Coupling an AGCM with an ISM to investigate the ice sheets mass balance at the Last Glacial Maximum

Abstract

The aim of this paper is to investigate the consistency between the ice sheets reconstruction at the LGM and the climate simulated by AGCM. In particular, to investigate whether the laurentian and the fennoscandian ice sheets have an equilibrated mass balance, we use two complementary approaches. First we analyze the changes of snow and water budgets over the ice sheets, only using the model results of LGM runs. Second, we use a thermomechanical ice sheet model [Ritz et al., 1997] forced with the AGCM simulated climate, to perform long term runs at finer spatial resolution. Analyzing the results obtained with both approaches, we show that the ice sheet mass balance computed directly from AGCM 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 drastically sensitive to the summer surface temperatures simulated by the AGCM.