Alaska’s Rust River
Scientific American | December 2023
In the remote Western Brooks Range of North West Alaska, the impact of climate change is impossible to miss. Permafrost the layer of soil that remains frozen throughout the year is thawing at an unprecedented rate and transforming what once were healthy rivers. These rivers and their tributaries are now flowing bright orange with oxidized iron and sulphuric acid, and scientist were there taking samples and accumulating data to determine exactly why.
2024 was the hottest year on global record and the Arctic is disproportionately affected by these elevated temperatures. Then Kobuk Valley National Park just next to the rivers you see here has recorded a 2.4-degree Celsius increase since 2006. This increase is enough to expose the pyrite-rich shale in the bedrock, which has been frozen underground since the last ice age to oxygenated water. The pyrite which until now has never caused a problem begins to breaks down into sulphites/iron2+ and is quite acidic (iron stays in solution at pH 2or3). It then flows over limestone in the area (carbonates) and neutralizes; pH raises to 7, iron comes out of solution and makes the rivers orange. The scary reality is that arsenic, lead, cadium, and other elements potentially present stay in solution at pH7 posing big environmental risks downstream.
The change to water quality, potential depletion of fish populations, and risks associated with metals in the water pose threats to the small communities that rely on these river systems. But the threat extend beyond these remote valleys as well, impacting biodiversity and animal populations in the region. Widespread permafrost thaw risks even larger repercussions. Permafrost is made up of animal and plant matter holding twice as much carbon as the atmosphere does. When permafrost thaws, microbes begin to digest this matter and emit carbon dioxide and methane; which further speeds up the rate in which our planet is warming.
The work that scientists do in these watersheds is crucial to our understanding of climate change and our ability to mitigate the effects on some of the world's most at risk places.
