Some of the Arctic's coldest and remotest rivers and tributaries are turning orange. It is believed that iron-bearing minerals in thawing permafrost soils are now subject to weathering, and meltwater transports them throughout local frozen river valleys. Local observations in Alaska have indicated that the abrupt change in water color indicates something is seriously wrong in the climate system. Researchers have found orange water has higher oxidizing iron content and lowered pH, resulting in sulfuric acidity than adjacent clearwater streams.
The phenomenon is not new or breaking news, as the observations began in 2006.
Alec Luhn writes in Scientific American:
It was a cloudy July afternoon in Alaska's Kobuk Valley National Park, part of the biggest stretch of protected wilderness in the U.S. We were 95 kilometers (60 miles) from the nearest village and 400 kilometers from the road system. Nature doesn't get any more unspoiled. But the stream flowing past our feet looked polluted. The streambed was orange, as if the rocks had been stained with carrot juice. The surface glistened with a gasolinelike rainbow sheen. “This is bad stuff,” said Patrick Sullivan, an ecologist at the University of Alaska Anchorage.
Sullivan, a short, bearded man with a Glock pistol strapped to his chest for protection against Grizzly Bears, was looking at the screen of a sensor he had dipped into the water. He read measurements from the screen to Roman Dial, a biology and mathematics professor at Alaska Pacific University. Dissolved oxygen was extremely low, and the pH was 6.4, about 100 times more acidic than the somewhat alkaline river into which the stream was flowing. The electrical conductivity, an indicator of dissolved metals or minerals, was closer to that of industrial wastewater than the average mountain stream. “Don't drink this water,” Sullivan said.
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Now, however, the Salmon is quite literally rusting. Tributary streams along one third of the 110-kilometer river are full of oxidized iron minerals and, in many cases, acid. “It was a famous, pristine river ecosystem,” Sullivan said, “and it feels like it's completely collapsing now.” The same thing is happening to rivers and streams throughout the Brooks Range—at least 75 of them in the past five to 10 years—and probably in Russia and Canada as well. This past summer a researcher spotted two orange streams while flying from British Columbia to the Northwest Territories. “Almost certainly it is happening in other parts of the Arctic,” said Timothy Lyons, a geochemist at the University of California, Riverside, who's been working with Dial and Sullivan.
Scientists who have studied these rusting rivers agree that the ultimate cause is climate change. Kobuk Valley National Park has warmed by 2.4 degrees Celsius (4.32 degrees Fahrenheit) since 2006 and could get another 10.2 degrees C hotter by 2100, a greater increase than projected for any other national park. The heat may already have begun to thaw 40 percent of the park's permafrost, the layer of earth just under the topsoil that normally remains frozen year-round. McPhee wanted to protect the Salmon River because humans had “not yet begun to change it.” Now, less than 50 years later, we have done just that. The last great wilderness in America, which by law is supposed to be “untrammeled by man,” is being trammeled from afar by our global emissions.
The U.S. Geological Survey and National Park Service first began documenting the eerie changes in the Salmon River, which at one time was full of chum and pink salmon runs. The river flows 70 miles from where the tundra transitions into boreal forests. The water was clear with a green gravel bottom that gave the river an otherworldly clarity. USGS left a water sensor in the river and returned many years later.
The green gravel bottom had turned to orange slime. There were no fish or insects left; biodiversity had collapsed. Biologist Mike Carey, who had placed the water sensor, thought it was a one-off due to a hot August, but the following July, it happened again, this time in the “Agashashok River, 96 kilometers west of the Salmon, turned from turquoise to orange-brown along part of its course. In the winter of 2019 the snowpack was abnormally high; that can insulate the ground, further encouraging permafrost thaw. Then came another hot summer and another snowy winter, and the rusting spread.”
The Scientific American article is well-written and compelling. The scientists document their time on the river and what they had found.