Alaskan streams turned orange by thawing permafrost are more corrosive than acid mine drainage
A UC Davis study of six watersheds in Alaska's Brooks Range found that the orange-colored water is more acidic and metallic than water from metal mines. Metal concentrations were about 70 times higher up to 60 miles downstream from the source. The discoloration is attributed to thawing permafrost releasing iron and sulfuric acid into streams.
The research tracked six watersheds within Alaskan national parks, sampling across three summers. The event's onset was pinpointed to 2019, following the region's hottest summer and a subsequent snowy winter. The snow acted as insulation, preventing deep soil refreezing, which allowed water to penetrate further and interact with previously frozen minerals.
Downstream, metal concentrations rose dramatically, reaching roughly 70 times baseline levels even 60 miles away. While the main river channels buffered acidity, dissolved metals increased with distance. Since the initial 2024 report, similar rust-colored waterways have appeared in Arctic Canada and other permafrost zones, a phenomenon absent from prior climate projections.
The release of acidic, metal-laden water into Arctic rivers could disrupt aquatic ecosystems and threaten subsistence resources for Indigenous communities who rely on these waterways. Downstream metal transport may compromise drinking water quality and fish habitats, potentially impacting food security. As permafrost thaw accelerates, this phenomenon could necessitate new monitoring and adaptation strategies for park managers and regional planners, serving as a broader warning for other cold regions.