In a rare case of river piracy, climate change is the culprit

Photo by Dan Shugar/University of Washington Tacoma

Scientists say they can pinpoint a day in May 2016 when the water levels in the Slims River dramatically dropped. (Photo by Dan Shugar/University of Washington Tacoma

Scientists are pointing to climate change as the reason a river that used to feed into the Yukon has nearly disappeared.

A report published in Nature Geoscience on Monday says it’s the first documented case of river piracy in modern times — linked to the planet heating up. River piracy is when one river steals the flow of another.

Scientists knew the Kaskawulsh Glacier in northern Canada was shrinking. But they didn’t expect it to cause a nearby lake to almost vanish. At least, not so quickly.

“Nobody’s documented this as basically occurring under our noses,” Shugar said.

Dan Shugar researches how landforms evolve at the University of Washington in Tacoma.

And last fall, he set out with his colleagues to study the Slims River. It’s fed by a series of ponds at the front of the Kaskawulsh Glacier.

When he arrived, Shugar says he expected the river’s current to be low.

“But as it turned out is was essentially no flow,” Shugar said. “So we couldn’t actually put our instruments in the water it was so shallow.”

Shugar didn’t spend the remainder of his time in Canada kicking back. His new mission became figuring out what happened to the Slims River.

The body of water used to flow into the Kluane Lake, and eventually into the Yukon River, which empties into the Bering Sea. But because of glacier melt, that water redirected.

“The Kaskawulsh River essentially stole all of that water that would have otherwise flowed into the Slims River,” Shugar said. “So it pirated that flow. It captured that flow.”

Now that water goes from the Kaskawulsh River to the Alsek River and all the way to the Gulf of Alaska.

Shugar says, due to the circumstances, this particular situation is unique. Still, the rapid pace at which it occurred serves as an important reminder.

“Climate change is happening and it’s happening here,” Shugar said. “So we need to be keeping in mind that we may get thrown a few curve balls moving forward.”

So while the Kaskawulsh River was the pirate, Shugar says human-caused climate change is ultimately to blame.

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