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Rivers and streams in Alaska are turning orange, USGS finds

Tukpahlearik Creek in northwestern Alaska's Brooks Range runs bright orange where permafrost is thawing
Tukpahlearik Creek in northwestern Alaska's Brooks Range runs bright orange where permafrost is thawing. (CREDIT: Taylor Roades)

In Alaska's remote wilderness, a transformation is taking place. Streams and rivers, once crystal clear, are turning a cloudy orange. This phenomenon, likely caused by minerals exposed by thawing permafrost, has been documented in new research published in Nature Communications: Earth and Environment.

For the first time, a collaborative team of researchers from the National Park Service (NPS), U.S. Geological Survey (USGS), University of California, Davis, and other institutions has studied these impaired waters. They pinpointed 75 locations across northern Alaska's Brooks Range, an area roughly the size of Texas.


Aerial Observations Reveal a Growing Issue

The lead author of the study, Jon O’Donnell, an ecologist with the NPS Arctic Inventory and Monitoring Network, first noticed the issue in 2018. He observed a river that had turned rusty, contrasting with its previously clear state. This prompted further investigations and the collection of water samples from these remote regions, accessible primarily by helicopter.

"The more we flew around, the more orange rivers and streams we saw," O'Donnell said. "Some sites look almost like milky orange juice. These orange streams can be problematic, potentially toxic, and might hinder fish migration to spawning areas."


Visible from Space

The stained rivers are not only noticeable on the ground but can also be seen from space. Brett Poulin, an assistant professor of environmental toxicology at UC Davis, and a principal investigator in the research, noted, "The stained rivers are so big we can see them from space. These have to be stained a lot to pick them up from space."

Poulin, who specializes in water chemistry, likened the staining to acid mine drainage. However, there are no mines near the impaired rivers, such as the Salmon River and other federally protected waters.


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The hypothesis is that thawing permafrost exposes minerals to water and oxygen, releasing acid and metals.

"Chemistry tells us minerals are weathering," Poulin explained. "Understanding what’s in the water is a fingerprint as to what occurred."


Analyzing the Water

The affected rivers are on federal lands managed by the Bureau of Land Management, Fish and Wildlife Service, and NPS, including Gates of the Arctic and Kobuk Valley national parks. Poulin and Ph.D. candidate Taylor Evinger analyzed initial samples and collected additional ones last August. Others gathered samples in June and July, with more trips planned this year.

Some water samples from these rivers have an extremely low pH of 2.3, compared to an average pH of 8 for the region's rivers. This indicates significant acidification due to sulfide mineral weathering, which releases metals into the water. Elevated levels of iron, zinc, nickel, copper, and cadmium have been detected.

"We see a lot of different types of metals in these waters," Evinger noted. "Iron is one of the most dominant metals, causing the color change."


Historical Context and Future Risks

Satellite images have revealed that the staining issue dates back to at least 2008. "The issue is slowly propagating from small headwaters into bigger rivers over time," O’Donnell said. "When emergent issues or threats arise, we need to understand them."

The researchers are in the second year of a three-year grant aimed at understanding the water chemistry changes, modeling at-risk areas, and assessing implications for drinking water and fisheries. This growing problem affects habitats, water quality, and other ecological systems, turning healthy areas into degraded habitats with fewer fish and invertebrates. Rural communities relying on these rivers for drinking water might eventually require treatment, and local fishing stocks could suffer.

"There are a lot of implications," O’Donnell emphasized. "As the climate continues to warm, we expect permafrost to continue thawing, potentially turning more streams orange and degrading water quality."


The Need for Further Research

More work is needed to understand whether these rivers and streams can recover, potentially during colder weather that might promote permafrost stability. "I think there will be a lot more detailed work to follow up on to address some of the uncertainties we currently have," O’Donnell added.

The research, involving contributions from scientists at Alaska Pacific University, Colorado State University, University of Alaska Anchorage, and UC Riverside, was funded by the USGS-NPS Water Quality Partnership program, the USGS Changing Arctic Ecosystem Initiative, and the NPS Arctic Inventory and Monitoring Program.


This study underscores the complex interactions between climate change and environmental health, highlighting the urgent need for ongoing research and monitoring to mitigate potential impacts on both ecosystems and human communities in the Arctic region.

For more science and technology news stories check out our New Innovations section at The Brighter Side of News.


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