As Tundra Thaws, an Alaskan River Turns Orange

Tukpahlearik Creek on July 23, 2023.

Tukpahlearik Creek on July 23, 2023. NASA

A dramatic shift in the Alaskan landscape is underway. As unprecedented heat melts long-frozen tundra, runoff is altering the composition of Arctic rivers and streams. One such waterway is Tukpahlearik Creek in northern Alaska, which recently turned a striking shade of orange.

Like dozens of other Arctic streams, Tukpahlearik is changing color as iron pours into the waterway, as shown in newly released satellite imagery from NASA. Just as iron reacts with oxygen to give rust its ocher hue, it is now doing the same in Alaskan rivers.

Scientists believe that melting permafrost is responsible for rising iron levels, though the possible reasons are disputed. One explanation is that as microbes consume the remains of plants liberated from melting ice, they are producing iron as a byproduct. It also may be that meltwater is, for the first time in potentially thousands of years, reacting with minerals in the soil to leach heavy metals such as iron.

The melting of permafrost is a growing risk to aquatic life, scientists say. In addition to seeing an uptick in iron, researchers have also recorded higher levels of acidity and lower levels of oxygen in rivers fed by thawing permafrost. The drop in oxygen in particular poses a threat to fish and those who depend on them.


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