Identification of Antarctic ablation areas using a regional atmospheric climate model

The occurrence of Antarctic ablation areas in Dronning Maud Land, the Lambert Glacier Basin, Victoria Land, the Transantarctic Mountains and the Antarctic Peninsula is realistically predicted by the regional atmospheric climate model RACMO2/ ANT, with snowdrift- related processes calculated offline. Antarctic ablation areas are characterized by a low solid precipitation flux in combination with strong sublimation, snowdrift erosion and/ or melt. The strong interaction between atmospheric circulation and topography plays a decisive role in the precipitation distribution and hence that of ablation areas. Three types of Antarctic ablation areas can be distinguished, all occurring in dry regions: Type 1 is the erosion- driven ablation area, caused by 1- D and/ or 2- D divergence in the katabatic wind field at high elevations ( 2000 - 3200 m asl). Type 2 is the sublimation- driven ablation area. This type occurs at lower elevations (< 2000 m) preferably at the foot of steep topographic barriers, where temperature and wind speed are high and relative humidity low. Type 3 represents the melt- driven ablation area, occurring in the northern Antarctic Peninsula. Combinations of types 1/ 2 and 2/ 3 are possible. Over the period considered here ( 1980 - 2004), no significant trend is found in the total area covered by Antarctic ablation areas, which equals about 2% of the total ice sheet surface ( including ice shelves).