Alaskan Rivers Turn Rusty Orange Due to Thawing Permafrost
Hundreds of streams across Alaska's Brooks Range have transformed from clear to orange, a change primarily observed within the last 10 to 12 years. Scientists attribute this widespread discoloration to thawing permafrost, which, accelerated by rising air and ground temperatures, exposes new ground and bedrock to water. This process leads to the leaching of iron, sulfuric acid, and trace metals into the streams, resembling acid mine drainage.
Orange streams are increasingly being observed in hundreds of watersheds across Alaska's Brooks Range. This environmental shift, where stream water changes from clear to a rusty orange hue, has largely occurred within the past decade to 12 years, coinciding with a notable increase in air and ground temperatures in the region.
Scientists surmise that the thawing of permafrost soils is the most probable cause of these "rusty" rivers. As permafrost thaws, water comes into contact with previously frozen ground and bedrock. This interaction initiates chemical weathering of minerals, releasing iron, sulfuric acid, and trace metals into the streams. Microbes may also play a role by producing soluble forms of iron as they process organic matter in the thawing soils, which then oxidizes and rusts in the flowing water.
Surveys covering over 600 miles (1,000 kilometers) across the Brooks Range have documented this change in more than 200 watersheds. Initial research in 2024 by a team of National Park Service, U.S. Geological Survey, and university scientists identified 75 northern Alaskan streams that had recently changed color. Subsequent exploration, largely utilizing high-resolution satellite imagery, added another 200 observations.
Researchers, including environmental toxicologist Brett Poulin from the University of California, Davis, who has monitored the region's streams since 2013, expressed surprise at the broad spatial scope of the observations. The discoloration has even been noted in designated National Wild & Scenic River corridors. Observations from NASA/USGS Landsat satellites helped determine the timing of these changes, with some streams turning rusty around 2018 and others showing intermittent periods of discoloration.
One specific example is the Agashashok River in Noatak National Preserve, which experienced a sudden change. The locations of these discolored streams were published in NOAA’s 2025 Arctic Report Card.
According to NASA Breaking News, this phenomenon highlights significant environmental changes unfolding in the Arctic.
