A POSSIBLE CHANGE IN MASS-BALANCE OF GREENLAND AND ANTARCTIC ICE SHEETS IN THE COMING CENTURY

A high-resolution GCM is found to simulate precipitation and surface e nergy balance of high latitudes with high accuracy, This opens new pos sibilities to investigate the future mass balance of polar glaciers an d its effect on sea level. The surface mass balance of the Greenland a nd the Antarctic ice sheets is simulated using the ECHAM3 GCM with T10 6 horizontal resolution. With this model, two 5-year integrations for the present and doubled carbon dioxide conditions based on the boundar y conditions provided by the ECHAM1/T21 transient experiment have been conducted. A comparison of the two experiments over Greenland and Ant arctica shows to what extent the effect of climate change on the mass balance on the two largest glaciers of the world can differ. On Greenl and one sees a slight decrease in accumulation and a substantial incre ase in melt, while on Antarctica a large increase in accumulation with out melt is projected. Translating the mass balances into terms of sea -level equivalent, the Greenland discharge causes a sea level rise of 1.1 mm yr(-1), while the accumulation on Antarctica tends to lower it by 0.9 mm yr(-1). The change in the combined mass balance of the two c ontinents is almost zero. The sea level change of the next century can be affected more effectively by the thermal expansion of seawater and the mass balance of smaller glaciers outside of Greenland and Antarct ica.