Scientists are warning of the danger of a “mercury bomb” lurking in the rapidly warming Arctic that could have devastating consequences for millions of people.
Huge stores of mercury that have been locked in permafrost for thousands of years are being released as the ice melts due to global warming. Recent studies offer a warning.
This toxic metal poses a serious threat to the environment and the health of five million people in and around the Arctic.
Mercury is a neurotoxin that can cause serious harm to the brain and nervous system, especially when it accumulates in the food chain.
Recent USC Dawn Seif Research They have demonstrated a more accurate way to measure the mercury being released, and the results are more dire than expected.
“The Arctic may have a giant mercury bomb waiting to explode,” said Josh West, a professor of geosciences and environmental studies at the University of Southern California’s Doonseif School of Earth Sciences and a co-author of the study.
A silent bomb lurking beneath the melting ice
The Arctic, at the center of climate crisis concerns, is warming four times faster than the global average, and as temperatures rise, permafrost, the frozen soil that covers much of the Arctic, is melting at an unprecedented rate.
Permafrost acts like a natural freezer, preserving not only organic matter but also hazardous substances like mercury. Metals accumulate in Arctic permafrost over thousands of years, are absorbed by plants, and as they die and decompose, they become part of the frozen soil.
When this permafrost thaws, mercury is released into the environment.
The Yukon River, which flows from Alaska to the Bering Sea, plays a key role in this process: the river erodes permafrost along its banks and carries mercury-rich sediments downstream, which contain potentially dangerous levels of the toxic metal and are deposited along the river’s course.
A new way to measure threats
Scientists at the University of Southern California, Doenseif, working with researchers from California Institute of Technology, Massachusetts Institute of Technology and other institutions, have developed a new way to assess how much mercury is being released from Arctic permafrost.
Previous studies have estimated mercury concentrations using core samples taken from the top few metres of permafrost, but these estimates vary widely and are limited by shallow sampling depths.
The new study took a different approach: Scientists analyzed mercury in sediments from riverbanks and sandbars, and probed deeper soil layers. This method gives them a more accurate picture of how much mercury is being released as Arctic permafrost continues to melt, and how much more could be on the way.
The researchers also used remote sensing data from satellites to track how the Yukon River’s course is changing over time. These changes are important because they affect how much mercury-laden sediments erode from the riverbanks, giving them a clearer picture of the potential threat.
“Rivers have the potential to transport large amounts of mercury-laden sediments quickly,” said lead study author Isabel Smith of the University of Southern California’s Doonseif School of Natural History.
“Analyzing these deposits will allow us to get a more accurate estimate of the total amount of mercury that could be released over the next few decades.”
How much mercury is there?
The amount of mercury locked up in Arctic permafrost is staggering: “It’s likely far more than the amount in the oceans, soils, atmosphere and biosphere combined,” West said.
“Mercury doesn’t accumulate by chance,” he explained. “Earth’s natural atmospheric circulation tends to transport pollutants to higher latitudes, which results in mercury accumulating in the Arctic. Because of its unique chemical properties, a lot of mercury pollutants have collected here and been locked in the permafrost for thousands of years.”
This poses a significant risk to the 5 million people living in the Arctic, especially the 3 million who live in areas where the permafrost is expected to disappear completely by 2050.
When mercury is released into the environment, it enters the food chain and accumulates in fish and game animals, which are staples of the traditional Arctic diet.
“Exposure over decades, particularly the increasing concentrations that come with increased mercury emissions, could cause enormous damage to the environment and the health of people living in these areas,” Smith warned.
Why is mercury dangerous?
Mercury is a tricky element. It moves from the atmosphere to the surface, to the water, and back to the atmosphere again. Because of Earth’s natural atmospheric circulation, pollutants like mercury tend to accumulate in the Arctic.
Once there, it becomes part of the ecosystem, cycling through plants, animals and soil.
The study found that fine-grained sediments in the Yukon River contained more mercury than coarse-grained sediments, suggesting that certain types of soil may pose a greater risk because they contain more mercury and are more likely to be eroded by the river.
Interestingly, while rivers erode their banks and transport mercury-rich sediments, they also redeposit some of the metal on sandbars and along the shoreline.
“Streams are recharged with significant amounts of mercury,” West said. “To really understand how much of a threat mercury poses, we need to understand both the erosion and recharge processes.”
Risks to Arctic communities
Although the immediate threat of mercury in the Arctic is not serious — meaning it is unlikely to cause sudden, widespread poisoning — the long-term effects could be devastating.
Mercury accumulates over time in the food chain and continued exposure to even low levels can pose serious health risks. In communities that rely heavily on fishing and hunting, this can mean a slow but steady rise in mercury levels in the diet.
However, the risk of mercury contamination through drinking water is minimal.
“We’re not facing a Flint, Michigan situation,” West said. “The majority of human exposure to mercury is through diet.”
Still, the potential damage is significant: As more permafrost melts in the coming decades, releasing more mercury, the cumulative effects could be severe.
But this isn’t just an Arctic issue: mercury can travel through the atmosphere and food chains, eventually reaching ecosystems and people far from the Arctic.
What’s next?
Understanding the full extent of mercury’s threat is an important first step, the researchers said, and by developing a more accurate way to measure mercury in the environment, they have provided a valuable tool for future research and policy development.
But there’s still a lot of work to be done, and scientists need to keep monitoring the situation, especially as the climate crisis accelerates the thawing of Arctic permafrost.
Governments and international organizations need to consider ways to mitigate the impact of this “mercury bomb” on vulnerable communities.
“Taking all these factors into account, we should be able to get a more accurate estimate of the total amount of mercury that could be released as permafrost continues to thaw over the next few decades,” Smith said.
With better data and a greater understanding of the processes taking place, we hope to be able to take steps to protect the Arctic and its people from this threat before it’s too late.
