The flow of meltwater into the North Atlantic is likely to disrupt the thermohaline circulation, which controls ocean currents such as the Gulf Stream. A massive arrival of cold fresh water caused by the melt of the Greenland ice sheet would reduce the density of the Gulf Stream which is normally salty. This ocean current, whose salinity allows it to sink along the coasts of Greenland, would no longer be able to sink deeply enough to return to the South. A catastrophic scenario would predict collapse of the Gulf Stream; this means it would stop to supply heat to the coasts of Europe and cause a significant drop in temperature even though the planet is heating up at a global scale. It is more likely, however, that the addition of fresh water to the Gulf Stream would not stop it but rather slow it down, and the consequence of this would be to mitigate the global warming in our regions. 

Between optimism and pessimism, an uncertain future

Quantifying and predicting the melt of the Greenland ice sheet is therefore not without interest, the destiny of the island of ice is intimately linked to our own. Xavier Fettweis is a modeler. From a regional climate model (the MAR model) and satellite observations, he is attempting to project the future of the ice sheet and the changes of its mass balance.

The GIEC, for its next assessment report in 2013, proposes several scenarios relative to our lifestyle and our future greenhouse gas emissions. The first, which is relatively optimistic, predicts a doubling of the current concentration of greenhouse gases. The contribution of the surface melt to sea levels in 2100 will be about 4 cm (4 ± 2 cm). Yet another more pessimistic scenario predicts a tripling of the current concentration of greenhouse gases. Sea level could rise by up to some ten centimeters in 2100 (10 ± 4 cm).