Evolution of the Antarctic surface mass balance by high-resolution downscaling and impact on sea-level change for the next centuries

• Main Authors: Agosta, Cécile, Favier, Vincent, Krinner, Gerhard, Gallée, Hubert, Genthon, Christophe
• Format: Conference Object
• Language: English
• Published: 2012
• Subjects: Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Antarc*; Antarctic; Antarctica; Ice Sheet
• Online Access: https://orbi.uliege.be/handle/2268/145011; https://orbi.uliege.be/bitstream/2268/145011/1/SCAR-2012.pdf

Most of the IPCC-AR4 Atmospheric Global Circulation Models (AGCM) predict an increase of the Antarctic Surface Mass Balance (SMB) during the 21st century that would mitigate global sea level rise. Present accumulation and predicted change are largest at the ice sheet margins because they are driven by snowfall, which mostly comes from warm, moist air arising over the land slopes. The coastal belt is also where complex processes of sublimation, melt and refreezing occur. Thus, high-resolution modelling is necessary to adequately capture the effects of small-scale variations in topography on the atmospheric variables in this area, but limitations in computing resources prevent such resolution at the scale of Antarctica in full climate models. We present here a downscaling method leading to 15-km SMB resolution for century time-scales over Antarctica. We compute the effect of the fine topography on orographic precipitation and on boundary layer processes that lead to sublimation, melt and refreezing. We first display the SMB downscaled from ERA-Interim and show that the downscaling improves the agreement between modelled and observed SMB for the end of the 20th century. We then present hi-resolution features of the Antarctic SMB evolution during the 21st century downscaled from LMDZ4 for different scenarios. We show that a higher resolution induce at the same time more run-off but a significantly higher mitigation of sea level rise.