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Canada’s big glacier-born river dries up in over four days

Canada’s big glacier-born river dries up in over four days The abrupt and unexpected disappearance of the Slims river, which spanned up to 150 meters at its widest points, is the first observed case of “river piracy”, in which the flow of one river is suddenly diverted into another.

This is reported by The Guardian.

For hundreds of years, the Slims carried meltwater northwards from the vast Kaskawulsh glacier in Canada’s Yukon territory into the Kluane river, then into the Yukon river towards the Bering Sea.

But in spring 2016, a period of intense melting of the glacier meant the drainage gradient was tipped in favor of a second river, redirecting the meltwater to the Gulf of Alaska, thousands of miles from its original destination.

The continental-scale rearrangement was documented by a team of scientists who had been monitoring the incremental retreat of the glacier for years.

The team flew a helicopter over the glacier and used drones to investigate what was happening in the other valley, which is less accessible.

“We found that all of the water that was coming out from the front of the glacier, rather than it being split between two rivers, it was going into just one,” said James Best, a geologist at the University of Illinois.

While the Slims had been reduced to a mere trickle, the reverse had happened to the south-flowing Alsek river, a popular whitewater rafting river that is a Unesco world heritage site. The previous year, the two rivers had been comparable in size, but the Alsek was now 60 to 70 times larger than the Slims, flow measurements revealed.

Prof Lonnie Thompson, a paleoclimatologist at Ohio State University who was not involved in the work, said the observations highlight how incremental temperature increases can produce sudden and drastic environmental impacts. “There are definitely thresholds which, once passed in nature, everything abruptly changes,” he said.
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