In 2018, unusual orange-colored rivers were first noticed in the Brooks Range of Alaska. A recent study by the University of California, Davis, published in the journal AGU Advances, reveals that these rivers contain metal concentrations as high as 70 times the normal levels, extending up to 60 miles downstream. These levels are higher than those typically seen in acid mine drainage, a process where water reacts with sulfur-containing minerals to produce acidic runoff. The study focused on six watersheds in national parks and preserves in northwest Alaska, with water samples collected from 2022 to 2024 to understand the effects of acid rock drainage on river chemistry. The phenomenon began in 2019, a year marked by Alaska’s hottest summer on record, followed by a heavy snowfall winter. According to the researchers, the orange discoloration and high metal content in the rivers are linked to the thawing of permafrost, a process that is becoming more frequent due to climate change. As permafrost thaws, it releases iron, sulfuric acid, and other metals into nearby streams. This process, known as "rusting rivers," has also been observed in boreal and Arctic regions of Canada and other permafrost areas. While the main rivers did not become more acidic overall, metal concentrations increased downstream and could travel long distances, affecting a wider area than initially thought. The study found that in 2019, there were sudden spikes in sulfate and zinc levels, followed by a gradual decline and recovery phase. Researchers believe that the heavy snowfall insulated the soil, preventing it from refreezing and allowing water to penetrate deeper into the ground. This interaction with thawed soil minerals triggered the phenomenon across multiple watersheds at roughly the same time. More than 200 rivers and streams in Alaska have been affected by this phenomenon. However, no negative effects on people or wildlife have been documented yet. Scientists continue to monitor the situation to better understand the potential risks. The study also raises concerns about the impact of thawing permafrost and ground subsidence on local infrastructure, such as roads and buildings, which may be vulnerable to the changes in the landscape.