Many rivers and streams in Alaska are turning bright orange, and scientists are still working to determine the exact cause of this phenomenon.
Tukpahlearik Stream in the Brooks Range of southwestern Alaska turns orange. (Photo: Taylor Roades).
In recent years, scientists have observed numerous streams turning a bright orange in the Arctic region of Alaska. The color change of the Salmon River, which flows through Kobuk Valley National Park, is particularly concerning, according to the National Park Service. Data show that the river water remained clear before 2019, but in the summer of that year, the Salmon River suddenly turned orange and green.
According to Scientific American, similar changes have occurred in streams throughout the Brooks Range in Alaska and could also be happening in many other areas of the Arctic. Patrick Sullivan, an ecologist at the University of Alaska Anchorage, and his colleagues believe the cause is linked to climate change. Research indicates that the Arctic is warming at a faster rate than the rest of the world. The rising temperatures are causing the permafrost in the national park to thaw. However, researchers are still unclear on how this thawing land is causing the rivers to turn orange. Some experts suggest that acids from minerals are leaching iron from the bedrock. When the sediments come into contact with flowing water and air, they oxidize and turn orange.
Another hypothesis is that the thawing of permafrost beneath wetlands allows bacteria to transform iron into its oxidized form. As groundwater carries this transformed iron into an oxygen-rich stream, it oxidizes again, turning the stream water orange.
Understanding the cause of this phenomenon is crucial for enhancing knowledge about ecological impacts, including risks to wildlife in the rivers and the communities that depend on these water sources. Many tributaries of the Wulik River have turned orange, which may affect Kivalina, a village of 444 residents that relies on fishing and drinking water from the river.
The U.S. Geological Survey (USGS) is conducting a study to survey the orange rivers and streams in Alaska and the timing of their color changes. The research aims to examine multiple hypotheses about the causes of the phenomenon and its relationship with warming weather and thawing land. USGS experts will also assess the impact on water quality and ecosystem health.
