Permafrost

The phenomenon known as “rusting rivers” happens when once-clear streams release highly acidic and metal-laden water, which pose a direct threat to fish and vegetation. It’s happening throughout Alaska’s Brooks Range.

“What we see in the Arctic is that plants will take [mercury] up and then store it, and when they die, rather than decaying and re-releasing that mercury, they're actually frozen and stored in the permafrost,” Smith said. “So you have this big accumulation in stores of mercury in permafrost.”

“It's getting faster and more dramatic. So there's quite a bit of change,” Grosse said. “We see lake change. Lots of lakes are draining in this region over the last years.”

“We noticed that the stream had changed color from this pristine, clear water to a bright orange,” O’Donnell said. “There were no fish — all the fish had left.”

In the Northwest Arctic, runoff from permafrost thaw is turning rivers and streams a rusty orange color, releasing extremely acidic water, and creating dead zones for plants and animals