Désagrégation du Bilan de Masse et du Bilan d’Energie en Surface de la calotte polaire Antarctique, application pour le 21ème siècle

Most of the IPCC-AR4 Atmospheric Global Circulation Models (AGCM) predict an increase of the Antarctic Surface Mass Balance (SMB) during the 21st century, driven by an increase of snow falls, which would mitigate the sea level rise. Much of the SMB change is expected to happen in the Antarctic coastal area, which concentrates the major part of the snow falls. This area is also were we find complex processes of precipitation, sublimation, melt and redistribution by the wind. High-resolution modeling (5 to 10 km) is necessary to accurately capture the effects of the fine topography on the atmospheric variables but limitations in computing resources prevent such resolution at the scale of Antarctica in full climate models. We present here a downscaling method yielding to a 10-km resolution of the SMB for the 21st century, from ~60-km resolution LMDZ4 AGCM outputs. We compute orographic precipitation induced by the finer topography, as well as the boundary layer processes leading to melt and sublimation. It shows a clear improvement of the SMB distribution in coastal regions with consequences on the grounded ice sheet SMB estimation.