A river that flowed from one of the largest glaciers in Canada vanished over a course of four days last year in what appears to be another unwanted impact of global warming.

First River Piracy Observed In Modern Times

Scientists said that climate change helped reverse the flow of water from the Kaskawulsh Glacier in Canada's Yukon territory, in a process known as river piracy.

The phenomenon, which happens when a river captures and diverts the flow of another river, ordinarily takes thousands of years or more but it just happened here over a short period in 2016.

Researchers have found evidence of this phenomenon having taken place in the distant past. It is the first time they have observed river piracy in modern times.

"Nobody to our knowledge has documented it happening in our lifetimes," said Daniel Shugar, from the University of Washington at Tacoma, who co-authored a study of the phenomenon published in the journal Nature Geoscience on Monday, April 17. "People had looked at the geological record, thousands or millions of years ago, not the 21st century, where it's happening under our noses."

Phenomenon Driven By Climate Change

For hundreds of years, the Slims River carried meltwater northward from the Kaskawulsh Glacier into the Kluane river and into the Yukon river toward the Bering Sea.

In Spring 2016, however, intense melting of the glacier led to the rerouting of the vast stream of meltwater. As a result of the retreat and thinning of the glacier driven by a warming world, the flow of meltwater to Yukon's largest lake was cut and freshwater was channeled to the Gulf of Alaska, which is thousands of miles away from the Bering Sea, the water's original destination.

The unusually warm spring resulted in the meltwater cutting a canyon through the ice and diverting water into the Alsec River, which flows to the south and into the Pacific, robbing waters that were supposed to go north.

The previous year, the rivers Alsec and Slims were comparable in size but the Alsec is now between 60 and 70 times larger than Slims, as shown by flow measurements. Researchers also found how abrupt the change had been. Slims' water flow dropped precipitously from May 26 to May 29, 2016.

The researchers attributed the phenomenon to man-made climate change, saying there is a small likelihood that the the melting of the Kaskawulsh Glacier would have occurred with constant climate change.

"We may be surprised by what climate change has in store for us - and some of the effects might be much more rapid than we are expecting," Shugar said.

River Piracy To Impact Communities

Researchers said that future river piracy may have an unwanted impact on human and biological communities that have sprung up around available water.

"Based on satellite image analysis and a signal-to-noise ratio as a metric of glacier retreat, we conclude that this instance of river piracy was due to post-industrial climate change," the researchers wrote in their study. "Rapid regional drainage reorganizations of this type can have profound downstream impacts on ecosystems, sediment and carbon budgets, and downstream communities that rely on a stable and sustained discharge."

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