Some of Alaska’s clear, icy blue waterways are turning a startling rust orange – so intense it’s visible from Earth’s orbit.

Samples from some of these waterways collected between June and September 2022 contained high concentrations of iron and other toxic metals, including zinc, copper, nickel, and lead, when compared to nearby healthy streams. In some cases, these pollutants ramped up the water’s acidity from the usual pH of 8 to 2.3.

Our working hypothesis is that the thawing of permafrost soil is allowing water to infiltrate deeper and interact with minerals that have been locked away for thousands of years.