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March 9, 2023

Permafrost thaw may be contributing to discoloration of Arctic rivers by exposing iron-bearing minerals that were previously frozen and are now subject to weathering and hydrologic transport. One consequence of these altered iron-cycling processes is the abrupt change in color (orange) of stream and river reaches, reflecting a dramatic shift in water quality.

In 2022, the U.S. Geological Survey began working with the National Park Service, University of California-Davis, University of Alaska-Anchorage, and Alaska Pacific University to study water quality of streams and rivers in the Arctic. Widespread permafrost thaw has altered the concentration and flux of organic carbon, nutrients, and trace metals in Arctic rivers. Recent observations indicate that waters draining permafrost landscapes may be susceptible to iron and carbon mobilization following thaw. Observations suggest that orange stream reaches have higher iron concentrations, less dissolved oxygen, and more acidic water than nearby clearwater streams. The conversion of streams from clear to orange water appears to reflect a considerable deterioration of habitat for benthic macroinvertebrates and fish.


Scientific America Article: Why Are Alaska's Rivers Turning Orange?


NPS Article: Rusting of Wild and Scenic Rivers in Alaska Arctic National Parks


Map of Arctic rivers study sites with six stars marking sites. Three aerial images with orange streams below map.
Map of orange stream observations across Arctic Inventory and Monitoring Network (ARCN) parks in northern Alaska. Picture inserts show aerial images of select iron-impacted, orange streams. The NPS units in ARCN are the Bering Land Bridge National Preserve (BELA), Cape Krusenstern National Monument (CAKR), Gates of the Arctic National Park and Preserve (GAAR), Kobuk Valley National Park (KOVA), and the Noatak National Preserve (NOAT).

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