A melting Arctic permafrost is unleashing a massive threat to the environment and millions of people’s health through the released toxic mercury at unprecedented rates. Scientists from USC Dornsife have developed a more accurate method to assess the potential hazards of this environmental crisis.
The Yukon River, which flows west across Alaska, is eroding permafrost along its banks and carrying mercury-laden sediment downstream. As temperatures rise across the Arctic—up to four times faster than the global average—the mercury that has been sequestered in permafrost for millennia is being released into the ecosystem.
USC Dornsife scientists have proposed a new method for measuring mercury release from permafrost. These results reflect a worrisome environmental and health danger for the 5 million people within the Arctic region, where more than 3 million of those currently dwell in an area where permafrost is projected to be totally lost prior to 2050.
Co-author Josh West, a professor of Earth sciences and environmental studies at USC Dornsife, warned, “There could be a massive mercury bomb in the Arctic ready to explode.” The natural circulation of the atmosphere carries pollutants to the poles, leading to the accumulation of mercury in the Arctic, which may reach levels way above that found in oceans, soils, and the atmosphere combined.
Plants store mercury in the Arctic. When they die, become part of the soil, and finally freeze into permafrost. When that permafrost thaws as climate change warms the world, all that mercury goes flowing out into the environment. The USC Dornsife team worked with researchers from Caltech, the Yukon River Inter-Tribal Watershed Council, MIT, and Delft University of Technology to survey the Yukon River Basin’s northern villages of Beaver and Huslia.
Earlier mercury estimation methods were narrow and patchy, based on core samples from the top three meters of permafrost. Their new method involves analyzing sediment from riverbanks and sandbars, which better tap into deeper layers for an accurate measurement of mercury. Confirming their suspicions that the sediment sample shall provide them with reliable mercury estimates, it opened deeper insights into the hidden risks of permafrost.
The researchers also used satellite data to determine any changes in the course of the Yukon River itself, which is the real determinant of how much mercury-laden sediment is eroded or deposited. They found that finer-grained sediments had more mercury in them, making some soil types more risky than others.
Coauthor and Ph.D. candidate Isabel Smith of USC Dornsife said, “Considering all these factors will give us a more accurate estimate of the total mercury that could be released as permafrost continues to melt in the coming decades.”.