“Uncovering the Arctic’s Mercury Bomb: How Thawing Permafrost is Putting Communities at Risk”

A 2022 drone image of the Yukon River and its floodplain downstream from Beaver, Alaska, has revealed accumulations of sediments harboring mercury, posing a significant threat to the environment and communities that rely on the river for sustenance. As global heating, driven by the climate crisis, warms the Arctic at an alarming rate, Alaska’s Yukon River is experiencing the erosion of thawing permafrost, releasing mercury-laden sediment that has been sequestered for thousands of years.

According to a press release from the University of California (USC), the toxic contaminant is endangering the food chain and communities that depend on it. A recent study led by researchers from the USC Dornsife College of Letters, Arts, and Sciences has developed a more accurate method of measuring mercury concentrations released from permafrost by the river and estimating the total amount of mercury yet to be released.

The study highlights the multiple threats posed by permafrost loss to the estimated 5 million people living in the Arctic, with 3.3 million residing in areas where permafrost is predicted to degrade and disappear by 2050. Thawing permafrost can damage critical infrastructure, impact navigable routes, decrease food security, and release contaminants that have been locked away in frozen soils for millennia, including mercury.

Researchers, including collaborators from the Yukon River Inter-Tribal Watershed Council and the California Institute of Technology, focused their study on two northern villages in the Yukon River Basin: Beaver and Huslia. By analyzing deeper soil layers of riverbank and sandbar sediments, the team found that sediment mercury levels were consistent with higher estimates from previous studies, indicating a more accurate assessment of the hidden dangers of permafrost.

Remote satellite sensing data was also used to monitor changes in the Yukon River’s course, which affects the erosion and deposition of mercury-laden sediments. The study revealed that finer-grained sediments contained more mercury, suggesting certain types of soil may pose higher risks.

While the immediate toxic threat from environmental mercury may be minimal, the long-term effects on the food chain and human health are concerning. Exposure to mercury through contaminated fish and game could have detrimental effects on Arctic communities that rely on fishing and hunting for sustenance.

The researchers hope that their findings will enable a more accurate assessment of the “mercury bomb” in Alaska and lead to strategies to mitigate its impact. The study, titled “Mercury stocks in discontinuous permafrost and their mobilization by river migration in the Yukon River Basin,” was published in the journal Environmental Research Letters.