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Altimetric observations of sea ice thickness : Towards global sea ice volume estimates from space

Séminaire de F. Garnier ( LEGOS), Jeudi 11 Octobre 2018 a 11h en salle Lliboutry, Bâtiment de Glaciologie

4 octobre 2018, par Fabien Gillet-Chaulet

Altimetric observations of sea ice thickness : Towards global sea ice volume estimates from space

Séminaire de : Florent Garnier (LEGOS)

Abstract :

Sea ice plays crucial role on the oceanic circulation, the development of plankton, the arctic weather, and more globally on the climate. These important roles are due to the physical properties of the sea ice that differ from the physical properties of the underneath ocean and change radically the ocean surface response to radiations and atmospheric forcing. Because of these processes, the undergoing rapidly changing sea ice in response to global warming leads to significant changes in the polar regions that can feed back on the climate system both regionally and globally (IPCC2013).
Sea ice extension, sea ice concentration and sea ice drift are fairly well observed since the 70ies, in particular with space visible imagery and satellite radiometers. However, before 2010, sea ice thickness observations remain sparse and un-homogeneously distributed over time and space (Lindsay and Shweiger 2015). Until now the altimetric observations of sea ice thickness have mainly been based on CryoSat-2 and remain limited in time. Based on these assumptions, an increasing effort has been made in the last few years at the LEGOS laboratory to extent our ability to measure sea ice thickness from altimetric measurements.
In this presentation, we present the main features of radar altimeter sea ice thickness measurements which consists in measuring the difference between the height of the ice floes and the height of the surrounding water in the fractures of the ice, or “leads”.
We also present results from recents studies (Guerreiro et al 2016, 2017) which show 1) that ice thickness measurements can be extended from LRM (Low Resolution Mode) altimeter data such as Envisat and 2) that the snow depth (which is necessary to retrieve sea ice thickness from freeboard measures) can de calculated from Ka-Ku bi-frequency altimetric observations.
We will also review the ongoing work on sea ice thickness including the first presentation of antarctic sea ice freeboards measurements from space. The development of a new satellite based estimate of sea ice freeboard, sea ice thickness and sea ice volume changes over 16 years with unprecedented resolution should be later used to revisit estimates of sea ice volume variability and trends and provide a new insights compared to previous estimates based on sparse in-situ and laser altimetry data.

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