Melting permafrost changes Yukon River

Ice fog on the Yukon River (Creative commons photo by Anthony DeLorenzo)

A new study shows melting permafrost is changing the chemistry of the Yukon River, just one of many climate-related changes affecting the Yukon and beyond.

Listen Now

Hydrologist Ryan Toohy with the USGS Alaska Climate Science Center said researchers tested water samples collected from the Yukon and Tanana rivers over a period of thirty years. The results show that as upper layers of the permafrost freeze later and melt earlier in the year, ground water percolates deeper into the soil and carries more materials into rivers.

“Essentially what we found is we found a lot of the common kind of minerals and some of the nutrients in the Yukon River, and the Tanana River, had greatly increased over those thirty years,” Toohy said.

Calcium, magnesium and sulfate levels were up. Increased weathering and erosion also released phosphorous, a key nutrient for plants and animals, which went up by as much as 200 percent. That may help fish populations, as well as invasive species. None of these changes are harmful to humans, though as the trend continues, it may harm water quality.

What happens to the Yukon, though, extends beyond Alaska’s shores. Melting sea ice was once a major source of fresh water for the Arctic Ocean, but as the sea ice shrinks, Toohy said six great Arctic rivers, including the Yukon, help make up for the loss of fresh water:

“A lot of change in the Arctic ocean is from the sea ice,” Toohy said. “The rivers act as a buffering capacity. So if there’s a lot of change in the sea ice, the rivers can somewhat buffer those changes.”

That’s important because fresh and warmer water floats while colder saltier water sinks, actions that drive vast ocean currents. 

Still, it’s hard to say exactly which changes will benefit people, and the plants and prey they rely upon, and which will make life more difficult. Etta Mutter is science director for the Yukon River Intertribal Watershed Council.

“It’s very, I would say, very overwhelming, but yeah, very challenging at this point,” Mutter said. “Because we all want to try to find kind of how it’s really going to affect our communities and how to really plan for that and to prepare for that but it’s very hard to do so because at the moment we really just don’t really understand all the pieces.”

Mutter said one change that’s already causing hardship is the decline in the number of salmon returning to spawn in the Yukon River. For unknown reasons, he said too few fish reach the Yukon’s headwaters in Canada, impacting tribes who relied on those salmon runs to put food on the table. Mutter said that’s also affecting cultural practices that go along with subsistence.

“Some communities, some nations are even now buying salmon from the Tlingit and Haida tribes to, just to maintain the traditional lifestyle and to show the kids how to do, to carve the fish,” Mutter said. “So, it’s been, yeah, it’s definitely an impact, a cultural impact too.”

The results of the multi-decade study of the Yukon River basin were published in early December in Geophysical Research Letters. The U.S. Geological Survey, Indigenous Observation Network, Pilot Station Tribal Council, and Yukon River Inter-Tribal Watershed Council funded and cooperated in the project.