in the snowpack.
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Lee, J., Brook, E., Bertler, N., Buizert, C., Baisden, T., Blunier, T., et al. (2020). An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica. Climate Of The Past, 16(5), 1691–1713.
Abstract: In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth-age relationship for the top 754m of the 763m core. RICE17 is a composite chronology combining annual layer interpretations for 0-343m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and delta O-18(atm) records to corresponding records from the WAIS Divide ice core and by modeling of the gas age-ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for preanthropogenic time periods (60-720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to similar to 65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.
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Legchenko, A., Baltassat, J., Duwig, C., Boucher, M., Girard, J., Soruco, A., et al. (2020). Time-lapse magnetic resonance sounding measurements for numerical modeling of water flow in variably saturated media. Journal Of Applied Geophysics, 175.
Abstract: We presented an innovative hydrogeophysical approach that allows numerical modeling of water flow in a variably saturated media. In our model, we approximated the subsurface by horizontally stratified porous media. The model output was a time varying water content profile. Then, we compared the water content provided by the model with the water content measurements carried out using the time-lapse Magnetic Resonance Sounding (MRS) method. Each MRS sounding provided a water content profile in the unsaturated zone down to twenty meters. The time shift between the profiles corresponded to the time lapse between individual MRS soundings. We minimized the discrepancy between the observed and the modeled MRS signals by varying hydraulic parameters of soil layers in the water flow model. For measuring and processing MRS data, we used NUMIS MRS instrument and SAMOVAR software. We carried out water flow modeling with HYDRUS-1D software. This paper reports our results and summarizes the limitations of the MRS method applied to water content measurements in the unsaturated zone. (C) 2020 Elsevier B.V. All rights reserved.
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Legchenko, A., Texier, B., Girard, J., Vouillamoz, J., Lawson, F., Alle, I., et al. (2020). Feasibility study of a surface-borehole NMR method. Journal Of Applied Geophysics, 177.
Abstract: We present results of a feasibility study of a borehole induction-coil sensor for surface-borehole NMR (SBNMR) investigations. This sensor of 7 cm diameter and 180 cm length is connected to a standard MRS (Magnetic Resonance Sounding) instrument. Thus, SBNMR is a cost-effective extension of the MRS method. Using a downhole sensor increases the depth of investigation and the resolution of MRS. In the near-horizontal Earth's magnetic field, the sensitive area of the sensor is represented by a cylinder of a few meters in diameter. A blind zone of 0.5 to 1 m around the borehole is due to the disturbance of the Earth's magnetic field by the magnetic core of the sensor. The relatively large volume investigated with SBNMR and the blind zone around borehole may represent an advantage of SBNMR over the NMR(nuclear magnetic resonance) borehole tool investigating a narrow zone around the borehole. However, using the Earth's magnetic field renders the SBNMR performance site dependent with an inherently low signal-to-noise ratio. Our first results show a good correspondence between SBNMR, MRS and borehole data. (C) 2020 Elsevier B.V. All rights reserved.
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Legrand, M., Mcconnell, J., Lestel, L., Preunkert, S., Arienzo, M., Chellman, N., et al. (2020). Cadmium Pollution From Zinc-Smelters up to Fourfold Higher Than Expected in Western Europe in the 1980s as Revealed by Alpine Ice. Geophysical Research Letters, 47(10).
Abstract: Estimates of past emission inventories suggest that toxic heavy metal pollution in Europe was highest in the mid-1970s for lead and in the mid-1960s for cadmium, but these previous estimates have not been compared to observations. Here, alpine ice-cores were used to document cadmium and lead pollution in western Europe between 1890 and 2000. The ice-core trends show that while lead pollution largely from leaded gasoline reached a maximum in similar to 1975 as expected, cadmium pollution primarily from zinc smelters peaked in the early-1980s rather than in similar to 1965 and was up to fourfold higher than estimated after 1975. Comparisons between ice-core trends, estimated past emissions, and state-of-the-art atmospheric aerosol transport and deposition modeling suggest that the estimated decreases in cadmium emissions after 1970 were based on overly optimistic emissions reductions from the introduction of pollution control devices and other technological improvements. Plain Language Summary Cadmium and lead are among the most toxic heavy-metal pollutants and identified by international conventions as priority contaminants for emissions reduction. Anthropogenic emissions in Europe previously estimated from commodity production statistics are uncertain; comparison with long-term pollution records extracted from well-dated ice cores provides a means of evaluating these estimates. Alpine ice-core records spanning 1890 to 2000 show that lead pollution, mainly related to leaded gasoline use since the mid-20th century, reached a maximum in the mid-1970s as predicted by estimated past emissions. Surprisingly, however, cadmium levels primarily arising from zinc smelter emissions were up to fourfold higher than expected and decreased only after 1980, suggesting that previous reconstructions of past cadmium pollution had assumed overly optimistic emissions reductions from the introduction of pollution control devices and other technological improvements particularly after 1975. Contrary to previous emissions estimates, these new alpine ice-core records show that western European pollution maxima for these two toxic metals coincided in the 1970s. This finding is important in terms of impact of Cd pollution on organisms that depends on concentration in the environment but also duration of exposure.
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Leni, Z., Cassagnes, L., Daellenbach, K., El Haddad, I., Vlachou, A., Uzu, G., et al. (2020). Oxidative stress-induced inflammation in susceptible airways by anthropogenic aerosol. Plos One, 15(11).
Abstract: Ambient air pollution is one of the leading five health risks worldwide. One of the most harmful air pollutants is particulate matter (PM), which has different physical characteristics (particle size and number, surface area and morphology) and a highly complex and variable chemical composition. Our goal was first to comparatively assess the effects of exposure to PM regarding cytotoxicity, release of pro-inflammatory mediators and gene expression in human bronchial epithelia (HBE) reflecting normal and compromised health status. Second, we aimed at evaluating the impact of various PM components from anthropogenic and biogenic sources on the cellular responses. Air-liquid interface (ALI) cultures of fully differentiated HBE derived from normal and cystic fibrosis (CF) donor lungs were exposed at the apical cell surface to water-soluble PM filter extracts for 4 h. The particle dose deposited on cells was 0.9-2.5 and 8.8-25.4 μg per cm(2) of cell culture area for low and high PM doses, respectively. Both normal and CF HBE show a clear dose-response relationship with increasing cytotoxicity at higher PM concentrations. The concurrently enhanced release of pro-inflammatory mediators at higher PM exposure levels links cytotoxicity to inflammatory processes. Further, the PM exposure deregulates genes involved in oxidative stress and inflammatory pathways leading to an imbalance of the antioxidant system. Moreover, we identify compromised defense against PM in CF epithelia promoting exacerbation and aggravation of disease. We also demonstrate that the adverse health outcome induced by PM exposure in normal and particularly in susceptible bronchial epithelia is magnified by anthropogenic PM components. Thus, including health-relevant PM components in regulatory guidelines will result in substantial human health benefits and improve protection of the vulnerable population.
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Lesparre, N., Girard, J., Jeannot, B., Weill, S., Dumont, M., Boucher, M., et al. (2020). Magnetic resonance sounding dataset of a hard-rock headwater catchment for assessing the vertical distribution of water contents in the subsurface. Data In Brief, 31.
Abstract: Magnetic Resonance Sounding (MRS) measurements are acquired at 16 stations in the Strengbach headwater catchment (Vosges Mountains – France). These data, rendering the vertical distribution of water contents in the subsurface, are used to show their potential in conditioning a hydrological model of the catchment, as described in the article “Magnetic resonance sounding measurements as posterior information to condition hydrological model parameters: Application to a hard-rock headwater catchment” – Journal of Hydrology (2020). Acquisition protocols follow a free induction decay scheme. Data are filtered by applying a band-pass filter at the Larmor frequency. A filter removing the 50 Hz noise is also applied with the exception of data at a Larmor frequency close to the 50 Hz harmonic. The signal envelopes are then fitted by a decaying exponential function over time to estimate the median characteristic relaxation time of each MRS sounding. (c) 2020 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license. (http://creativecommons.org/licenses/by/4.0/)
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Lesparre, N., Girard, J., Jeannot, B., Weill, S., Dumont, M., Boucher, M., et al. (2020). Magnetic resonance sounding measurements as posterior information to condition hydrological model parameters: Application to a hard-rock headwater catchment. Journal Of Hydrology, 587.
Abstract: In headwater catchment, the calibration of hydrological models is complex due to the scarcity of data in mountainous areas. Here, an innovative methodology is developed to condition hydrological model parameters by using magnetic resonance sounding (MRS) measurements in combination with stream flow rate data. MRS has the specificity in the various geophysical imaging techniques of being mainly sensitive to the vertical distribution of water content among the subsurface. In a way very similar to hydraulic head observations, these local distributions of water content may serve as information in a hydrological model to pattern subsurface flow by seeking model parameters. Simulations are run with different sets of parameters of a hydrological model. Each simulation provides as an output a 4-D map (3-D spatial plus time) of the vertical water content distributions over the whole catchment and their fluctuations over time. This output is then used to simulate the MRS signal that would be produced by the estimated water content. The simulated MRS signal is compared to measured MRS data to determine which hydrological simulations (which model parameters) are close to observations. The approach is applied on a hard-rock headwater catchment housing a very shallow and thin aquifer where an MRS survey covers the whole studied site. Hydraulic parameters of an integrated hydrological model of the catchment are spatially distributed by zones with uniform values, the prior delineation of the zones being guided by pedological studies. As MRS measurements supply local but spatially distributed information, the method conditions the various zones on their parameter values in a much better way than the classical (in headwater catchments) measure of the stream flow rate at the outlet of the system. Finally, hydrological simulation and time-dependent MRS forward calculations can help identifying possible locations for MRS stations to monitor the transient behavior of the hydrological state of the catchment.
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Li, Y., Sen Gupta, A., Taschetto, A., Jourdain, N., Di Luca, A., Done, J., et al. (2020). Assessing the role of the ocean-atmosphere coupling frequency in the western Maritime Continent rainfall. Climate Dynamics, .
Abstract: High-frequency interactions between the ocean and atmosphere have the potential to affect lower frequency or mean state climate in various regions. Here we examine the importance of sub-daily air-sea interactions over the Maritime Continent region to the rectification of longer timescale variation. In order to determine the importance of these high-frequency interactions, we conducted two regional ocean-atmosphere coupled simulations over the Maritime Continent where exchanges between the oceanic and atmospheric components are performed either every hour (i.e. resolving diurnal changes) or every day. We find that coupling frequency has a significant influence on mean sea surface temperature (SST) and the mean state and diurnal cycle of rainfall over certain regions of the western Maritime Continent where air-sea interactions are strong during the Asian monsoon season, with little effect in other regions or seasons. Without sub-daily air-sea interactions, the mean SST along the southwest off Sumatra is similar to 2 degrees C warmer during the period from June to October as a result of a deepening of thermocline along the coast. This deepening is linked to anomalous downwelling equatorial eastward propagating Kelvin waves triggered by westerly anomalies in the eastern equatorial Indian Ocean. In addition, the mean rainfall in the vicinity of ocean warming increases, thereby producing an enhanced barrier layer that also provides a positive warming feedback. Although the coupling frequency has little impact on the timing of the rainfall diurnal cycle, suppression of sub-daily coupling significantly changes the diurnal rainfall amplitude causing a relative decrease (increase) in amplitude over the coast of Northwestern (Southwestern) Sumatra during the South Asian monsoon season.
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Licciulli, C., Bohleber, P., Lier, J., Gagliardini, O., Hoelzle, M., & Eisen, O. (2020). A full Stokes ice-flow model to assist the interpretation of millennial-scale ice cores at the high-Alpine drilling site Colle Gnifetti, Swiss/Italian Alps. Journal Of Glaciology, 66(255), 35–48.
Abstract: The high-Alpine ice-core drilling site Colle Gnifetti (CG), Monte Rosa, Swiss/Italian Alps, provides climate records over the last millennium and beyond. However, the full exploitation of the oldest part of the existing ice cores requires complementary knowledge of the intricate glacio-meteorological settings, including glacier dynamics. Here, we present new ice-flow modeling studies of CG, focused on characterizing the flow at two neighboring drill sites in the eastern part of the glacier. The3-D full Stokes ice-flow model is thermo-mechanically coupled and includes firn rheology, firn densification and enthalpy transport, and is implemented using the finite element software Elmer/Ice. Measurements of surface velocities, accumulation, borehole inclination, density and englacial temperatures are used to validate the model output. We calculate backward trajectories and map the catchment areas. This constrains, for the first time at this site, the so-called upstream effects for the stable water isotope time series of the two ice cores drilled in 2005 and 2013. The model also provides a 3-D age field of the glacier and independent ice-core chronologies for five ice-core sites. Model results are a valuable addition to the existing glaciological and ice-core datasets. This especially concerns the quantitative estimate of upstream conditions affecting the interpretation of the deep ice-core layers.
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Lima, I., Ramos, O., Munoz, M., Aguirre, J., Duwig, C., Maity, J., et al. (2020). Spatial dependency of arsenic, antimony, boron and other trace elements in the shallow groundwater systems of the Lower Katari Basin, Bolivian Altiplano. Science Of The Total Environment, 719.
Abstract: Spatial patterns, cluster or dispersion trends are statistically different from random patterns of trace elements (TEs), which are essential to recognize, e.g., how they are distributed and change their behavior in different environmental processes and/or in the polluted/contaminated areas caused by urban and industrial pollutant located in upstream basins and/or by different natural geological conditions. The present study focused on a statistical approach to obtain the spatial variability of TEs (As, B and Sb) in shallow groundwater (GW) in a high-altitude arid region (Lower Katari Basin, Bolivian Altiplano), using multivariate analysis (PCA and HCA), geochemical modeling (PHREEQC, MINTEQ) and spatial analyses (Moran's 1 and LISA), considering the community supply wells. The results indicate that despite of the outliers there is a good autocorrelation in all cases, since Moran's I values are positive. The global spatial dependence analysis indicated a positive and statistically significant spatial autocorrelation (SA) for all cases and TEs are not randomly distributed at 99% confidence level. The results of hydrochemical modeling suggested the precipitation and stability of Fe (III) phases such as goethite. The re-adsorption of As and Sb on the mineral surface in the aquifer could be limiting the concentrations of both metalloids in southern regions. Spatial autocorrelation was positive (High-High) in northwestern (arsenic), southeastern (boron) and northeastern (antimony) region. The results reflected that the As and Sb are the main pollutants linked to the natural geological conditions, but B is a main pollutant due to the anthropogenic activities. Furthermore, >50% shallow groundwater exceeded the WHO limit and NB-512 guideline values for Sb (87%), B (56%) and As (50%); therefore the spatial distribution and concentrations of these TEs in GW raise a significant concern about drinking water quality in the study area. (C) 2020 Elsevier B.V. All rights reserved.
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Lindner, F., Walter, F., Laske, G., & Gimbert, F. (2020). Glaciohydraulic seismic tremors on an Alpine glacier. Cryosphere, 14(1), 287–308.
Abstract: Hydraulic processes impact viscous and brittle ice deformation. Water-driven fracturing as well as turbulent water flow within and beneath glaciers radiate seismic waves which provide insights into otherwise hard-to-access englacial and subglacial environments. In this study, we analyze glaciohydraulic tremors recorded by four seismic arrays installed in different parts of Glacier de la Plaine Morte, Switzerland. Data were recorded during the 2016 melt season including the sudden subglacial drainage of an ice-marginal lake. Together with our seismic data, discharge, lake level, and ice flow measurements provide constraints on glacier hydraulics. We find that the tremors are generated by subglacial water flow, in moulins, and by icequake bursts. The dominating process can vary on sub-kilometer and sub-daily scales. Consistent with field observations, continuous source tracking via matched-field processing suggests a gradual upglacier progression of an efficient drainage system as the melt season progresses. The ice-marginal lake likely connects to this drainage system via hydrofracturing, which is indicated by sustained icequake signals emitted from the proximity of the lake basin and starting roughly 24 h prior to the lake drainage. To estimate the hydraulics associated with the drainage, we use tremor-discharge scaling relationships. Our analysis suggests a pressurization of the subglacial environment at the drainage onset, followed by an increase in the hydraulic radii of the conduits and a subsequent decrease in the subglacial water pressure as the capacity of the drainage system increases. The pressurization is in phase with the drop in the lake level, and its retrieved maximum coincides with ice uplift measured via GPS. Our results highlight the use of cryo-seismology for monitoring glacier hydraulics.
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Lopez-Moreno, J., Leppanen, L., Luks, B., Holko, L., Picard, G., Sanmiguel-Vallelado, A., et al. (2020). Intercomparison of measurements of bulk snow density and water equivalent of snow cover with snow core samplers: Instrumental bias and variability induced by observers. Hydrological Processes, .
Abstract: Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Reported uncertainties refer to a shallow, homogeneous tundra-taiga snowpack less than 1 m deep (loose, mostly recrystallised snow and no wind impact). Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.
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Marelle, L., Myhre, G., Steensen, B., Hodnebrog, O., Alterskjaer, K., & Sillmann, J. (2020). Urbanization in megacities increases the frequency of extreme precipitation events far more than their intensity. Environmental Research Letters, 15(12).
Abstract: More than half of the world's population lives in urban areas (UN Population Division 2018 The World's cities in 2018 (UN: New York)), which are especially vulnerable to climate extremes (Field et al 2012 Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation: Special Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press)). Urbanization itself is known to increase surface temperatures, but its quantitative effect on extreme precipitation remains very uncertain. Using decadal convection-permitting climate simulations in four midlatitude megacities (Paris, France; New York City, USA; Tokyo, Japan; Shanghai, China), we show that urbanization can strongly increase the frequency and intensity of extreme urban precipitation. Frequency increases far more than intensity, by +16% (11%-22%) (95% confidence interval) for 1 year daily extremes, and +26% (11%-41%) for 1 year hourly extremes, downwind of city centers. Intensities of the same events increase by +5% (3.2%-6.4%) (daily extremes) and +6% (3.2%-9.8%) (hourly extremes), respectively. The intensity and frequency of extremes increases more for the rarest, most extreme events considered, and there is some indication that hourly extremes increase more than daily extremes. Our simulations also show that direct urban anthropogenic emissions of heat could be an important factor driving these changes. Urbanization is expected to continue in the future, and our results indicate that these effects should be considered in urban planning decisions to make cities more resilient to extreme precipitation.
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Martin, L., Blard, P., Lave, J., Jomelli, V., Charreau, J., Condom, T., et al. (2020). Antarctic-like temperature variations in the Tropical Andes recorded by glaciers and lakes during the last deglaciation. Quaternary Science Reviews, 247.
Abstract: The respective impacts of Northern and Southern Hemispheric climatic changes on the Tropics during the last deglaciation remain poorly understood. In the High Tropical Andes, the Antarctic Cold Reversal (ACR, 14.3-12.9 ka BP) is better represented among morainic records than the Younger Dryas (12.9-11.7 ka BP). However, in the Altiplano basin (Bolivia), two cold periods of the Northern Hemisphere (Heinrich Stadial la, 16.5-14.5 ka BP, and the Younger Dryas) are synchronous with (i) major advances or standstills of paleoglaciers and (ii) the highstands of giant paleolakes Tauca and Coipasa. Here, we present new cosmic ray exposure (CRE) ages from glacial landforms of the Bolivian Andes that formed during the last deglaciation (Termination 1). We reconstruct the equilibrium line altitudes (ELA) associated with each moraine and use them in an inverse algorithm combining paleoglaciers and paleolake budgets to derive temperature and precipitation during the last deglaciation. Our temperature reconstruction (AT relative to present day) yields a consistent regional trend of progressive warming from Delta T = -5 to -2.5 degrees C during 17-14.5 ka BP, followed by a return to colder conditions around -4 degrees C during the ACR (14.5-12.9 ka BP). The Coipasa highstand (12.9-11.8 ka BP) is coeval with another warming trend followed by AT stabilization at the onset of the Holocene (ca. 10 ka BP), around -3 degrees C. Our results suggest that, during the last deglaciation (20-10 ka BP) atmospheric temperatures in the Tropical Andes mimicked Antarctic variability, whereas precipitation over the Altiplano was driven by changes in the Northern Hemisphere. (C) 2020 Elsevier Ltd. All rights reserved.
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Martinez-Carvajal, G., Oxarango, L., Clement, R., Molle, P., & Forquet, N. (2020). Assessment of spatial representativity of X-ray tomography to study Vertical Flow Treatment wetlands. Science Of The Total Environment, 713.
Abstract: French Vertical Flow (VF) treatment wetlands receive raw wastewater and provide simultaneous sludge and wastewater treatment. For proper sludge handling, the treatment wetland must be designed adequately and specific operational conditions must be maintained. When these conditions are not met, accumulation of biosolids may lead to clogging. Filtration in French VF Treatment wetlands is governed by mechanisms at the pore-scale. They must be better understood to predict reliably biosolid accumulation. X-ray Computed Tomography (Xray-CT) is a promising technique to characterize in detail the morphology of the filtering media in treatment wetlands. In order to set a solid basis for the use of Xray-CT, the spatial representativity of measurements must be assessed. This issue is addressed in this study by successively analyzing spatial properties at the filter scale using Frequency Domain Electromagnetic Measurements (FDEMs), and at the pore scale using Xray-CT. A map of the electric conductivity at the surface of a French VF Treatment wetland is obtained by FDEM that indicates a homogeneous distribution of biosolids to which electrical conductivity is highly correlated. Different morphological properties were computed from Xray-CT after phase segmentation: phase volume fraction profiles, Specific Surface Area profiles and pore size distributions. Samples show several similarities of pore scale properties obtained by Xray-CT independently of the sampling region and especially the same vertical gradients. FDEM measurements and Xray-CT analysis are in agreement to indicate a good influent distribution at the surface of a full-scale mature French VF Treatment wetland. A criterion to define the limits of the deposit layer and gravel layer is introduced. This division allows to compare layers independently. Finally, a 2D-REV analysis suggests that the selected sample diameter of 5 cm is large enough to be representative of the heterogeneous distribution of phases at the pore-scale as long as no Phragmites are present. (C) 2020 Elsevier B.V. All rights reserved.
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Marzeion, B., Hock, R., Anderson, B., Bliss, A., Champollion, N., Fujita, K., et al. (2020). Partitioning the Uncertainty of Ensemble Projections of Global Glacier Mass Change. Earths Future, 8(7).
Abstract: Glacier mass loss is recognized as a major contributor to current sea level rise. However, large uncertainties remain in projections of glacier mass loss on global and regional scales. We present an ensemble of 288 glacier mass and area change projections for the 21st century based on 11 glacier models using up to 10 general circulation models and four Representative Concentration Pathways (RCPs) as boundary conditions. We partition the total uncertainty into the individual contributions caused by glacier models, general circulation models, RCPs, and natural variability. We find that emission scenario uncertainty is growing throughout the 21st century and is the largest source of uncertainty by 2100. The relative importance of glacier model uncertainty decreases over time, but it is the greatest source of uncertainty until the middle of this century. The projection uncertainty associated with natural variability is small on the global scale but can be large on regional scales. The projected global mass loss by 2100 relative to 2015 (79 +/- 56 mm sea level equivalent for RCP2.6, 159 +/- 86 mm sea level equivalent for RCP8.5) is lower than, but well within, the uncertainty range of previous projections.
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Masiokas, M., Rabatel, A., Rivera, A., Ruiz, L., Pitte, P., Ceballos, J., et al. (2020). A Review of the Current State and Recent Changes of the Andean Cryosphere. Frontiers In Earth Science, 8.
Abstract: The Andes Cordillera contains the most diverse cryosphere on Earth, including extensive areas covered by seasonal snow, numerous tropical and extratropical glaciers, and many mountain permafrost landforms. Here, we review some recent advances in the study of the main components of the cryosphere in the Andes, and discuss the changes observed in the seasonal snow and permanent ice masses of this region over the past decades. The open access and increasing availability of remote sensing products has produced a substantial improvement in our understanding of the current state and recent changes of the Andean cryosphere, allowing an unprecedented detail in their identification and monitoring at local and regional scales. Analyses of snow cover maps has allowed the identification of seasonal patterns and long term trends in snow accumulation for most of the Andes, with some sectors in central Chile and central-western Argentina showing a clear decline in snowfall and snow persistence since 2010. This recent shortage of mountain snow has caused an extended, severe drought that is unprecedented in the hydrological and climatological records from this region. Together with data from global glacier inventories, detailed inventories at local/regional scales are now also freely available, providing important new information for glaciological, hydrological, and climatological assessments in different sectors of the Andes. Numerous studies largely based on field measurements and/or remote sensing techniques have documented the recent glacier shrinkage throughout the Andes. This observed ice mass loss has put Andean glaciers among the highest contributors to sea level rise per unit area. Other recent studies have focused on rock glaciers, showing that in extensive semi-arid sectors of the Andes these mountain permafrost features contain large reserves of freshwater and may play a crucial role as future climate becomes warmer and drier in this region. Many relevant issues remain to be investigated, however, including an improved estimation of ice volumes at local scales, and detailed assessments of the hydrological significance of the different components of the cryosphere in Andean river basins. The impacts of future climate changes on the Andean cryosphere also need to be studied in more detail, considering the contrasting climatic scenarios projected for each region. The sustained work of various monitoring programs in the different Andean countries is promising and will provide much needed field observations to validate and improve the analyses made from remote sensors and modeling techniques. In this sense, the development of a well-coordinated network of high-elevation hydro-meteorological stations appears as a much needed priority to complement and improve the many glaciological and hydro-climatological assessments that are being conducted across the Andes.
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Massari, C., Brocca, L., Pellarin, T., Abramowitz, G., Filippucci, P., Ciabatta, L., et al. (2020). A daily 25km short-latency rainfall product for data-scarce regions based on the integration of the Global Precipitation Measurement mission rainfall and multiple-satellite soil moisture products. Hydrology And Earth System Sciences, 24(5), 2687–2710.
Abstract: Rain gauges are unevenly spaced around the world with extremely low gauge density over developing countries. For instance, in some regions in Africa the gauge density is often less than one station per 10 000 km(2). The availability of rainfall data provided by gauges is also not always guaranteed in near real time or with a timeliness suited for agricultural and water resource management applications, as gauges are also subject to malfunctions and regulations imposed by national authorities. A potential alternative is satellite-based rainfall estimates, yet comparisons with in situ data suggest they are often not optimal. In this study, we developed a short-latency (i.e. 2-3 d) rainfall product derived from the combination of the Integrated Multi-Satellite Retrievals for GPM (Global Precipitation Measurement) Early Run (IMERG-ER) with multiplesatellite soil-moisture-based rainfall products derived from ASCAT (Advanced Scatterometer), SMOS (Soil Moisture and Ocean Salinity) and SMAP (Soil Moisture Active and Passive) L3 (Level 3) satellite soil moisture (SM) retrievals. We tested the performance of this product over four regions characterized by high-quality ground-based rainfall datasets (India, the conterminous United States, Australia and Europe) and over data-scarce regions in Africa and South America by using triple-collocation (TC) analysis. We found that the integration of satellite SM observations with in situ rainfall observations is very beneficial with improvements of IMERG-ER up to 20% and 40% in terms of correlation and error, respectively, and a generalized enhancement in terms of categorical scores with the integrated product often outperforming reanalysis and ground-based long-latency datasets. We also found a relevant overestimation of the rainfall variability of GPM-based products (up to twice the reference value), which was significantly reduced after the integration with satellite soil-moisture-based rainfall estimates. Given the importance of a reliable and readily available rainfall product for water resource management and agricultural applications over data-scarce regions, the developed product can provide a valuable and unique source of rainfall information for these regions.
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Massicotte, P., Amiraux, R., Amyot, M., Archambault, P., Ardyna, M., Arnaud, L., et al. (2020). Green Edge ice camp campaigns: understanding the processes controlling the under-ice Arctic phytoplankton spring bloom. Earth System Science Data, 12(1), 151–176.
Abstract: The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on land-fast sea ice southeast of Qikiqtarjuaq Island in Baffin Bay (67.4797 degrees N, 63.7895 degrees W). During both expeditions, a large suite of physical, chemical and biological variables was measured beneath a consolidated sea-ice cover from the surface to the bottom (at 360m depth) to better understand the factors driving the PSB. Key variables, such as conservative temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured at the ice camp. Meteorological and snow-relevant variables were also monitored. Here, we present the results of a joint effort to tidy and standardize the collected datasets, which will facilitate their reuse in other Arctic studies.
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Massonnet, F., Menegoz, M., Acosta, M., Yepes-Arbos, X., Exarchou, E., & Doblas-Reyes, F. (2020). Replicability of the EC-Earth3 Earth system model under a change in computing environment. Geoscientific Model Development, 13(3), 1165–1178.
Abstract: Most Earth system models (ESMs) are running under different high-performance computing (HPC) environments. This has several advantages, from allowing different groups to work with the same tool in parallel to leveraging the burden of ensemble climate simulations, but it also offers alternative solutions in the case of shutdown (expected or not) of any of the environments. However, for obvious scientific reasons, it is critical to ensure that ESMs provide identical results under changes in computing environment. While strict bit-for-bit reproducibility is not always guaranteed with ESMs, it is desirable that results obtained under one computing environment are at least statistically indistinguishable from those obtained under another environment, which we term a “replicability” condition following the metrology nomenclature. Here, we develop a protocol to assess the replicability of the EC-Earth ESM. Using two versions of EC-Earth, we present one case of non-replicability and one case of replicability. The non-replicable case occurs with the older version of the model and likely finds its origin in the treatment of river runoff along Antarctic coasts. By contrast, the more recent version of the model provides replicable results. The methodology presented here has been adopted as a standard test by the EC-Earth consortium (27 institutions in Europe) to evaluate the replicability of any new model version across platforms, including for CMIP6 experiments. To a larger extent, it can be used to assess whether other ESMs can safely be ported from one HPC environment to another for studying climate-related questions. Our results and experience with this work suggest that the default assumption should be that ESMs are not replicable under changes in the HPC environment, until proven otherwise.
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Matthes, L., Mundy, C., L-Girard, S., Babin, M., Verin, G., & Ehn, J. (2020). Spatial Heterogeneity as a Key Variable Influencing Spring-Summer Progression in UVR and PAR Transmission Through Arctic Sea Ice. Frontiers In Marine Science, 7.
Abstract: The transmission of ultraviolet (UVR) and photosynthetically available radiation (PAR) through sea ice is a key factor controlling under-ice phytoplankton growth in seasonally ice-covered waters. The increase toward sufficient light levels for positive net photosynthesis occurs concurrently with the sea ice melt progression in late spring when ice surface conditions shift from a relatively homogeneous high-albedo snow cover to a less reflective mosaic of bare ice and melt ponds. Here, we present a detailed dataset on the spatial and temporal progression of transmitted UVR and PAR in relation to changing quantities of snow, sea ice and melt ponds. Data were collected with a remotely operated vehicle (ROV) during the GreenEdge landfast sea ice campaign in June-July 2016 in southwestern Baffin Bay. Over the course of melt progression, there was a 10-fold increase in spatially averaged UVR and PAR transmission through the sea ice cover, reaching a maximum transmission of 31% for PAR, 7% for UVB, and 26% for UVA radiation. The depth under the sea ice experiencing spatial variability in light levels due to the influence of surface heterogeneity in snow, white ice and melt pond distributions increased from 7 +/- 4 to 20 +/- 6 m over our study. Phytoplankton drifting in under-ice surface waters were thus exposed to variations in PAR availability of up to 43%, highlighting the importance to account for spatial heterogeneity in light transmission through melting sea ice. Consequently, we demonstrate that spatial averages of PAR transmission provided more representative light availability estimates to explain underice bloom progression relative to single point irradiance measurements during the sea ice melt season. Encouragingly, the strong dichotomy between white ice and melt pond PAR transmittance and surface albedo permitted a very good estimate of spatially averaged light transmission from drone imagery of the surface and point transmittance measurements beneath different ice surface types.
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Mayta, V., Silva, N., Ambrizzi, T., Dias, P., & Espinoza, J. (2020). Assessing the skill of all-season diverse Madden-Julian oscillation indices for the intraseasonal Amazon precipitation. Climate Dynamics, 54(7-8), 3729–3749.
Abstract: Madden-Julian Oscillation (MJO) impact on the Amazon intraseasonal precipitation assessed by different MJO indices is investigated through an analysis of composite events and observed case studies. The MJO indices diagnosing skill is described in detail using reanalysis, satellite, and gauge-based gridded rainfall data. Three types of existing MJO indices are considered: (1) OLR-based MJO (OMI index); (2) dynamically- or circulation-based MJO (VPM index); and (3) combined convectively- and dynamically-based MJO (Wheeler-Hendon RMM index). Our results suggest that, in the large-scale (i.e., around the global tropics), even in the regional domain, the MJO OLR-only index well-represent the dynamical and convective features associated with the intraseasonal variability. On the other hand, each index gives diverging results on rainfall characterization over the Amazon Basin (AB). For instance, the cumulative distribution of precipitation for each MJO phase and index depicts considerable differences in the main climatic regions of the AB, indicating a diverging intraseasonal representation for extreme rainfall values. In addition, when event-by-event is assessed, details as well as the identification of events themselves can differ among indices. This characteristic is particularly observed during extreme rainfall events in the AB. A significant percentage of MJO activity is detected only by the MJO OLR-based index. Because the large-scale zonal circulation dominates the dynamically-based indices (RMM and VPM), the MJO impact in these indices is not an appropriate measure of convective MJO activity. Since the convective component of the MJO is our primary objective, the results presented in this study show that the OLR-based MJO index is able to better account for the MJO impacts over the AB. The indices considered in this study are often used for monitoring and forecasting the MJO activity over South America. However, given the dissimilarity of the representation of precipitation in the AB, our findings also support the consideration of a regional index for monitoring and forecasting the MJO impacts.
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Mazzilli, N., Chalikakis, K., Carriere, S., & Legchenko, A. (2020). Surface Nuclear Magnetic Resonance Monitoring Reveals Karst Unsaturated Zone Recharge Dynamics during a Rain Event. Water, 12(11).
Abstract: Understanding karst unsaturated zone (UZ) recharge dynamics is crucial for achieving sustainable management of karst hydrosystems. In this paper, we provide the first report of the application of surface nuclear magnetic resonance (SNMR) monitoring of a karst UZ during a typical Mediterranean rain event. This 79 days' SNMR monitoring is a part of a more than 2 years of SNMR monitoring at the Low Noise Underground Laboratory (LSBB) experimental site located within the Fontaine de Vaucluse karst hydrosystem (southeastern France). We present eight SNMR soundings conducted before and after the rain event that accumulated 168 mm in 5 days. The obtained results demonstrate the applicability and the efficiency of SNMR for investigating infiltration dynamics in karst UZs at the time scale of a few days. We present the SNMR amplitudes that highlight strong signal variations related to water dynamics in the karst UZ. Infiltrated water cause increased SNMR signal during 5 days after the rain event. A significant draining process of the medium starts 15 days after the main event. Finally, after 42 days, the SNMR signal returns close to the initial state.
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Menegoz, M., Valla, E., Jourdain, N., Blanchet, J., Beaumet, J., Wilhelm, B., et al. (2020). Contrasting seasonal changes in total and intense precipitation in the European Alps from 1903 to 2010. Hydrology And Earth System Sciences, 24(11), 5355–5377.
Abstract: Changes in precipitation over the European Alps are investigated with the regional climate model MAR (Modele Atmospherique Regional) applied with a 7 km resolution over the period 1903-2010 using the reanalysis ERA-20C as forcing. A comparison with several observational datasets demonstrates that the model is able to reproduce the climatology as well as both the interannual variability and the seasonal cycle of precipitation over the European Alps. The relatively high resolution allows us to estimate precipitation at high elevations. The vertical gradient of precipitation simulated by MAR over the European Alps reaches 33% km(-1) (1.21mm d(-1) km(-1)) in summer and 38% km(-1) (1.15 mm d(-1) km(-1)) in winter, on average, over 1971-2008 and shows a large spatial variability. A significant (p value < 0.05) increase in mean winter precipitation is simulated in the northwestern Alps over 1903-2010, with changes typically reaching 20% to 40% per century. This increase is mainly explained by a stronger simple daily intensity index (SDII) and is associated with less-frequent but longer wet spells. A general drying is found in summer over the same period, exceeding 20% to 30% per century in the western plains and 40% to 50% per century in the southern plains surrounding the Alps but remaining much smaller (< 10 %) and not significant above 1500 ma.s.l. Below this level, the summer drying is explained by a reduction in the number of wet days, reaching 20% per century over the northwestern part of the Alps and 30% to 50% per century in the southern part of the Alps. It is associated with shorter but more-frequent wet spells. The centennial trends are modulated over the last decades, with the drying occurring in the plains in winter also affecting high-altitude areas during this season and with a positive trend of autumn precipitation occurring only over the last decades all over the Alps. Maximum daily precipitation index (Rx1day) takes its highest values in autumn in both the western and the eastern parts of the southern Alps, locally reaching 50 to 70 mm d(-1) on average over 1903-2010. Centennial maxima up to 250 to 300 mm d(-1) are simulated in the southern Alps, in France and Italy, as well as in the Ticino valley in Switzerland. Over 1903-2010, seasonal Rx1day shows a general and significant increase at the annual timescale and also during the four seasons, reaching local values between 20% and 40% per century over large parts of the Alps and the Apennines. Trends of Rx1day are significant (p value < 0.05) only when considering long time series, typically 50 to 80 years depending on the area considered. Some of these trends are nonetheless significant when computed over 1970-2010, suggesting a recent acceleration of the increase in extreme precipitation, whereas earlier periods with strong precipitation also occurred, in particular during the 1950s and 1960s.
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Metref, S., Cosme, E., Le Guillou, F., Le Sommer, J., Brankart, J., & Verron, J. (2020). Wide-Swath Altimetric Satellite Data Assimilation With Correlated-Error Reduction. Frontiers In Marine Science, 6.
Abstract: For decades now, satellite altimetric observations have been successfully integrated in numerical oceanographic models using data assimilation (DA). So far, sea surface height (SSH) data were provided by one-dimensional nadir altimeters. The next generation Surface Water and Ocean Topography (SWOT) satellite altimeter will provide two-dimensional wide-swath altimetric information with an unprecedented high resolution. This new type of SSH data is expected to strongly improve altimetric assimilation. However, the SWOT data is also expected to be affected by spatially correlated errors and, hence, can not be assimilated as easily as nadir altimeters. The present paper proposes to embed a state-of-the-art correlated-error reduction (CER) method for the SWOT data into an ensemble-based DA scheme. The DA with the new correlated-error reduced-data (CER-data) is implemented and tested in a simple SSH reconstruction problem using artificial SWOT data and a quasi-geostrophic model. The results show that, in an energetic large scale region, the DA with CER-data – in comparison to the classical DA- reduces the root-mean-square-error (RMSE) of the reconstruction in SSH by approximately 10%, in relative vorticity by 5% and in surface currents by 5-10%, and also slightly improves the noise-to-signal ratio and spectral coherence of the SSH signal at mesoscale (100-200 km) but with a small degradation on the large scales (>300 km). In a less energetic region, the DA with CER-data cuts down the RMSE in SSH by more than 50% on average therefore allowing a significantly more accurate reconstruction of SSH at mesoscale in terms of noise-to-signal ratio, spectral coherence, and power spectral density.
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Millan, R., St-Laurent, P., Rignot, E., Morlighem, M., Mouginot, J., & Scheuchl, B. (2020). Constraining an Ocean Model Under Getz Ice Shelf, Antarctica, Using A Gravity-Derived Bathymetry. Geophysical Research Letters, 47(13).
Abstract: Getz Ice Shelf, the largest producer of ice shelf meltwater in Antarctica, buttresses glaciers that hold enough ice to raise sea level by 22 cm. We present a new bathymetry of its sub-ice shelf cavity using a three-dimensional inversion of airborne gravity data constrained by multibeam bathymetry at sea and a reconstruction of the bedrock from mass conservation on land. The new bathymetry is deeper than previously estimated with differences exceeding 500 m in a number of regions. When incorporated into an ocean model, it yields a better description of the spatial distribution of ice shelf melt, specifically along glacier grounding lines. While the melt intensity is overestimated because of a positive bias in ocean thermal forcing, the study reveals the main pathways along which warm oceanic water enters the cavity and corroborates the observed rapid retreat of Berry Glacier along a deep channel with a retrograde bed slope.
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Miller, O., Solomon, D., Miege, C., Koenig, L., Forster, R., Schmerr, N., et al. (2020). Hydrology of a Perennial Firn Aquifer in Southeast Greenland: An Overview Driven by Field Data. Water Resources Research, 56(8).
Abstract: Firn aquifers have been discovered across regions of the Greenland ice sheet with high snow accumulation and melt rates, but the processes and rates that sustain these aquifers have not been fully quantified or supported by field data. A quantitative description of the hydrology of a firn aquifer upslope from Helheim Glacier that integrates field measurements is presented to constrain melt and recharge rates and timing, temporal variations in temperature and water levels, and liquid-water residence time. Field measurements include weather data, firn temperatures, water levels, geochemical tracers, and airborne radar data. Field measurements show that once the firn column is temperate (0 degrees C), meltwater from the surface infiltrates to the water table in less than 2 days and raises the water table. Average recharge is 22 cm/year (lower 95% confidence interval is 13 cm/year and upper 95% confidence interval is 33 cm/year). Meltwater within the recently formed aquifer, which flows laterally downslope and likely discharges into crevasses, has a mean residence time of similar to 6.5 years. Airborne radar data suggest that the aquifer in the study area continues to expand inland, presumably from Arctic warming. These comprehensive field measurements and integrated description of aquifer hydrology provide a comprehensive, quantitative framework for modeling fluid flow through firn, and understanding existing and yet undiscovered firn aquifers, and may help researchers evaluate the role of firn aquifers in climate change impacts.
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Ming, A., Winton, V., Keeble, J., Abraham, N., Dalvi, M., Griffiths, P., et al. (2020). Stratospheric Ozone Changes From Explosive Tropical Volcanoes: Modeling and Ice Core Constraints. Journal Of Geophysical Research-Atmospheres, 125(11).
Abstract: Major tropical volcanic eruptions have emitted large quantities of stratospheric sulfate and are potential sources of stratospheric chlorine although this is less well constrained by observations. This study combines model and ice core analysis to investigate past changes in total column ozone. Historic eruptions are good analogs for future eruptions as stratospheric chlorine levels have been decreasing since the year 2000. We perturb the preindustrial atmosphere of a chemistry-climate model with high and low emissions of sulfate and chlorine. The sign of the resulting Antarctic ozone change is highly sensitive to the background stratospheric chlorine loading. In the first year, the response is dynamical, with ozone increases over Antarctica. In the high HCl (2Tg emission) experiment, the injected chlorine is slowly transported to the polar regions with subsequent chemical ozone depletion. These model results are then compared to measurements of the stable nitrogen isotopic ratio, delta N-15(NO3-), from a low snow accumulation Antarctic ice core from Dronning Maud Land (recovered in 2016-2017). We expect ozone depletion to lead to increased surface ultraviolet (UV) radiation, enhanced air-snow nitrate photochemistry and enrichment in delta N-15(NO3-) in the ice core. We focus on the possible ozone depletion event that followed the largest volcanic eruption in the past 1,000 years, Samalas in 1257. The characteristic sulfate signal from this volcano is present in the ice core but the variability in delta N-15(NO3-) dominates any signal arising from changes in ultraviolet from ozone depletion. Prolonged complete ozone removal following this eruption is unlikely to have occurred over Antarctica. Plain Language Summary Chlorine in the stratosphere destroys ozone that protects the Earth from harmful ultraviolet radiation. Volcanic eruptions in the tropics can emit sulfate and chlorine into the stratosphere. Chlorine levels are currently decreasing and to understand the impact of a volcanic eruption on stratospheric ozone in a future climate, historical eruptions are a useful analog since the preindustrial climate also had low chlorine levels. Using a chemistry-climate model, we run a set of experiments where we inject different amounts of sulfate and chlorine into the stratosphere over the tropics to simulate different types and strengths of explosive volcanoes and we find that the ozone over Antarctica initially increases over the first year following the eruption. If the volcano emits a large amount of chlorine, ozone then decreases over Antarctica in years two to four following the eruption. We also compare our results to ice core data around a large historic volcanic eruption, Samalas (1257).
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Misset, C., Recking, A., Legout, C., Bakker, M., Bodereau, N., Borgniet, L., et al. (2020). Combining multi-physical measurements to quantify bedload transport and morphodynamics interactions in an Alpine braiding river reach. Geomorphology, 351.
Abstract: Understanding the interactions between bedload transport and morpholdynamics in braided streams has important applications in river management and restoration. Direct field measurements addressing this question are however scarce as they are often challenging to perform. Here, we report an extensive two-month field campaign in an Alpine braided reach (La Severaisse river, French Alps) that experienced predictable daily peak discharge (48 events observed) generating significant bedload transport and morphological changes during the melting season. We monitored these processes using a wide range of direct and indirect techniques (bedload sampling, continuous seismic measurements, pebbles tracking, topographic surveys, remote sensing using ground control cameras and drone flights). Doing so, surrogate measurements allowed to extend temporally discrete manual bedload sampling, and to extend spatially local riverbed cross section measurements. These measurements provide unique complementary constraints on the targeted physics, at various spatial and temporal scales which enabled us to draw robust conclusions. Data showed a progressive decrease in bedload transport for a given flow rate along the two months period. Simultaneously, river morphology in the braided sections changed from an incised to a more distributed configuration which led to a decrease of local maxima in dimensionless shear stresses in the braided reach for similar flow conditions. This control of bedload transport by maximum local shear stresses was in line with tracked pebble surveys indicating that coarse bedload particles were mostly transported in the main active channel. At the reach scale, this transport was found to be more efficient in laterally confined sections than in braided ones which has important implications in terms of bedload estimation in alternative confined and braided (unconfined) rivers. Finally, this study highlight the interest to combine a large variety of traditional and innovative measurements techniques to better understand complex sediment transport processes in the field. (C) 2019 Elsevier B.V. All rights reserved.
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Montagnat, M., Chambon, G., Gaume, J., Hagenmuller, P., & Sandells, M. (2020). Editorial: About the Relevance of Snow Microstructure Study in Cryospheric Sciences. Frontiers In Earth Science, 8.
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Montagnat, M., Lowe, H., Calonne, N., Schneebeli, M., Matzl, M., & Jaggi, M. (2020). On the Birth of Structural and Crystallographic Fabric Signals in Polar Snow: A Case Study From the EastGRIP Snowpack. Frontiers In Earth Science, 8.
Abstract: The role of near-surface snow processes for the formation of climate signals through densification into deep polar firn is still barely understood. To this end we have analyzed a shallow snow pit (0-3 meters) from EastGRIP (Greenland) and derived high-resolution profiles of different types of mechanically relevant fabric tensors. The structural fabric, which characterizes the anisotropic geometry of ice matrix and pore space, was obtained by X-ray tomography. The crystallographic fabric, which characterizes the anisotropic distribution of thec-axis (or optical axis) orientations of snow crystals, was obtained from automatic analysis of thin sections. The structural fabric profile unambiguously reveals the seasonal cycles at EastGRIP, as a consequence of temperature gradient metamorphism, and in contrast to featureless signals of parameters like density or specific surface area. The crystallographic fabric profile unambiguously reveals a signal of cluster-type texture already at shallow depth. We make use of order of magnitude estimates for the formation time of both fabric signals and discuss potential coupling effects in the context of snow and firn densification.
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Moquet, J., Morera, S., Turcq, B., Poitrasson, F., Roddaz, M., Moreira-Turcq, P., et al. (2020). Control of seasonal and inter-annual rainfall distribution on the Strontium-Neodymium isotopic compositions of suspended particulate matter and implications for tracing ENSO events in the Pacific coast (Tumbes basin, Peru). Global And Planetary Change, 185.
Abstract: The geochemistry of riverine sediments exported to the oceans is important for paleo-hydro-climatic reconstruction. However, climate reconstruction requires a good understanding of the relationship between geochemistry and hydrological variability and sediment sources. In this study, we analyzed the major elements, the strontium-neodymium radiogenic isotopes signatures (Sr-87/Sr-86 and eNd) and the mineralogy of the suspended particulate matter (SPM) sampled monthly during two hydrologic years (2007-2008, a wet year, and 2010-2011, a normal hydrological year) upstream the Tumbes River outlet. The hydroclimate of this Ecuador-Peru binational basin is particularly sensitive to ENSO (El Nino Southern Oscillation) events. While mineralogy (dominated by illite) and the chemical alteration index (from 75 to 82) remain almost constant along the two hydrological years, Sr-87/Sr-86 (0.7115 to 0.7176) and eNd (-7.8 to -1.9) signatures are particularly sensitive to discharge and SPM concentration variations. Along the hydrological year, two sources control the eNd variability: (1) volcanic rocks, which dominate during the dry season, and (2) plutonic/metamorphic sources, whose contribution increases during the wet season. This behavior is confirmed by the correlation between eNd signature and the monthly rainfall contribution from volcanic area (R = 0.58; p-value < 0.01), and also with the daily discharge at the outlet (R = -0.73; p-value < 0.01). For most of the samples, Sr-87/Sr-86 is less variable along the hydrological year. However, two exceptional high discharge and SPM concentration conditions sampled exhibit more radiogenic (higher) Sr-87/Sr-86 signatures when plutonic/metamorphic rocks derived sediments are released in sufficient quantities to notably change the SPM isotopic Sr value of the Tumbes River. Hence, this study demonstrates that Sr-87/Sr-86 and eNd signatures can be used as powerful proxies for paleoclimate reconstructions based on sediment core's analysis in relation with spatial rainfall distribution and intensity in Pacific sedimentary basins submitted to the diversity of ENSO events.
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Moreaux, V., Longdoz, B., Berveiller, D., Delpierre, N., Dufrene, E., Bonnefond, J., et al. (2020). Environmental control of land-atmosphere CO2 fluxes from temperate ecosystems: a statistical approach based on homogenized time series from five land-use types. Tellus Series B-Chemical And Physical Meteorology, 72(1), 1–25.
Abstract: We assembled homogenized long-term time series, up to 19 years, of measurements of net ecosystem exchange of CO2 (NEE) and its partitioning between gross primary production (GPP) and respiration (R-eco) for five different ecosystems representing the main plant functional types (PFTs) in France. Part of these data was analyzed to determine the influence of the main environmental variables on carbon fluxes between temperate ecosystems and the atmosphere, and to investigate the temporal patterns of their variations. A multi-temporal statistical analysis of the time series was conducted using random forest (RF) and wavelet coherence approaches. The RF analysis showed that, in all ecosystems, the incident solar radiation was highly correlated with GPP and that GPP was better correlated with the temporal variations of NEE than R-eco. The air temperature was the second most important driver in ecosystems with seasonal foliage, i.e., deciduous forest, cropland and grassland; whereas variables related to air or soil drought were prominent in evergreen forest sites. The environmental control on CO2 fluxes was tighter at high frequency suggesting an increased resilience to environmental variations at longer time spans. The spectral analysis performed on three of the five sites selected revealed contrasting temporal patterns of the cross-coherence between CO2 fluxes and climate variables among ecosystems; these were related to the respective PFT, management and soil conditions. In all PFTs, the power spectrum of GPP was well correlated with NEE and clearly different from R-eco. The spectral correlation analysis showed that the canopy phenology and disturbance regime condition the spectral correlation patterns of GPP and R-eco with the soil moisture and atmospheric vapour deficit.
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Moreaux, V., Martel, S., Bosc, A., Picart, D., Achat, D., Moisy, C., et al. (2020). Energy, water and carbon exchanges in managed forest ecosystems: description, sensitivity analysis and evaluation of the INRAE GO plus model, version 3.0. Geoscientific Model Development, 13(12), 5973–6009.
Abstract: The mechanistic model GO+ describes the functioning and growth of managed forests based upon biophysical and biogeochemical processes. The biophysical and biogeochemical processes included are modelled using standard formulations of radiative transfer, convective heat exchange, evapotranspiration, photosynthesis, respiration, plant phenology, growth and mortality, biomass nutrient content, and soil carbon dynamics. The forest ecosystem is modelled as three layers, namely the tree overstorey, understorey and soil. The vegetation layers include stems, branches and foliage and are partitioned dynamically between sunlit and shaded fractions. The soil carbon submodel is an adaption of the Roth-C model to simulate the impact of forest operations. The model runs at an hourly time step. It represents a forest stand covering typically 1 ha and can be straightforwardly upscaled across gridded data at regional, country or continental levels. GO+ accounts for both the immediate and long-term impacts of forest operations on energy, water and carbon exchanges within the soil-vegetation-atmosphere continuum. It includes exhaustive and versatile descriptions of management operations (soil preparation, regeneration, vegetation control, selective thinning, clear-cutting, coppicing, etc.), thus permitting the effects of a wide variety of forest management strategies to be estimated: from close to nature to intensive. This paper examines the sensitivity of the model to its main parameters and estimates how errors in parameter values are propagated into the predicted values of its main output variables.The sensitivity analysis demonstrates an interaction between the sensitivity of variables, with the climate and soil hydraulic properties being dominant under dry conditions but the leaf biochemical properties being most influential with wet soil. The sensitivity profile of the model changes from short to long timescales due to the cumulative effects of the fluxes of carbon, energy and water on the stand growth and canopy structure. Apart from a few specific cases, the model simulations are close to the values of the observations of atmospheric exchanges, tree growth, and soil carbon and water stock changes monitored over Douglas fir, European beech and pine forests of different ages. We also illustrate the capacity of the GO+ model to simulate the provision of key ecosystem services, such as the long-term storage of carbon in biomass and soil under various management and climate scenarios.
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Morlighem, M., Rignot, E., Binder, T., Blankenship, D., Drews, R., Eagles, G., et al. (2020). Deep glacial troughs and stabilizing ridges unveiled beneath the margins of the Antarctic ice sheet. Nature Geoscience, 13(2), 132–+.
Abstract: The Antarctic ice sheet has been losing mass over past decades through the accelerated flow of its glaciers, conditioned by ocean temperature and bed topography. Glaciers retreating along retrograde slopes (that is, the bed elevation drops in the inland direction) are potentially unstable, while subglacial ridges slow down the glacial retreat. Despite major advances in the mapping of subglacial bed topography, significant sectors of Antarctica remain poorly resolved and critical spatial details are missing. Here we present a novel, high-resolution and physically based description of Antarctic bed topography using mass conservation. Our results reveal previously unknown basal features with major implications for glacier response to climate change. For example, glaciers flowing across the Transantarctic Mountains are protected by broad, stabilizing ridges. Conversely, in the marine basin of Wilkes Land, East Antarctica, we find retrograde slopes along Ninnis and Denman glaciers, with stabilizing slopes beneath Moscow University, Totten and Lambert glacier system, despite corrections in bed elevation of up to 1 km for the latter. This transformative description of bed topography redefines the high- and lower-risk sectors for rapid sea level rise from Antarctica; it will also significantly impact model projections of sea level rise from Antarctica in the coming centuries.
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Mortier, A., Gliss, J., Schulz, M., Aas, W., Andrews, E., Bian, H., et al. (2020). Evaluation of climate model aerosol trends with ground-based observations over the last 2 decades – an AeroCom and CMIP6 analysis. Atmospheric Chemistry And Physics, 20(21), 13355–13378.
Abstract: This study presents a multiparameter analysis of aerosol trends over the last 2 decades at regional and global scales. Regional time series have been computed for a set of nine optical, chemical-composition and mass aerosol properties by using the observations from several ground-based networks. From these regional time series the aerosol trends have been derived for the different regions of the world. Most of the properties related to aerosol loading exhibit negative trends, both at the surface and in the total atmospheric column. Significant decreases in aerosol optical depth (AOD) are found in Europe, North America, South America, North Africa and Asia, ranging from -1.2 % yr(-1) to -3.1 % yr(-1). An error and representativity analysis of the spatially and temporally limited observational data has been performed using model data subsets in order to investigate how much the observed trends represent the actual trends happening in the regions over the full study period from 2000 to 2014. This analysis reveals that significant uncertainty is associated with some of the regional trends due to time and space sampling deficiencies. The set of observed regional trends has then been used for the evaluation of 10 models (6 AeroCom phase III models and 4 CMIP6 models) and the CAMS reanalysis dataset and of their skills in reproducing the aerosol trends. Model performance is found to vary depending on the parameters and the regions of the world. The models tend to capture trends in AOD, the column Angstrom exponent, sulfate and particulate matter well (except in North Africa), but they show larger discrepancies for coarse-mode AOD. The rather good agreement of the trends, across different aerosol parameters between models and observations, when co-locating them in time and space, implies that global model trends, including those in poorly monitored regions, are likely correct. The models can help to provide a global picture of the aerosol trends by filling the gaps in regions not covered by observations. The calculation of aerosol trends at a global scale reveals a different picture from that depicted by solely relying on ground-based observations. Using a model with complete diagnostics (NorESM2), we find a global increase in AOD of about 0.2 % yr(-1) between 2000 and 2014, primarily caused by an increase in the loads of organic aerosols, sulfate and black carbon.
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Mudryk, L., Santolaria-Otin, M., Krinner, G., Menegoz, M., Derksen, C., Brutel-Vuilmet, C., et al. (2020). Historical Northern Hemisphere snow cover trends and projected changes in the CMIP6 multi-model ensemble. Cryosphere, 14(7), 2495–2514.
Abstract: This paper presents an analysis of observed and simulated historical snow cover extent and snow mass, along with future snow cover projections from models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 6 (CMIP6). Where appropriate, the CMIP6 output is compared to CMIP5 results in order to assess progress (or absence thereof) between successive model generations. An ensemble of six observation-based products is used to produce a new time series of historical Northern Hemisphere snow extent anomalies and trends; a subset of four of these products is used for snow mass. Trends in snow extent over 1981-2018 are negative in all months and exceed – 50 x 10(3) km(2) yr(-1) during November, December, March, and May. Snow mass trends are approximately -5 Gt yr(-1) or more for all months from December to May. Overall, the CMIP6 multi-model ensemble better represents the snow extent climatology over the 1981-2014 period for all months, correcting a low bias in CMIP5. Simulated snow extent and snow mass trends over the 1981-2014 period are stronger in CMIP6 than in CMIP5, although large inter-model spread remains in the simulated trends for both variables. There is a single linear relationship between projected spring snow extent and global surface air temperature (GSAT) changes, which is valid across all CMIP6 Shared Socioeconomic Pathways. This finding suggests that Northern Hemisphere spring snow extent will decrease by about 8 % relative to the 1995-2014 level per degree Celsius of GSAT increase. The sensitivity of snow to temperature forcing largely explains the absence of any climate change pathway dependency, similar to other fast-response components of the cryosphere such as sea ice and near-surface permafrost extent.
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Nanni, U., Gimbert, F., Vincent, C., Graff, D., Walter, F., Piard, L., et al. (2020). Quantification of seasonal and diurnal dynamics of subglacial channels using seismic observations on an Alpine glacier. Cryosphere, 14(5), 1475–1496.
Abstract: Water flowing below glaciers exerts a major control on glacier basal sliding. However, our knowledge of the physics of subglacial hydrology and its link with sliding is limited because of lacking observations. Here we use a 2-year-long dataset made of on-ice-measured seismic and in situ-measured glacier basal sliding speed on Glacier d'Argentiere (French Alps) to investigate the physics of subglacial channels and its potential link with glacier basal sliding. Using dedicated theory and concomitant measurements of water discharge, we quantify temporal changes in channels' hydraulic radius and hydraulic pressure gradient. At seasonal timescales we find that hydraulic radius and hydraulic pressure gradient respectively exhibit a 2- and 6-fold increase from spring to summer, followed by comparable decrease towards autumn. At low discharge during the early and late melt season channels respond to changes in discharge mainly through changes in hydraulic radius, a regime that is consistent with predictions of channels' behaviour at equilibrium. In contrast, at high discharge and high short-term water-supply variability (summertime), channels undergo strong changes in hydraulic pressure gradient, a behaviour that is consistent with channels behaving out of equilibrium. This out-of-equilibrium regime is further supported by observations at the diurnal scale, which prove that channels pressurize in the morning and depressurize in the afternoon. During summer we also observe high and sustained basal sliding speed, which supports that the widespread in-efficient drainage system (cavities) is likely pressurized concomitantly with the channel system. We propose that pressurized channels help sustain high pressure in cavities (and therefore high glacier sliding speed) through an efficient hydraulic connection between the two systems. The present findings provide an essential basis for testing the physics represented in subglacial hydrology and glacier sliding models.
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Nehrbass-Ahles, C., Shin, J., Schmitt, J., Bereiter, B., Joos, F., Schilt, A., et al. (2020). Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions. Science, 369(6506), 1000–+.
Abstract: Pulse-like carbon dioxide release to the atmosphere on centennial time scales has only been identified for the most recent glacial and deglacial periods and is thought to be absent during warmer climate conditions. Here, we present a high-resolution carbon dioxide record from 330,000 to 450,000 years before present, revealing pronounced carbon dioxide jumps (CDJ) under cold and warm climate conditions. CDJ come in two varieties that we attribute to invigoration or weakening of the Atlantic meridional overturning circulation (AMOC) and associated northward and southward shifts of the intertropical convergence zone, respectively. We find that CDJ are pervasive features of the carbon cycle that can occur during interglacial climate conditions if land ice masses are sufficiently extended to be able to disturb the AMOC by freshwater input.
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Nguyen, T., N?Mery, J., Gratiot, N., Garnier, J., Strady, E., Nguyen, D., et al. (2020). Nutrient budgets in the Saigon-Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam). River Research And Applications, 36(6), 974–990.
Abstract: Ho Chi Minh City (HCMC, Vietnam) is one of the fastest growing megacities in the world. In this paper, we attempt to analyse the dynamics of nutrients, suspended sediments, and water discharges in its aquatic systems today and in the future. The work is based on nine sampling sites along the Saigon River and one on the Dongnai River to identify the reference water status upstream from the urban area and the increase in fluxes that occur within the city and its surroundings. For the first time, the calculated fluxes allow drawing up sediment and nutrient budgets at the basin scale and the quantification of total nutrient loading to the estuarine and coastal zones (2012-2016 period). Based on both national Vietnamese and supplementary monitoring programs, we estimated the water, total suspended sediment, and nutrients (Total N, Total P, and dissolved silica: DSi) fluxes at 137 m(3)year(-1), 3,292 x 10(3)tonSS year(-1), 5,323 tonN year(-1), 450 tonP year(-1), and 2,734 tonSi year(-1)for the Saigon River and 1,693 m(3)year(-1), 1,175 x 10(3)tonSS year(-1), 31,030 tonN year(-1), 1,653 tonP year(-1), and 31,138 tonSi year(-1)for the Dongnai River, respectively. Nutrient fluxes provide an indicator of coastal eutrophication potential (indicator of coastal eutrophication potential), using nutrient stoichiometry ratios. Despite an excess of nitrogen and phosphorus over silica, estuarine waters downstream of the megacity are not heavily impacted by HCMC. Finally, we analysed scenarios of future trends (2025-2050) for the nutrient inputs on the basis of expected population growth in HCMC and improvement of wastewater treatment capacity. We observed that without the construction of a large number of additional wastewater treatment plants, the eutrophication problem is likely to worsen. The results are discussed in the context of the wastewater management policy.
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Noncent, D., Strady, E., Nemery, J., Thanh-Nho, N., Denis, H., Mourier, B., et al. (2020). Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City-Vietnam. Data In Brief, 31.
Abstract: Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated. (C) 2020 The Author(s). Published by Elsevier Inc.
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Nord, G., Michielin, Y., Biron, R., Esteves, M., Freche, G., Geay, T., et al. (2020). An autonomous low-power instrument platform for monitoring water and solid discharges in mesoscale rivers. Geoscientific Instrumentation Methods And Data Systems, 9(1), 41–67.
Abstract: We present the development of the River Platform for Monitoring Erosion (RIPLE) designed for monitoring at high temporal frequency (similar to 10 min) of water discharge, solid fluxes (bedload and suspended load) and properties of fine particles (settling velocity) in mesoscale rivers, i.e. which drain mesoscale catchments (approximate to 10-10(3) km(2)). This platform responds to a request to continuously measure these variables in rivers using a single, centralized device, and to do this in the most direct way possible. The platform integrates the following instruments: (i) for water discharge, water level radar, and surface velocity radar, digital cameras and an echo sounder; (ii) for fine sediment load, turbidimeters and automatic samplers including the SCAF (a sediment settling velocity characterization device); (iii) for bedload, a hydrophone; and (iv) for water quality, a conductivity probe and water sampling. As far as water discharge monitoring is concerned, priority has been given to non-intrusive instruments to improve the robustness of the system. All the instruments are driven by a data logger (Campbell (R) CR6), which locally stores the data and then uploads them to a remote server every hour during the day using a 3G modem. SMS (Short Message Service) alerts can be sent depending on scheduled conditions (e.g. low battery voltage, water level threshold, all samples of the automatic sampler collected). The platform has been designed to be as autonomous as possible: it is powered by a battery that is supplied by a solar panel. Limiting the power consumption of the platform was one of the main technical challenges because of the quantity of instruments integrated. A simple 100W solar panel is sufficient to power the entire platform, even during winter or low insulation conditions. A user-friendly interface has been developed, enabling to visualize the data collected by the platform from an internet connection. It is also possible to remotely configure the platform within this interface, e.g. to modify water sampling thresholds or alert thresholds. Finally, the platform is relatively easy to move from one site to another, because its installation requires little civil engineering. To date, RIPLE has been tested on two rivers of the Alps in France: the Romanche river in Bourg d'Oisans from September 2016 to July 2018 and the Galabre river in La Robine sur Galabre since October 2018, demonstrating the proper functioning of the platform.
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Nour, A., Vallet-Coulomb, C., Bouchez, C., Ginot, P., Doumnang, J., Sylvestre, F., et al. (2020). Geochemistry of the Lake Chad Tributaries Under Strongly Varying Hydro-climatic Conditions. Aquatic Geochemistry, .
Abstract: The Lake Chad Basin (LCB) is one of the main endorheic basins in the world and has undergone large-level and surface variations during the last decades, particularly during the Sahelian dry period in the 1970s and the 1980s. The Chari-Logone River system covers 25% of the LCB but accounts for up to 82% of the Lake Chad water supply. The aim of this study is to investigate the dissolved phase transported by the Chari-Logone system, in order (1) to elucidate the origin and the behavior of major elements and the weathering processes in the watershed; (2) to estimate the total dissolved flux, its variability over the last decades and the driving factors. To do so, samples were collected monthly between January 2013 and November 2016 at three representative sites of the basin: in the Chari River in “Chagoua,” in the Logone River in “Ngueli” just before the confluence of both rivers, and at a downstream site in “Douguia,” 30 km after the confluence. Concentrations in major elements displayed significant seasonal variations in the Chari and Logone waters. At the seasonal time scale, the comparison between the concentrations of chemical elements and the flow rates showed a hysteresis loop. This hysteresis behavior corresponds to a variable contribution over time of two water bodies, fast surface water, and slow groundwater, the latter carrying higher concentrations and Ca/Na ratio, which may result from the contribution of pedogenic carbonate weathering to the dominant signature of silicate weathering. At the annual time scale, similar average concentrations are observed in the Chari and Logone Rivers, despite contrasted annual runoff. In addition, an interannual stability of ionic concentrations was observed in the Chari-Logone River during the flood regime, both during the years covered by our monitoring (2013-2016) and during the pre-drought period (1969, 1972 and 1973). This situation corresponds to a chemostatic behavior, where the annual river discharge is the main factor controlling the interannual variation of chemical fluxes.
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Nour, A., Vallet-Coulomb, C., Bouchez, C., Ginot, P., Doumnang, J., Sylvestre, F., et al. (2020). Geochemistry of the Lake Chad Tributaries Under Strongly Varying Hydro-climatic Conditions. Aquatic Geochemistry, 26(1), 3–29.
Abstract: The Lake Chad Basin (LCB) is one of the main endorheic basins in the world and has undergone large-level and surface variations during the last decades, particularly during the Sahelian dry period in the 1970s and the 1980s. The Chari-Logone River system covers 25% of the LCB but accounts for up to 82% of the Lake Chad water supply. The aim of this study is to investigate the dissolved phase transported by the Chari-Logone system, in order (1) to elucidate the origin and the behavior of major elements and the weathering processes in the watershed; (2) to estimate the total dissolved flux, its variability over the last decades and the driving factors. To do so, samples were collected monthly between January 2013 and November 2016 at three representative sites of the basin: in the Chari River in “Chagoua,” in the Logone River in “Ngueli” just before the confluence of both rivers, and at a downstream site in “Douguia,” 30 km after the confluence. Concentrations in major elements displayed significant seasonal variations in the Chari and Logone waters. At the seasonal time scale, the comparison between the concentrations of chemical elements and the flow rates showed a hysteresis loop. This hysteresis behavior corresponds to a variable contribution over time of two water bodies, fast surface water, and slow groundwater, the latter carrying higher concentrations and Ca/Na ratio, which may result from the contribution of pedogenic carbonate weathering to the dominant signature of silicate weathering. At the annual time scale, similar average concentrations are observed in the Chari and Logone Rivers, despite contrasted annual runoff. In addition, an interannual stability of ionic concentrations was observed in the Chari-Logone River during the flood regime, both during the years covered by our monitoring (2013-2016) and during the pre-drought period (1969, 1972 and 1973). This situation corresponds to a chemostatic behavior, where the annual river discharge is the main factor controlling the interannual variation of chemical fluxes.
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Nowicki, S., Goelzer, H., Seroussi, H., Payne, A., Lipscomb, W., Abe-Ouchi, A., et al. (2020). Experimental protocol for sea level projections from ISMIP6 stand-alone ice sheet models. Cryosphere, 14(7), 2331–2368.
Abstract: Projection of the contribution of ice sheets to sea level change as part of the Coupled Model Intercomparison Project Phase 6 (CMIP6) takes the form of simulations from coupled ice sheet-climate models and stand-alone ice sheet models, overseen by the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). This paper describes the experimental setup for process-based sea level change projections to be performed with stand-alone Greenland and Antarctic ice sheet models in the context of ISMIP6. The ISMIP6 protocol relies on a suite of polar atmospheric and oceanic CMIP-based forcing for ice sheet models, in order to explore the uncertainty in projected sea level change due to future emissions scenarios, CMIP models, ice sheet models, and parameterizations for ice-ocean interactions. We describe here the approach taken for defining the suite of ISMIP6 stand-alone ice sheet simulations, document the experimental framework and implementation, and present an overview of the ISMIP6 forcing to be used by participating ice sheet modeling groups.
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Osmont, D., Brugger, S., Gilgen, A., Weber, H., Sigl, M., Modini, R., et al. (2020). Tracing devastating fires in Portugal to a snow archive in the Swiss Alps: a case study. Cryosphere, 14(11), 3731–3745.
Abstract: Recent large wildfires, such as those in Portugal in 2017, have devastating impacts on societies, economy, ecosystems and environments. However, wildfires are a natural phenomenon, which has been exacerbated by land use during the past millennia. Ice cores are one of the archives preserving information on fire occurrences over these timescales. A difficulty is that emission sensitivity of ice cores is often unknown, which constitutes a source of uncertainty in the interpretation of such archives. Information from specific and well-documented case studies is therefore useful to better understand the spatial representation of ice-core burning records. The wildfires near Pedrogao Grande in central Portugal in 2017 provided a test bed to link a fire event to its footprint left in a high-alpine snowpack considered a surrogate for high-alpine ice-core sites. Here, we (1) analysed black carbon (BC) and microscopic charcoal particles deposited in the snowpack close to the high-alpine research station Jungfraujoch in the Swiss Alps; (2) calculated backward trajectories based on ERA-Interim reanalysis data and simulated the transport of these carbonaceous particles using a global aerosol-climate model; and (3) analysed the fire spread, its spatial and temporal extent, and its intensity with remote-sensing (e.g. MODIS) Active Fire and Burned Area products. According to modelled emissions of the FINN v1.6 database, the fire emitted a total amount of 203.5 t BC from a total burned area of 501 km(2) as observed on the basis of satellite fire products. Backward trajectories unambiguously linked a peak of atmospheric-equivalent BC observed at the Jungfraujoch research station on 22 June – with elevated levels until 25 June – with the highly intensive fires in Portugal. The atmospheric signal is in correspondence with an outstanding peak in microscopic charcoal observed in the snow layer, depositing nearly as many charcoal particles as during an average year in other ice archives. In contrast to charcoal, the amount of atmospheric BC deposited during the fire episode was minor due to a lack of precipitation. Simulations with a global aerosol-climate model suggest that the observed microscopic charcoal particles originated from the fires in Portugal and that their contribution to the BC signal in snow was negligible. Our study revealed that microscopic charcoal can be transported over long distances (1500 km) and that snow and ice archives are much more sensitive to distant events than sedimentary archives, for which the signal is dominated by local fires. The findings are important for future ice-core studies as they document that, for BC as a fire tracer, the signal preservation depends on precipitation. Single events, like this example, might not be preserved due to unfavourable meteorological conditions.
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Osterwalder, S., Eugster, W., Feigenwinter, I., & Jiskra, M. (2020). Eddy covariance flux measurements of gaseous elemental mercury over a grassland. Atmospheric Measurement Techniques, 13(4), 2057–2074.
Abstract: Direct measurements of the net ecosystem exchange (NEE) of gaseous elemental mercury (Hg-0) are important to improve our understanding of global Hg cycling and, ultimately, human and wildlife Hg exposure. The lack of long-term, ecosystem-scale measurements causes large uncertainties in Hg-0 flux estimates. It currently remains unclear whether terrestrial ecosystems are net sinks or sources of atmospheric Hg-0. Here, we show a detailed validation of direct Hg-0 flux measurements based on the eddy covariance technique (Eddy Mercury) using a Lumex RA-915 AM mercury monitor. The flux detection limit derived from a zero-flux experiment in the laboratory was 0.22 ng m(-2) h(-1) (maximum) with a 50% cutoff at 0.074 ng m(-2) h(-1). We present eddy covariance NEE measurements of Hg-0 over a low-Hg soil (41-75 ng Hg g(-1) in the topsoil, referring to a depth of 0-10 cm), conducted in summer 2018 at a managed grassland at the Swiss FluxNet site in Chamau, Switzerland (CH-Cha). The statistical estimate of the Hg-0 flux detection limit under outdoor conditions at the site was 5.9 ng m(-2) h(-1') (50% cutoff). We measured a net summertime emission over a period of 34 d with a median Hg-0 flux of 2.5 ng m(-2) h(-1) (with a -0.6 to 7.4 ng m(-2) h(-1) range between the 25th and 75th percentiles). We observed a distinct diel cycle with higher median daytime fluxes (8.4 ng m(-2) h(-1)) than night-time fluxes (1.0 ng m(-2) h(-1)). Drought stress during the measurement campaign in summer 2018 induced partial stomata closure of vegetation. Partial stomata closure led to a midday depression in CO2 uptake, which did not recover during the afternoon. The median CO2 flux was only 24% of the median CO2 flux measured during the same period in the previous year (2017). We suggest that partial stomata closure also dampened Hg-0 uptake by vegetation, resulting in a NEE of Hg-0 that was dominated by soil emission. Finally, we provide suggestions to further improve the precision and handling of the “Eddy Mercury” system in order to assure its suitability for long-term NEE measurements of Hg-0 over natural background surfaces with low soil Hg concentrations (< 100 ng g(-1)). With these improvements, Eddy Mercury has the potential to be integrated into global networks of micrometeorological tower sites (FluxNet) and to provide the long-term observations on terrestrial atmosphere Hg-0 exchange necessary to validate regional and global mercury models.
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Pabon-Caicedo, J., Arias, P., Carril, A., Espinoza, J., Borrel, L., Goubanova, K., et al. (2020). Observed and Projected Hydroclimate Changes in the Andes. Frontiers In Earth Science, 8.
Abstract: The Andes is the most biodiverse region across the globe. In addition, some of the largest urban areas in South America are located within this region. Therefore, ecosystems and human population are affected by hydroclimate changes reported at global, regional and local scales. This paper summarizes progress of knowledge about long-term trends observed during the last two millennia over the entire Andes, with more detail for the period since the second half of the 20th century, and presents a synthesis of climate change projections by the end of the 21st century. In particular, this paper focuses on temperature, precipitation and surface runoff in the Andes. Changes in the Andean cryosphere are not included here since this particular topic is discussed in other paper in this Frontiers special issue, and elsewhere (e.g. IPCC,2019b). While previous works have reviewed the hydroclimate of South America and particular sectors (i.e., Amazon and La Plata basins, the Altiplano, Northern South America, etc.) this review includes for the first time the entire Andes region, considering all latitudinal ranges: tropical (North of 27 degrees S), subtropical (27 degrees S-37 degrees S) and extratropical (South of 37 degrees S). This paper provides a comprehensive view of past and recent changes, as well as available climate change projections, over the entire Andean range. From this review, the main knowledge gaps are highlighted and urgent research necessities in order to provide more mechanistic understanding of hydroclimate changes in the Andes and more confident projections of its possible changes in association with global climate change.
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Padrón, R., Gudmundsson, L., Decharme, B., Ducharne, A., Lawrence, D., Mao, J., et al. (2020). Observed changes in dry-season water availability attributed to human-induced climate change. Nature Geoscience, 13(7), 477–+.
Abstract: Regional changes in dry-season water availability over recent decades can be attributed to human-induced climate change, according to analyses of global reconstructions. Human-induced climate change impacts the hydrological cycle and thus the availability of water resources. However, previous assessments of observed warming-induced changes in dryness have not excluded natural climate variability and show conflicting results due to uncertainties in our understanding of the response of evapotranspiration. Here we employ data-driven and land-surface models to produce observation-based global reconstructions of water availability from 1902 to 2014, a period during which our planet experienced a global warming of approximately 1 degrees C. Our analysis reveals a spatial pattern of changes in average water availability during the driest month of the year over the past three decades compared with the first half of the twentieth century, with some regions experiencing increased and some decreased water availability. The global pattern is consistent with climate model estimates that account for anthropogenic effects, and it is not expected from natural climate variability, supporting human-induced climate change as the cause. There is regional evidence of drier dry seasons predominantly in extratropical latitudes and including Europe, western North America, northern Asia, southern South America, Australia and eastern Africa. We also find that the intensification of the dry season is generally a consequence of increasing evapotranspiration rather than decreasing precipitation.
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Pastorello, G., Trotta, C., Canfora, E., Chu, H., Christianson, D., Cheah, Y., et al. (2020). The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data. Scientific Data, 7(1).
Abstract: The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.
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Paul, F., Rastner, P., Azzoni, R., Diolaiuti, G., Fugazza, D., Le Bris, R., et al. (2020). Glacier shrinkage in the Alps continues unabated as revealed by a new glacier inventory from Sentinel-2. Earth System Science Data, 12(3), 1805–1821.
Abstract: The ongoing glacier shrinkage in the Alps requires frequent updates of glacier outlines to provide an accurate database for monitoring, modelling purposes (e.g. determination of run-off, mass balance, or future glacier extent), and other applications. With the launch of the first Sentinel-2 (S2) satellite in 2015, it became possible to create a consistent, Alpine-wide glacier inventory with an unprecedented spatial resolution of 10 m. The first S2 images from August 2015 already provided excellent mapping conditions for most glacierized regions in the Alps and were used as a base for the compilation of a new Alpine-wide glacier inventory in a collaborative team effort. In all countries, glacier outlines from the latest national inventories have been used as a guide to compile an update consistent with the respective previous interpretation. The automated mapping of clean glacier ice was straightforward using the band ratio method, but the numerous debris-covered glaciers required intense manual editing. Cloud cover over many glaciers in Italy required also including S2 scenes from 2016. The outline uncertainty was determined with digitizing of 14 glaciers several times by all participants. Topographic information for all glaciers was obtained from the ALOS AW3D30 digital elevation model (DEM). Overall, we derived a total glacier area of 1806 +/- 60 km(2) when considering 4395 glaciers > 0.01 km(2). This is 14% (-1.2% a(-1)) less than the 2100 km(2) derived from Landsat in 2003 and indicates an unabated continuation of glacier shrinkage in the Alps since the mid-1980s. It is a lower-bound estimate, as due to the higher spatial resolution of S2 many small glaciers were additionally mapped or increased in size compared to 2003. Median elevations peak around 3000ma.s.l., with a high variability that depends on location and aspect. The uncertainty assessment revealed locally strong differences in interpretation of debris-covered glaciers, resulting in limitations for change assessment when using glacier extents digitized by different analysts. The inventory is available at https.//doi.org/10.1594/PANGAEA.909133 (Paul et al., 2019).
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Pellarin, T., Roman-Cascon, C., Baron, C., Bindlish, R., Brocca, L., Camberlin, P., et al. (2020). The Precipitation Inferred from Soil Moisture (PrISM) Near Real-Time Rainfall Product: Evaluation and Comparison. Remote Sensing, 12(3).
Abstract: Near real-time precipitation is essential to many applications. In Africa, the lack of dense rain-gauge networks and ground weather radars makes the use of satellite precipitation products unavoidable. Despite major progresses in estimating precipitation rate from remote sensing measurements over the past decades, satellite precipitation products still suffer from quantitative uncertainties and biases compared to ground data. Consequently, almost all precipitation products are provided in two modes: a real-time mode (also called early-run or raw product) and a corrected mode (also called final-run, adjusted or post-processed product) in which ground precipitation measurements are integrated in algorithms to correct for bias, generally at a monthly timescale. This paper describes a new methodology to provide a near-real-time precipitation product based on satellite precipitation and soil moisture measurements. Recent studies have shown that soil moisture intrinsically contains information on past precipitation and can be used to correct precipitation uncertainties. The PrISM (Precipitation inferred from Soil Moisture) methodology is presented and its performance is assessed for five in situ rainfall measurement networks located in Africa in semi-arid to wet areas: Niger, Benin, Burkina Faso, Central Africa, and East Africa. Results show that the use of SMOS (Soil Moisture and Ocean Salinity) satellite soil moisture measurements in the PrISM algorithm most often improves the real-time satellite precipitation products, and provides results comparable to existing adjusted products, such as TRMM (Tropical Rainfall Measuring Mission), GPCC (Global Precipitation Climatology Centre) and IMERG (Integrated Multi-satellitE Retrievals for GPM), which are available a few weeks or months after their detection.
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Perneger, T., Kevorkian, A., Grenet, T., Gallee, H., & Gayet-Ageron, A. (2020). Alternative graphical displays for the monitoring of epidemic outbreaks, with application to COVID-19 mortality. Bmc Medical Research Methodology, 20(1), 248 (265).
Abstract: Background Classic epidemic curves – counts of daily events or cumulative events over time -emphasise temporal changes in the growth or size of epidemic outbreaks. Like any graph, these curves have limitations: they are impractical for comparisons of large and small outbreaks or of asynchronous outbreaks, and they do not display the relative growth rate of the epidemic. Our aim was to propose two additional graphical displays for the monitoring of epidemic outbreaks that overcome these limitations. Methods The first graph shows the growth of the epidemic as a function of its size; specifically, the logarithm of new cases on a given day, N(t), is plotted against the logarithm of cumulative cases C(t). Logarithm transformations facilitate comparisons of outbreaks of different sizes, and the lack of a time scale overcomes the need to establish a starting time for each outbreak. Notably, on this graph, exponential growth corresponds to a straight line with a slope equal to one. The second graph represents the logarithm of the relative rate of growth of the epidemic over time; specifically, log(10)(N(t)/C(t-1)) is plotted against time (t) since the 25th event. We applied these methods to daily death counts attributed to COVID-19 in selected countries, reported up to June 5, 2020. Results In most countries, the log(N) over log(C) plots showed initially a near-linear increase in COVID-19 deaths, followed by a sharp downturn. They enabled comparisons of small and large outbreaks (e.g., Switzerland vs UK), and identified outbreaks that were still growing at near-exponential rates (e.g., Brazil or India). The plots of log(10)(N(t)/C(t-1)) over time showed a near-linear decrease (on a log scale) of the relative growth rate of most COVID-19 epidemics, and identified countries in which this decrease failed to set in in the early weeks (e.g., USA) or abated late in the outbreak (e.g., Portugal or Russia). Conclusions The plot of log(N) over log(C) displays simultaneously the growth and size of an epidemic, and allows easy identification of exponential growth. The plot of the logarithm of the relative growth rate over time highlights an essential parameter of epidemic outbreaks.
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Perneger, T., Kevorkian, A., Grenet, T., Gallee, H., & Gayet-Ageron, A. (2020). Alternative graphical displays for the monitoring of epidemic outbreaks, with application to COVID-19 mortality (vol 20, 248, 2020). Bmc Medical Research Methodology, 20(1).
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Perry, L., Matthews, T., Guy, H., Koch, I., Khadka, A., Elmore, A., et al. (2020). Precipitation Characteristics and Moisture Source Regions on Mt. Everest in the Khumbu, Nepal. One Earth, 3(5), 594–607.
Abstract: Precipitation is critical to the water towers of the Hindu Kush-Himalaya-Karakoram region, exerting an important control on glacier mass balance and the water resources for 1.65 billion people. Given that hydroclimatic extremes and water stress have emerged as key hazards in the context of climate change, Nepal's Khumbu region overlaps key vulnerabilities. Here, we investigate the region's precipitation characteristics and moisture sources through analysis of data from a new high-altitude network of automatic weather stations, which allows for a more complete understanding of the climatological precipitation data that are critical information for local communities in the Khumbu region, visitors, and downstream populations. Our findings demonstrate that the northern Bay of Bengal is potentially an important moisture source during the monsoon period (June to August) and that westerly trajectories over land predominate for precipitation events during the postmonsoon, winter, and pre-monsoon seasons.
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Perry, L., Yuter, S., Matthews, T., Wagnon, P., Khadka, A., Aryal, D., et al. (2020). Direct observations of a Mt Everest snowstorm from the world's highest surface-based radar observations. Weather, , 3854.
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Petaja, T., Duplissy, E., Tabakova, K., Schmale, J., Altstadter, B., Ancellet, G., et al. (2020). Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results. Atmospheric Chemistry And Physics, 20(14), 8551–8592.
Abstract: The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.
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Petit, J., & Raynaud, D. (2020). Forty years of ice-core records of CO2. Nature, 579(7800), 505–506.
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Peyaud, V., Bouchayer, C., Gagliardini, O., Vincent, C., Gillet-Chaulet, F., Six, D., et al. (2020). Numerical modeling of the dynamics of the Mer de Glace glacier, French Alps: comparison with past observations and forecasting of near-future evolution. Cryosphere, 14(11), 3979–3994.
Abstract: Alpine glaciers are shrinking and rapidly loosing mass in a warming climate. Glacier modeling is required to assess the future consequences of these retreats on water resources, the hydropower industry and risk management. However, the performance of such ice flow modeling is generally difficult to evaluate because of the lack of long-term glaciological observations. Here, we assess the performance of the Elmer/Ice full Stokes ice flow model using the long dataset of mass balance, thickness change, ice flow velocity and snout fluctuation measurements obtained between 1979 and 2015 on the Mer de Glace glacier, France. Ice flow modeling results are compared in detail to comprehensive glaciological observations over 4 decades including both a period of glacier expansion preceding a long period of decay. To our knowledge, a comparison to data at this detail is unprecedented. We found that the model accurately reconstructs the velocity, elevation and length variations of this glacier despite some discrepancies that remain unexplained. The calibrated and validated model was then applied to simulate the future evolution of Mer de Glace from 2015 to 2050 using 26 different climate scenarios. Depending on the climate scenarios, the largest glacier in France, with a length of 20 km, could retreat by 2 to 6 km over the next 3 decades.
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Picard, G., Dumont, M., Lamare, M., Tuzet, F., Larue, F., Pirazzini, R., et al. (2020). Spectral albedo measurements over snow-covered slopes: theory and slope effect corrections. Cryosphere, 14(5), 1497–1517.
Abstract: Surface albedo is an essential variable to determine the Earth's surface energy budget, in particular for snow-covered areas where it is involved in one of the most powerful positive feedback loops of the climate system. In situ measurements of broadband and spectral albedo are therefore common However they are subject to several artefacts. Here we investigate the sensitivity of spectral albedo measurements to surface slope, and we propose simple correction algorithms to retrieve the intrinsic albedo of a slope from measurements, as if it were flat. For this, we first derive the analytical equations relating albedo measured on a slope to intrinsic direct and diffuse albedo, the apportionment between diffuse and direct incoming radiation, and slope inclination and aspect. The theory accounts for two main slope effects. First, the slope affects the proportion of solar radiation intercepted by the surface relative to that intercepted by the upward-looking, horizontal, sensor. Second, the upward- and downward-looking sensors receive reduced radiation from the sky and the surface respectively and increased radiation from neighbouring terrain. Using this theory, we show that (i) slope has a significant effect on albedo (over 0.01) from as little as a approximate to 1 degrees inclination, causing distortions of the albedo spectral shape; (ii) the first-order slope effect is sufficient to fully explain measured albedo up to approximate to 15 degrees, which we designate “small-slope approximation”; and (iii) for larger slopes, the theory depends on the neighbouring slope geometry and land cover, leading to much more complex equations. Next, we derive four correction methods from the small-slope approximation, to be used depending on whether (1) the slope inclination and orientation are known or not, (2) the snow surface is free of impurities or dirty, and (3) a single or a time series of albedo measurements is available. The methods applied to observations taken in the Alps on terrain with up to nearly 20 degrees slopes prove the ability to recover intrinsic albedo with a typical accuracy of 0.03 or better. From this study, we derive two main recommendations for future field campaigns: first, sloping terrain requires more attention because it reduces the measurement accuracy of albedo even for almost invisible slopes (1-2 degrees). Second, while the correction of the slope effect is possible, it requires additional information such as the spectral diffuse and direction partitioning and if possible the actual slope inclination and aspect, especially when the absence of impurities can not be assumed.
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Pomerleau, P., Royer, A., Langlois, A., Cliche, P., Courtemanche, B., Madore, J., et al. (2020). Low Cost and Compact FMCW 24 GHz Radar Applications for Snowpack and Ice Thickness Measurements. Sensors, 20(14).
Abstract: Monitoring the evolution of snow on the ground and lake ice-two of the most important components of the changing northern environment-is essential. In this paper, we describe a lightweight, compact and autonomous 24 GHz frequency-modulated continuous-wave (FMCW) radar system for freshwater ice thickness and snow mass (snow water equivalent, SWE) measurements. Although FMCW radars have a long-established history, the novelty of this research lies in that we take advantage the availability of a new generation of low cost and low power requirement units that facilitates the monitoring of snow and ice at remote locations. Test performance (accuracy and limitations) is presented for five different applications, all using an automatic operating mode with improved signal processing: (1) In situ lake ice thickness measurements giving 2 cm accuracy up to approximate to 1 m ice thickness and a radar resolution of 4 cm; (2) remotely piloted aircraft-based lake ice thickness from low-altitude flight at 5 m; (3) in situ dry SWE measurements based on known snow depth, giving 13% accuracy (RMSE 20%) over boreal forest, subarctic taiga and Arctic tundra, with a measurement capability of up to 3 m in snowpack thickness; (4) continuous monitoring of surface snow density under particular Antarctic conditions; (5) continuous SWE monitoring through the winter with a synchronized and collocated snow depth sensor (ultrasonic or LiDAR sensor), giving 13.5% bias and 25 mm root mean square difference (RMSD) (10%) for dry snow. The need for detection processing for wet snow, which strongly absorbs radar signals, is discussed. An appendix provides 24 GHz simulated effective refractive index and penetration depth as a function of a wide range of density, temperature and wetness for ice and snow.
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Poveda, G., Espinoza, J., Zuluaga, M., Solman, S., Garreaud, R., & Van Oevelen, P. (2020). High Impact Weather Events in the Andes. Frontiers In Earth Science, 8.
Abstract: Owing to the extraordinary latitudinal extent, a strong orographic variability with very high mountain tops, and the presence of deep valleys and steep slopes, the Andes and the population of the region are highly prone and vulnerable to the impacts of a large suite of extreme weather events. Here we provide a review of the most salient events in terms of losses of human and animal lives, economic and monetary losses in costs and damages, and social disruption, namely: (1) extreme precipitation events and related processes (Mesoscale Convective Systems, lightning), (2) cold spells, frosts, and high winds, (3) the impacts of ENSO on extreme hydro-meteorological events, (4) floods, (5) landslides, mudslides, avalanches, and (6) droughts, heat waves and fires. For our purposes, we focus this review on three distinctive regions along the Andes: Northern tropical (north of 8 degrees S), Southern tropical (8 degrees S-27 degrees S) and Extratropical Andes (south of 27 degrees S). Research gaps are also identified and discussed at the end of this review. It is very likely that climate change will increase the vulnerability of the millions of inhabitants of the Andes, impacting their livelihoods and the sustainable development of the region into the twenty first century amidst urbanization, deforestation, air, soil and water pollution, and land use changes.
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Qi, L., Vogel, A., Esmaeilirad, S., Cao, L., Zheng, J., Jaffrezo, J., et al. (2020). A 1-year characterization of organic aerosol composition and sources using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Atmospheric Chemistry And Physics, 20(13), 7875–7893.
Abstract: The aerosol mass spectrometer (AMS), combined with statistical methods such as positive matrix factorization (PMF), has greatly advanced the quantification of primary organic aerosol (POA) sources and total secondary organic aerosol (SOA) mass. However, the use of thermal vaporization and electron ionization yields extensive thermal decomposition and ionization-induced fragmentation, which limit chemical information needed for SOA source apportionment. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) provides mass spectra of the organic aerosol fraction with a linear response to mass and no thermal decomposition or ionization-induced fragmentation. However, the costs and operational requirements of online instruments make their use impractical for long-term or spatially dense monitoring applications. This challenge was overcome for AMS measurements by measuring re-nebulized water extracts from ambient filter samples. Here, we apply the same strategy for EESI-TOF measurements of 1 year of 24 h filter samples collected approximately every fourth day throughout 2013 at an urban site. The nebulized water extracts were measured simultaneously with an AMS. The application of positive matrix factorization (PMF) to EESI-TOF spectra resolved seven factors, which describe water-soluble OA: less and more aged biomass burning aerosol (LABB(EESI) and MABB(EESI), respectively), cigarette-smoke-related organic aerosol, primary biological organic aerosol, biogenic secondary organic aerosol, and a summer mixed oxygenated organic aerosol factor. Seasonal trends and relative contributions of the EESI-TOF OA sources were compared with AMS source apportionment factors, measured water-soluble ions, cellulose, and meteorological data. Cluster analysis was utilized to identify key factor-specific ions based on PMF. Both LABB and MABB contribute strongly during winter. LABB is distinguished by very high signals from C6H10O5 (levoglucosan and isomers) and C8H12O6, whereas MABB is characterized by a large number of CxHyOz and CxHyOzN species of two distinct populations: one with low H : C and high O : C and the other with high H : C and low O : C. Two oxygenated summertime SOA sources were attributed to terpene-derived biogenic SOA, a major summertime aerosol source in central Europe. Furthermore, a primary biological organic aerosol factor was identified, which was dominated by plant-derived fatty acids and correlated with free cellulose. The cigarette-smoke-related factor contained a high contribution of nicotine and high abundance of organic nitrate ions with low m/z.
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Rapuc, W., Jacq, K., Develle, A., Sabatier, P., Fanget, B., Perrette, Y., et al. (2020). XRF and hyperspectral analyses as an automatic way to detect flood events in sediment cores. Sedimentary Geology, 409.
Abstract: Long-term changes in flood activity have often been reconstructed to understand their relationships to climate changes. This requires identification of flood layers according to certain characteristics (e.g., texture, geochemical composition, grain-size) and then to count them using naked-eye observation. This method is, however, time-consuming, and intrinsically characterized by a low resolution that may lead to bias and misidentification. To overcome this limitation, high-resolution analytical approaches can be used, such as X-ray fluorescence spectroscopy (XRF), X-ray computed tomography, or hyperspectral imaging (HSI). When coupled with discriminant algorithms, HSI allows for automatic identification of event layers. Here, we propose a new method of flood layers identification and counting based on the combination of both HSI and XRF core scanner analyses, applied to a Lake Bourget (French Alps) sediment sequence. We use a hyperspectral sensor from the short wave-infrared spectral range to create a discrimination model between event layers and continuous sedimentation. This first step allows the estimation of a classification map, with a prediction accuracy of 0.96, and then the automatic reconstruction of a reliable chronicle of event layers (induding their occurrence and deposit thicknesses). XRF signals are then used to discriminate flood layers among all identified event layers based on site-specific geochemical elements (in the case of Lake Bourget: Mn and Ti). This results in an automatically generated flood chronide. Changes in flood occurrence and event thickness through time reconstructed from the automatically generated floods chronicle are in good agreement with the naked-eye-generated chronicle. In detail, differences rely on a larger number of detected flood events (i.e., increase of 9% of the number of layers detected) and a more precise layer thickness estimation, thanks to a higher resolution. Therefore, the developed methodology opens a promising avenue to increase both the efficiency (time-saving) and robustness ( higher accuracy) of paleoflood reconstructions from lake sediments. Also, this methodology can be applied to identify any specific layers (e.g., varve, tephra, mass-movement turbidite, tsunami) and, thereby, it has a direct implication in paleolimnology. paleoflood hydrology and paleoseismology from sediment archives. (C) 2020 Elsevier B.V. All rights reserved.
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Rauly, D., Vindret, M., Chamberod, E., Martins, J., & Xavier, P. (2020). Distribution of AC Electric Field-Induced Transmembrane Voltage in Escherichia coli Cell Wall Layers. Bioelectromagnetics, 41(4), 279–288.
Abstract: On the basis of Gram-negative bacterium Escherichia coli models previously published in the literature, the transmembrane voltage induced by the application of an alternating current (AC) electric field on a bacterial suspension is calculated using COMSOL Multiphysics software, in the range 1-20 MHz, for longitudinal and transverse field orientations. The voltages developed on each of the three layers of the cell wall are then calculated using an electrical equivalent circuit. This study shows that the overall voltage on the cell wall, whose order of magnitude is a few tens of μV, is mainly distributed on inner and outer layers, while a near-zero voltage is found on the periplasm, due to its much higher electrical conductivity compared with the other layers. Although the outer membrane electrical conductivity taken in the model is a thousand times higher than that of the inner membrane, the voltage there is about half of that on the inner membrane, due to capacitive effects. It follows that the expression of protein complexes anchored in the inner membrane could potentially be disrupted, inducing in particular a possible perturbation of biological processes related to cellular respiration and proton cycle, and leading to growth inhibition as a consequence. Protein complexes anchored in the outer membrane or constituting a bridge between the three layers of the cell wall, such as some porins, may also undergo the same action, which would add another growth inhibition factor, as a result of deficiency in porin filtration function when the external environment contains biocides. Bioelectromagnetics. 2020;41:279-288 (c) 2020 Bioelectromagnetics Society.
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Raynaud, D., Hingray, B., Evin, G., Favre, A., & Chardon, J. (2020). Assessment of meteorological extremes using a synoptic weather generator and a downscaling model based on analogues. Hydrology And Earth System Sciences, 24(9), 4339–4352.
Abstract: Natural risk studies such as flood risk assessments require long series of weather variables. As an alternative to observed series, which have a limited length, these data can be provided by weather generators. Among the large variety of existing ones, resampling methods based on analogues have the advantage of guaranteeing the physical consistency between local weather variables at each time step. However, they cannot generate values of predictands exceeding the range of observed values. Moreover, the length of the simulated series is typically limited to the length of the synoptic meteorological records used to characterize the large-scale atmospheric configuration of the generation day. To overcome these limitations, the stochastic weather generator proposed in this study combines two sampling approaches based on atmospheric analogues: (1) a synoptic weather generator in a first step, which recombines days of the 20th century to generate a 1000-year sequence of new atmospheric trajectories, and (2) a stochastic downscaling model in a second step applied to these atmospheric trajectories, in order to simulate long time series of daily regional precipitation and temperature. The method is applied to daily time series of mean areal precipitation and temperature in Switzerland. It is shown that the climatological characteristics of observed precipitation and temperature are adequately reproduced. It also improves the reproduction of extreme precipitation values, overcoming previous limitations of standard analogue-based weather generators.
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Rees, W., Golubeva, E., Tutubalina, O., Zimin, M., & Derkacheva, A. (2020). Relation between leaf area index and NDVI for subarctic deciduous vegetation. International Journal Of Remote Sensing, 41(22), 8573–8589.
Abstract: We consider the relationship between leaf area index (LAI) and normalized difference vegetation index (NDVI) for green-leaf vegetation from a subarctic study site, specifically to test whether relationships optimized for lower-latitude vegetation can be assumed to hold at higher latitudes. We focus attention particularly on dwarf-shrub vegetation, which has received little previous investigation. We have collected hyperspectral measurements of the optical properties (reflectance and absorptance) of single leaves from dwarf shrub and tree species common to northern European Russia, and have developed a simple physical model of the properties of assemblages ('leaf stacks') of these leaves. The model is shown to provide a satisfactory explanation of the effect of varying the number of leaves in a stack on its NDVI, and can be easily adapted to make simple measurements using relatively inexpensive equipment. Our results show that the LAI-NDVI relationship for a vegetation canopy will saturate (approach within 10% of its limiting value) when the LAI reaches a value of around 2 to 3. Values this low are not uncommon in subarctic vegetation. It is also shown that dwarf shrub vegetation may show lower NDVI than trees for the same LAI.
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Revuelto, J., Billecocq, P., Tuzet, F., Cluzet, B., Lamare, M., Larue, F., et al. (2020). Random forests as a tool to understand the snow depth distribution and its evolution in mountain areas. Hydrological Processes, .
Abstract: The small scale distribution of the snowpack in mountain areas is highly heterogeneous, and is mainly controlled by the interactions between the atmosphere and local topography. However, the influence of different terrain features in controlling variations in the snow distribution depends on the characteristics of the study area. As this leads to uncertainties in high spatial resolution snowpack simulations, a deeper understanding of the role of terrain features on the small scale distribution of snow depth is required. This study applied random forest algorithms to investigate the temporal evolution of snow depth in complex alpine terrain using as predictors various topographical variables and in situ snow depth observations at a single location. The high spatial resolution (1 m x 1 m) snow depth distribution database used in training and evaluating the random forests was derived from terrestrial laser scanner (TLS) devices at three study sites, in the French Alps (2 sites) and the Spanish Pyrenees (1 site). The results show the major importance of two topographic variables, the topographic position index and the maximum upwind slope parameter. For these variables the search distances and directions depended on the characteristics of each site and the TLS acquisition date, but are consistent across sites and are tightly related to main wind directions. The weight of the different topographic variables on explaining snow distribution evolves while major snow accumulation events still take place and minor changes are observed after reaching the annual snow accumulation peak. Random forests have demonstrated good performance when predicting snow distribution for the sites included in the training set with R-2 values ranging from 0.82 to 0.94 and mean absolute errors always below 0.4 m. Oppositely, this algorithm failed when used to predict snow distribution for sites not included in the training set, with mean absolute errors above 0.8 m.
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Richter, K., Meyssignac, B., Slangen, A., Melet, A., Church, J., Fettweis, X., et al. (2020). Detecting a forced signal in satellite-era sea-level change. Environmental Research Letters, 15(9).
Abstract: In this study, we compare the spatial patterns of simulated geocentric sea-level change to observations from satellite altimetry over the period 1993-2015 to assess whether a forced signal is detectable. This is challenging, as on these time scales internal variability plays an important role and may dominate the observed spatial patterns of regional sea-level change. Model simulations of regional sea-level change associated with sterodynamic sea level, atmospheric loading, glacier mass change, and ice-sheet surface mass balance changes are combined with observations of groundwater depletion, reservoir storage, and dynamic ice-sheet mass changes. The resulting total geocentric regional sea-level change is then compared to independent measurements from satellite altimeter observations. The detectability of the climate-forced signal is assessed by comparing the model ensemble mean of the 'historical' simulations with the characteristics of sea-level variability in pre-industrial control simulations. To further minimize the impact of internal variability, zonal averages were produced. We find that, in all ocean basins, zonally averaged simulated sea-level changes are consistent with observations within sampling uncertainties associated with simulated internal variability of the sterodynamic component. Furthermore, the simulated zonally averaged sea-level change cannot be explained by internal variability alone-thus we conclude that the observations include a forced contribution that is detectable at basin scales.
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Rigler, M., Drinovec, L., Lavric, G., Vlachou, A., Prevot, A., Jaffrezo, J., et al. (2020). The new instrument using a TC-BC (total carbon-black carbon) method for the online measurement of carbonaceous aerosols. Atmospheric Measurement Techniques, 13(8), 4333–4351.
Abstract: We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 ittg C, which corresponds to a concentration of 0.3 μg Cm-3 at a sample flow rate of 16.7 L min(-1) and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer (R) , from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC-EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC = 1.8, in the expected range.
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Robinson, A., Alvarez-Solas, J., Montoya, M., Goelzer, H., Greve, R., & Ritz, C. (2020). Description and validation of the ice-sheet model Yelmo (version 1.0). Geoscientific Model Development, 13(6), 2805–2823.
Abstract: We describe the physics and features of the ice-sheet model Yelmo, an open-source project intended for collaborative development. Yelmo is a thermomechanical model, solving for the coupled velocity and temperature solutions of an ice sheet simultaneously. The ice dynamics are currently treated via a “hybrid” approach combining the shallow-ice and shallow-shelf/shelfy-stream approximations, which makes Yelmo an apt choice for studying a wide variety of problems. Yelmo's main innovations lie in its flexible and user-friendly infrastructure, which promotes portability and facilitates long-term development. In particular, all physics subroutines have been designed to be self-contained, so that they can be easily ported from Yelmo to other models, or easily replaced by improved or alternate methods in the future. Furthermore, hard-coded model choices are eschewed, replaced instead with convenient parameter options that allow the model to be adapted easily to different contexts. We show results for different ice-sheet benchmark tests, and we illustrate Yelmo's performance for the Antarctic ice sheet.
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Roman-Cascon, C., Lothon, M., Lohou, F., Ojha, N., Merlin, O., Aragones, D., et al. (2020). Can We Use Satellite-Based Soil-Moisture Products at High Resolution to Investigate Land-Use Differences and Land-Atmosphere Interactions? A Case Study in the Savanna. Remote Sensing, 12(11).
Abstract: The use of soil moisture (SM) measurements from satellites has grown in recent years, fostering the development of new products at high resolution. This opens the possibility of using them for certain applications that were normally carried out using in situ data. We investigated this hypothesis through two main analyses using two high-resolution satellite-based soil moisture (SBSM) products that combined microwave with thermal and optical data: (1) The Disaggregation based on Physical And Theoretical scale Change (DISPATCH) and, (2) The Soil Moisture Ocean Salinity-Barcelona Expert Center (SMOS-BEC Level 4). We used these products to analyse the SM differences among pixels with contrasting vegetation. This was done through the comparison of the SM measurements from satellites and the measurements simulated with a simple antecedent precipitation index (API) model, which did not account for the surface characteristics. Subsequently, the deviation of the SM from satellite with respect to the API model (bias) was analysed and compared for contrasting land use categories. We hypothesised that the differences in the biases of the varied categories could provide information regarding the water retention capacity associated with each type of vegetation. From the satellite measurements, we determined how the SM depended on the tree cover, i.e., the denser the tree cover, the higher the SM. However, in winter periods with light rain events, the tree canopy could dampen the moistening of the soil through interception and conducted higher SM in the open areas. This evolution of the SM differences that depended on the characteristics of each season was observed both from satellite and from in situ measurements taken beneath a tree and in grass on the savanna landscape. The agreement between both types of measurements highlighted the potential of the SBSM products to investigate the SM of each type of vegetation. We found that the results were clearer for DISPATCH, whose data was not smoothed spatially as it was in SMOS-BEC. We also tested whether the relationships between SM and evapotranspiration could be investigated using satellite data. The answer to this question was also positive but required removing the unrealistic high-frequency SM oscillations from the satellite data using a low pass filter. This improved the performance scores of the products and the agreement with the results from the in situ data. These results demonstrated the possibility of using SM data from satellites to substitute ground measurements for the study of land-atmosphere interactions, which encourages efforts to improve the quality and resolution of these measurements.
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Roussel, M., Lemonnier, F., Genthon, C., & Krinner, G. (2020). Brief communication: Evaluating Antarctic precipitation in ERA5 and CMIP6 against CloudSat observations. Cryosphere, 14(8), 2715–2727.
Abstract: CMIP5, CMIP6, and ERAS Antarctic precipitation is evaluated against CloudSat data. At continental and regional scales, ERAS and the median CMIP models are biased high, with insignificant improvement from CMIPS to CMIP6. However, there are fewer positive outliers in CMIP6. AMIP configurations perform better than the coupled ones, and, surprisingly, relative errors in areas of complex topography are higher (up to 50 %) in the five higher-resolution models. The seasonal cycle is reproduced well by the median of the CMIP models, but not by ERAS . . Progress from CMIPS to CMIP6 being limited, there is still room for improvement.
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Ruiz-Vasquez, M., Arias, P., Martinez, J., & Espinoza, J. (2020). Effects of Amazon basin deforestation on regional atmospheric circulation and water vapor transport towards tropical South America. Climate Dynamics, .
Abstract: The water cycle over the Amazon basin is a regulatory mechanism for regional and global climate. The atmospheric moisture evaporated from this basin represents an important source of humidity for itself and for other remote regions. The deforestation rates that this basin has experienced in the past decades have implications for regional atmospheric circulation and water vapor transport. In this study, we analyzed the changes in atmospheric moisture transport towards tropical South America during the period 1961-2010, according to two deforestation scenarios of the Amazon defined by Alves et al. (Theor Appl Climatol 100(3-4):337-350, 2017). These scenarios consider deforested areas of approximately 28% and 38% of the Amazon basin, respectively. The Dynamic Recycling Model is used to track the transport of water vapor from different sources in tropical South America and the surrounding oceans. Our results indicate that under deforestation scenarios in the Amazon basin, continental sources reduce their contributions to northern South America at an annual scale by an average of between 40 and 43% with respect to the baseline state. Our analyses suggest that these changes may be related to alterations in the regional Hadley and Walker cells. Amazon deforestation also induces a strengthening of the cross-equatorial flow that transports atmospheric moisture from the Tropical North Atlantic and the Caribbean Sea to tropical South America during the austral summer. A weakening of the cross-equatorial flow is observed during the boreal summer, reducing moisture transport from the Amazon to latitudes further north. These changes alter the patterns of precipitable water contributions to tropical South America from both continental and oceanic sources. Finally, we observed that deforestation over the Amazon basin increases the frequency of occurrence of longer dry seasons in the central-southern Amazon (by between 29 and 57%), depending on the deforestation scenario considered, as previous studies suggest.
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Saavedra, M., Junquas, C., Espinoza, J., & Silva, Y. (2020). Impacts of topography and land use changes on the air surface temperature and precipitation over the central Peruvian Andes. Atmospheric Research, 234.
Abstract: This paper focuses on the representation of the air surface temperature and precipitation using high spatiotemporal simulations (3 km-1 h) of the WRF3.7.1 model in the central Peruvian area. It covers, from east to west, the coastal zone, the western slope of the Andes, the Andean Mantaro basin (500-5000 masl), and the Andes-Amazon transition region in the eastern Andes. The study covers the January months from 2004 to 2008. Three experiments were conducted using different topography and land use data sources: (1) a control simulation using the default WRF topography and land use datasets from the United States Geological Survey (USGS); (2) a simulation changing only the topography by using the SRTM topography dataset; and (3) a simulation changing the land use data of (2) by a new dataset adapted from Eva et al. (2004). SRTM topography performed better than the control simulation for representing the actual altitudes of 57 meteorological stations that were used for precipitation and surface air temperature data. As a result, the simulations of experiments (2) and (3) produced lower bias values than that of (1). Topography change (experiment (2)) showed improvements in temperature bias that were directly associated with linear modifications of -5.6 and -6.7 degrees C.km(-1) in minimum and maximum temperature, respectively. Increasing (decreasing) precipitation with topography or land use change was clearly controlled by changes in the moisture flux patterns and its convergence (divergence) in the Andes-Amazon transition. On the western slope, precipitation increase could be associated with the increase in easterly flow by the smaller altitudes of the Andes mountains in SRTM topography and by increasing evaporation with new land use. Inside the Mantaro Basin, low level moisture flux seems to control the rainfall changes. Overall, relative changes (positive or negative) in precipitation due to topography or land use change could reach values above 25%.
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Saito, T., Spadini, L., Saito, H., Martins, J., Oxarango, L., Takemura, T., et al. (2020). Characterization and comparison of groundwater quality and redox conditions in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the Tokyo Metropolitan area, Japan. Science Of The Total Environment, 722.
Abstract: Groundwater is essential for the Earth biosphere but is often contaminated by harmful chemical compounds due to both anthropogenic and natural causes. A key factor controlling the fate of harmful chemicals in groundwater is the reduction/oxidation (redox) conditions. The formation factors for the groundwater redox conditions are insufficiently understood. In this study, long-term groundwater quality beneath one of the world megacities was monitored and evaluated. We measured and compared hydrogeochemical conditions including groundwater quality (35 chemical parameters) and redox conditions of five aquifers in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the TokyoMetropolitan area, Japan. Monitoring results suggested the following: The main origin of groundwater is precipitation in both the Lowland and Upland areas. The three aquifers in the Arakawa Lowland are likely fully separated, with one unconfined and two confined aquifers under iron reducing and methanogenic conditions, respectively. Oppositely, in the Musashino Upland, the water masses in the two aquifers are likely partly connected, under aerobic conditions, and undergoing the same groundwater recharge and flow processes under similar hydrogeological conditions. The different groundwater redox conditions observed are likely caused by the very different groundwater residence times for the Arakawa Lowland and Musashino Upland. (C) 2020 Elsevier B.V. All rights reserved.
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Samake, A., Bonin, A., Jaffrezo, J., Taberlet, P., Weber, S., Uzu, G., et al. (2020). High levels of primary biogenic organic aerosols are driven by only a few plant-associated microbial taxa. Atmospheric Chemistry And Physics, 20(9), 5609–5628.
Abstract: Primary biogenic organic aerosols (PBOAs) represent a major fraction of coarse organic matter (OM) in air. Despite their implication in many atmospheric processes and human health problems, we surprisingly know little about PBOA characteristics (i.e., composition, dominant sources, and contribution to airborne particles). In addition, specific primary sugar compounds (SCs) are generally used as markers of PBOAs associated with bacteria and fungi, but our knowledge of microbial communities associated with atmospheric particulate matter (PM) remains incomplete. This work aimed at providing a comprehensive understanding of the microbial fingerprints associated with SCs in PM10 (particles smaller than 10 μm) and their main sources in the surrounding environment (soils and vegetation). An intensive study was conducted on PM10 collected at a rural background site located in an agricultural area in France. We combined high-throughput sequencing of bacteria and fungi with detailed physicochemical characterizations of PM10, soil, and plant samples and monitored meteorological and agricultural activities throughout the sampling period. Results show that in summer SCs in PM10 are a major contributor of OM in air, representing 0.8 % to 13.5 % of OM mass. SC concentrations are clearly determined by the abundance of only a few specific airborne fungal and bacterial taxa. The temporal fluctuations in the abundance of only four predominant fungal genera, namely Cladosporium, Alternaria, Sporobolomyces, and Dioszegia, reflect the temporal dynamics in SC concentrations. Among bacterial taxa, the abundance of only Massilia, Pseudomonas, Frigoribacterium, and Sphingomonas is positively correlated with SC species. These microbes are significantly enhanced in leaf over soil samples. Interestingly, the overall community structure of bacteria and fungi are similar within PM10 and leaf samples and significantly distinct between PM10 and soil samples, indicating that surrounding vegetation is the major source of SC-associated microbial taxa in PM10 in this rural area of France.
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Santana-Falcon, Y., Brasseur, P., Brankart, J., & Garnier, F. (2020). Assimilation of chlorophyll data into a stochastic ensemble simulation for the North Atlantic Ocean. Ocean Science, 16(5), 1297–1315.
Abstract: Satellite-derived surface chlorophyll data are assimilated daily into a three-dimensional 24-member ensemble configuration of an online-coupled NEMO (Nucleus for European Modeling of the Ocean)-PISCES (Pelagic Interaction Scheme of Carbon and Ecosystem Stu dies) model for the North Atlantic Ocean. A 1-year multivariate assimilation experiment is performed to evaluate the impacts on analyses and forecast ensembles. Our results demonstrate that the integration of data improves surface analysis and forecast chlorophyll representation in a major part of the model domain, where the assimilated simulation outperforms the probabilistic skills of a non-assimilated analogous simulation. However, improvements are dependent on the reliability of the prior free ensemble. A regional diagnosis shows that surface chlorophyll is overestimated in the northern limit of the subtropical North Atlantic, where the prior ensemble spread does not cover the observation's variability. There, the system cannot deal with corrections that alter the equilibrium between the observed and unobserved state variables producing instabilities that propagate into the forecast. To alleviate these inconsistencies, a 1-month sensitivity experiment in which the assimilation process is only applied to model fluctuations is performed. Results suggest the use of this methodology may decrease the effect of corrections on the correlations between state vectors. Overall, the experiments presented here evidence the need of refining the description of model's uncertainties according to the biogeochemical characteristics of each oceanic region.
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Santolaria-Otin, M., & Zolina, O. (2020). Evaluation of snow cover and snow water equivalent in the continental Arctic in CMIP5 models. Climate Dynamics, .
Abstract: Spatial and temporal patterns of snow cover extent (SCE) and snow water equivalent (SWE) over the terrestrial Arctic are analyzed based on multiple observational datasets and an ensemble of CMIP5 models during 1979-2005. For evaluation of historical simulations of the Coupled Model Intercomparison Project (CMIP5) ensemble, we used two reanalysis products, one satellite-observed product and an ensemble of different datasets. The CMIP5 models tend to significantly underestimate the observed SCE in spring but are in better agreement with observations in autumn; overall, the observed annual SCE cycle is well captured by the CMIP5 ensemble. In contrast, for SWE, the annual cycle is significantly biased, especially over North America, where some models retain snow even in summer, in disagreement with observations. The snow margin position (SMP) in the CMIP5 historical simulations is in better agreement with observations in spring than in autumn, when close agreement across the CMIP5 models is only found in central Siberia. Historical experiments from most CMIP5 models show negative pan-Arctic trends in SCE and SWE. These trends are, however, considerably weaker (and less statistically significant) than those reported from observations. Most CMIP5 models can more accurately capture the trend pattern of SCE than that of SWE, which shows quantitative and qualitative differences with the observed trends over Eurasia. Our results demonstrate the importance of using multiple data sources for the evaluation of snow characteristics in climate models. Further developments should focus on the improvement of both dataset quality and snow representation in climate models, especially ESM-SnowMIP.
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Santolaria-Otin, M., Garcia-Serrano, J., Menegoz, M., & Bech, J. (2020). On the observed connection between Arctic sea ice and Eurasian snow in relation to the winter North Atlantic Oscillation. Environmental Research Letters, 15(12).
Abstract: Sea ice concentration (SIC) in the eastern Arctic and snow cover extent (SCE) over central Eurasia in late autumn have been proposed as potential predictors of the winter North Atlantic Oscillation (NAO). Here, maximum covariance analysis is used to further investigate the links between autumn SIC in the Barents-Kara Seas (BK) and SCE over Eurasia (EUR) with winter sea level pressure (SLP) in the North Atlantic-European region over 1979-2019. As shown by previous studies, the most significant covariability mode of SIC/BK is found for November. Similarly, the covariability with SCE/EUR is only statistically significant for November, not for October. Changes in temperature, specific humidity, SIC/BK and SCE/EUR in November are associated with a circulation anomaly over the Ural-Siberian region that appears as a precursor of the winter NAO; where the advection of climatological temperature/humidity by the anomalous flow is related to SCE/EUR and SIC/BK anomalies.
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Seehaus, T., Malz, P., Sommer, C., Soruco, A., Rabatel, A., & Braun, M. (2020). Mass balance and area changes of glaciers in the Cordillera Real and Tres Cruces, Bolivia, between 2000 and 2016. Journal Of Glaciology, 66(255), 124–136.
Abstract: Climate change has led to a significant shrinkage of glaciers in the Tropical Andes during the last decades. Recent multi-temporal quantifications of ice mass loss at mountain range to regional scale are missing. However, this is fundamental information for future water resource planning and glacier change projections. In this study, we measure temporally consistent glacier area changes and geodetic mass balances throughout the Bolivian Cordillera Real and Tres Cruces based on multi-sensor remote-sensing data. By analyzing multi-spectral satellite images and interferometric SAR data, a glacier recession of 81 +/- 18 km(2) (29%; 5.1 +/- 1.1 km(2) a(-1)), a geodetic mass balance of -403 +/- 78 kg m(-2) a(-1) and a total ice mass loss of 1.8 +/- 0.5 Gt is derived for 2000-2016. In the period 2013-2016, ice mass loss was 21% above the average rate. A retreat rate of 15 +/- 5 km(2) a(-1) and a mass budget of -487 +/- 349 kg m(-2) a(-1) are found in this more recent period. These higher change rates can be attributed to the strong El Nino event in 2015/16. The analyses of individual glacier changes and topographic variables confirmed the dependency of the mass budget and glacier recession on glacier aspect and median elevation.
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Segura, H., Espinoza, J., Junquas, C., Lebel, T., Vuille, M., & Garreaud, R. (2020). Recent changes in the precipitation-driving processes over the southern tropical Andes/western Amazon. Climate Dynamics, .
Abstract: Analyzing December-February (DJF) precipitation in the southern tropical Andes-STA (12 circle S}; > 3000 m.a.s.l) allows revisiting regional atmospheric circulation features accounting for its interannual variability over the past 35 years (1982-2018). In a region where in-situ rainfall stations are sparse, the CHIRPS precipitation product is used to identify the first mode of interannual DJF precipitation variability (PC1-Andes). A network of 98 rain-gauge stations further allows verifying that PC1-Andes properly represents the spatio-temporal rainfall distribution over the region; in particular a significant increase in DJF precipitation over the period of study is evident in both in-situ data and PC1-Andes. Using the ERA-Interim data set, we found that aside from the well-known relationship between precipitation and upper-level easterlies over the STA, PC1-Andes is also associated with upward motion over the western Amazon (WA), a link that has not been reported before. The ascent over the WA is a component of the meridional circulation between the tropical North Atlantic and western tropical South America-WTSA (80 circle W). Indeed, the precipitation increase over the last 2 decades is concomitant with the strengthening of this meridional circulation. An intensified upward motion over the WA has moistened the mid-troposphere over WTSA, and as a consequence, a decreased atmospheric stability between the mid- and the upper troposphere is observed over this region, including the STA. We further show that, over the last 15 years or so, the year-to-year variability of STA precipitation (periodicity < 8 years) has been significantly associated with upward motion over the WA, while upper-level easterlies are no longer significantly correlated with precipitation. These observations suggests that the STA have experienced a transition from a dry to a wet state in association with a change in the dominant mode of atmospheric circulation. In the former dominant state, zonal advection of momentum and moisture from the central Amazon, associated with upper-level easterlies, is necessary to develop convection over the STA. Since the beginning of the 21st century, DJF precipitation over the STA seems to respond directly and primarily to upward motion over the WA. Beyond improving our understanding of the factors influencing STA precipitation nowadays, these results point to the need of exploring their possible implications for the long-term evolution of precipitation in a context of global warming.
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Sergeant, A., Chmiel, M., Lindner, F., Walter, F., Roux, P., Chaput, J., et al. (2020). On the Green's function emergence from interferometry of seismic wave fields generated in high-melt glaciers: implications for passive imaging and monitoring. Cryosphere, 14(3), 1139–1171.
Abstract: Ambient noise seismology has revolutionized seismic characterization of the Earth's crust from local to global scales. The estimate of Green's function (GF) between two receivers, representing the impulse response of elastic media, can be reconstructed via cross-correlation of the ambient noise seismograms. A homogenized wave field illuminating the propagation medium in all directions is a prerequisite for obtaining an accurate GF. For seismic data recorded on glaciers, this condition imposes strong limitations on GF convergence because of minimal seismic scattering in homogeneous ice and limitations in network coverage. We address this difficulty by investigating three patterns of seismic wave fields: a favorable distribution of icequakes and noise sources recorded on a dense array of 98 sensors on Glacier d'Argentiere (France), a dominant noise source constituted by a moulin within a smaller seismic array on the Greenland Ice Sheet, and crevasse-generated scattering at Gornergletscher (Switzerland). In Glacier d'Argentiere, surface melt routing through englacial channels produces turbulent water flow, creating sustained ambient seismic sources and thus favorable conditions for GF estimates. Analysis of the cross-correlation functions reveals non-equally distributed noise sources outside and within the recording network. The dense sampling of sensors allows for spatial averaging and accurate GF estimates when stacked on lines of receivers. The averaged GFs contain high-frequency ( > 30 Hz) direct and refracted P waves in addition to the fundamental mode of dispersive Rayleigh waves above 1 Hz. From seismic velocity measurements, we invert bed properties and depth profiles and map seismic anisotropy, which is likely introduced by crevassing. In Greenland, we employ an advanced preprocessing scheme which includes matchfield processing and eigenspectral equalization of the cross spectra to remove the moulin source signature and reduce the effect of inhomogeneous wave fields on the GFs. At Gornergletscher, cross-correlations of icequake coda waves show evidence for homogenized incident directions of the scattered wave field. Optimization of coda correlation windows via a Bayesian inversion based on the GF cross coherency and symmetry further promotes the GF estimate convergence. This study presents new processing schemes on suitable array geometries for passive seismic imaging and monitoring of glaciers and ice sheets.
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Seroussi, H., Nowicki, S., Payne, A., Goelzer, H., Lipscomb, W., Abe-Ouchi, A., et al. (2020). ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century. Cryosphere, 14(9), 3033–3070.
Abstract: Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and assess the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimates of the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes, forcings employed and initial states of ice sheet models. This study presents results from ice flow model simulations from 13 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100 as part of the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6). They are forced with outputs from a subset of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), representative of the spread in climate model results. Simulations of the Antarctic ice sheet contribution to sea level rise in response to increased warming during this period varies between 7:8 and 30.0 cm of sea level equivalent (SLE) under Representative Concentration Pathway (RCP) 8.5 scenario forcing. These numbers are relative to a control experiment with constant climate conditions and should therefore be added to the mass loss contribution under climate conditions similar to present-day conditions over the same period. The simulated evolution of the West Antarctic ice sheet varies widely among models, with an overall mass loss, up to 18.0 cm SLE, in response to changes in oceanic conditions. East Antarctica mass change varies between 6 :1 and 8.3 cm SLE in the simulations, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional simulated mass loss of 28mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the climate forcing, the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 climate models show an additional mass loss of 0 and 3 cm of SLE on average compared to simulations done under present-day conditions for the two CMIP5 forcings used and display limited mass gain in East Antarctica.
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Serrano-Vincenti, S., Condom, T., Campozano, L., Guaman, J., & Villacis, M. (2020). An Empirical Model for Rainfall Maximums Conditioned to Tropospheric Water Vapor Over the Eastern Pacific Ocean. Frontiers In Earth Science, 8.
Abstract: One of the most difficult weather variables to predict is rain, particularly intense rain. The main limitation is the complexity of the fluid dynamic equations used by predictive models with increasing uncertainties over time, especially in the description of brief, local, and high intensity precipitation events. Although computational, instrumental and theoretical improvements have been developed for models, it is still a challenge to estimate high intensity rainfall events, especially in terms of determining the maximum rainfall rates and the location of the event. Within this context, this research presents a statistical and relationship analysis of rainfall intensity rates, total precipitable water (TPW), and sea surface temperature (SST) over the ocean. An empirical model to estimate the maximum rainfall rates conditioned to TPW values is developed. The performance of the maximum rainfall rate model is spatially evaluated for a case study. High-resolution TRMM 2A12 satellite data with a resolution of 5.1 x 5.1 km and 1.67 s was used from January 2009 to December 2012, over the Eastern Pacific Nino area in the tropical Pacific Ocean (0-5 degrees S; 90-81 degrees W), comprising 326,092 rain pixels. After applying the model selection methodology, i.e., the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC), an empirical exponential model between the maximum possible rain rates conditioned to TPW was found with R-2 = 0.96, indicating that the amount of TPW determines the maximum amount of rain that the atmosphere can precipitate exponentially. Spatially, this model unequivocally locates the rain event; however, the rainfall intensity is underestimated in the convective nucleus of the cloud. Thus, these results provide an additional constraint for maximum rain intensity values that should be adopted in dynamic models, improving the quantification of heavy rainfall event intensities and the correct location of these events.
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Shaw, T., Caro, A., Mendoza, P., Ayala, A., Pellicciotti, F., Gascoin, S., et al. (2020). The Utility of Optical Satellite Winter Snow Depths for Initializing a Glacio-Hydrological Model of a High-Elevation, Andean Catchment. Water Resources Research, 56(8).
Abstract: Information about end-of-winter spatial distribution of snow depth is important for seasonal forecasts of spring/summer streamflow in high-mountain regions. Nevertheless, such information typically relies upon extrapolation from a sparse network of observations at low elevations. Here, we test the potential of high-resolution snow depth data derived from optical stereophotogrammetry of Pleiades satellites for improving the representation of snow depth initial conditions (SDICs) in a glacio-hydrological model and assess potential improvements in the skill of snowmelt and streamflow simulations in a high-elevation Andean catchment. We calibrate model parameters controlling glacier mass balance and snow cover evolution using ground-based and satellite observations, and consider the relative importance of accurate estimates of SDICs compared to model parameters and forcings. We find that Pleiades SDICs improve the simulation of snow-covered area, glacier mass balance, and monthly streamflow compared to alternative SDICs based upon extrapolation of meteorological variables or statistical methods to estimate SDICs based upon topography. Model simulations are found to be sensitive to SDICs in the early spring (up to 48% variability in modeled streamflow compared to the best estimate model), and to temperature gradients in all months that control albedo and melt rates over a large elevation range (>2,400 m). As such, appropriately characterizing the distribution of total snow volume with elevation is important for reproducing total streamflow and the proportions of snowmelt. Therefore, optical stereo-photogrammetry offers an advantage for obtaining SDICs that aid both the timing and magnitude of streamflow simulations, process representation (e.g., snow cover evolution) and has the potential for large spatial domains. Key Points Pleiades snow depths aid simulation of snow cover extent, glacier mass balance, and monthly streamflow Alternative snow depth initial conditions underestimate early spring streamflow by up to 48% Sensitivity to temperature means estimating total snow volume with elevation is most important to model snowmelt and streamflow
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Shepherd, A., Ivins, E., Rignot, E., Smith, B., van den Broeke, M., Velicogna, I., et al. (2020). Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature, 579(7798), 233–+.
Abstract: The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades(1,2), and it is expected to continue to be so(3). Although increases in glacier flow(4-6) and surface melting(7-9) have been driven by oceanic(10-12) and atmospheric(13,14) warming, the magnitude and trajectory of the ice sheet's mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet's volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 +/- 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 +/- 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 +/- 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 +/- 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 +/- 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 +/- 37 billion tonnes per year in the 1990s to 87 +/- 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 +/- 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions(15) and ocean temperatures fell at the terminus of Jakobshavn Isbr AE(16). Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario(17), which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.
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Shin, J., Nehrbass-Ahles, C., Grilli, R., Beeman, J., Parrenin, F., Teste, G., et al. (2020). Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190-135 ka). Climate Of The Past, 16(6), 2203–2219.
Abstract: Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka) the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO2 variation is small (similar to 5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60-27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5 +/- 0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240 +/- 320 years. However, during CDM 6iv (171.1 +/- 0.2 ka) and CDM 6iii (175.4 +/- 0.4 ka) the lag is much longer: 1290 +/- 540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbonrich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.
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Slemr, F., Martin, L., Labuschagne, C., Mkololo, T., Angot, H., Magand, O., et al. (2020). Atmospheric mercury in the Southern Hemisphere – Part 1: Trend and inter-annual variations in atmospheric mercury at Cape Point, South Africa, in 2007-2017, and on Amsterdam Island in 2012-2017. Atmospheric Chemistry And Physics, 20(13), 7683–7692.
Abstract: The Minamata Convention on Mercury (Hg) entered into force in 2017, committing its 116 parties (as of January 2019) to curb anthropogenic emissions. Monitoring of atmospheric concentrations and trends is an important part of the effectiveness evaluation of the convention. A few years ago (in 2017) we reported an increasing trend in atmospheric Hg concentrations at the Cape Point Global Atmosphere Watch (GAW) station in South Africa (34.3535 degrees S, 18.4897 degrees E) for the 2007-2015 period. With 2 more years of measurements at Cape Point and the 2012-2017 data from Amsterdam Island (37.7983 degrees S, 77.5378 degrees E) in the remote southern Indian Ocean, a more complex picture emerges: at Cape Point the upward trend for the 2007-2017 period is still significant, but no trend or a slightly downward trend was detected for the period 2012-2017 at both Cape Point and Amsterdam Island. The upward trend at Cape Point is driven mainly by the Hg concentration minimum in 2009 and maxima in 2014 and 2012. Using ancillary data on Rn-222, CO, O-3, CO2, and CH4 from Cape Point and Amsterdam Island, the possible reasons for the trend and its change are investigated. In a companion paper this analysis is extended for the Cape Point station by calculations of source and sink regions using backward-trajectory analysis.
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Sommar, J., Osterwalder, S., & Zhu, W. (2020). Recent advances in understanding and measurement of Hg in the environment: Surface-atmosphere exchange of gaseous elemental mercury (Hg-0). Science Of The Total Environment, 721.
Abstract: The atmosphere is the major transport pathway for distribution of mercury (Hg) globally. Gaseous elemental mercury (GEM, hereafter Hg0) is the predominant form in both anthropogenic and natural emissions. Evaluation of the efficacy of reductions in emissions set by the UN's Minamata Convention (UN-MC) is critically dependent on the knowledge of the dynamics of the global Hg cycle. Of these dynamics including e.g. red-ox reactions, methylation-demethylation and dry-wet deposition, poorly constrained atmosphere-surface Hg-0 fluxes especially limit predictability of the timescales of its global biogeochemical cycle. This review focuses on Hg-0 flux field observational studies, namely the theory, applications, strengths, and limitations of the various experimental methodologies applied to gauge the exchange flux and decipher active sub-processes. We present an in-depth review, a comprehensive literature synthesis, and methodological and instrumentation advances for terrestrial and marine Hg0 flux studies in recent years. In particular, we outline the theory of a wide range of measurement techniques and detail the operational protocols. Today, the most frequently used measurement techniques to determine the net Hg-0 flux (>95% of the published flux data) are dynamic flux chambers for small-scale and micrometeorological approaches for large-scale measurements. Furthermore, top-down approaches based on Hg-0 concentration measurements have been applied as tools to better constrain Hg emissions as an independent way to e.g. challenge emission inventories. This review is an up-dated, thoroughly revised edition of Sommar et al. 2013 (DOI: 10.1080/10643389.2012.671733). To the tabulation of >100 cited flux studies 1988-2009 given in the former publication, we have here listed corresponding studies published during the last decade with a few exceptions (2008-2019). During that decade, Hg stable isotope ratios of samples involved in atmosphere-terrestrial interaction is at hand and provide in combination with concentration and/or flux measurements novel constraints to quantitatively and qualitatively assess the bi-directional Hg-0 flux. Recent efforts in the development of relaxed eddy accumulation and eddy covariance Hg-0 flux methods bear the potential to facilitate long-term, ecosystem-scale flux measurements to reduce the prevailing large uncertainties in Hg-0 flux estimates. Standardization of methods for Hg-0 flux measurements is crucial to investigate how land-use change and how climate warming impact ecosystem-specific Hg-0 sink-source characteristics and to validate frequently applied model parameterizations describing the regional and global scale Hg cycle. (C) 2020 Elsevier B.V. All rights reserved.
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Strady, E., Kieu-Le, T., Gasperi, J., & Tassin, B. (2020). Temporal dynamic of anthropogenic fibers in a tropical river-estuarine system. Environmental Pollution, 259.
Abstract: Anthropogenic fibers, gathering synthetic fibers, artificial fibers and natural fibers are ubiquitous in the natural environment. Tremendous concentrations of anthropogenic fibers were previously measured in the tropical Saigon River (Vietnam), i.e. a river impacted by textile and apparel industries. In the present study, we want to examine the role of contrasted seasonal variation (e.g., dry and rainy seasons), via the rainfall and monthly water discharges, and of water's physico-chemical conditions on the concentrations of anthropogenic fibers in the surface water. The one year and half monthly survey evidenced that concentrations of anthropogenic fibers varied from 22 to 251 items L-1 and their variations were not related to rainfall, water discharge or abiotic factors. However, their color and length distribution varied monthly suggesting variations in sources and sinks. Based on the 2017 survey, we estimated an annual emission of anthropogenic fibers from the river to the downstream coastal zone of 115-164 x 10(12) items yr(-1). (C) 2020 Elsevier Ltd. All rights reserved.
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Sun, S., Pattyn, F., Simon, E., Albrecht, T., Cornford, S., Calov, R., et al. (2020). Antarctic ice sheet response to sudden and sustained ice-shelf collapse (ABUMIP). Journal Of Glaciology, 66(260), 891–904.
Abstract: Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their 'buttressing' effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the 'end-member' scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1-12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91-5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments.
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Svensson, A., Dahl-Jensen, D., Steffensen, J., Blunier, T., Rasmussen, S., Vinther, B., et al. (2020). Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period. Climate Of The Past, 16(4), 1565–1580.
Abstract: The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12-60 ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (delta O-18 and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt delta O-18 transitions by 122 +/- 24 years. The time difference between Antarctic signals in deuterium excess and delta O-18, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic delta O-18 lag behind Greenland of 152 +/- 37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.
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Swingedouw, D., Speranza, C., Bartsch, A., Durand, G., Jamet, C., Beaugrand, G., et al. (2020). Early Warning from Space for a Few Key Tipping Points in Physical, Biological, and Social-Ecological Systems. Surveys In Geophysics, .
Abstract: In this review paper, we explore latest results concerning a few key tipping elements of the Earth system in the ocean, cryosphere, and land realms, namely the Atlantic overturning circulation and the subpolar gyre system, the marine ecosystems, the permafrost, the Greenland and Antarctic ice sheets, and in terrestrial resource use systems. All these different tipping elements share common characteristics related to their nonlinear nature. They can also interact with each other leading to synergies that can lead to cascading tipping points. Even if the probability of each tipping event is low, they can happen relatively rapidly, involve multiple variables, and have large societal impacts. Therefore, adaptation measures and management in general should extend their focus beyond slow and continuous changes, into abrupt, nonlinear, possibly cascading, high impact phenomena. Remote sensing observations are found to be decisive in the understanding and determination of early warning signals of many tipping elements. Nevertheless, considerable research still remains to properly incorporate these data in the current generation of coupled Earth system models. This is a key prerequisite to correctly develop robust decadal prediction systems that may help to assess the risk of crossing thresholds potentially crucial for society. The prediction of tipping points remains difficult, notably due to stochastic resonance, i.e. the interaction between natural variability and anthropogenic forcing, asking for large ensembles of predictions to correctly assess the risks. Furthermore, evaluating the proximity to crucial thresholds using process-based understanding of each system remains a key aspect to be developed for an improved assessment of such risks. This paper finally proposes a few research avenues concerning the use of remote sensing data and the need for combining different sources of data, and having long and precise-enough time series of the key variables needed to monitor Earth system tipping elements.
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Talalay, P., Li, Y., Augustin, L., Clow, G., Hong, J., Lefebvre, E., et al. (2020). Geothermal heat flux from measured temperature profiles in deep ice boreholes in Antarctica. Cryosphere, 14(11), 4021–4037.
Abstract: The temperature at the Antarctic Ice Sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modeling has been used to estimate the geothermal heat flux (GHF) under the ice sheet. During the last 5 decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching or nearly reaching the bed at inland locations in Antarctica. When temperature profiles in these boreholes and steady-state heat flow modeling are combined with estimates of vertical velocity, the heat flow at the ice-sheet base is translated to a geothermal heat flux of 57.9 +/- 6.4mW m(-2) at Dome C, 78.9 +/- 5.0mW m(-2) at Dome F, and 86.9 +/- 16.6mW m(-2) at Kohnen, all higher than the predicted values at these sites. This warm base under the East Antarctic Ice Sheet (EAIS) could be caused by radiogenic heat effects or hydrothermal circulation not accounted for by the models. The GHF at the base of the ice sheet at Vostok has a negative value of -3.6 +/- 5.3mW m(-2), indicating that water from Lake Vostok is freezing onto the ice-sheet base. Correlation analyses between modeled and measured depth-age scales at the EAIS sites indicate that all of them can be adequately approximated by a steady-state model. Horizontal velocities and their variation over ice-age cycles are much greater for the West Antarctic Ice Sheet than for the interior EAIS sites; a steady-state model cannot precisely describe the temperature distribution here. Even if the correlation factors for the best fitting age-depth curve are only moderate for the West Antarctic sites, the GHF values estimated here of 88.4 +/- 7.6mW m(-2) at Byrd and 113.3 +/- 16.9mW m(-2) at WAIS Divide can be used as references before more precise estimates are made on the subject.
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Tencaliec, P., Favre, A., Naveau, P., Prieur, C., & Nicolet, G. (2020). Flexible semiparametric generalized Pareto modeling of the entire range of rainfall amount. Environmetrics, 31(2).
Abstract: Precipitation amounts at daily or hourly scales are skewed to the right, and heavy rainfall is poorly modeled by a simple gamma distribution. An important yet challenging topic in hydrometeorology is to find a probability distribution that is able to model well low, moderate, and heavy rainfall. To address this issue, we present a semiparametric distribution suitable for modeling the entire range of rainfall amount. This model is based on a recent parametric statistical model called the class of extended generalized Pareto distributions (EGPDs). The EGPD family is in compliance with extreme value theory for both small and large values, while it keeps a smooth transition between these tails and bypasses the hurdle of selecting thresholds to define extremes. In particular, return levels beyond the largest observation can be inferred. To add flexibility to this EGPD class, we propose to model the transition function in a nonparametric fashion. A fast and efficient nonparametric scheme based on Bernstein polynomial approximations is investigated. We perform simulation studies to assess the performance of our approach. It is compared to two parametric models: a parametric EGPD and the classical generalized Pareto distribution (GPD), the latter being only fitted to excesses above a high threshold. We also apply our semiparametric version of EGPD to a large network of 180 precipitation time series over France.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Amato, P., Joly, M., et al. (2020). Seasonal shift in airborne microbial communities. Science Of The Total Environment, 716.
Abstract: Microorganisms are ubiquitous in the atmosphere. Global investigations on the geographical and temporal distribution of airborne microbial communities are critical for identifying the sources and the factors shaping airborne communities. At mid-latitude sites, a seasonal shift in both the concentration and diversity of airborne microbial communities has been systematically observed in the planetary boundary layer. While the factors suspected of affecting this seasonal change were hypothesized (e.g., changes in the surface conditions, meteorological parameters and global air circulation), our understanding on how these factors influence the temporal variation of airborne microbial communities, especially at the microbial taxon level, remains limited. Here, we investigated the distribution of both airborne bacterial and fungal communities on a weekly basis over more than one year at the mid-latitude and continental site of puy de Dame (France; +1465 m altitude above sea level). The seasonal shift in microbial community structure was likely correlated to the seasonal changes in the characteristics of puy de DOme's landscape (croplands and natural vegetation). The airborne microbial taxa that were the most affected by seasonal changes trended differently throughout the seasons in relation with their trophic mode. In addition, the windy and variable local meteorological conditions found at puy de Mine were likely responsible for the intraseasonal variability observed in the composition of airborne microbial communities. (C) 2020 Elsevier B.V. All rights reserved.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Vogel, T., & Larose, C. (2020). Microbial functional signature in the atmospheric boundary layer. Biogeosciences, 17(23), 6081–6095.
Abstract: Microorganisms are ubiquitous in the atmosphere, and some airborne microbial cells were shown to be particularly resistant to atmospheric physical and chemical conditions (e.g., ultraviolet – UV – radiation, desiccation and the presence of radicals). In addition to surviving, some cultivable microorganisms of airborne origin were shown to be able to grow on atmospheric chemicals in laboratory experiments. Metagenomic investigations have been used to identify specific signatures of microbial functional potential in different ecosystems. We conducted a comparative metagenomic study on the overall microbial functional potential and specific metabolic and stress-related microbial functions of atmospheric microorganisms in order to determine whether airborne microbial communities possess an atmosphere-specific functional potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
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Tignat-Perrier, R., Dommergue, A., Thollot, A., Magand, O., Vogel, T., & Larose, C. (2020). Microbial functional signature in the atmospheric boundary layer. Biogeosciences, 17(23), 6081–6095.
Abstract: Microorganisms are ubiquitous in the atmosphere, and some airborne microbial cells were shown to be particularly resistant to atmospheric physical and chemical conditions (e.g., ultraviolet – UV – radiation, desiccation and the presence of radicals). In addition to surviving, some cultivable microorganisms of airborne origin were shown to be able to grow on atmospheric chemicals in laboratory experiments. Metagenomic investigations have been used to identify specific signatures of microbial functional potential in different ecosystems. We conducted a comparative metagenomic study on the overall microbial functional potential and specific metabolic and stress-related microbial functions of atmospheric microorganisms in order to determine whether airborne microbial communities possess an atmosphere-specific functional potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
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Tignat-Perrier, R., Dommergue, A., Vogel, T., & Larose, C. (2020). Microbial Ecology of the Planetary Boundary Layer. Atmosphere, 11(12).
Abstract: Aerobiology is a growing research area that covers the study of aerosols with a biological origin from the air that surrounds us to space through the different atmospheric layers. Bioaerosols have captured a growing importance in atmospheric process-related fields such as meteorology and atmospheric chemistry. The potential dissemination of pathogens and allergens through the air has raised public health concern and has highlighted the need for a better prediction of airborne microbial composition and dynamics. In this review, we focused on the sources and processes that most likely determine microbial community composition and dynamics in the air that directly surrounds us, the planetary boundary layer. Planetary boundary layer microbial communities are a mix of microbial cells that likely originate mainly from local source ecosystems (as opposed to distant sources). The adverse atmospheric conditions (i.e., UV radiation, desiccation, presence of radicals, etc.) might influence microbial survival and lead to the physical selection of the most resistant cells during aerosolization and/or aerial transport. Future work should further investigate how atmospheric chemicals and physics influence microbial survival and adaptation in order to be able to model the composition of planetary boundary layer microbial communities based on the surrounding landscapes and meteorology.
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Todzo, S., Bichet, A., & Diedhiou, A. (2020). Intensification of the hydrological cycle expected in West Africa over the 21st century. Earth System Dynamics, 11(1), 319–328.
Abstract: This study uses the high-resolution outputs of the recent CORDEX-Africa climate projections to investigate the future changes in different aspects of the hydrological cycle over West Africa. Over the twenty-first century, temperatures in West Africa are expected to increase at a faster rate (+0.5 degrees C per decade) than the global average (+0.3 degrees C per decade), and mean precipitation is expected to increase over the Guinea Coast (+0.03 mm d(-1) per decade) but decrease over the Sahel (-0.005 mm d(-1) per decade). In addition, precipitation is expected to become more intense (+0.2 mm d(-1) per decade) and less frequent (-1.5 d per decade) over all of West Africa as a result of increasing regional temperature (precipitation intensity increases on average by +0.35 mm d(-1) degrees C-1 and precipitation frequency decreases on average by -2.2 d degrees C -1). Over the Sahel, the average length of dry spells is also expected to increase with temperature (+4 % d degrees C-1), which increases the likelihood for droughts with warming in this subregion. Hence, the hydrological cycle is expected to increase throughout the twenty-first century over all of West Africa, on average by +11 % degrees C-1 over the Sahel as a result of increasing precipitation intensity and lengthening of dry spells, and on average by +3 % degrees C-1 over the Guinea Coast as a result of increasing precipitation intensity only.
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Tran, H., Zhang, J., Cohard, J., Condon, L., & Maxwell, R. (2020). Simulating Groundwater-Streamflow Connections in the Upper Colorado River Basin. Groundwater, 58(3), 392–405.
Abstract: In mountain, snow driven catchments, snowmelt is supposed to be the primary contribution to river streamflows during spring. In these catchments the contribution of groundwater is not well documented because of the difficulty to monitor groundwater in such complex environment with deep aquifers. In this study we use an integrated hydrologic model to conduct numerical experiments that help quantify the effect of lateral groundwater flow on total annual and peak streamflow in predevelopment conditions. Our simulations focus on the Upper Colorado River Basin (UCRB; 2.8 x 10(5) km(2)) a well-documented mountain catchment for which both streamflow and water table measurements are available for several important sub-basins. For the simulated water year, our results suggest an increase in peak flow of up to 57% when lateral groundwater flow processes are included-an unexpected result for flood conditions generally assumed independent of groundwater. Additionally, inclusion of lateral groundwater flow moderately improved the model match to observations. The correlation coefficient for mean annual flows improved from 0.84 for the no lateral groundwater flow simulation to 0.98 for the lateral groundwater flow one. Spatially we see more pronounced differences between lateral and no lateral groundwater flow cases in areas of the domain with steeper topography. We also found distinct differences in the magnitude and spatial distribution of streamflow changes with and without lateral groundwater flow between Upper Colorado River Sub-basins. A sensitivity test that scaled hydraulic conductivity over two orders of magnitude was conducted for the lateral groundwater flow simulations. These results show that the impact of lateral groundwater flow is as large or larger than an order of magnitude change in hydraulic conductivity. While our results focus on the UCRB, we feel that these simulations have relevance to other headwaters systems worldwide.
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Tran, V., Nguyen, P., & Strady, E. (2020). Bioaccumulation of trace elements in the hard clam, Meretrix lyrata, reared downstream of a developing megacity, the Saigon-Dongnai River Estuary, Vietnam. Environmental Monitoring And Assessment, 192(9).
Abstract: A large number of white hard clam farms are in the estuary shoreline of Saigon-Dongnai Rivers, which flow through Ho Chi Minh City, a megacity, and numerous industrial zones in the basin catchment area. In this study, eleven trace elements (Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in the hard clam Meretrix lyrata and its habitats including surface water, suspended particulate matter, and sediment were evaluated to understand the bioaccumulation of trace metals from the environment into the whole tissues of the hard clam as well as its different organs. The samples were collected monthly in dry, transition, and wet seasons of the southern part of Vietnam from March to September 2016. The results showed that seasonal and spatial variations of the studied metal concentrations in the hard clam M. lyrata might be influenced by the sea current as well as the surface runoff in the rainy season. The relationship between condition index and the element concentrations in M. lyrata might be affected by the living environment conditions and farming methods. In addition, the hazard index values of all trace elements in the hard clam M. lyrata harvested in the sampling time show that the hard clams farmed in the study area were safe for local consumers.
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Tuzet, F., Dumont, M., Picard, G., Lamare, M., Voisin, D., Nabat, P., et al. (2020). Quantification of the radiative impact of light-absorbing particles during two contrasted snow seasons at Col du Lautaret (2058ma.s.l., French Alps). Cryosphere, 14(12), 4553–4579.
Abstract: The presence of light-absorbing particles (LAPs) in snow leads to a decrease in short-wave albedo affecting the surface energy budget. However, the understanding of the impacts of LAPs is hampered by the lack of dedicated datasets, as well as the scarcity of models able to represent the interactions between LAPs and snow metamorphism. The present study aims to address both these limitations by introducing a survey of LAP concentrations over two snow seasons in the French Alps and an estimation of their impacts based on the Crocus snowpack model that represents the complex interplays between LAP dynamics and snow metamorphism. First, a unique dataset collected at Col du Lautaret (2058ma.s.l., above sea level, French Alps) for the two snow seasons 2016-2017 and 2017-2018 is presented. This dataset consists of spectral albedo measurements, vertical profiles of snow specific surface area (SSA), density and concentrations of different LAP species. Spectral albedos are processed to estimate SSA and LAP absorption-equivalent concentrations near the surface of the snowpack. These estimates are then compared to chemical measurements of LAP concentrations and SSA measurements. Our dataset highlights, among others, large discrepancies between two measurement techniques of black carbon (BC) concentrations in snow (namely thermal-optical and laser-induced incandescence). Second, we present ensemble snowpack simulations of the multi-physics version of the detailed snowpack model Crocus, forced with in situ meteorological data, as well as dust and BC deposition fluxes from an atmospheric model. The temporal variations of near-surface LAP concentrations and SSA are most of the time correctly simulated. The simulated seasonal radiative forcing of LAPs is 33% higher for the 2017-2018 snow season than for the 2016-2017 one, highlighting a strong variability between these two seasons. However, the shortening of the snow season caused by LAPs is similar with 10 +/- 5 and 11 +/- 1 d for the first and the second snow seasons, respectively. This counter-intuitive result is attributed to two small snowfalls at the end of the first season and highlights the importance in accounting for meteorological conditions to correctly predict the impact of LAPs. The strong variability of season shortening caused by LAPs in the multi-physics ensemble for the first season (10 +/- 5 d) also points out the sensitivity of model-based estimations of LAP impact on modelling uncertainties of other processes. Finally, the indirect impact of LAPs (i.e. the enhancement of energy absorption due to the acceleration of the metamorphism by LAPs) is negligible for the 2 years considered here, which is contrary to what was found in previous studies for other sites.
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Valente, M., Reichert, J., Legout, C., Tiecher, T., Cavalcante, R., & Evrard, O. (2020). Quantification of sediment source contributions in two paired catchments of the Brazilian Pampa using conventional and alternative fingerprinting approaches. Hydrological Processes, .
Abstract: The knowledge of the contribution of sediment sources to river networks is a prerequisite to understand the impact of land use change on sediment yield. We calculated the relative contributions of sediment sources in two paired catchments, one with commercial eucalyptus plantations (0.83 km(2)) and the other with grassland used for livestock farming (1.10 km(2)), located in the Brazilian Pampa biome, using different combinations of conventional [geochemical (G), radionuclide (R) and stable isotopes and organic matter properties (S)] and alternative tracer properties [spectrocolorimetric visible-based-colour parameters (V)]. Potential sediment sources evaluated were stream channel, natural grassland and oat pasture fields in the grassland catchment, and stream channel, unpaved roads and eucalyptus plantation in the eucalyptus catchment. The results show that the best combination of tracers to discriminate the potential sources was using GSRV tracers in the grassland catchment, and using GSRV, GSV and GS tracers in the eucalyptus catchment. In all these cases, samples were 100% correctly classified in their respective groups. Considering the best tracers results (GSRV) in both catchments, the sediment source contributions estimated in the catchment with eucalyptus plantations was 63, 30 and 7% for stream channel, eucalyptus stands and unpaved roads, respectively. In the grassland catchment, the source contributions to sediment were 84, 14 and 2% for natural grassland, stream channel and oats pasture fields, respectively. The combination of these source apportionment results with the annual sediment loads monitored during a 3-year period demonstrates that commercial eucalyptus plantations supplied approximately 10 times less sediment (0.1 ton ha(-1) year(-1)) than the traditional land uses in this region, that is, 1.0 ton ha(-1) year(-1) from grassland and 0.3 ton ha(-1) year(-1) from oats pasture fields. These results demonstrate the potential of combining conventional and alternative approaches to trace sediment sources originating from different land uses in this region. Furthermore, they show that well-managed forest plantations may be less sensitive to erosion than grassland used for intensive livestock farming, which should be taken into account to promote the sustainable use of land in this region of South America.
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Vargel, C., Royer, A., St-Jean-Rondeau, O., Picard, G., Roy, A., Sasseville, V., et al. (2020). Arctic and subarctic snow microstructure analysis for microwave brightness temperature simulations. Remote Sensing Of Environment, 242.
Abstract: Passive microwave (PMW) remote sensing has proven to be a useful approach to characterize the volume of seasonal snowpack in remote northern regions at the synoptic scale. Modeling emitted microwave brightness temperatures (TB) is made possible using a physical radiative transfer model that takes into account microstructural and stratigraphic structure of the snowpack. However, prescribing the microstructure remains a difficult task. This paper aims to find proper microstructure parametrization and the snow emission model formulation that best optimize TB simulations for Arctic and Subarctic snowpacks. Surfaced-based radiometric measurements in conjunction with in-situ snowpack characterization were used for testing different configurations based on the Snow Microwave Radiative Transfer model (SMRT), with two electromagnetic models (Dense Media Radiative Transfer Quasi Crystalline Approximation, DMRT, and Improved Born Approximation, IBA) and two microstructure description theories (Sticky Hard Sphere, SHS, and Exponential, Exp). We compare the performance of three configurations (DMRT-SHS, IBA-SHS and IBA-Exp) with a unique large dataset (119 snowpits with concomitant microwave ground-based radiometer observations) covering a wide range of Arctic and Subarctic snow types in Northern and Eastern Canada. Results show that the input measured microstructure parameters must be scaled up in order to better match simulated and observed TB at 11, 19, 37 and 89 GHz. We show that the IBA-Exp gives the best results, with a Root-Mean-Square Error (RMSE) lower by up to 30% for Subarctic snow and 24% for Arctic snow compare to the other model configurations we used. In addition, we undertake a complementary experiment on isolated homogeneous snow slabs to investigate the sensitivity of the scaling factor to snow microstructure. The retrieved microwave correlation length appears significantly different than the in-situ Debye correlation length. At high frequencies, the observed variability of these scaling factors with frequency and snowpack types means that density, SSA and estimated correlation length seem insufficient to appropriately fully characterize snow microstructure for microwave modeling purposes.
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Vecchiato, M., Gambaro, A., Kehrwald, N., Ginot, P., Kutuzov, S., Mikhalenko, V., et al. (2020). The Great Acceleration of fragrances and PAHs archived in an ice core from Elbrus, Caucasus. Scientific Reports, 10(1).
Abstract: The Great Acceleration of the anthropogenic impact on the Earth system is marked by the ubiquitous distribution of anthropogenic materials throughout the global environment, including technofossils, radionuclides and the exponential increases of methane and carbon dioxide concentrations. However, personal care products as direct tracers of human domestic habits are often overlooked. Here, we present the first research combining fragrances, as novel personal care products, and polycyclic aromatic hydrocarbons (PAHs) as combustion and industrial markers, across the onset of the Great Acceleration in the Elbrus, Caucasus, ice core. This archive extends from the 1930s to 2005, spanning the profound changes in the relationship between humans and the environment during the twentieth century. Concentrations of both fragrances and PAHs rose throughout the considered period, reflecting the development of the Anthropocene. However, within this rising trend, remarkable decreases of the tracers track the major socioeconomic crises that occurred in Eastern Europe during the second half of the twentieth century.
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Vegas-Vilarrubia, T., Rull, V., Trapote, M., Cao, M., Rosell-Mele, A., Buchaca, T., et al. (2020). Modern Analogue Approach Applied to High-Resolution Varved Sediments-A Synthesis for Lake Montcortes (Central Pyrenees). Quaternary, 3(1).
Abstract: In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of different modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Different biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortes as a case study and proposing new working hypotheses for future research.
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Velicogna, I., Mohajerani, Y., Geruo, A., Landerer, F., Mouginot, J., Noel, B., et al. (2020). Continuity of Ice Sheet Mass Loss in Greenland and Antarctica From the GRACE and GRACE Follow-On Missions. Geophysical Research Letters, 47(8).
Abstract: We examine data continuity between the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (FO) missions over Greenland and Antarctica using independent data from the mass budget method, which calculates the difference between ice sheet surface mass balance and ice discharge at the periphery. For both ice sheets, we find consistent GRACE/GRACE-FO time series across the data gap, at the continental and regional scales, and the data gap is confidently filled with mass budget method data. In Greenland, the GRACE-FO data reveal an exceptional summer loss of 600 Gt in 2019 following two cold summers. In Antarctica, ongoing high mass losses in the Amundsen Sea Embayment of West Antarctica, the Antarctic Peninsula, and Wilkes Land in East Antarctica cumulate to 2130, 560, and 370 Gt, respectively, since 2002. A cumulative mass gain of 980 Gt in Queen Maud Land since 2009, however, led to a pause in the acceleration in mass loss from Antarctica after 2016.
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Vignon, E., Picard, G., Duran-Alarcon, C., Alexander, S., Gallee, H., & Berne, A. (2020). Gravity Wave Excitation during the Coastal Transition of an Extreme Katabatic Flow in Antarctica. Journal Of The Atmospheric Sciences, 77(4), 1295–1312.
Abstract: The offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of polynyas. In this study, we make use of a combination of ground-based remotely sensed and meteorological measurements at Dumont d'Urville (DDU) station, satellite images, and simulations with the Weather Research and Forecasting Model to analyze a major katabatic wind event in Adelie Land. Once well developed over the slope of the ice sheet, the katabatic flow experiences an abrupt transition near the coastal edge consisting of a sharp increase in the boundary layer depth, a sudden decrease in wind speed, and a decrease in Froude number from 3.5 to 0.3. This so-called katabatic jump manifests as a turbulent “wall” of blowing snow in which updrafts exceed 5 m s(-1). The wall reaches heights of 1000 m and its horizontal extent along the coast is more than 400 km. By destabilizing the boundary layer downstream, the jump favors the trapping of a gravity wave train-with a horizontal wavelength of 10.5 km-that develops in a few hours. The trapped gravity waves exert a drag that considerably slows down the low-level outflow. Moreover, atmospheric rotors form below the first wave crests. The wind speed record measured at DDU in 2017 (58.5 m s(-1)) is due to the vertical advection of momentum by a rotor. A statistical analysis of observations at DDU reveals that katabatic jumps and low-level trapped gravity waves occur frequently over coastal Adelie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics.
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Vincent, C., Gilbert, A., Jourdain, B., Piard, L., Ginot, P., Mikhalenko, V., et al. (2020). Strong changes in englacial temperatures despite insignificant changes in ice thickness at Dome du Gaiter glacier (Mont Blanc area). Cryosphere, 14(3), 925–934.
Abstract: The response of very-high-elevation glaciated areas on Mont Blanc to climate change has been analysed using observations and numerical modelling over the last 2 decades. Unlike the changes at low elevations, we observe very low glacier thickness changes, of about – 2.6 m on average since 1993. The slight changes in horizontal ice flow velocities and submergence velocities suggest a decrease of about 10 % in ice flux and surface mass balance. This is due to less snow accumulation and is consistent with the precipitation decrease observed in meteorological data. Conversely, measurements performed in deep boreholes since 1994 reveal strong changes in englacial temperature reaching a 1.5 degrees C increase at a depth of 50 m. We conclude that at such very high elevations, current changes in climate do not lead to visible changes in glacier thickness but cause invisible changes within the glacier in terms of englacial temperatures. Our analysis from numerical modelling shows that glacier near-surface temperature warming is enhanced by increasing melt frequency at high elevations although the impact on surface mass balance is low. This results in a non-linear response of englacial temperature to currently rising air temperatures. In addition, borehole temperature inversion including a new dataset confirms previous findings of similar air temperature changes at high and low elevations in the Alps.
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Wegmann, M., Rohrer, M., Santolaria-Otin, M., & Lohmann, G. (2020). Eurasian autumn snow link to winter North Atlantic Oscillation is strongest tor Arctic warming periods. Earth System Dynamics, 11(2), 509–524.
Abstract: In recent years, many components of the connection between Eurasian autumn snow cover and wintertime North Atlantic Oscillation (NAO) have been investigated, suggesting that November snow cover distribution has strong prediction power for the upcoming Northern Hemisphere winter climate. However, the non-stationarity of this relationship could impact its use for prediction routines. Here we use snow products from long-term reanalyses to investigate interannual and interdecadal links between autumnal snow cover and atmospheric conditions in winter. We find evidence for a negative NAO-like signal after November with a strong west-to-east snow cover gradient, which is valid throughout the last 150 years. This correlation is consistently linked to a weak stratospheric polar vortex state. Nevertheless, decadal evolution of this link shows episodes of decreased correlation strength, which co-occur with episodes of low variability in the November snow index. By contrast, periods with high prediction skill for winter NAO are found in periods of high November snow variability, which co-occur with the Arctic warming periods of the 20th century, namely the early 20th-century Arctic warming between 1920 and 1940 and the ongoing anthropogenic global warming at the end of the 20th century. A strong snow dipole itself is consistently associated with reduced Barents-Kara sea ice concentration, increased Ural blocking frequency and negative temperature anomalies in eastern Eurasia.
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