Permafrost in Alaska is thawing, and a new study finds 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.

(John A. Kelley, USDA Natural Resources Conservation)

At a Glance

Newly discovered mercury stores in permafrost are the largest known on the planet, a study found.They store nearly twice as much mercury as all other soils, the ocean and the atmosphere combined.And they are 10 times greater than all the mercury humans have pumped into the atmosphere from coal-burning and other pollution sources over the last 30 years.

Melting permafrost is expected to release massive amounts of dangerous mercury into the environment in the coming years as climate change warms the planet, a new study says.

Scientists with the U.S. Geological Survey discovered the world's largest known store of mercury in the northern Arctic during a nearly 15-year study that entailed the drilling of 13 permafrost soil cores at various Alaskan sites.

"Prior to the start of the study, people assumed permafrost contained ," study co-authorKevin Schaeferof the National Snow and Ice Data Center at the University of Colorado said in a press release. "But it turns out that not only is there mercury in permafrost, it's also the biggest pool of mercury on the planet."

(MORE: )

While it remains unclear how much mercury might make its way into the atmosphere and food chain, the study, in the journalGeophysical Research Letters, says the permafrost contains 32 million gallonsof mercury, which is "twice as much mercury as the rest of all soils, the atmosphereand ocean combined."

"This is a complete gamechanger for mercury," lead author Paul Schuster, a USGS hydrologist, said in the press release. "It's a natural source, but some of it will be released through what we're doing with climate change."

The USGS researchers notethat the amount of mercury trapped in the permafrost since the last Ice Age is 10 times higher than all the mercury humans have emitted into the atmosphereover the last 30 years,based onfrom 2016.

In another attempt toput the amount of mercury found in the reserves into context, the scientists pointout that the amount of the neurotoxin trapped in the permafrost is equivalentto 50 Olympic-sized swimming pools.

Mercury is a naturally occurring substance that accumulates in aquatic and terrestrial food chains. When ingested, it can have harmful neurological and reproductive effects on animals and humans.

"There would be no environmental problem if everything remained frozen, but we know the Earth is getting warmer," said Schuster. "Although measurement of the rate of permafrost thaw was not part of this study, the thawing permafrost provides a potential for mercury to be released – that’s just physics."

James Shanley, a USGS research hydrologist, notes that the study provides important new information on how mercury is stored.

"This study is very novel and makes a big discovery in an area that was previously somewhat ignored," Shanley, who was not involved in the project, said in the press release. "It shows permafrost represents a huge source of mercury, and if it thaws due to climate change the mercury could be released and could significantly add to the global mercury burden."