[LINK] "A lake in the Northwest Territories is about to fall off a cliff"

[rfmcdonald]

The Globe and Mail shared Bob Weber's Canadian Press article describing how global warming will lead to a lake in the Northwest Territories falling off a cliff.

Some time in the next few months, a small northern lake will burst through the shrinking earthen rampart holding it back and fall off a cliff.

“It’s got a ways to travel,” says Steve Kokelj of the Northwest Territories Geological Survey. “This lake happens to be perched about 600 feet above the Mackenzie Valley.”

[. . .]

The doomed lake, which has no name and sits in the northern corner of the territory near the community of Fort McPherson, is a victim of the region’s geology and changing climate.

Permafrost in this part of the N.W.T. contains a high percentage of ice in headwalls, which can be up to 30 metres thick. That ice has been there since the retreat of the Laurentide Ice Sheet 20,000 years ago.

Trouble starts when parts of the headwalls are exposed by erosion from wind or rain. The ice melts, which causes the soil and rock on top to collapse. That exposes more ice, which also melts and extends the collapse, and the cycle keeps repeating.

“It thaws in the summertime and will continue to work its way back upslope until you run out of ice or the headwall gets covered by sediment,” Kokelj says. “The slumps chew their way upslope.”