Why Arctic rivers are turning rust orange

A new study found that the phenomenon is directly linked to the thawing of permafrost, the layer of ground that has remained frozen for thousands of years. As Arctic temperatures rise, this frozen soil is beginning to melt, releasing iron and other substances into rivers and streams.

Researchers examined affected waterways in Alaska's Brooks Range and discovered two different processes behind the rust-colored contamination.

In mountainous areas, thawing ground exposes a mineral called pyrite, often known as "fool's gold." When pyrite comes into contact with water and air, it breaks down and releases iron, sulfur and other metals. The iron eventually oxidizes, creating rust-like particles that give rivers their distinctive orange color.

In lower-lying wetland regions, a different process is taking place. As permafrost melts, wetlands expand and soils become waterlogged and low in oxygen. Microorganisms in these environments convert iron in the soil into a dissolved form that is carried into nearby streams. Once the iron-rich water reaches the surface and mixes with oxygen, it forms the same rusty particles seen in affected rivers.

The researchers say these two mechanisms explain why orange waterways are appearing across large areas of northern Alaska, particularly in regions where permafrost is rapidly thawing.

The study also identified a delayed effect that may help scientists forecast future contamination. Iron released during one summer can remain trapped underground before being washed into rivers the following year. By comparing long-term ground temperature records with water chemistry data, researchers found that rising soil temperatures could serve as an early warning sign of worsening river conditions.

The environmental impact could be significant. Fine iron particles can remain suspended in water for more than 100 kilometers, reducing water clarity, covering algae, disrupting insect populations and damaging fish gills.

Scientists are particularly concerned about salmon in Alaska and neighboring Canada. The fish depend on clean riverbeds for spawning and healthy aquatic food webs during their early stages of life.

Researchers warn that the problem is unlikely to remain limited to Alaska. Similar combinations of thawing permafrost and metal-rich rocks exist in other parts of the world, including northern Canada, the Andes and the Alps. Evidence suggests comparable changes are already occurring in Russia.

Earlier, Qazinform News Agency reported that researchers from the Wegener Institute discovered an unknown island in Antarctica.