Canada’s last intact ice shelf breaks up

THE LAST whole ice shelf in Canada’s Arctic was no match for this summer’s heatwave. In northern Ellesmere Island temperatures since May have been 5⁰C warmer than the 30-year average of 0-1⁰C. On July 30th-31st, the 80-metre (260-foot) thick Milne ice shelf, which juts out from the island’s north-western coast, split in two. A slab measuring 80 square km (31 square miles), more than 40% of the shelf’s surface area, broke away. By August 3rd the wandering wedge of ice split again. The two strays will now drift on the Beaufort Gyre current as they melt away (see map).

A century ago Ellesmere’s northern coast had one 8,600 square km shelf, a floating island of ice driven onto shore some 4,000 years ago. During the 20th century it broke apart. The Milne shelf is the biggest remaining constituent. Derek Mueller, a geography professor at Carleton University in Ottawa who began documenting the ice shelves’ erosion in 2005, has seen the smaller ones collapse. Until now the Milne shelf had been protected by the high walls of the narrow 30km fjord along which it stretches.