Climate Change Oddity: Rivers in Alaska Are Turning Orange

An aerial view of the rust-colored Kutuk River in Gates of the Arctic National Park in Alaska. Thawing permafrost is exposing minerals to weathering, increasing the acidity of the water, which releases metals like iron, zinc and copper. Credit: Ken Hill / National Park Service

Thawing permafrost in Alaska is staining rivers orange, impacting water quality and ecosystems.

In Alaska, numerous remote streams and rivers are shifting from their natural crystal-clear blue to an unsettling cloudy orange. According to a recent publication in the Nature journal Communications: Earth and Environment, this could be caused by minerals exposed by thawing permafrost.

In a collaborative research effort, a team of scientists from the National Park Service (NPS), U.S. Geological Survey (USGS), the University of California, Davis, and other institutions have documented and sampled these impaired waters, identifying 75 locations across an area as large as Texas in northern Alaska’s Brooks Range.

Implications of Water Quality Degradation

The degradation of these water bodies could significantly impact drinking water and fisheries in Arctic watersheds as the climate continues to change. “The more we flew around, we started noticing more and more orange rivers and streams,” said lead author Jon O’Donnell, an ecologist for the NPS’ Arctic Inventory and Monitoring Network. “There are certain sites that look almost like a milky orange juice.” He notes that these orange streams pose risks of toxicity and may obstruct fish migration to spawning areas.

An aerial view of the Kutuk River in Alaska’s Gates of the Arctic National Park that looks like orange paint spilling into the clear blue water. Credit: Ken Hill / National Park Service

Discovery and Analysis of Stained Rivers

O’Donnell first noticed the issue when he visited a river in 2018 that appeared rusty despite being clear in the previous year. He began asking around and compiling locations while collecting water samples when possible in the remote region, where helicopters are generally the only way to access the rivers and streams.

“The stained rivers are so big we can see them from space,” said Brett Poulin, an assistant professor of environmental toxicology at UC Davis who was a principal investigator in the research. “These have to be stained a lot to pick them up from space.” Poulin, who specializes in water chemistry, said the staining resembled the effects of acid mine drainage, but there are no mines near the impacted rivers.

Hypothesis on Permafrost and Mineral Release

Researchers hypothesize that as the climate warms, permafrost thaws. This unleashes previously locked minerals into water bodies, leading to acid and metal release. “Chemistry tells us minerals are weathering,” Poulin said. “Understanding what’s in the water is a fingerprint as to what occurred.” These findings come from ongoing research on federal lands, including national parks like Gates of the Arctic and Kobuk Valley.

Analyzing Water Samples and Metal Concentrations

Some samples from the impaired waters have a pH of 2.3 compared to the average pH of 8 for these rivers. This means the sulfide minerals are weathering, resulting in highly acidic and corrosive conditions that release additional metals. Elevated or high levels of iron, zinc, nickel, copper, and cadmium have been measured.

“We see a lot of different types of metals in these waters,” Evinger said. “One of the most dominant metals is iron. That’s what is causing the color change.”

While O’Donnell first noticed a change in 2018, satellite images have turned up stained waters dating back to 2008. “The issue is slowly propagating from small headwaters into bigger rivers over time,” he said. “When emergent issues or threats come about, we need to be able to understand them.”

Ongoing Research and Future Concerns

The researchers are in the second year of a three-year grant aimed at understanding what is happening in the water, modeling what other areas may be at risk, and assessing implications for drinking water and fishing stocks.

The problem is growing and affecting habitat, water quality, and other ecological systems, turning healthy areas into degraded habitats with fewer fish and invertebrates. If rural communities rely on these rivers for drinking water, they could require treatment eventually, and the fishing stocks that feed local residents could be affected.

“There’s a lot of implications,” O’Donnell said. “As the climate continues to warm, we would expect permafrost to continue to thaw and so wherever there are these types of minerals, there’s potential for streams to be turning orange and becoming degraded in terms of water quality.”

More work is needed to gain a better understanding of the issue and to determine if rivers and streams can rebound, perhaps after cold weather promotes permafrost recovery. “I think there will be a lot more detailed work to follow up to address some of the uncertainties that we currently have,” O’Donnell said.

Reference: “Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams” by Jonathan A. O’Donnell, Michael P. Carey, Joshua C. Koch, Carson Baughman, Kenneth Hill, Christian E. Zimmerman, Patrick F. Sullivan, Roman Dial, Timothy Lyons, David J. Cooper and Brett A. Poulin, 20 May 2024, Communications Earth & Environment.
DOI: 10.1038/s43247-024-01446-z

Scientists from Alaska Pacific University, Colorado State University, University of Alaska Anchorage, and UC Riverside also contributed to the research.

The research was funded by U.S. Geological Survey–NPS Water Quality Partnership program, the U.S. Geological Survey Changing Arctic Ecosystem Initiative, and the NPS Arctic Inventory and Monitoring Program.