Arctic ice shelf splits; ice loss 10x expected this summer...

The landscape surrounding Ellesmere Island in the Canadian Arctic is a shadow of its former self, thanks in part to last month's departure of 55 square kilometers of the Markham Ice Shelf. Ellesmere Island anchors one of only five remaining ice shelves in the Arctic, although how long it will retain that distinction remains to be seen. Including the Markham loss, Ellesmere Island has now lost 10 times more shelf ice this summer than scientists predicted on July 30.

Located just west of Greenland, Ellesmere Island is Canada’s most northerly landmass. Prior to the 20th Century, it was covered by one continuous 9,000-square-kilometer ice shelf. The Arctic has warmed more rapidly than the rest of the planet, though, over the past 100 years, and Ellesmere's ice shelf soon split into five distinct entities. In summer 2008 alone, Ellesmere Island's other ice shelves, the Ward Hunt and the Serson. have lost 43 square kilometers and 120 square kilometers respectively. The Markham split is the latest loss, leaving Ellesmere with only around 800 square kilometers of shelf ice.

Arctic sea ice has been disappearing at near record pace this summer. While the ice retreat has traditionally slowed in early August, this year's downward trend appeared unflappable in those telling few weeks. Scientists are concerned other cracks in the largest remaining shelf, the Ward Hunt, will continue the trend over the next few years.

Ellesmere Island's ice shelves are estimated to be around 4,000 years old, and experts do not expect them to reform under current climate conditions. "These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for thousands of years are no longer present," said Derek Mueller, Arctic expert at Trent University in Canada.

Ice shelves like those found around Ellesmere Island support unique ecosystems, many of which have gone unstudied. The Ward Hunt Ice Shelf, for example, dammed the mouth of the Disraeli Fjord to form a 3,000-year-old freshwater ecosystem. As the glaciers on the island melted each summer, their runoff fed the "epishelf lake" that was suspended atop the denser seawater. Between 2000 and 2002, the Ward Hunt Ice Shelf cracked and drained the lake, whisking its rare inhabitants out to sea.

Ellesmere Island lost much of its original ice shelf in the 1930s and 1940s, a particularly warm period in the last century. Since 2002, though, ice loss has again accelerated as Arctic temperatures overtop those seen in the first half of the 20th Century.