DISCOVER MAGAZINE - In the northern Alaskan wilderness, a bizarre symptom of climate change is emerging: The rivers there are turning unnaturally orange. This phenomenon paints a worrisome picture for watersheds all across the Arctic, now faced with toxic metals being released by melting permafrost.
A new study published in the Proceedings of the National Academy of Sciences shows how orange rivers may start to become a familiar sight in the Arctic as the planet warms. But for ecosystems like those along the Brooks Range — a mountain range stretching from northern Alaska to Canada’s Yukon Territory — the color change underlies a host of problems.
The Rivers Turning Orange
When the water in a river or stream appears orange, it usually comes as a byproduct of mining activities. Oftentimes, sulfide minerals within abandoned mines are exposed to air and water, causing them to oxidize.
This process, called acid mine drainage (AMD), creates dissolved iron that changes the color of streams as it precipitates to form red, orange, or yellow sediments at the bottom of a stream. AMD also infuses streams with sulfuric acid that dissolves other heavy metals like copper, lead, and mercury into the water.
These rust-colored, highly acidic streams are often found where surface coal mining is prevalent — in the U.S., it occurs mostly in Central Appalachia and the Great Plains.
But much farther north, the orange rivers observed in the Brooks Range have nothing to do with AMD. The color-changing culprit, instead, is melting permafrost.
“This is what acid mine drainage looks like,” said author Tim Lyons, a biogeochemist at the University of California, Riverside, in a statement. “But here, there’s no mine. The permafrost is thawing and changing the chemistry of the landscape.”