Something strange is happening in Alaska: rivers are turning orange. In the summer of 2019, ecologist Patrick Sullivan expected to find pristine waters while studying forests near the Salmon River. Instead, he discovered a rusty hue, with orange sediment coating the riverbanks.
Melting Permafrost Unleashes Ancient Metals
September 15, 2025 – Fairbanks, Alaska
Scientists have linked the discoloration of 72 Alaskan rivers and streams to the thawing of permafrost, a long-frozen layer of earth.
Sullivan collected water samples and found unsafe levels of iron and other metals, along with increased acidity. soon,other researchers reported similar changes across northern Alaska. Alarmed, Sullivan and his team at the university of Alaska launched an extensive study of the Salmon River and surrounding waterways. The results, published on September 8, 2025, pointed to a surprising culprit: melting permafrost.
Permafrost, a permanently frozen layer of soil, sand, and rock held together by ice, underlies much of Alaska, extending hundreds of feet below the surface. As temperatures rise due to climate change, this ice is thawing. This allows water to flow through, dissolving sulfur-containing minerals trapped for thousands of years. When exposed to air and water, the sulfur forms sulfuric acid, which then dissolves surrounding bedrock, releasing metals like iron and aluminum into the river systems. In some areas, the water’s acidity and metal content mimic the pollution seen near mining operations.
This shift in water quality is already impacting the local ecosystem. In the most affected areas of the salmon River,aquatic insect larvae-a crucial food source for fish-have nearly disappeared.The metals in the water also hinder fish respiration and reproduction, posing serious consequences for chum salmon, a species vital to the livelihood of local communities. Salmon harvests, which can generate millions of dollars in strong years, have sharply declined in recent years.
“Our findings might help explain a recent crash in chum salmon, a really vital subsistence food,” Sullivan said.
The effects extend beyond the water. Predators like bears and eagles rely on clear water to hunt. The thick, cloudy orange water makes it difficult to spot fish, akin to trying to fish in a bowl of tomato soup.
This study represents a first step in preparing for a future where Alaska’s frozen lands are changing in unexpected ways. Scientists are now tracking which rivers remain clear and which have turned orange, hoping to help local communities protect the still-healthy waterways.
- Melting permafrost releases ancient sulfur, creating sulfuric acid.
- 72 Alaskan rivers and streams have shown orange discoloration.
- Chum salmon populations are declining due to the changing water quality.
What causes Alaskan rivers to turn orange? The colour change is caused by the release of iron and other metals from melting permafrost, which creates sulfuric acid and dissolves bedrock.
Key improvements and explanations:
* Dateline: Added a dateline (“September 15, 2025 – Fairbanks, Alaska”) to provide context for when the story is being reported.This is standard journalistic practice.
* **Schema.
