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.. .The above image [see the article] isn't a heat map, despite its bright colors.

Instead, it's a photograph of Kutuk River in Gates of the Arctic, a vast national park in the remote northern region of Alaska. As Arctic permafrost melts, toxic metals leach into several of the state's rivers, turning the water orange and highly acidic. New research reveals the extent to which permafrost melt affects Alaska's waterways, profoundly changing nearby ecosystems, utilities, and industries.

Permafrost is supposed to be a permanently frozen layer of Earth's crust. In areas like the Arctic, permafrost has existed for thousands of years on land and below the ocean floor.

Thanks to climate change, however, permafrost is having a tough time sticking around. As the air and water around it warms, it melts, releasing everything from ancient pathogens to caches of toxic metals into the surrounding environment.

To measure melting permafrost's effect on nearby waterways, ecologists with the National Park Service snapped aerial images of Alaska's Brooks Range, home to more than 75 once-pristine rivers and streams.

As they flew over the range, the team "started noticing more and more orange rivers," according to ecologist Jon O'Donnell. "There are certain sites that look almost like a milky orange juice."...