COUPLING AN AGCM WITH AN ISM TO INVESTIGATE THE ICE SHEETS MASS-BALANCE AT THE LAST GLACIAL MAXIMUM

The aim of this paper is to investigate the consistency between the ic e sheets reconstruction at the LGM and the climate simulated by AGCM. In particular, to investigate whether the laurentian and the fennoscan dian ice sheets have an equilibrated mass balance, we use two compleme ntary approaches. First we analyze the changes of snow and water budge ts over the ice sheets, only using the model results of LGM runs. Seco nd, we use a thermomechanical ice sheet model [Ritz ei al., 1997] forc ed with the AGCM simulated climate, to perform long term runs at finer spatial resolution. Analyzing the results obtained with both approach es, we show that the ice sheet mass balance computed directly from AGC M results may be biaised. Moreover we show, using two versions of the LMD AGCM, that the ice sheet mass balance computed by the ISM is drast ically sensitive to the summer surface temperatures simulated by the A GCM.