An Unmistakable Stain in America’s Most Pristine Rivers

Climate change is rusting Alaska’s waterways.

The Salmon River in the Brooks Range runs orange in the early fall of 2020.
The Salmon River in the Brooks Range runs orange in the early fall of 2020. (Roman Dial)

This article was originally published in High Country News.

Dozens of once crystal-clear streams and rivers in Arctic Alaska are now running bright orange and cloudy—and in some cases, they may be becoming more acidic. This otherwise-undeveloped landscape now looks as if an industrial mine has been in operation there for decades, and scientists want to know why.

Roman Dial, a professor of biology and mathematics at Alaska Pacific University, first noticed the starkest water-quality changes while doing field work in the Brooks Range in 2020. He spent a month there with a team of six graduate students, and they could not find adequate drinking water. “There’s so many streams that are not just stained; they’re so acidic that they curdle your powdered milk,” he says. In other streams, the water was clear, “but you couldn’t drink it [because] it had a really weird mineral taste and tang.”

Dial, who has spent the past 40 years exploring the Arctic, was gathering data on climate-change-driven changes in Alaska’s tree line for a project that also includes work from the ecologists Patrick Sullivan—the director of the Environment and Natural Resources Institute at the University of Alaska Anchorage—and Becky Hewitt, an environmental-studies professor at Amherst College. Now the team is digging into the water-quality mystery. “I feel like I’m a grad student all over again in a lab that I don’t know anything about, and I’m fascinated by it,” Dial says.

Many of the rusting waterways are located within some of Alaska’s most remote protected lands: the Arctic National Wildlife Refuge, the Gates of the Arctic National Park and Preserve, the Kobuk Valley National Park, and the Selawik Wildlife Refuge.

The phenomenon is visually striking. “It seems like something’s been broken open or something’s been exposed in a way that has never been exposed before,” Dial says. “All the hard-rock geologists who look at these pictures, they’re like, ‘Oh, that looks like acid mine waste.’” But it’s not mine waste. According to the researchers, the rusty coating on rocks and stream banks is coming from the land itself.

The prevailing hypothesis is that climate warming is causing underlying permafrost to degrade. This releases sediments rich in iron, and when those sediments hit running water and open air, they oxidize and turn a deep rusty-orange color. The oxidation of minerals in the soil may also be making the water more acidic. The research team is still early in the process of identifying the cause in order to better explain the consequences. “I think the pH issue”—the acidity of the water — “is truly alarming,” Hewitt says. Although pH regulates many biotic and chemical processes in streams and rivers, the exact effects on the intricate food webs that exist in these waterways are unknown. The research team is unsure what changes may result for fish, streambed bugs, plant communities, and more.

The rusting of Alaska’s rivers will also likely have an impact on human communities. Rivers such as the Kobuk and the Wulik, where rusting has been observed, also serve as drinking-water sources for many predominantly Alaska Native communities in Northwest Alaska. One major concern, Sullivan says, is how the water quality, if it continues to deteriorate, may affect the species that serve as a main source of food for Alaska Native residents who live a subsistence lifestyle.

The Wulik River terminates at the village of Kivalina, a community of slightly more than 400 people, 80 miles north of the Arctic Circle, that relies on the river. “We are always worried about drinking water,” the tribal administrator Millie Hawley says, adding in a written message that her friends and neighbors fish for trout in the river year-round. The community has seen the river become more and more turbid in recent years, she says, and some people blame the nearby Red Dog Mine. But Hawley says everyone is aware that the permafrost around them is melting, and that increased erosion is causing the level of dissolved minerals and salts in the Wulik to rise.

In addition to present-day impacts, the researchers are also considering the historical record. “I’m sure it has happened [previously],” Dial says, “because, in some sense, this is a natural phenomenon.” But Dial and Sullivan note that the rate of climate warming is greater than anything recorded in the past. “So it’s very possible that something like this has happened before, but it happened really slowly. And maybe there wasn’t just this massive pulse of orange that wound up in these streams,” Sullivan says.

The team believes there could be more than one climate-change-related factor at play. Two of the warmest summers on record, 2019 and 2020, were both followed by winters with unusually high snowpacks. “Snow is a great insulator of soils, and it can be a potentially potent driver of permafrost thaw,” Sullivan says. He likens it to adding an extra blanket to the ground before it freezes. For now, none of the researchers know for sure whether the orange streams and rivers are an anomalous occurrence coinciding with a handful of unseasonably warm seasons followed by high snowpack. And only time will tell how long it might continue.