Professor Dan Shugar and a team of colleagues made international news this spring with their discovery of a sudden case of “river piracy” — one stream taking the water that fed another one.
Usually, it’s a development that plays out on a time scale only geologic study can document. A terrain shift, over thousands of years, gives a river easier path, and its former channel slowly disappears.
But in the Yukon Territory in May 2016, a river shut off in four days, Shugar, a University of Washington Tacoma professor, found. Climate change is believed to be behind it.
An unusually warm spring melted so much water on the Kaskawulsh Glacier that a new canyon was carved and water flowed through it.
“Think of like a hill with a little pond on either side,” Shugar said. “It’s going to flow in opposite directions. But if that hill were to shrink, the pond over here would eventually drain in that other direction. And that’s essentially what’s happened.”
The glacier’s runoff had for 300 years gone largely north, from a lake into the Slims River into the Bering Sea. The canyon instead sent more water into a different lake, and south to the Pacific Ocean via the Alsek River.
The change is likely permanent, Shugar and other geoscientists reported in their study.
He discussed the study and its implications with The News Tribune in his office in the Science Building of UW Tacoma.
Q: How substantial a change was this?
A: It was dramatic and extremely fast when this happened.
The shutoff of this river we think took about four days, or at least that’s the record that we have downstream. We have a gauge sitting about there that records how much water is in the (Slims) River. That basically plummeted over the course of about four days, almost like draining a bathtub.”
Q: What are the implications of these two rivers that I never heard of in Canada changing directions?
A: The implication for you down here in Tacoma of this particular event is nothing. These aren’t going to change how flavorful your coffee is in the morning or whether you can have a house on the coast.
There are implications for people who live up there. The story here is really more about climate impacts that aren’t the normal impacts that we hear about, (such as) sea level rise and increased storminess.
This is a story about a climate impact that is a little bit out of the norm and occurred extremely rapidly. This kind of switch has happened before. We’ve just never noticed it over the last 100-odd years.
It could not have occurred, or there was almost a zero percent chance that this would have occurred, if we hadn’t seen the warming that we’ve seen in the last hundred years.
So we’re not saying this occurred due to us, but the warming that we’ve seen in the last 100 years, much of that is due to greenhouse gas emissions. Not all of it, but much of it.
And if we took out that warming trend, the glacier could not have retreated as much as it has, which eventually allowed this to occur.
Q: When you hear glacial retreat, the classic association we have is that the main thing this does is make the sea level rise. Would you call this an unanticipated consequence?
A: It actually was predicted 10 years ago by one of my coauthors, John Clague, in a paper he wrote in 2006. He was thinking more like hundreds of years, not 10 years.
And 10 years later, that happened. So it’s unanticipated in some ways, but it was predicted ironically in others. But it is certainly a different, underappreciated kind of a consequence or impact of climate change.
Climate change is occurring much more dramatically in the north than down here, so people who live in these areas are experiencing these changes firsthand. Down here, in southern North America, it’s easier to think, ‘Well, climate change is only happening in the South Pacific. It doesn’t affect us,’ but it definitely does.
Q: Is there any demonstrated social consequence for folks up there?
A: The Slims, the river that basically disappeared, fed this very large lake, Kluane Lake, which is the biggest lake in the Yukon Territory. This is the biggest source of water to the lake and it’s basically turned off.
The docks that are in the lake now don’t necessarily extend into deep enough water to put your boat in. The river that drains the lake was substantially lower last year. It was unbelievable how low it was. There’s still water in it, but really, really low.
And the fish that are in there, that some of these communities rely on and eventually go into Alaska, those fish may be impacted. There’s flow and the water will be warmer, because there’s less water to heat up by the sun. So there are impacts on fish habitat, with implications for people that rely on those fish.
Q: This is pretty stark evidence of climate change having real consequences. Did you expect your scientific work to put you in the middle of a political debate?
A: If you read the comments on a lot of the media stories, which I try not to do, people who don’t read the scientific paper don’t always necessarily understand the rigor, the statistical analyses and the rigor that were put into saying, ‘Yes, this is a climate effect.’
It’s not just a hunch that we have. It’s not an agenda that we’re trying to push.
We gather up all this evidence and see what comes out of it. And so to me it’s not surprising that there was a real climate link here, but I can see how that may have become a bit of a lightning rod. I think it’s an excellent example of, a good case for us continuing to study these kinds of things.
If this is something that is an underappreciated consequence of climate change, it’s likely that we’re going to get a few more surprises thrown at us. It would be imprudent to pretend like nothing’s going to happen. Just because you don’t believe the science doesn’t mean that these impacts aren’t going to happen. They are, and if you aren’t prepared, they’re going to be worse.
As scientists and as a global community, we should be trying to understand our Earth system, and how it is changing, as best we can. That means robust science in a whole variety of disciplines.