Orange, acidic waters in Alaska's Igning River. Taylor Evinger / UC Davis

As the Arctic warms and tundra thaws, minerals long trapped in frozen soil are leaching into rivers, turning them orange and acidic. A study from northern Alaska found “rusting” waters to be more metallic and acidic than drainage from metal mines.

Researchers found iron and sulfuric acid from thawing tundra throughout watersheds in the Brooks Range. On the Salmon River, they determined, leaching raised metal levels as much as seventy-fold some 60 miles downstream. The findings were published in AGU Advances.

Analyzing records of water quality, researchers also determined that rusting began in the summer of 2019, the hottest summer on record in the state of Alaska. Since then, rusting has been recorded in more than 200 rivers in Alaska, as well as in waterways across much of northern Canada.

Researchers are only beginning to grapple with the implications for wildlife.…