The Greenland ice sheet contribution to sea level changes during the last 150,000 years

Because of a possible greenhouse warming, it is expected that the Greenland ice sheet will retreat due to increased melting. By reconstructing the past evolution of the ice sheet, it is possible to obtain some insight as to the type of variations that are possible, as well as the contribution to sea level. The Greenland ice sheet is presently the second largest ice sheet of the world, and its contribution to sea level changes is not negligible. The evolution of the Greenland ice sheet has been computed by means of a thermo-mechanical ice sheet model. The surface accumulation and ablation, which are climate dependent, are driven by the temperature record obtained from the Greenland ice margin studies. Some sensitivity experiments have shown that the model results are strongly dependent on the mass balance history. The simulation of the Greenland ice sheet provides a continuous volume changes record, which can easily be converted into sea level changes. It shows that at the last glacial maximum, the ice sheet was larger, which created a 1-m lowering of sea level. During the last interglacial, 130,000 years B.P., the ice sheet was substantially more restricted than today, part of Southern Greenland being ice free. This corresponds to a 2-m rise in sea level. However, this is not the only warm episode; around 100,000 years B.P., a warm period about 20,000 years long (sub-stage 5c) also creates a restricted ice sheet, and hence a sea level 2 m higher than today for that period. During the ice age, the ice sheet, bounded by the steep slopes of the coastline, did not extend much further. The amount of ice stored corresponds then to a sea level decrease of one meter, which is only a small fraction of the 130-m lowering at the end of that period