Climate change reroutes a river
For the first time in recorded history human-induced climate change has altered the course of an entire river, transforming the geological landscape in a matter of days. The immense Slims River in Canada’s Yukon carried meltwater northward, from the Kaskawulsh G lacier into the Bering Sea, for hundreds of years. But intense melting from unusually warm temperatures last spring caused the glacier to retreat; the melting water then carved a new channel through the ice, a new study reveals, redirecting the flow south to the Pacific Ocean via the Alsek River. The once raging Slims River basin is now almost dry—sheep graze on vegetation in the drained riverbed—and that change is probably permanent. Essentially, one river has captured and diverted the flow of another, a well-documented process known as river piracy. The phenomenon normally takes thousands of years, but events in the Yukon unfolded in less than a week. The researchers have little doubt human greenhouse gas emissions are responsible for the Slims’ change of course. “The river essentially shut off in four days, but it was caused by a century’s worth of warming,” lead author Daniel Shugar tells Scientific American. This particular event took place in a largely deserted wilderness, but climate scientists warn that as the planet warms, other drastic changes could rapidly alter water supplies, coastal flooding, ecosystems, and other factors affecting human populations.