ANTARCTIC CLIMATE MODELING WITH GENERAL-CIRCULATION MODELS OF THE ATMOSPHERE

The abilities of the National Aeronautic and Space Administration Godd ard Institute for Space Studies (GISS) and METEO-FRANCE Arpege General Circulation Models (GCMs) of the atmosphere to simulate surface clima te variables that have direct and indirect impacts on the mass balance of the Antarctic ice sheet are evaluated. Deficiencies in reproducing the surface temperature are identified. Some of the flaws are associa ted with an incorrect specification of the Antarctic continent real to pography, a problem which can be partially corrected by an adequate pr ocessing of model output. Shortcomings can also be consequent to the u se of inappropriate climate variable formulations and prescribed bound ary conditions. A coarse-resolution version of the GISS GCM is used to demonstrate how model results can be improved if snow albedo and sea ice coverage are more adequately set. A barrier to thoroughly analyzin g and validating model results is die lack of numerous and reliable en ough observational data. This point is particularly critical for accum ulation, a first-order term in the ice sheet mass balance. Although ac cumulation is very different in the GISS and Arpege models, uncertaint ies about the available observational references preclude firmly asser ting that one model is better than the other. Finally, typical GCM res olution remains an essential limitation to improving model performance s and promoting the effective use of model results for the Antarctic r egion.