Thawing Tundra Turns Arctic Rivers Orange and Highly Acidic
A new study in AGU Advances finds that thawing permafrost in Alaska's Brooks Range is releasing iron and sulfuric acid into rivers, making them more metallic and acidic than mine drainage. Metal levels increased up to seventy-fold downstream, with the phenomenon first appearing during Alaska's hottest summer on record in 2019. The rusting has now spread to over 200 rivers in Alaska and parts of northern Canada, raising concerns about the collapse of local chinook salmon fisheries.
The study, published in AGU Advances, traced iron and sulfuric acid releases across watersheds in Alaska's Brooks Range. On the Salmon River, leaching elevated metal concentrations as much as seventy-fold roughly sixty miles downstream, a severity exceeding typical mine drainage.
Researchers pinpointed the onset to the summer of 2019, Alaska's hottest on record. The phenomenon has since appeared in over two hundred rivers across Alaska and much of northern Canada. Coauthor Brett Poulin of UC Davis noted this process was never forecast in any climate assessment for the Arctic.
The rusting of Arctic waterways could disrupt regional ecosystems and livelihoods. If chinook salmon fisheries collapse as feared, Indigenous communities and commercial fishers in Alaska and northern Canada may face significant economic and food-security challenges. The phenomenon may also signal broader, unanticipated consequences of permafrost thaw, suggesting current climate models may underestimate the speed and scale of Arctic environmental change. Water treatment and monitoring efforts could become necessary in affected regions.