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 the once-untouched rivers and streams. Map of orange stream observations across Arctic Inventory and Monitoring Network (ARCN) parks in northern Alaska. Picture inserts show aerial images of select iron-impacted, orange streams. Map created by Carson Baughman, U.S. Geological Survey. Photos by Kenneth Hill, National Park Service. Public domain. Water samples collected from the affected streams revealed lower pH levels and higher concentrations of sulfates and trace metals compared to nearby unaffected waterways. In some cases, the pH levels dropped to 2.3,…This article was originally published on Mongabay
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