Alaska’s Rivers Turns Orange as Thawing Permafrost Releases Metals

A new study identifies at least 75 Arctic streams where minerals, especially iron, are staining water with a rusty hue, The Smithsonian Magazine reports. In recent years, the typical purples, blues and greens that color Alaska’s tundra ecosystems have been cut through with an unexpected hue as rivers run orange. The phenomenon was first widely noted by scientists in 2018, and satellite imagery confirmed that as far back as 2008, certain waterways in the state have been changing from clear to rusted.

In research recently published in the journal Communications: Earth & Environment, a team of scientists suggest they have pinpointed the cause of this color shift - and it is linked to climate change.

As the Arctic warms, its permafrost is thawing. When this occurs, acid and metals - including zinc, nickel, copper, cadmium, iron and aluminum - are released from the loosening soil and exposed to water and oxygen through weathering. This process causes the metals—especially iron—to essentially rust, staining the rivers a muddy orange-brown.

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