NASA handout image of a British Columbia glacier

A British Columbia glacier is seen from NASA’s DC-8 ASCENDS II flight in this August 2011 handout photo courtesy of the agency. Canadian glaciers that are the world’s third biggest store of ice after Antarctica and Greenland seem headed for an irreversible melt that will push up sea levels, scientists said on Thursday. About 20 percent of the ice in glaciers, on islands such as Ellesmere or Devon off northern Canada, could vanish by the end of the 21st century in a melt that would add 3.5 cm (1.4 inch) to global sea levels, they said. REUTERS/NASA/E.Shaller/ASCENDS II /Handout (CANADA – Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS