Dozens of once-crystal-clear streams and rivers in Arctic Alaska are now bright orange and murky, and in some cases more acidic. This otherwise undeveloped landscape now looks like an industrial mine has been in operation for decades, and scientists want to know why.
Roman Dayal, a professor of biology and mathematics at Alaska Pacific University, first noticed dramatic changes in water quality during fieldwork in the Brooks Range in 2020. He spent a month with a team of six graduate students and they couldn’t find enough drinking water. “There are so many streams that are not just colored, they are so sour that they curdle your milk powder,” he said. In others, the water was clear, “but it was not to be drunk, because it had a very strange mineral taste and a pungent smell.”
Dayal, who has devoted the last 40 years to Arctic research, has been collecting data on changes to the Alaska forest belt caused by climate change for a project that also involved ecologist Patrick Sullivan, director of the university’s Institute for Environment and Natural Resources. Anchorage, Alaska and Becky Hewitt, professor of environmental studies at Amherst College. The team is now investigating the water quality mystery. “I feel like a graduate student again in a lab I don’t know anything about and I’m fascinated by it,” Dayal said.
Most rusty waterways are located within some of Alaska’s most remote protected areas: the Arctic National Wildlife Refuge, the Arctic Gateway National Park and Preserve, the Kobuk Valley National Park, and the Selawik Wildlife Sanctuary.
The phenomenon is striking. “It seems like something has been hacked or something has been put on display in a way that has never been seen before,” Dayal said. “All the hard rock geologists who look at these pictures are like, ‘Oh, that looks like acid mine tailings.’ But this is not mine waste. According to the researchers, the rusty coating on the rocks and river banks comes from the earth itself.
The prevailing hypothesis is that climate warming is causing degradation of the underlying permafrost. This releases iron-rich deposits, and when these deposits enter running water and outdoors, they oxidize and take on a deep rusty orange color. Oxidation of minerals in the soil can also make water more acidic. The research team is still in the early stages of the process of identifying the cause in order to better explain the consequences. “I think the pH issue” — the acidity of the water — is “really worrisome,” Hewitt said. While pH regulates many of the biotic and chemical processes in streams and rivers, the exact effects on the complex food webs found in these waterways are unknown. From fish to bed bugs to plant communities, the research team isn’t sure what changes could happen.
The rusting of Alaska’s rivers is also likely to affect human communities. Rivers such as the Kobuk and Wulik, where rust has been observed, also serve as sources of drinking water for many predominantly indigenous communities in northwest Alaska. One of the main concerns, Sullivan said, is how water quality, if it continues to deteriorate, could affect species that serve as a primary food source for subsistence Alaska Natives.