‘River Piracy’ Cuts Off Flow to Kluane Lake, Yukon’s Largest; Level Drops ‘Several Meters’

Apr 28, 2017

The downstream impacts of last year’s “river piracy” …


Many in the scientific community are still buzzing over the so-called “river piracy” event that occurred last year in the St. Elias Mountains of the Yukon Territory. That’s where the Kaskawulsh Glacier had thinned and receded so far that its meltwater burst through the ice, halting the flow to one of two rivers that were fed by the glacier, and turning the other river into a raging torrent.

Chunks of recently collapsed ice blocks litter the ice-walled canyon at the terminus of the Kaskawulsh Glacier in this Sept. 2, 2016 photo. The canyon now carries almost all meltwater from the toe of the glacier down the Kaskawulsh Valley and toward the Gulf of Alaska. The river piracy event redirected the flow from the Kaskawulsh and Slims rivers, which empty into Kluane Lake.
Credit Jim Best/University of Illinois

“We’ve got reports from colleagues where they’ve seen this kind of thing happen, but not in  modern times,” says Dan Shugar, a geoscientist with the University of Washington-Tacoma and lead author of a recent study that recounts the river piracy, also called river capture.

“I think part of that is because it’s a fairly unique story of a climate-change impact that most people haven’t sort of expected. Or is underappreciated, even in some scientific circles,” he said.

Shugar says the event has sparked followup studies to the one that he coauthored and that was published earlier this month in the journal Nature Geoscience. He hopes those studies will analyze the downstream impacts of the river piracy on Kluane Lake, which has dropped precipitously since its main tributary, the Slims River, was reduced to a near-trickle.

“The water level has already dropped by several meters last year, relative to its long-term average,” he said, “and about a meter lower than it’s ever been recorded.”

Shugar expects continued low or no flow from the Slims River will effect many more changes on the lake, the largest in the Yukon.

“You know,” he said, “in the next few years, as the Kluane Lake level drops even further, what happens to the chemistry of the lake, and the structure, water temperatures, et cetera.”

Ken Tape is an ecologist who works for the University of Alaska Fairbanks, agrees.

University of Washington Tacoma geoscientist Dan Shugar, leftt, and Ken Tape, a University of Alaska Fairbanks ecologist.
Credit University of Washington, Amherst College

“I imagine the thermal regime and the ecology will totally change,” he said. “Y’know, the biota in the lake, things like that.”

Tape says Kluane Lake is likely to undergo more changes if, as Shugar and his coauthors predict, its level drops so low that it cuts off the outflow into the Kluane River. That would make the lake a so-called closed basin, fed only by snow on surrounding terrain. 

Both Tape and Shugar agree the loss of flow from the Kluane River is unlikely to have much impact on the much-larger Yukon River, which the Kluane empties into farther north.

But, Shugar says he sees the possibility of more river piracy events in the Arctic and high-elevation areas in lower latitudes, brought on by glaciers melting and receding more quickly due to the warming climate.