Slims River Flow, 2015-2016 (credit: Sentinel-2 Earth Observing satellite, ESA)
Catastrophic events happen infrequently but when they do, they can leave profound geographic, ecological, and even economic impacts. In the equalivant of a geological 'blink of an eye', a Canadian river vanished in little more than 3 days. The Kaskawulsh Glacier abruptly altered its drainage patterns in May 2016 when an ice canyon collapsed at the head of the massive frozen river. Satellite photography and river sensors showed that glacial meltwater had been rerouted from originally discharging northwards to the Bering Sea, instead it was flowing south into the Pacific Ocean now. Researchers with the Universities of Washington and Illinois called the dramatic alterations a case of 'river piracy'.
The Kaskawulsh Glacier originally had formed a barrier over a rock divide that segregated meltwater into two glacial outflows: one flowed into the Slims River that eventually reached the Bering Sea while the second flowed into the Kaskawulsh River, which emptied into the Pacific Ocean. As the glacier retreated, its terminus had contracted so far that the glacial outflow waters were allowed to change course and now joined the Kaskawulsh River. River gauges showed an abrupt drop over just four days and in the process the Slims River went dry. Jim Best, one of the lead Illinois researchers, said an event like this typically happens over very long time periods, tens of thousands of years, but nothing this short had ever been observed in modern times.
Kaskawulsh Glacier Ice Canyon Carrying Meltwater Towards the Gulf of Alaska. (credit: Jim Best, U. of Illinois)
According to a release on the new rivers' study:
Dan Shugar of the Sediments Hazards Earth-surface Lab at the University of Washington said: "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 field data was just published in Nature Geoscience and suggests that the abrupt changes observed can be attributed to human-induced climate change. The researchers determined that the chance of the glacial collapse, and the resulting river reversal, having occurred from natural variability was 0.5%. Jim Best, another author of the study said: “So it’s 99.5% that this event occurred due to warming over the industrial era."
Expect ever more examples of dramatic events like what occurred to the Slims River as climate change accelerates. Remember, once a river ran through it but now in the Slims, salmon will not be swimming again there any time soon.