Photo: Retreating toe of Kaskawush Glacier; view to the east down the Kaskawulsh River valley. All meltwater issuing from the glacier now routes down the Kaskawulsh valley (Mike Schmidt photo).
Photo: Google Earth image of Kaskawulsh Glacier, Kaskawulsh valley extending to the east (right), Slims valley north of the glacier terminus, and the southern end of Kluane Lake (top middle).

River piracy caused by climate change

The event – In the Yukon, much of the meltwater issuing from Kaskawulsh Glacier has for centuries flowed into Kluane Lake, 24 km to the north.  This situation changed suddenly during the summer of 2016, shortly before researchers from Simon Fraser University (SFU), the University of Illinois, and the University of Washington (UW) arrived on the scene.  The group, led by UW’s Dan Shugar, found that the Slims River, which carried water from the glacier, had nearly run dry and the level of Kluane Lake had dropped significantly.  To investigate this mystery, Shugar along with his former Ph.D. supervisor John Clague of SFU, and Jim Best of University of Illinois, travelled up to the source, the Kaskawulsh Glacier, and found a remarkable change.

The discovery – The team showed that the Slims River, which is within the watershed of the Yukon River that flows into the Bering Sea, had been captured by another river (Kaskawulsh River) that flows south into the North Pacific Ocean. They further demonstrated that this change was caused by 20th and early 21st century climate change, and that the change is likely irreversible.

Its significance – Prior to this event, the Slims River was the most important single source of water entering Kluane Lake, which is the largest lake in Yukon Territory. Since 2016 when the piracy event occurred, the level of Kluane Lake has fallen about one meter. If the level of the lake falls another two meters, the lake will no longer overflow to the north into the Kluane River. If this were to happen, Kluane Lake would cease to have an outlet and would become a closed basin, with consequences for the chemistry and ecology of the lake. More importantly, the event is a 'poster child' for a wide variety of sudden and large changes that climate warming might cause. Most people mistakenly believe that the impacts of climate change will slowly emerge, much as climate itself slowly changes. Climate change, however, can drive Earth systems from one condition or state into another condition or state very rapidly, with unforeseen consequences for people forced to adapt to the suddenness of the change.

Read the paper“River piracy and drainage basin reorganization led by climate-driven glacier retreat” by Daniel H. Shugar, John J. Clague, James L. Best, Christian Schoof, Michael J. Willis, Luke Copland & Gerard H. Roe. Nature Geoscience Published online 17 April 2017. doi:10.1038/ngeo2932.

This high-profile discovery also has been featured by the Globe and Mail, The New York Times, BBC News, and over 100 other media outlets. The paper is ranked as first among 30 tracked articles of a similar age in Nature Geoscience and has garnered a high level of attention, reaching an Altmetric score of >1000 within days of online publication.

Website article compiled by Jacqueline Watson with Theresa Kitos