Thawing permafrost is altering chemistry of northern rivers, researchers say

Researchers in Alaska say they're seeing significant changes in freshwater chemistry in the Yukon River basin, which they attribute to thawing permafrost.

It's also believed the changes are big enough to have "global implications" by changing the composition of the Arctic Ocean, said lead researcher Ryan Toohey, a hydrologist with the U.S. Department of the Interior's Alaska Climate Science Centre.

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"A lot of these big rivers, you don't really see these changes too often, so it's very unique," Toohey said.

The research is based on data collected at two Yukon River monitoring stations in Alaska over the past three decades — a large historic data set that Toohey says "is very rare in the Arctic and the boreal ecosystems, and our northern systems."

Toohey says it shows that minerals that had been locked in permafrost — such as calcium, magnesium, and sodium, as well as sulfate — are making their way into the river basin and from there, to the Arctic. 

​"Permafrost contains a lot of different things that have been deposited there over thousands of years, and so as that kind of [thaws], sometimes some of those things can be of concern," Toohey said.

The Yukon River is one of the six main Arctic discharge rivers (along with the Mackenzie, and several rivers in Russia such as the Lena and Yenisey), so Toohey says changes to the river could alter the composition of the Arctic Ocean.

That would have "global implications, of changed currents and weather patterns," Toohey said, as well as impacts on fish and wildlife habitat.

Carbon in the Mackenzie River

Similar research done from the University of Alberta found long-term changes in the Mackenzie River, as well. 

Researcher Suzanne Tank analysed decades of data to discover that the amount of dissolved carbon flowing from the Mackenzie into the Arctic Ocean had increased by 39 per cent over the last 40 years.

She's also suggested the changes can be attributed to thawing permafrost. As the soil thaws, carbon is unearthed and makes its way into waterways, with unknown results.

"We're documenting change in the Arctic at a very alarming rate," Tank told Radio-Canada International last spring, after her research was published. "Certainly the degree of the increase that we observed was just incredibly striking."

Toohey agrees that the trends are "definitely something to pay attention to.

"We're seeing a lot of changes in the hydrology over the Arctic and the boreal ecosystems. That can have all kinds of implications for our aquatic ecosystems."

Toohey's research also found a significant increase in phosphorus in the Yukon River system in recent decades, which is a product of soil erosion. The study says the river is tending to freeze later and later in the year, and thaw earlier, making its banks and soils more susceptible to erosion. 

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