How a Receding Yukon Glacier Made an Entire River Disappear

Today it looks like a few scattered puddles, but the Yukon's Slims River was once a sizeable waterway that required a 200-metre bridge to cross. In just one season, it went from a place hikers occasionally drowned to a dried-up valley prone to dust storms.

According to Jeff Bond of the Yukon Geological Survey, that's because a nearby glacier has receded to a point where it's no longer blocking melt water from flowing west to the Pacific. That means there will be less water draining into nearby Kluane Lake, a salmon spawning ground for the last 350 years. The surprise comes as a climate change report released earlier this year found the territory has lost 22 percent of its glacial cover over the past 50 years, and is experiencing higher levels of warming than the rest of Canada. And though scientists consider the disappearing river somewhat of a geological anomaly, what happens next could offer a taste of the kind of disruptions to wildlife and humans expected under some long-term climate models. To understand how a river could vanish so quickly, Bond says you have to understand some unusual geological history. "The Slims River as we know it is one of these features that has only existed for the last 350 years," Bond told VICE. In other words, if you're looking back 10,000 years, this river wasn't around that long anyway. READ MORE: That Lake That Was Going to Fall Off a Cliff in Canada Actually Did During what's called "The Little Ice Age" that ended around 1680, the Kaskawulsh Glacier rallied and cut off one of the rivers draining out of nearby Kluane Lake. Both the glacier and lake grew, and Kaskawulsh melt water started draining into the lake via the Slims Valley. Hence the Slims River was born. Thanks to a whole bunch of factors including climate change, the Kaskawulsh isn't damming river flows the way it used to, and now its melt water has decided to flow in the total opposite direction. "If you look at some of the research on the history of the lake, it was predicted this could happen," Bond said, "but for it to actually happen is a bit startling." In other words, it's no surprise that the melt water changed directions, but geologists are kind of surprised by how fast it happened. Now they're left to figure out what could happen next. One expected outcome is the level of Kluane Lake is going to drop. But by how much, Bond says scientists can't be sure. Since salmon access that lake via a network of streams and rivers, lower water levels in the area could also change how those fish travel and spawn. "You don't need much water for the salmon to pass, so they'll probably be fine, but that would be one potential implication," said Bond. As for other impacts, scientists will have to wait and see. Bond says sees similar receding trends at other glacier sites, but he doubts the region will see another spooky melt water switcheroo. "I'm not aware of a situation quite like this," he told VICE. Follow Sarah Berman on Twitter.