Record-setting temperatures and rainfall in the Arctic over the past year sped up the melting of permafrost and washed toxic minerals into more than 200 rivers across northern Alaska, threatening vital salmon runs.
The report, compiled by dozens of academic and government scientists and coordinated by the National Oceanic and Atmospheric Administration (NOAA), documented rapid environmental changes from Norway’s Svalbard Island to the Greenland ice sheet and Canada and Alaska.
Between October 2024 and September 2025, the period from when the ground begins to freeze until the end of summer, surface air temperatures were the warmest on record dating back 125 years, the report found.
The report card was written by scientists from academic institutions in the US, Canada and Europe, as well as researchers from Nasa and other federal science agencies. NOAA has been monitoring changes in the Arctic region for 20 years. Over this year’s study period, there was a record amount of precipitation, both snow and rain.
“To see both of these historical records being set in the same year is quite remarkable,” said Matthew Druckenmiller, a senior scientist at the National Snow and Ice Data Center in Boulder, Colorado, US, and a lead author of the report.
“Since 1980, the Arctic annual air temperatures have warmed nearly three times faster than the rest of the planet,” Druckenmiller said. He said the warming is affecting the timing and amount of rain and snow in the Arctic, which affects fisheries, wildlife and the people who live there.
Permafrost, a mixture of soil, rocks and organic matter that remains frozen year-round, covers much of the Arctic’s land surface. That permafrost has been melting since the early 2000s, and researchers have now discovered toxic chemicals leaching into rivers in northern Alaska. The troubling phenomenon was first noted in 2019 and has now been seen in more than 200 river basins north of Alaska’s Brooks Range mountains, according to Joshua Koch, a research hydrologist at the US Geological Survey in Anchorage, Alaska.
Koch and others have been conducting aerial and satellite surveys of the North Slope, an area of about 2,46,050 square kilometres that stretches from the Canadian border to the Arctic Ocean.
“We started to see some of these streams turning orange,” Koch said. “These are really pristine areas that don’t have impacts from mines or human activity.”
The melting permafrost exposed naturally occurring deposits of pyrite, an iron sulphide mineral, to air and water, causing a chemical reaction known as oxidation. As the climate warms and permafrost thaws, groundwater seeps into deep soil layers.
Once the researchers got on the ground, they discovered that the rust-coloured water was coming from springs and hillsides rich in pyrite. They also detected toxic levels of naturally occurring aluminium, copper and zinc from the tundra soil leaching into waterways.
The acidic and toxic water is killing insects and other aquatic life relied on by salmon and other fish that are a key food source for the region’s 10,000 residents. During a 2024 survey in Kobuk Valley National Park, researchers found that the Akillik river rapidly changed from clear to orange in the summer, killing all the fish and aquatic life.
So far, there is no evidence that the fish have been contaminated by the toxic chemicals, however the scientists are continuing to monitor the streams and salmon.
But if the rusting rivers phenomenon spreads to larger watersheds, such as the Yukon river, it could threaten Alaska’s $541 million salmon industry. Salmon are sensitive to chemicals in the water, according to Nicole Kimball, vice- president for Alaskan operations at the Pacific Seafood Processors Association.
“It doesn’t take a lot to make salmon less reproductively successful if they are fighting off toxicity,” said Kimball, who is also a commissioner on the North Pacific Marine Fisheries Management Council, which regulates harvests of commercial fisheries. “They can become confused on where they go to spawn.”
NYTNS