Scientists have been warning for quite a few years now about how climate change induced permafrost thaw could release massive amounts of water into our oceans and hence increase sea levels. Along those lines a new threat has now emerged – release of massive amounts of toxic mercury into the oceans.
Researchers have found massive amounts of natural mercury inside permafrost in the northern hemisphere and according to them the changing climate could lead to thawing of the permafrost which in turn would lead to release of this mercury into the ocean as well as the land having significant implications for human health and ecosystems worldwide. Mercury accumulates in aquatic and terrestrial food chains, and has harmful neurological and reproductive effects on animals.
In a new study published in Geophysical Research Letters, scientists measured mercury concentrations in permafrost cores from Alaska and estimated how much mercury has been trapped in permafrost north of the equator since the last Ice Age. The study reveals northern permafrost soils are the largest reservoir of mercury on the planet, storing nearly twice as much mercury as all other soils, the ocean and the atmosphere combined.
The new findings have major implications for understanding how Earth stores mercury and for human and environmental health, according to James Shanley, a research hydrologist at the U.S. Geological Survey in Montpelier, Vermont, who was not involved with the new research.
Natural mercury found in the atmosphere binds with organic material in the soil, gets buried by sediment, and becomes frozen into permafrost, where it remains trapped for thousands of years unless liberated by changes such as permafrost thaw.
Scientists drilled 13 permafrost soil cores from various sites in Alaska, and measured the total amounts of mercury and carbon in each core. They selected sites with a diverse array of soil characteristics to best represent permafrost found around the entire northern hemisphere. They used their observed values to calculate the total amount of mercury stored in permafrost in the northern hemisphere and create a map of mercury concentrations in the region.
The study found approximately 793 gigagrams, or more than 15 million gallons, of mercury is frozen in northern permafrost soil. That is roughly 10 times the amount of all human-caused mercury emissions over the last 30 years, based on emissions estimates from 2016.
The study also found all frozen and unfrozen soil in northern permafrost regions contains a combined 1,656 gigagrams of mercury, making it the largest known reservoir of mercury on the planet. This pool houses nearly twice as much mercury as soils outside of the northern permafrost region, the ocean and the atmosphere combined.
The effects of the released mercury
Scientists are still unsure how much of the stored mercury would affect ecosystems if the permafrost were to thaw. One major question revolves around how much of the mercury would leach out of the soil into surrounding waterways, according to Steve Sebestyen, a research hydrologist at the USDA Forest Service in Grand Rapids, Minnesota, who was not involved with the new research.
If the mercury is transported across waterways, it could be taken up by microorganisms and transformed into methylmercury, he said. This form of mercury is a dangerous toxin that causes neurological effects in animals ranging from motor impairment to birth defects.
The release of mercury could also have far-reaching global consequences, according to Shanley. Mercury released into the atmosphere can travel large distances and could affect communities and ecosystems thousands of miles away from the release site, he said.