Denise Müller-Dum und Jens Kube

Poisonous permafrost legacy

Not only is Arctic permafrost a carbon sink, it also stores pollutants from industrial activity. Researchers warn that such pollutants can be released when the permafrost thaws, threatening people and ecosystems.

On about a quarter of the land area in the northern hemisphere, the top few meters of soil is frozen. This is called permafrost. These landscapes are found in the Arctic regions of North America, Europe and Russia, and also at high elevations in some mountain ranges further south. Permafrost stores carbon, keeping it out of the atmosphere. But that could soon be a thing of the past as global warming thaws soil that has been frozen for millennia. Microorganisms can then decompose the organic material in the permafrost, producing greenhouse gases such as methane and carbon dioxide.

Thawing permafrost releases pollutants

Researchers from the Alfred Wegener Institute in Potsdam also warn that thawing permafrost will release industrial pollutants. In a study, they identified industrial sites on Arctic permafrost, among them mines, gas and oil extraction facilities and military installations. For each of these site types, they analyzed the contamination risk. “Waste materials like heavy metals are left behind where resources are extracted,” says Moritz Langer of the Alfred Wegener Institute and Vrije Universiteit Amsterdam. Organic pollutants and radioactive waste have also accumulated in the Arctic permafrost or have been stored there intentionally.

When permafrost thaws, the poisonous substances in it can enter rivers and lakes. In addition, the ground can become unstable and damage the facilities built on it, further increasing the risk of contamination. Using a computer simulation, the AWI researchers showed that thousands of sites would be affected by the end of this century, even in the most optimistic climate scenario with less than two degrees of warming. “That endangers the northern ecosystems and the people living there,” Langer says; the sites need to be secured or their contaminated materials removed as soon as possible.

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