The Kaskawulsh Glacier is nestled in the St. Elias Mountains, within Kluane National Park in Canada’s Yukon Territory. It is immense, covering 15,000 square miles (25,000 square kilometers). For years and years, its meltwaters drained into two rivers that fed two watersheds.
The glacier terminates at the head of two river valleys, with its meltwater draining into the Slims River and the Kaskawulsh River. Up until May 2016, about 80 percent of the meltwater flowed northwards, through the Slims River and into Kluane Lake, while the other 20 percent flowed into the Kaskawulsh River and then flowed east and south into the Alsek River, draining into the Pacific Ocean.
However, in the spring of 2016, a period of intense melting took place, causing a gradient change that redirected the meltwaters to the Kaskawulsh River, causing the Slims River to disappear in a period of four days. This capture of a river was documented by scientists from the University of Washington Tacoma and published April 17 in the journal Nature Geoscience.
It is the first known case of “river piracy” in modern times. River piracy is also known as “stream capture” and can occur with the tectonic motion of the Earth’s crust, like a river changing course as the result of an earthquake. Landslides, erosion and in this case, changes in a glacial dam can also cause river piracy. What’s remarkable bout this particular study is that it documents the less than anticipated effects of climate change on our environment.
“Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes,” said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. “People had looked at the geological record—thousands or millions of years ago—not the 21st century, where it’s happening under our noses.”
The climate change warnings we hear today describe what could or will happen in the near future, like sea levels rising or tropical diseases spreading northward. But according to river gauges on the Slims River, there was an abrupt drop over four days from May 26 to 29, 2016.
Shugar and his associates had planned on doing fieldwork last summer on the Slims River. But when they arrived in August, the river had disappeared. Puzzled, the researchers got permission to use a mapping drone and the resulting paper they produced was essentially a postmortem of the Slims River’s demise.
In describing the Kluane River, by late summer, “there was barely any flow whatsoever. It was essentially a long, skinny lake,” Shugar said. “The water was somewhat treacherous to approach because you’re walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping.”
Changes in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to not having a river, Shugar said. And because there was no water flowing in, Kluane Lake did not refill last spring, and by the summer of 2016, it had dropped about 3 feet (1 meter) lower than ever recorded for that time of year. reports Phys.Org.
As global warming accelerates, we could expect to see more of these river piracy events taking place. More worrying to many scientists are the effects on the environment and local communities, human and wildlife, if sudden changes in river flows are suddenly changed.
