By the end of the century, a fifth of the Canadian ice sheet – the world's third largest – could be gone for good, raising average global sea levels by 3.5 centimetres.

If the whole ice sheet melts, it would raise the global sea level by about 20 centimetres, a fraction of the 70 and 7 metre rises expected respectively if Antarctica and Greenland each shed all their ice.

The Canadian melt seems paltry in comparison, but it becomes significant when the effects of other smaller ice fields melting are taken into account, says David Vaughan, leader of ice2sea, the European Union programme that supported the work.