In the summer of 2019, pilot Paddy Sullivan was flying his research team over Alaska’s pristine Salmon River when he noticed something deeply wrong. The crystal-clear waters that naturalist John McPhee had once described as “gin-clear” and “the purest water” he’d ever seen had turned a muddy orange, as if someone had dumped rust into the entire watershed.¹
Sullivan, who directs the Environment and Natural Resources Institute at the University of Alaska Anchorage, had been studying Arctic forests for decades. But this was something entirely new—and terrifying.
What Sullivan witnessed that day has now been documented in 75 streams across Alaska’s Brooks Range, all turning orange within the last decade. A groundbreaking study published in September 2025 in the Proceedings of the National Academy of Sciences reveals that thawing permafrost is releasing toxic metals into some of Earth’s most pristine rivers at concentrations that exceed federal safety thresholds by up to five times.²
The contamination reads like a catalog of industrial pollution: iron, aluminum, cadmium, zinc, copper, nickel. Yet there isn’t a mine for hundreds of miles.
When Ice Becomes Acid
“This is what acid mine drainage looks like,” explains Tim Lyons, the UC Riverside biogeochemist who led the study. “But here, there’s no mine. The permafrost is thawing and changing the chemistry of the landscape.”³
Lyons, who recently won geology’s highest honor for his work tracking Earth’s chemical evolution, sees these rusting rivers as harbingers of an Arctic transformation that scientists are only beginning to understand. “There’s no fixing this once it starts,” he warns. “It’s another irreversible shift driven by a warming planet.”⁴
The mechanism turning Alaska’s rivers toxic reads like a dark alchemy. For millennia, permafrost has locked away sulfide-rich rocks like pyrite—fool’s gold—keeping them frozen and chemically inert. But as Arctic temperatures rise at four times the global average, that ancient ice is disappearing.⁵
When water and oxygen penetrate newly exposed soil layers, they trigger chemical reactions that generate sulfuric acid. This acid then leaches naturally occurring metals from surrounding rocks, creating a toxic cocktail that flows into groundwater and eventually into streams.
The transformation is stark and sudden. In the Salmon River watershed alone, nine of ten major tributaries now exceed EPA thresholds for at least one metal.⁶ Aluminum concentrations reach nearly five times the safe limit in some locations.
Most concerning is cadmium, present almost exclusively in dissolved form—a state that makes it particularly toxic to aquatic life. The contamination extends hundreds of miles downstream to Kotzebue Sound, where it threatens both marine ecosystems and the communities that depend on them.
David Cooper of Colorado State University, who has worked in the Brooks Range since 1976, calls the recent changes “truly astounding.”⁷ Cooper has watched this landscape for nearly half a century, documenting its slow evolution. But what’s happening now defies all precedent. “I’ve seen gradual changes over decades,” he reflects, “but nothing like this rapid transformation of entire river systems.”
The Vanishing Harvest
For the five Iñupiaq communities along the Kobuk River—about 1,800 people in total—these orange waters represent more than an environmental curiosity. They threaten a way of life that has sustained Arctic peoples for thousands of years.
In 2018, the Kotzebue Sound commercial salmon harvest reached a record 695,153 fish, valued at more than $2.25 million. But since the rivers began turning orange in 2019, chum salmon returns have crashed.⁸
“That fish is just a part of our lives,” says Replogle Swan, president of the Kivalina Volunteer Search and Rescue, watching tributaries of the Wulik River turn orange near his village.⁹ Rural Alaskans harvest an average of 295 pounds of wild foods per person annually, with fish comprising 56% of those harvests. In some regions, wild foods contribute up to half of total energy intake.
The loss of these resources isn’t just economic—it’s existential.
China Kantner, who grew up fishing the Kobuk River and now lives in Kotzebue, understands the interconnected nature of Arctic food systems. “People of the Upper Kobuk are really feeding people from Point Hope to Palmer,” she explains. “It really feeds the whole state.”¹⁰
When asked about her connection to the land, she reflects: “I can’t imagine it any other way. I’d be an entirely different person.”
The changes aren’t subtle. Community surveys reveal that 92% of respondents agree permafrost is thawing more now compared to 20-30 years ago.¹¹ Elders describe rivers running lower, break-up happening earlier, freeze-up occurring later.
A Noatak resident observes simply: “Our weather change from when I was a young kid… Everything changed. You can see our river right now. It’s low water.”¹²
A Circumpolar Crisis Emerges
Alaska’s rusting rivers aren’t an isolated phenomenon. Similar contamination has been documented across the Arctic’s permafrost regions.
In Canada’s Yukon Territory, natural acid rock drainage creates pH levels as low as 3.0 and zinc concentrations up to 475 mg/L.¹³ In Russia’s Siberian rivers, the 2020 Norilsk diesel spill released 21,000 tons of fuel after permafrost thaw destabilized storage tanks.
In the European Alps, high-alpine streams downstream of rock glaciers show elevated concentrations of aluminum, nickel, and manganese as these frozen features become “highly efficient chemical reactors.”¹⁴
The scale is staggering. Forty percent of global permafrost—some 2.5 million square miles—could disappear by 2100.¹⁵ Currently, four million people live directly on permafrost, with 70% of Arctic infrastructure at risk by 2050.
The economic implications reach far beyond the Arctic: permafrost carbon emissions alone could add $43 trillion in climate damages by 2200.¹⁶
What makes this contamination particularly insidious is its mechanism. Unlike pollution from mines, which can theoretically be contained or treated, these toxic releases emerge from hundreds of natural sources scattered across remote wilderness.
There’s no plug to pull, no containment dam to build. Once the process begins, only the restoration of permafrost—requiring massive global emissions reductions—could stop it.
The Scientists Who Sounded the Alarm
The research team that documented this crisis represents a convergence of complementary expertise. Tim Lyons brings his understanding of Earth’s ancient chemistry, having spent decades studying how our planet’s atmosphere evolved.
His colleague Roman Dial, a National Geographic Explorer and professor emeritus at Alaska Pacific University, pioneered “pixel walking”—ground-truthing satellite imagery across 639 kilometers of Brooks Range wilderness.¹⁷ Together with Sullivan and Cooper, they’ve created the most comprehensive picture yet of Arctic river contamination.
Their findings validate decades of observations by Indigenous communities who’ve watched their rivers change. But the scientists bring quantitative rigor to what many already knew: something fundamental has shifted in the Arctic’s chemistry.
Satellite data constrains the timing of stream discoloration to the last 10 years, coinciding with the period of most rapid Arctic warming.¹⁸
Crossing the Point of No Return
The rusting rivers represent just one facet of what climate scientists call Arctic tipping points—thresholds beyond which changes become self-reinforcing and irreversible. At current warming of 1.1°C above pre-industrial levels, we’re already within the uncertainty ranges of multiple permafrost tipping thresholds.¹⁹
At 1.5°C, near-surface permafrost could decline by up to 66%. At 2°C, losses could reach 99%.²⁰
But it’s not just about carbon. Permafrost contains an estimated 800,000 tons of mercury, nearly twice the amount in all other environmental reservoirs combined.²¹ As permafrost thaws, this mercury enters Arctic food webs, bioaccumulating in fish and marine mammals that sustain northern communities.
The contamination creates cascading effects. Iron clouds water, reducing light penetration and smothering insect larvae. Aluminum and other metals accumulate in fish gills, causing respiratory distress and death.
Brett Poulin, an environmental toxicologist at UC Davis who wasn’t involved in the study, places the findings in global context. “Arctic environments are warming up to four times faster than the globe as a whole,” he notes, “and this is resulting in deterioration of water quality in the most pristine rivers in North America.”²²
The Weight of Irreversibility
What distinguishes the Arctic’s rusting rivers from other environmental crises is their permanence. Unlike oil spills that can be cleaned or dams that can be removed, these changes represent a fundamental alteration of Earth’s chemistry.
The carbon released from thawing permafrost will remain in the atmosphere for centuries to millennia. The physical landscape changes—collapsed shorelines, drained lakes, transformed watersheds—cannot be reversed on human timescales.
Patrick Sullivan frames the challenge starkly: “If there were a mine operating in the headwaters of the Salmon, they would be facing regulatory intervention at this point.”²³ But nature recognizes no regulations. The only solution, Sullivan suggests, lies in “pretty massive emissions reductions” that could allow permafrost to recover—a prospect that grows more remote with each passing year.
For the Iñupiaq communities along these transformed rivers, adaptation means reimagining millennia-old relationships with the land. Ice cellars that once preserved food through permafrost’s natural refrigeration are failing.
Traditional travel routes across frozen rivers become treacherous as ice conditions grow unpredictable. The knowledge passed down through generations—when to fish, where to hunt, how to read the land—loses its relevance in a rapidly changing Arctic.
Everywhere and Nowhere
Tim Lyons offers a sobering final assessment: “There are few places left on Earth as untouched as these rivers. But even here, far from cities and highways, the fingerprint of global warming is unmistakable. No place is spared.”²⁴
His words carry particular weight given the remoteness of these watersheds—some accessible only by bush plane or weeks of wilderness trekking.
The Arctic’s rusting rivers force us to confront an uncomfortable truth: we’ve crossed into a new epoch where human influence reaches Earth’s most remote corners, transforming them in ways we’re only beginning to understand. These orange waters aren’t just a local tragedy but a planetary warning.
They tell us that some changes, once set in motion, cannot be undone—that there are points of no return written not in policy documents but in the chemistry of stone and ice.
As the pilot banks away from another rust-stained tributary, the scale becomes clear. This isn’t about one river or even 75. It’s about an entire region—an entire planet—crossing thresholds from which there’s no return.
The Arctic’s rivers are rusting, staining the wilderness with the indelible mark of a warming world. And all we can do is bear witness to the transformation, document what’s being lost, and fight for what remains.
Bibliography
“Arctic Amplification.” Climate Signals. Accessed September 26, 2025. https://www.climatesignals.org/climate-signals/arctic-amplification.
Battarbee, Richard W., and Naomi E. Binney. “Natural Acid Rock Drainage in the Yukon Territory, Canada.” Applied Geochemistry 67 (2015): 408-418.
Cooper, David. “Landscape Changes in Alaska’s Brooks Range, 1976-2025.” Interview by Roman Dial. September 2025.
Dial, Roman, Patrick Sullivan, Tim Lyons, and David Cooper. “Wild, Scenic, and Toxic: Recent Degradation of an Iconic Arctic Watershed with Permafrost Thaw.” Proceedings of the National Academy of Sciences 122, no. 39 (2025): 1-9.
IPCC. “Special Report on Ocean and Cryosphere: Permafrost Loss Projections.” Geneva: IPCC, 2024.
Kantner, China. Interview by Mongabay. September 2025. http://news.mongabay.com/2025/09/alaskan-rivers-turn-orange.
“Kotzebue Sound Commercial Fisheries Statistics.” Alaska Department of Fish and Game. 2018-2025.
Lyons, Tim. “Orange Rivers Signal Toxic Shift in Arctic Wilderness.” Interview. UC Riverside News, September 8, 2025.
National Oceanic and Atmospheric Administration. “Emissions from Thawing Permafrost Add Trillions in Economic Impacts.” Climate Program Office, 2024.
National Park Service. “Community Observations of Changing Conditions in Northwest Alaska.” Arctic Network, 2024.
———. “Observations of Changing Conditions and Impacts on Subsistence Fishing Practices.” Arctic Network, 2025.
O’Donnell, Jonathan A., et al. “Metal Mobilization from Thawing Permafrost to Aquatic Ecosystems Is Driving Rusting of Arctic Streams.” Nature Communications Earth & Environment 5 (2024): 1-12.
Poulin, Brett. Quoted in “Arctic Rivers Turning Orange from Permafrost Thaw.” UC Davis News, September 2025.
Schuster, Paul F., et al. “Permafrost Stores a Globally Significant Amount of Mercury.” Geophysical Research Letters 45, no. 4 (2018): 1783-1792.
Schuur, Edward A. G., et al. “No Respite from Permafrost-Thaw Impacts in the Absence of a Global Tipping Point.” Nature Climate Change 14 (2024): 531-539.
Sullivan, Patrick. “Recent Changes in Alaska’s Salmon River Watershed.” Environmental and Natural Resources Institute Report. University of Alaska Anchorage, 2025.
———. Quoted in “Orange Rivers Signal Toxic Shift.” UC Riverside News, September 8, 2025.
Swan, Replogle. Interview. Mongabay, September 2025. http://news.mongabay.com/2025/09/alaskan-rivers-turn-orange.
Zarroca, Mario, et al. “Water-Rock Interaction and Freeze-Thaw Cycles as Drivers of Acid Rock Drainage Generation by Rock Glaciers in the European Alps.” ACS ES&T Water 4, no. 8 (2024): 198-211.
Notes
¹ Sullivan, “Recent Changes,” 3.
² Dial et al., “Degradation of Arctic Watershed,” 1-9.
³ Lyons, “Orange Rivers,” interview.
⁴ Ibid.
⁵ “Arctic Amplification,” Climate Signals.
⁶ Dial et al., “Degradation of Arctic Watershed,” 5.
⁷ Cooper, “Brooks Range Changes,” quoted in Dial et al., 7.
⁸ “Kotzebue Sound Fisheries,” Alaska Department of Fish and Game.
⁹ Swan, interview, Mongabay.
¹⁰ Kantner, interview, Mongabay.
¹¹ “Community Observations,” National Park Service.
¹² Noatak resident, quoted in “Subsistence Fishing,” National Park Service.
¹³ Battarbee and Binney, “Acid Drainage Yukon,” 412.
¹⁴ Zarroca et al., “Rock Glaciers Alps,” 203.
¹⁵ IPCC, “Permafrost Loss Projections.”
¹⁶ NOAA, “Economic Impacts.”
¹⁷ Dial, “Pixel Walking Method,” 45.
¹⁸ O’Donnell et al., “Stream Discoloration,” Nature Communications.
¹⁹ Schuur et al., “Permafrost Tipping Points,” Nature Climate Change.
²⁰ Ibid.
²¹ Schuster et al., “Mercury in Permafrost,” 1789.
²² Poulin, quoted in UC Davis News.
²³ Sullivan, quoted in UC Riverside News.
²⁴ Lyons, quoted in UC Riverside News.