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Modélisation du bilan de masse en surface de la calotte glaciaire antarctique

Abstract : The Antarctic ice sheet surface mass balance (SMB, snow accumulation minus ablation) is sensitive to climate parameters and directly contributes to global mean sea level variations. Therefore, in the perspective of climate change, it is useful to develop tools that can simulate the physical processes involved in the Antarctic surface mass balance. The approach developed in this thesis consists in using a cascade of atmospheric models from large scale to local scale. Thus, a regional climate model (Modèle atmosphérique régional, hereinafter referred to as MAR), forced by European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis, provides a diagnostic physical-based rain- and snowfall disaggregation model with meteorological fields at the regional scale (typically 40-km resolution). In a first part, it is shown that the SMB calculated by MAR is in good agreement with observations in most regions. Nonetheless, runoff appears to be overestimated; the problem vanishes when introducing a dependency of albedo with solar zenithal distance. In a second part, it is shown that although the parameterizations invoked in the disaggregation model are fairly simple, the knowledge of small-scale topography (5-km resolution) is efficiently used to improve the spatial variability of precipitation - and therefore SMB - over coastal regions of Antarctica. Model validation is carried out with the help of snow height measurements provided by automatic weather stations. Over the coastal place of Law Dome, the net accumulation gradient is mostly due to orographic forcing of precipitation (rather than blowing snow). The disaggregation model dramatically underestimates precipitation over the Antarctic Plateau, where polar stratospheric clouds associated with radiative cooling could play a role in the formation of precipitation during the polar night.
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https://tel.archives-ouvertes.fr/tel-00189139
Contributor : Luc Gential <>
Submitted on : Tuesday, November 20, 2007 - 12:13:23 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Monday, April 12, 2010 - 2:48:06 AM

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  • HAL Id : tel-00189139, version 1

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Luc Gential. Modélisation du bilan de masse en surface de la calotte glaciaire antarctique. Modélisation et simulation. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00189139⟩

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