ANAKTUVUK RIVER, September 25 — A study published in the journal Environmental Science & Technology on May 20, 2024, has documented a striking change across Arctic waterways: thawing permafrost is turning rivers orange and making their waters more acidic and metallic than acid mine drainage. The research, led by scientists at the University of California, Davis, and the University of Alaska Fairbanks, examined 75 rivers across Alaska, Canada, and Russia. The team identified 12 rivers in Alaska’s Brooks Range and Canada’s Yukon Territory that have turned orange since 2018.
The most dramatic color change was observed in the Anaktuvuk River in Alaska.
What the chemistry shows
The discoloration is attributed to the release of iron, zinc, nickel, copper, and cadmium as permafrost thaws. Under the hood, the numbers are stark. Researchers measured pH levels as low as 3.5 in some orange rivers, against a normal pH range of 6.5 to 8.5 for Arctic rivers.
Acid mine drainage typically sits between pH 3 and 4. Dissolved iron concentrations reached up to 10 milligrams per liter in orange rivers, compared with less than 0.1 milligrams per liter in clear Arctic rivers.
The technical reality is that these are not merely aesthetic changes. The researchers noted that the orange rivers have lower biodiversity, with fewer fish and aquatic insects.
A widespread and increasing phenomenon
Dr. Jon O’Donnell, an ecologist with the National Park Service’s Arctic Inventory and Monitoring Network and the study’s lead author, stated that the phenomenon is widespread and increasing. The research was funded by the National Science Foundation and the U.S. Geological Survey. The study warns that as permafrost continues to thaw, more rivers could turn orange, impacting drinking water sources for indigenous communities and wildlife.
The Arctic is warming nearly four times faster than the rest of the world, according to a 2022 study in Communications Earth & Environment. Permafrost covers about 25% of the Northern Hemisphere’s land area and holds an estimated 1,500 billion tons of organic carbon, roughly twice the amount currently in the atmosphere.
As ever, the detail that matters is the mechanism. Permafrost acts as a frozen vault for minerals and organic material. When it thaws, those materials mobilise into waterways.
The metals released — iron, zinc, nickel, copper, cadmium — are the same suite that makes acid mine drainage so destructive to aquatic life. The difference is that no mine is involved.
The thaw itself is doing the work. The study’s findings were first reported by the Associated Press on May 21, 2024. For communities and wildlife across the Arctic, the question now is how many more rivers will follow the Anaktuvuk’s path as the ground beneath them continues to warm.
