Greenland's ice-cap has thickened slightly despite the predictions of a thaw triggered by global warming.
A total melt of the 3000m-thick ice would raise world sea levels by about 7m and slow the Gulf Stream which keeps the North Atlantic region warm.
Satellite measurements show more snowfall was thickening the ice-cap, especially at high altitudes, a report in the Science journal said.
The ice thickened half a metre over 11 years, researchers said.
But they said the thickening seemed consistent with theories of global warming, as warmer air, even if it is still below freezing, could carry more moisture.