Greenland is already losing ice to the oceans, contributing to the gradual rise in sea levels. The ice cap holds enough water to lift sea levels globally by about 7m (22ft) if it all melted.

Natural climatic cycles such as the Arctic Oscillation play a role in year-to-year variations in ice cover. But Julienne Stroeve believes the sea ice is now so thin that there is little chance of the melting trend turning round.

"If the ice were as thin as it was in the 1970s, last year's conditions would have brought a dip in cover, but nothing exceptional.

"But now it's so thin that you would have to have an exceptional sequence of cold winters and cold summers in order for it to rebuild."