ALASKA RIVERS WITNESSED FROM SPACE TURNING ORANGE

Alaska is renowned for its vast, breathtaking, and eerie wilderness. The state is made up of miles of roaring rivers, thick forests, and mountains. Many places, especially the more isolated Arctic regions, can only be reached by bush plane or helicopter. Scientist Jon O'Donnell was taken aback to discover the waters had turned a murky, rusty orange in 2018 while on a visit to one of the state's numerous isolated rivers. An investigation into the reasons behind Alaska's rivers turning orange was sparked by the stark contrast to the pristine waters during his previous visit the year before. The results, which were just released in Nature Communications: Earth and Environment, point to climate change as the cause. Arctic rivers are becoming contaminated with metals and acids due to the warming permafrost.

Scientists from organisations like the National Park Service, the U.S. Geological Survey, and the University of California, Davis, along with O'Donnell, started surveying rivers and collecting samples of their water after discovering the Lone Orange Stream in 2018. According to satellite imagery, the colours of the rivers were changing and could be seen from space as early as 2008. Lead author Jon O'Donnell states in a statement, "The more we flew around, the more and more orange rivers and streams we started noticing." Some websites have an almost milky orange juice-like appearance. In addition to being poisonous, those orange streams may also impede fish migration to spawning grounds.

After testing the water, iron, zinc, nickel, copper, and cadmium were found. The pH of the waters was frequently much lower than the usual 8, more like 2.3. We see a lot of different types of metals in these waters, says PhD student Taylor Evinger, who assisted in sample analysis. Iron is one of the most common metals. The color shift is being caused by that. Rust-coloured tributaries are those that turn orange when iron oxidises. After that, they feed into bigger rivers where they mix with the clear waters. "Many ramifications exist," O'Donnell continued. 

“As the climate continues to warm, we would expect permafrost to continue to thaw and so wherever there are these types of minerals, there’s potential for streams to be turning orange and becoming degraded in terms of water quality.”

There could be dangerous consequences for wildlife and drinking water if permafrost melts and changes the water in rivers. Alaska's salmon populations might be especially impacted. Other long-trapped items, like frozen viruses or ancient plant DNA, can also be released by permafrost.

While scientists race to understand how the changing world will affect people and animals, climate change poses a threat to human life and the Earth's ecosystems in many ways.