Publications scientifiques

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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).

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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%).

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.