Greenland glacier from the air (photo E Wallace, October 2009)

Greenland’s ice mass is melting at a quicker pace than previously believed and consequently adding more water to the oceans, reports Science magazine 13 November. The increased run-off will cause the sea-level to rise by more than was estimated by the Intergovernmental Panel on Climate Change’s (IPCC) 2007 projection for 2100.

Altogether some 1,500 gigatonnes of ice melted between 2000 and 2008, the researchers say, contributing about 4.1 millimetres to sea levels. The ice melt is equally divided between increased run-off and precipitation on the one hand, and ice dynamics, meaning faster-moving glaciers, on the other. Since 2006 ice melting in Greenland has accelerated and contributes 0.75mm per year to the global rise in sea levels.

New measurements have allowed the team of researchers led by Michiel van den Broeke of Utrecht University in the Netherlands to quantify more precisely the sources of the melt since 2000. Several warm summers have increased the melting of the ice mass faster than can be fixed during the winters by snowing and refreezing.

The scientist confirmed their data using GRACE, a space-based system that detects  subtle changes in the earth’s gravitational field due to shifts, such as ice-melt, in the earth’s mass. BBC, TSR