Rusty rivers in Alaska: Melting permafrost releases heavy metals

Just a decade ago, the rivers winding through the majestic Brooks Range mountains in northern Alaska delighted with crystal-clear water. Today, they increasingly resemble rusty orange streams. The first disturbing signals appeared in 2018, when scientists observed orange streaks in the water. Since then, this phenomenon has been intensifying, and the number of "rusty" rivers increases from year to year.

A team of researchers used helicopters to reach the remotest reaches of the Brooks Range to collect water samples. The analysis results were surprising. It turned out that the water in many places is not only clearly colored, but also more acidic and contains much higher concentrations of metals than water flowing from nearby mines. Interestingly, there are no industrial plants or mines in the area that could be a source of pollution.

Melting permafrost is to blame

The latest research, published in the prestigious scientific journal "AGU Advances", clearly indicates the cause of this phenomenon - melting Arctic permafrost, or permafrost.

As the climate warms, the previously frozen ground begins to thaw. Water that penetrates deep into the soil encounters minerals that have been trapped in rocks for thousands of years. As a result of chemical reactions, metals such as iron, aluminum, manganese, zinc, nickel, cadmium and rare earth elements are released into the environment.

Between 2022 and 2024, scientists collected water samples from six different drainage basins in the Brooks Range. Analyzes showed that in some places metal levels were up to 70 times higher than usual, and the water had a much lower pH than that from industrial areas. Particularly disturbing were the results from the Salmon River, where even 100 kilometers from the source, metal concentrations remained very high.

Climate dominoes: warm summer and snowy winter

Researchers linked the spike in pollution to a record-breaking summer in 2019 followed by an exceptionally snowy winter. The thick layer of snow acted as insulation, preventing the soil from refreezing. This, in turn, allowed the water to penetrate deeper and release even more metals into the rivers.

Although there have been no mass fish kills or problems with drinking water quality at this time, scientists warn that the situation could quickly deteriorate. Elsewhere in the Arctic, vegetation is already dying off along acidified rivers and declining numbers of fish such as salmon and whitefish. Local communities are particularly vulnerable, including Alaska Natives, for whom rivers are the primary source of water and food.