Alaska's pristine rivers are turning a rusty orange even when seen from space, likely because of melting permafrost: study

  • Scientists say that dozens of waterways in Alaska are "rusting," or turning into a dirty orange.

  • They said permafrost thawing in the summer is now exposing minerals to the surface, releasing metals and acid.

  • Some brooks and streams are turning so acidic that they're comparable to lemon or orange juice.

At least 75 of Alaska's brooks and streams have been turning a dirty orange likely due to thawing permafrost, with some rivers so impacted that the discoloration can be seen via satellite, a new study says.

This phenomenon, which researchers say comes amid unusually rapid warming in the region, was first observed in the northwestern state in 2018, scientists told Business Insider's Jenny McGrath in January.

The researchers have been stumped by it for years. But their findings, published Monday in the peer-reviewed Communications Earth & Environment journal, say that the waterways' rusty color likely comes from minerals uncovered by the thaw.

Previously locked beneath Alaska's permafrost, these minerals are now exposed to water and oxygen, causing them to release acid and metals like zinc, copper, iron, and aluminum, the study said.

The dissolved iron is thought to be the main culprit behind the "rusting" of the rivers, which typically occurs in July and August when the thaw is the most pronounced.

But the implications of the melt go far beyond color. These waters are becoming so acidic that some are registering pH levels of 2.6, or between the equivalent of the acidity of lemon juice and orange juice.

Pure water has a pH value of 7. Rivers and lakes typically have a pH value of 6.5 to 8, and acid rain has a pH value of 4.2 to 4.4.

An image of the clear Akillik River in 2016 and the orange river in 2018
A stream tributary of the Akillik River in Kobuk Valley National Park, Alaska turned orange between 2016 (left) and 2018 (right).Jon O'Donnell/National Park Service

"These findings have considerable implications for drinking water supplies and subsistence fisheries in rural Alaska," researchers wrote.

They added that the region has already suffered the "complete loss" of two fish species due to the acidity: juvenile Dolly Varden trout and the Slimy Sculpin. Chum salmon and whitefish are also at risk of population decline, they said.

The changes could be devastating for indigenous tribes in the region, which rely heavily on fishing, researchers noted.

The 75 orange streams observed were scattered across northern Alaska over a span of about 600 miles, the study said. All of them were in remote areas, miles away from human activity that could impact land, such as roads or mining.

Researchers highlighted satellite images of the Agashashok River, a tributary of the Kuguroruk River, and the Anaktok Creek tributary of the Salmon River in northwest Alaska. They said all three have turned considerably redder in the summer months of the last 10 years.

An orange tributary joins the Kugaroruk River in Alaska.
An orange tributary joins the Kuguroruk River in Alaska.Joshua Koch, US Geological Survey

Scientists warn that Alaska is warming at a rate two to three times the global average.

The Biden administration projected in November that the state would need an estimated $4.8 billion in infrastructure repair and adaptation over the next 50 years due to rising temperatures and damage from flooding, erosion, and permafrost thaw.

According to the administration's multiagency report, Alaska's fishing and tourism industries, which collectively provide more than 90,000 jobs and $2.57 billion in wages, are also at risk, with fish stocks expected to collapse and winter tourism likely falling.

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