In Alaska, streams are turning orange as permafrost thaws. Scientists are acutely aware that the loss of permafrost - the year-round frozen ground prevalent in the Arctic - generally does not bode well for the future of the planet. Thawing of the permafrost would release the potent greenhouse gas methane, exacerbating climate warming and thawing, while also destabilizing the ground and potentially releasing dormant pathogens.

Satellite image of Tukpahlearik Creek taken by the Land Imager-2 on Landsat 9 on July 23, 2023,

Researchers suspect melting permafrost is also responsible for dozens of Alaskan streams turning orange. Researchers found that in addition to their strange appearance, Alaskan streams tend to have higher iron content, lower dissolved oxygen, and are more acidic than nearby clear rivers.

Permafrost is defined as soil, rock and any other subsurface earth material that exists at or below 0°C for two or more consecutive years. The current map of permafrost in the Northern Hemisphere (20°N to 90°N) is based on this map produced by the International Permafrost Association in 1997. Source: International Permafrost Association

Tukpahlearik Creek is one such stream that takes on a new hue. On July 23, 2023, Landsat 9's OLI-2 (Land Imager 2) photographed this rusty stream. This creek flows through northwestern Alaska, adjacent to Kobuk Valley National Park and just north of the Arctic Circle.

The exact reason why these streams appear orange and change their chemical composition is still debated, but several hypotheses have emerged. One hypothesis is that bacteria produce a reduced form of soluble iron along with methane as they digest plant and animal matter in thawing permafrost. When this iron reaches flowing streams, it turns into oxygenated iron or "rust," turning the water orange.

This second version of the 1997 Permafrost Map, updated on February 21, 2012, has been digitized and simplified to show continuous permafrost, discontinuous/sporadic permafrost, isolated permafrost areas, and ice sheets and glaciers. Source: International Permafrost Association

Another idea, not exclusive of bacterial processes, is that water encountered sulfide mineral-rich bedrock beneath thawing permafrost, something that likely hasn't happened in thousands of years. The ensuing chemical reaction spikes sulfuric acid in the water, and the acidic water may leach heavy metals from the rocks and carry them downstream. These processes are similar to those in which mining activities contaminate nearby bodies of water.

Changes in water chemistry can degrade habitat for fish, small aquatic animals and insect larvae. The precipitated iron will hinder the breathing of fish and suffocate fish eggs. Drastic changes in water quality are likely to be felt most acutely by villages that rely on rivers that originate in permafrost areas for fish and drinking water.

NASA Earth Observatory image, taken by Ross Walter and Michala Garrison using U.S. Geological Survey Landsat data.

Compiled source: ScitechDaily