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In the coming months, a lake in the Northwest Territories is expected to breach the earthen embankment containing it and flow over a cliff, sending tens of thousands of cubic meters of water crashing into a neighboring valley. An advisory updated this week by the Northwest Territories Geological Survey warns that the small lake near the Gwich'in community of Fort McPherson is expected "to drain catastrophically during 2015, resulting in a flash flood and possibly a debris flow."
Although the hamlet is not threatened by the anticipated flood, scientists say the destruction of the nameless lake is one example of the climate change that is expected to continue to alter the environment of Alaska, Siberia and Canada's Far North.
"It's just another piece in the puzzle showing how the climate is changing in regions that are especially sensitive to even small changes," said Michael Pisaric, a professor of geography at Ontario's Brock University who has been monitoring that lake for the last five years. "As we change the atmosphere and alter the way systems operate, these events are going to become more and more frequent."
The destruction of the lake, which is expected in late summer or early fall, will be the result of increased heavy rainfall and temperatures, which Pisaric said have risen several degrees since recording began in the 1940s.
These forces are gradually melting arctic permafrost, which in much of the NWT is contained in ice headwalls, sometimes as much as 30 meters thick. Heat and rain are melting headwall ice, exposing soil and sediment which is in turn washed away, revealing more ice, in a process that creates large slumps in the landscape. One of these slumps is eroding backwards into the land around the doomed lake, eating away at what now may be fewer than five meters of soil and sediment holding back the water.
"Sometime, probably this summer, it's just going to erode so far back that it's just going to catastrophically drain," Pisaric told VICE News.
The ensuing flood waters are expected to flow into another larger lake in the Mackenzie Valley, leaving the nearby community unscathed.
But Wilbert Firth, a resident of Fort McPherson and the president of the Land Claims Council for the Designated Gwich'in Organizations, which administers land and capital assets for the local Aboriginal people, said the slumping permafrost is causing other problems. Firth told VICE News the runoff and sediment from the melting headwalls creates pools of sucking mud that moose sometimes get stuck in and residents take care to avoid. The displaced sediment also runs into previously clear mountain streams and lakes, choking the gills of fish.
There is also concern that a slump bordering the Dempster Highway — the only land route in and out of Fort McPherson — may eventually damage or destroy a section of the road.
These worries, Firth said, are part of how life at the northern edges of the Northwest Territories is increasingly colored by the changing environment.
"We're seeing more of it now," he said, "because of the temperatures."
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