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River Delta's Rise Puts Arctic's Future in Flux

  • Climate change in Arctic seas is driving summer water levels at the Mackenzie's mouth to three times normal, B.C. researchers find
    By Mark Hume
    Toronto Globe and Mail, April 4, 2008
    Straight to the Source

VANCOUVER -- In the Mackenzie River Delta, where there are about 45,000 lakes separated by thin arms of land, researchers have found that global warming is causing water-level increases three times greater than expected. When Lance Lesack a Simon Fraser University geographer, and Philip Marsh, an Environment Canada scientist, began to study the myriad lakes of the delta, they thought they would find more evidence of the impact of global warming.

They were surprised by just how rapid and extensive those changes are, Dr. Lesack said yesterday.

"In the case of the Mackenzie Delta, it's three times what we thought it would be ... and that's quite dramatic," said Dr. Lesack, who found a 30-centimetre rise in summer water levels of low-elevation lakes over the past 30 years.

"This is not something that's just of pertinence to the Mackenzie Delta. I think what this work indicates is that receding sea ice is going to have a huge effect around the entire circumpolar region," he said.

Dr. Lesack and Dr. Marsh studied a sample of lakes spread across the 13,000 square kilometres of the delta, near the Arctic communities of Inuvik and Tuktoyaktuk, where Canada's longest river, the 4,421-kilometre Mackenzie, flows into the Beaufort Sea.

The lakes there were formed when water pooled on the frozen landscape. Most of the lakes are isolated from the Mackenzie for most of the year, but are "recharged" each spring when the river overflows its banks.

But with Arctic temperatures rising and sea-ice retreating earlier each year, the river ice jams that caused the massive spring floods have begun to diminish.

Despite the reduction in ice-jam floods, however, the researchers found water levels rising in the lower-lying lakes, which were being swamped by river waters for longer periods each year. The flooding of Lake 80, for example, has increased to 138 days from 101 days since 1973. In the same period, Lake 129 has gone from 145 days of flooding to 169 days.

Full Story: http://www.theglobeandmail.com/servlet/story/LAC.20080404
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