Metals released from thawing permafrost are rusting Arctic streams

Congratulations to the authors!

This article was selected as one of the top 25 papers of 2024 in Communication Earth and Environment (a branch of the prestigious journal, Nature).

Also see:

Alaska's rusting rivers: The alarming impact of permafrost thaw on Arctic Rivers (video)

Rusting Rivers: Assessing the Causes and Consequences in Alaska and Across the Arctic. Arctic Report Card: Update for 2025. December 2025.

Alaska's Rusting Rivers, Living on Earth: Public Radio's Environmental News Magazine, June 7, 2024

New Research Shows Why Arctic Streams are Turning Orange, Park Science, Summer 2024

Alaskan rivers are turning "milky orange" and toxic, Newsweek, May 21, 2024

Alaska's rusting waters: Pristine rivers and streams turning orange—Thawing permafrost may be driving degradation, University of California, Davis, May 20, 2024

What is causing the rusting of northern Alaska streams? Anchorage Daily News, February 10, 2024

Why Are Alaska's Rivers Turning Orange? Scientific American, January 2024

OPINION: The degradation of a wild and scenic river in Alaska's Brooks Range, Anchorage Daily News, November 15, 2022

More than 75 Arctic streams have turned orange in recent years. Climate change-induced permafrost thaw is releasing metals into the water, discoloring the streams and changing (or eliminating) fish and macroinvertebrates. Metals are toxic and impair water quality for people living in the area. NPS

Large amounts of organic carbon, nutrients, mercury, and other metals are stored in Arctic permafrost—perennially frozen ground. But as the Arctic warms, permafrost is thawing, and these compounds are being released into waterways. Metals are particularly concerning because they can be toxic to aquatic life and to people.

In recent years, air and ground temperatures have abruptly increased compared to the preceding 30-year record, exceeding the freezing threshold for near-surface permafrost. Thawing permafrost can alter stream chemistry through changes in watershed hydrology and biogeochemical cycling in the Arctic. Altered soil saturation, groundwater flow, and warmer soil temperatures enhance microbial and weathering processes, which can change the chemistry of groundwater inputs to streams. The weathering process releases sulfides that lower pH and drives stream discoloration. High levels of iron, nickel, zinc, cadmium, and copper have been found in the infected waters. Iron is what is likely turning the streams orange.

Arctic rivers provide habitat for subsistence, sport, and commercial fisheries. Climate change is already impacting high-latitude fish species, including Pacific salmon, due to the effects of warming marine and freshwater ecosystems. Adding to these stresses, the mobilization of iron and toxic metals to Arctic streams in northern Alaska is degrading water quality and reducing habitat.

The emergence of orange streams in northern Alaska represents an unexpected threat to subsistence fisheries and rural drinking water supplies. Communities in northwest Alaska are isolated and depend socioeconomically and culturally on subsistence foods such as fish, large ungulates, and marine mammals. Our preliminary data suggest that metal mobilization may increase the vulnerability of important subsistence fish species—such as Dolly Varden, chum salmon, and whitefish—to population decline. The metals transported downstream from headwater streams to higher-order rivers may also impact drinking water supplies to rural communities.

Our initial findings indicate that orange streams are an indicator of impaired water quality and are associated with declines in stream biodiversity and habitat degradation. Understanding the magnitude, spatial extent, persistence, and timing of stream degradation may inform management responses by federal and state agencies and adaptation by rural communities and subsistence users.

Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams

Abstract

Climate change in the Arctic is altering watershed hydrologic processes and biogeochemistry. Here, we present an emergent threat to Arctic watersheds based on observations from 75 streams in Alaska’s Brooks Range that recently turned orange, reflecting increased loading of iron and toxic metals. Using remote sensing, we constrain the timing of stream discoloration to the last 10 years, a period of rapid warming and snowfall, suggesting impairment is likely due to permafrost thaw. Thawing permafrost can foster chemical weathering of minerals, microbial reduction of soil iron, and groundwater transport of metals to streams. Compared to clear reference streams, orange streams have lower pH, higher turbidity, and higher sulfate, iron, and trace metal concentrations, supporting sulfide mineral weathering as a primary mobilization process. Stream discoloration was associated with dramatic declines in macroinvertebrate diversity and fish abundance. These findings have considerable implications for drinking water supplies and subsistence fisheries in rural Alaska.

O'Donnell, J. A., M. P. Carey, J. C. Koch, C. Baughman, K. Hill, C. E. Zimmerman, P. F. Sullivan, R. Dial, T. Lyons, D. J. Cooper, and B. A. Poulin. 2024. Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams. Communications Earth & Environment 5: 268.

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