Melting Permafrost and Its Environmental Impact

As global temperatures rise, the permafrost in the Arctic—soil that has remained frozen for thousands of years—is beginning to thaw. Water and oxygen are seeping into the newly exposed soil, causing the breakdown of sulfide-rich rocks and creating sulfuric acid, which leaches natural metals like iron, cadmium, and aluminum from the rocks into the river.

The Phenomenon of Melting Permafrost

Geochemical processes like these are typically associated with mining operations, but this is not the case here. According to Tim Lyons, a biogeochemist at the University of California, Riverside, what’s happening is akin to acid mine drainage, but without any mines. The melting permafrost is altering the landscape’s chemistry.

A new research paper published in the Proceedings of the National Academy of Sciences highlights the severity of the pollution. Although the study focuses on the Salmon River, researchers warn that similar shifts are occurring in dozens of other Arctic watersheds.

Environmental Impacts of Geochemical Shifts

Ecologist Paddy Sullivan from the University of Alaska first noticed the dramatic changes in 2019 during field research on polar forests moving northward—another consequence of climate change. A pilot transporting Sullivan to the field warned that the Salmon River looked “like sewage” following the ice melt.

Sullivan joined a team of scientists, including Tim Lyons and Roman Dial from Alaska Pacific University, to investigate the causes and environmental effects. Their analysis confirmed that melting permafrost was triggering geochemical reactions that oxidize sulfide-rich rocks, generating acidity and mobilizing a wide range of metals.

Challenges in Preserving Ecosystems

In small amounts, metals are not necessarily toxic. However, the study showed that metal levels in the river water exceed toxicity thresholds for aquatic life according to the U.S. Environmental Protection Agency. Additionally, iron-laden waters reduce the amount of light reaching the riverbed and suffocate insect larvae that serve as food for salmon and other fish.

Although current metal concentrations in edible fish tissues are not considered hazardous to humans, the changes in the rivers pose indirect yet serious threats.

Conclusion

The Salmon River is not the only one affected; this phenomenon is occurring across the Arctic. Wherever suitable rocks are present and permafrost thaws, this process can begin. Unlike mining sites, where acid drainage can be mitigated with containment systems, these remote areas may have hundreds of pollution sources and lack the infrastructure to manage them. Once this chemical shift starts, only the restoration of permafrost can halt it.

The study, funded by the National Science Foundation, highlights the potential risk to other Arctic regions. Researchers hope to assist communities and land managers in anticipating and preparing for future impacts where possible.

As Lyons states, “There are few places left on Earth as untouched as these rivers. But even here, far from cities and highways, the footprint of global warming is unmistakable. Nowhere is safe.”