A vast glacier-fed river which flowed from Canada's Yukon province across Alaska to drain into the Bering Sea has disappeared in just four days in what scientists believe is the first observed case of "river piracy".
High average temperatures in the first three months of 2016 caused a dramatic spike in the amount of meltwater flowing from the Kaskawulsh glacier, carving a deep canyon in the ice and redirecting the flow toward the Alsek River in the south, rather than the north-flowing Slims River.
That changed the Slims River from a three-metre-deep, raging torrent to a place where "massive afternoon dust storms occurred almost daily", according to a scientific paper published in the journal Nature Geoscience.
"We were really surprised when we got there and there was basically no water in the river," lead author Daniel Shugar said of the Slims River.
The scientists had previously been to the edge of the Kaskawulsh glacier in 2013 when the Slims River was "swift, cold and deep" and flowing fast enough that it could be dangerous to wade through.
Receding glacier causes immense Canadian river to vanish in four days
An immense river that flowed from one of Canada’s largest glaciers vanished over the course of four days last year, scientists have reported, in an unsettling illustration of how global warming dramatically changes the world’s geography.
The abrupt and unexpected disappearance of the Slims river, which spanned up to 150 metres at its widest points, is the first observed case of “river piracy”, in which the flow of one river is suddenly diverted into another.
For hundreds of years, the Slims carried meltwater northwards from the vast Kaskawulsh glacier in Canada’s Yukon territory into the Kluane river, then into the Yukon river towards the Bering Sea. But in spring 2016, a period of intense melting of the glacier meant the drainage gradient was tipped in favour of a second river, redirecting the meltwater to the Gulf of Alaska, thousands of miles from its original destination.
The continental-scale rearrangement was documented by a team of scientists who had been monitoring the incremental retreat of the glacier for years. But on a 2016 fieldwork expedition they were confronted with a landscape that had been radically transformed.