Monday, September 01, 2008

Surging B.C. glacier threatens to block river

HIde the news that doesn't fit your story. Here is a computer-generated 50,000-foot view of the Alsek River, just west of Glacier Bay Natonal Park.
A mammoth-sized glacier is dangerously on the move in remote northwestern B.C., threatening to seal off the Alsek River and create a lake that would ultimately burst and pose a flood hazard to rafters and anyone else downstream. Glaciers are supposed to be receding in this era of global warming. But a buildup of water beneath the Tweedsmuir Glacier is causing it to surge ahead at a rate of several metres a day. It is now midway across the Alsek River. "There is a reasonable chance this glacier will seal off the route of the Alsek," Garry Clarke, a professor of glaciology at the University of B.C., confirmed in an interview. "The end result has got to be a big flood. It would render the whole river downstream quite dangerous." Clarke visited the site as recently as Aug. 1 and said the glacier's 65-metre-high face is calving off pieces of ice which are being carried downstream to the Tatshenshini River. He figures it's just a matter of time before the volume of ice exceeds the river's ability to carry it away, creating a temporary lake upstream. Because ice floats, the lake would eventually tunnel underneath the glacier with a giant rush of water, known as a jökulhlaup to Icelanders. River rafters already must watch out for floating ice, and would have to get off the river entirely once a reservoir is formed. About 350 rafters, both private and commercial, travel the river system every year. Federal NDP leader Jack Layton took a guided trip in July. The Tatshenshini River flows into Alaska's Glacier Bay National Park and Preserve, where authorities are developing an emergency plan to ensure notification of about 50 rafters, hunters, fishermen, and park staff who could be at risk from a sudden flood.

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