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This is why rivers in Alaska are turning orange and becoming acidic

“The third angel poured out his bowl on the rivers and springs of water, and they became blood.” Photo: Nature


The inertia

Something strange has happened to the rivers in Alaska: They change color from clean and clear to a burnt, acidic orange. According to a new study published in NatureIt is due to the release of metals from the thawing permafrost.

Over the last decade or so, the changing colors have been hard to ignore. A team of researchers from the National Park Service decided they should probably try to figure out what exactly was going on, so they dipped their proverbial toes in the flowing water of 75 waterways that run through the Brooks Range.

The Brooks Range is a stunningly beautiful area. It stretches nearly 1,000 miles from northern Alaska to the Yukon Territory in Canada, and its highest point is Mount Isto. It is approximately 126 million years old, and rivers have been carving their way through it for a very, very long time.

After taking these samples, researchers found that the water was full of metals. Mainly iron, zinc, nickel, copper and lead, most of which are toxic in higher concentrations. These minerals have been locked in the permafrost for thousands of years, but as this permafrost melts rapidly, they are being released at an alarming rate.

“We're used to seeing this in parts of California and Appalachia where there's mining history,” said Brett Poulin, a co-author of the study. “This is a classic process that happens in rivers here in the Americas that have been impacted since the mining boom in the 1850s over 100 years ago. But it's very frightening to see this when you're in one of the most remote wilderness areas and far from a mining source.”

Like everywhere else, the soils in the Arctic are not free of metals. However, if these metals are released much faster than they are currently, the rivers will turn red.

“We believe that the thawing of the ground there is happening faster than it would elsewhere,” Poulin said. “This is really an unexpected consequence of climate change.”

The study found that the most drastic increases in metal pollution occurred in 2017 and 2018, which, not coincidentally, were the warmest years on record.

And it's not just an eyesore. High levels of metals in the water are terrible for the animals that depend on the water, not to mention the communities downstream.

The study will continue in the coming years, and researchers hope to answer more questions about how big the impact of the rusty rivers will be in the future. And with any luck, they can give us a starting point for cleaning up the mess we've made.

“Thawing permafrost can promote chemical weathering of minerals, microbial reduction of iron in soil, and transport of metals through groundwater into rivers,” the researchers warned. “Compared to clear reference rivers, orange rivers have lower pH, higher turbidity, and higher concentrations of sulfates, iron, and trace metals, supporting weathering of sulfide minerals as the primary mobilization process. River discoloration was associated with dramatic declines in macroinvertebrate diversity and fish abundance. These findings have significant implications for drinking water supplies and subsistence fisheries in rural Alaska.”

Anna Harden

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