Climatic Impact of a Greenland Deglaciation and Its Possible Irreversibility

Abstract

Warmer climate conditions persisting for a period of many centuries could lead to the disappearance of the Greenland ice sheet, with a related 7-m rise in sea level. The question is addressed of whether the ice sheet could be regenerated if preindustrial climate conditions were reestablished after its melting. The HadCM3 coupled atmosphere?ocean GCM is used to simulate the global and regional climate with preindustrial atmospheric greenhouse gas composition and with the Greenland ice sheet removed. Two separate cases are considered. In one, the surface topography of Greenland is given by that of the bedrock currently buried under the ice sheet. In the other, a readjustment to isostatic equilibrium of the unloaded orography is taken into account, giving higher elevations. In both cases, there is greater summer melting than in the current climate, leading to partially snow-free summers with much higher temperatures. On the long-term average, there is no accumulation of snow. The implication of this result is that the removal of the Greenland ice sheet due to a prolonged climatic warming would be irreversible.