How a major B.C. river disappeared in four days. And what it means for all of us
THE CASE CAPTIVATED SCIENTISTS and headline writers when it became public last year: the Slims, a once mighty river in Yukon, had vanished in just four days. It was the victim of geological theft.
While geologists had plenty of ancient examples of what they call “river piracy,” a phenomenon in which the headwaters of one river get stolen by another, they had never before documented it unfolding in real time. More surprising still, this one was “geologically instantaneous,” wrote Daniel Shugar, the earth scientist at the University of Washington in Tacoma who detailed the thievery in a 2017 paper for Nature Geoscience.
And while some scientists had predicted the vanishing act, they weren’t expecting it just then. In fact, Shugar went to the southwest corner of Yukon territory in the summer of 2016 for the express purpose of measuring currents in the Slims River. By the time he arrived in August, the Slims had practically disappeared.
He enlisted the help of colleagues, including John Clague, who is Canada Research Chair in natural hazard research at Simon Fraser University in Vancouver, to do a forensic investigation. The group sent drones over the area to take stock and looked at measurements of the river’s flow over time.
The mystery revolved around the massive Kaskawulsh Glacier, part of Kluane National Park in the St. Elias Mountains, whose toe straddled a dividing line between two watersheds. On one side were the headwaters of the south-flowing Kaskawulsh River. On the other, the north-flowing Slims, born nearly 200 years ago when the glacier began blocking an old river that had once drained south to the Pacific Ocean.
Then came climate change, a geologically swift pulse of carbon-based gases into the atmosphere from burning fossil fuels. The Kaskawulsh Glacier began to melt, losing both height and reach. From 1956 to 2007 alone, it retreated 655 metres.
The crisis came in May 2016. Temperatures that spring had been unusually warm. At the glacier, they were 3.6 degrees Celsius warmer than the decade’s average — and that was likely the warmest decade of the century. That led to a fast melt of the glacier’s surface, which prompted an ice-walled channel to form at the Kaskawulsh River. Then the channel began to fall apart.
On May 26, the Slims began a four-day collapse, its north-bound waters rerouted south into the Kaskawulsh River and from there eventually the Pacific Ocean. By the end, the Slims was a mere trickle, never to regrow. That summer, the Slims floodplain became a dustbowl.
Why does the death of a river matter? Many reasons. It affects the lakes and riverbanks that depend on it, altering water levels, sediment deposit, chemistry and the populations of fish and other species that live there. It affects the people who use the river for recreation or food or making money or hydroelectricity.
For example, because Slims River died, water levels in Kluane Lake, Yukon’s biggest body of water, have fallen by 1.7 metres. Now the water is so low that the popular Canada Day fishing derby at Burwash Landing on the lake’s western shore has been cancelled. It’s too dangerous to launch boats.
And it matters because the Slims is not the only one. Other rivers are destined to suffer the same fate, Shugar and Clague explain in an essay for the Alpine Club of Canada’s 2018 State of the Mountains report. There’s a wholesale geological resculpting of the Earth underway as glaciers, ice sheets and permafrost melt in this high-carbon world we’ve made.
In North America, that means more landslides. It means newly unfrozen water raises sea levels. It means the land, now free from the weight of the glaciers, is actually lifting up. It means more volcanoes as melting ice uncovers the tops of shallow magma chambers.
Ultimately, it means changes in how we see the world around us. We’ve been schooled to think that something as vast as a glacier or a river will be there forever. The theft of the Slims over just four days shows us that enormous change can happen in the blink of an eye.
This rapid change is what climate scientists sometimes refer to as a tipping point, or a regime change. Everything’s going along the same… until it isn’t. It’s like your finger pressing on a light switch: one nanosecond the light is off; the next it’s on.
The lesson here is that nature has a mind of her own. You can push her only so far until she changes course, like a river that is there one day and gone the next.1
IN MAY 2016, THE SLIMS RIVER SLOWED TO A TRICKLE, THEN DIED. WITHIN A FEW MONTHS, ITS FLOODPLAIN WAS A DUSTBOWL