Friday, August 27, 2010

Ice breakup on Ellesmere coast 'significant'

Breakup on the Ward Hunt Ice Shelf

Earth Observatory: In mid- to late August 2010, a Bermuda-sized ice island broke free from the Ward Hunt Ice Shelf along the northern coast of Canada's Ellesmere Island... The breakup on this ice shelf continued a years-long pattern of retreat on the Ward Hunt Ice Shelf, and a decades-long pattern of retreat of the ice shelves along the Ellesmere coast...

The ice chunk... was much smaller than the ice island that calved from Greenland's Petermann Glacier a few weeks earlier, but in some ways, the Ward Hunt fracture was more significant.

Fed by the Greenland Ice Sheet, the Petermann Glacier is a floating ice tongue that periodically calves large icebergs, and is replenished by new ice upstream. In contrast, the Ward Hunt Ice Shelf formed from compressed sea ice that was gradually replaced by accumulated snow... The calving cycle on the Ward Hunt is slow, and to recover from the recent retreat would require centuries.

Driftwood and narwhal remains found along the Ellesmere coast have radiocarbon dates from roughly 3,000 to 6,800 years ago, implying that the ice has been intact since those remains were deposited. Breakup along the Ward Hunt indicates a change in the conditions that previously allowed this ice shelf to persist for millennia.
Image source here.