The cap has an average thickness of one kilometre and covers an area 1.5 times the size of Texas.

BBC: By BBC News Online Science Editor Dr David Whitehouse

Figures indicate an average ice thickness of 1.15-3.75m, much of which might be expected to melt between June and September.

BBC: Arctic team gives up on ice radar

In recent times, average winter Arctic thickness has been about 2.5m, down from 3.5-4.0m based on climatological data.

BBC: Arctic team targets key ice data