There’s a Ticking Mercury Bomb in the Arctic. Scientists Are Racing to Defuse It.
Permafrost covers roughly 25 percent of exposed land surface in the Northern hemisphere, and it plays a vital role in locking away carbon and toxic metals like mercury.
A new study says that a looming “mercury bomb” could impact northern communities as permafrost continues to thaw, releasing mercury into the local food chain.
Although rivers do rebury some of this mercury into sediment, further research will be needed to understand this erosion-reburial cycle.
Permafrost is a vital feature of the Earth’s coldest climates. While some can be found in the south, permafrost covers roughly 25 percent of exposed land surface in the Northern hemisphere. Its key feature, as its name suggests, is that it’s always frozen—never thawing, even during the warm summer months. Thanks to this unending icy state and its impressive size (with some stretches extending 1500 meters into the ground), permafrost has locked away an estimated 1,500 gigatons of carbon. That’s around twice as much as what’s found in the atmosphere.
Keeping that carbon locked away so that bacteria can’t release CO2 and methane into the atmosphere (two gasses we definitely don’t need more of) is enough reason to make sure these landmasses don’t melt. In fact, that’s why some scientists consider the health of our permafrost a potential climactic tipping point.
However, researchers at the University of Southern California (USC) Dornsife—along with collaborators from Caltech, the Yukon River Inter-Tribal Watershed Council, MIT, and Delft University of Technology in the Netherlands—are worried about another side effect of these slowly melting landmasses. Because while permafrost locks away lots of carbon, it also contains high amounts of toxic metals like mercury.
A new study published in the journal Environmental Research Letters analyzes the threat of permafrost melting, releasing these metals, and potentially setting off a “mercury bomb” that could greatly impact some five million people living in these cold climates.
“There could be this giant mercury bomb in the Arctic waiting to explode,” USC Dornsife’s Josh West, a co-author of the study, said in a press statement. “Because of the way it behaves chemically, a lot of mercury pollution ends up in the Arctic. Permafrost has accumulated so much mercury that it could dwarf the amount in the oceans, soils, atmosphere, and biosphere combined.”
Mercury levels in the Arctic are already elevated above normal levels, despite the fact that these areas have no typical mercury-producing sources—outside mercury makes its way to the Arctic through the air. Thankfully, plants absorb that mercury and are then entombed in permafrost, but as that permafrost begins to thaw due to climate change, the mercury it is entombing could resurface and wreak havoc on the local food chain.
The research team focused their study around two Alaskan villages—Beaver and Huslia, which are both located close to Fairbanks. Because it’s difficult to extract deep soil cores from permafrost for study, West and his colleagues focused on riverbanks and sandbars in order to get the most accurate readings possible. Rivers can erode sediment and deposit mercury-laden soil along sandbars, so these readings give scientists a good understanding of what dangers are lurking in the permafrost.
This data—along with satellite readings of how fast the Yukon River changes course (and erodes yet more mercury-packed riverbank)—helped scientists to discern that mercury levels were consistent with higher estimates from previous studies, and that the element could find its way into local food sources. This isn’t good new, since humans consume the most mercury through food rather than drinking water.
Although the rushing rivers like the Yukon do rebury some of this mercury (and scientists hope to study this erosion-reburial process more closely), the net gain of mercury could devastate local economies and food systems upon which millions of humans depend.
“Taking into account all of these factors should give us a more accurate estimate of the total mercury that could be released as permafrost continues to melt over the next few decades,” Isabel Smith, USC Dornsife doctoral candidate and lead author of the study, said in a press statement. “Decades of exposure, especially with increasing levels as more mercury is released, could take a huge toll on the environment and the health of those living in these areas.”
For millennia, the Arctic has been locking away toxic metals and keeping the planet healthy and happy. But after two centuries of an unyielding fossil fuel addiction, this particular environmental bill might soon be coming due.
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