June 3, 2024 — Dozens of once-pristine rivers and streams in Alaska’s Brooks Range are turning an alarming shade of orange. The discoloration, according to a new study published in the journal Communications Earth and Environment, is likely caused by the thawing of permafrost, which is exposing previously frozen minerals that are now leaching into the waterways.
The research team, led by ecologist Jon O’Donnell from the U.S. National Park Service, documented 75 locations across a vast area of northern Alaska where the crystal-clear waters now appear heavily stained. Using satellite imagery and field observations, the scientists determined that the onset of this discoloration coincided with a period of warming and increased snowfall in the region over the past decade.
Permafrost, which is ground that remains frozen year-round, acts as a storage vault for various minerals. As rising temperatures cause this frozen layer to thaw, these minerals are exposed to water and oxygen, triggering chemical reactions that release iron and other metals into the groundwater. This metal-rich water then makes its way into rivers and streams.
“Our recent study highlights an unforeseen consequence of climate change on Arctic rivers,” study co-author Brett Poulin, an environmental toxicologist from the University of California, Davis, told Mongabay. “Arctic environments are warming up to four times faster than the globe as a whole, and this is resulting in deterioration of water quality in the most pristine rivers in North America.”