Climate change reverses flow of a Yukon river in geological instant

Geronimo Vena
Aprile 19, 2017

The study was published in Nature Geoscience.

Dan Shugar and the rest of the team, including Jim Best of the University of IL and John Clague of Simon Fraser University in Canada, were expected to observe the Slims River in August 2016.

For the past century, the massive Kaskawulsh Glacier in northern Canada has been steadily retreating, but as documented in a study led by the University of Washington Tacoma, this retreat has now resulted in a rare geological phenomenon known as "river piracy".

Between 1956 and 2007, the Kaskawulsh glacier retreated by 600-700 meters. Both the Sims and the Kaskawulsh are fed by the Kaskawulsh glacier; as the glacier melts, the water goes into the river and flows into other, larger bodies of water.

The current change occurred over what is believed to be one day - last May 26, based on data.

The scientists had been to the edge of the Kaskawulsh glacier in 2013.

The Slims River in Canda is the first in modern history to have disappeared at such a speed, according to scientists who observed the process.

"This is a kind of unanticipated effect of climate change that, until it happened, we didn't know it was going to happen", Shugar says. The delta top that we'd been sailing over in a small boat was now a dust storm.

The Kaskawulsh glacier covers about 9,650 square miles (25,000 square kilometers), about the size of Vermont. The front has retreated almost 1.9 kilometres since 1899.

"Day after day, we could see the level of the river down", recalls the researcher.

But outside scientists praised Monday's study and said it was significant.

The researchers directly link the change in the rivers to human-caused climate change and its impact on glaciers, which Shugar told Popular Science, "is happening much faster than can be explained by natural causes".

With the Slims' flow greatly reduced, water levels in Kluane Lake dropped to 5.5 feet below their mid-summer average and 3 feet lower than they had ever been measured at that time of year. "It was essentially a long, skinny lake", Dr Shugar said. "If it drops enough that the lake level is below its other outlet, at the north end, it becomes what is called a closed basin". "The chemistry and biology of the water changed dramatically".

An huge river that flowed from one of Canada's largest glaciers vanished over the course of four days previous year, scientists have reported, in an unsettling illustration of how global warming dramatically changes the world's geography.

The Slims river has been flowing through Canada for 300 years, but in 2016 something happened that caused it to vanish in the blink of an eye.

The geologic event has redrawn the local landscape.

The beneficiary of the change, in hydrologic terms, is the Alsek River, known for its whitewater rafting.

The newly exposed bed of Kluane Lake, which used to be fed by the Slims River. The receding toe of Kaskawulsh Glacier is seen at the bottom.

But when they arrived in August, the river was not flowing. Now, all of this is changing.

Geologists are calling it an unprecedented side effect of climate change.

The askawulsh Glacier seen from lower slopes of Vulcan Mountain.

Thompson, who has documented glacial retreat on Mount Kilimanjaro, predicts that there will be an acceleration in the observations of river piracy events as glaciers retreat globally.

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