Pittsburgh Post-Gazette

Scientists: Human-caused climate change has rerouted an entire river for first time

- By Chris Mooney

The Washington Post

A team of scientists Monday documented what they’re describing as the first case of large-scale river reorganiza­tion as a result of human-caused climate change.

They found that in mid2016, the retreat of a very large glacier in Canada’s Yukon territory led to the rerouting of its vast stream of meltwater from one river system to another — cutting down flow to the Yukon’s largest lake, and channeling freshwater to the Pacific Ocean south of Alaska, rather than to the Bering Sea.

The researcher­s dubbed the reorganiza­tion an act of “rapid river piracy,” saying that such events had often occurred in the Earth’s geologic past, but never before, to their knowledge, as a sudden present-day event. They also called it “geological­ly instantane­ous.”

A process that would ordinarily take thousands of years — or more — happened in just a few months in 2016.

“The river wasn’t what we had seen a few years ago. It was a faded version of its former self,” said lead study author Daniel Shugar of the University of Washington, Tacoma of the Slims River, which lost much of its flow due to the glacial change. “It was barely flowing at all. Literally, every day, we could see the water level dropping, we could see sandbars popping out in the river.”

The scientists concluded that the so-called river theft “is likely to be permanent.”

The study was published in Nature Geoscience. Mr. Shugar conducted the study with researcher­s from six different Canadian and U.S. universiti­es. The study found that the choking of the Slims River in turn deprived Kluane Lake, the largest body of water in the Yukon Territory. The lake level was at a record low last August.

The precipitat­ing event for all of this happened in summer 2016, when meltwater from the retreating Kaskawulsh glacier burst through a channel of ice, suddenly draining a glacial lake that had fed Slims river and directing waters into a different river that ultimately heads south toward the Gulf of Alaska. Previously, these waters had ultimately fed into the vast Yukon river, which empties on Alaska’s west coast.

The researcher­s found only a minuscule probabilit­y that the retreat of Kaskawulsh glacier — which retracted by nearly half a mile from 1956 to 2007 — could have occurred in what they called a “constant climate.” They therefore inferred that the events in question could be attributed to humancause­d climate change.

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