Rivers and streams in Alaska have begun changing color from their usual clean, clear blue to a rusty orange due to toxic metals released by thawing permafrost, a new study reveals. This surprising discovery was made by researchers from the National Park Service, the University of California at Davis, and the US Geological Survey, who tested 75 locations in Alaska’s Brooks Range waterways.
Over the past five to ten years, these water bodies have shown signs of rusting and becoming cloudy and orange. The study, published in the journal Communications: Earth & Environment, attributes this discolouration to the release of metals such as iron, zinc, copper, nickel, and lead. As the permafrost thaws, it exposes minerals that have been locked underground for thousands of years, some of which are toxic to river and stream ecosystems.
“We’re used to seeing this in parts of California, parts of Appalachia where we have a mining history. This is a classic process that happens in rivers here in the continental US that have been impacted for over 100 years since some of the mining rushes in the 1850s,” said Prof Brett Poulin, co-author of the study and professor of environmental toxicology at UC Davis. “But it’s very startling to see it when you’re in some of the most remote wilderness and far from a mine source.”
Arctic soils naturally contain organic carbon, nutrients, and metals such as mercury within their permafrost. The study explains that high temperatures have caused these minerals to mix with water as the permafrost melts. The Arctic is warming four times faster than the rest of the world, accelerating this process.
Prof Poulin noted, “What we believe we’re seeing is this thawing of soil that’s happening faster there than it would happen elsewhere. It’s really an unexpected consequence of climate change.” The researchers used satellite imagery to determine when the color change occurred in various rivers and streams, noting the most drastic changes happened between 2017 and 2018, coinciding with some of the warmest years on record.
This discolouration has been linked to dramatic declines in aquatic life, raising concerns about the impact on communities relying on these waterways for drinking and fishing. Alaska’s Arctic rivers, home to a variety of fish critical for subsistence, sport, and commercial fisheries, are particularly affected.
Alaska is not alone in experiencing this phenomenon. A similar study in Colorado’s Rocky Mountains noted increased metal concentrations in mountain streams due to reduced streamflow and thawing frozen ground, which releases minerals from the bedrock. Other regions such as the Chilean Andes, European Alps, and the Pyrenees in northern Spain have also reported increases in metal concentrations due to climate change.
Researchers in Alaska will continue their studies to pinpoint the sources of the metals and minerals and assess the long-term impact on aquatic and human life. This ongoing research highlights the broader implications of climate change on water quality and ecosystem health in mountain regions worldwide.