‘Rusting rivers’ threatening Alaska’s Arctic after years of permafrost thaw, wildfires
NOAA’s Arctic Report Card shows more than 200 Arctic watersheds in Alaska’s Brooks Range have begun “rusting.”
AccuWeather’s Anna Azallion explains what is turning some Arctic rivers a rust color. One hint: it isn’t pollution.
Arctic rivers flowing through Alaska are increasingly turning orange as wildfires, thawing permafrost and other factors contribute to an influx of heavy metals in these waterways.
NOAA’s annual Arctic Report Card, released this week, highlights the growing issue, noting that more than 200 Arctic watersheds in Alaska’s Brooks Range have been affected. Iron and other naturally occurring elements released by thawing permafrost have turned what were once “pristine rivers and streams orange over the past decade,” according to the report.
An orange tributary of the Kugururok River in Noatak National Preserve, Alaska. Orange streams are increasingly common in the Brooks Range of northern Alaska. The orange stream color reflects oxidized iron, but also often indicates elevated heavy metal concentrations. (Image credit: Mike Carey, U.S. Geological Survey)
In a 2024 study, NOAA documented at least 75 streams that had already turned orange.
Known as the “rusting rivers” phenomenon, scientists say the process is driven by increased acidity and elevated levels of toxic metals, which degrade water quality and threaten aquatic ecosystems.
The new report points to permafrost thaw as a key factor, as a warming climate exposes previously inaccessible minerals, such as sulfides, that can release metals into nearby waterways.
Photographs of rusting rivers and time series plots of Redness Index for watersheds in Alaska’s Brooks Range, including the Agashashok River, the Kugururok River and Anaktok Creek, a tributary of the Salmon Wild and Scenic River in Kobuk Valley National Park. The time-series data were generated from Landsat satellite images using average Redness Index values for summer months of each year from 1985 through 2022. Redness index, which represents the presence of iron oxides, was calculated as the ratio of surface reflectance of the red and blue bands. The orange circles with mean. Redness Index values > 1.5 indicate waters discolored by iron particles. Grey circles represent mean Redness Index values < 1.5, indicating clear water or streams unimpacted by iron mobilization. (Photo credits: Jonathan O’Donnell/NPS, Michael Carey/USGS, and Joshua Koch/USGS)
NOAA, the U.S. Geological Survey, the National Park Service and research partners have been tracking the rusting of Alaska’s rivers for about a decade.
Experts describe the rusting rivers as “visually striking,” with changes easily visible in satellite imagery.
Scientists continue to study the causes of the phenomenon and its potential impacts on rural drinking water supplies and fisheries.
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