Melting Arctic permafrost would release 15 mn gallons of mercury

A new study has estimated that over 15 million gallons of mercury lies trapped in the permafrost north of the equator.

This would amount to 10 times the mercury emissions produced by humans over the past 30 years, raising concerns among researchers from the American Geophysical Union about the effects it could have.

According to experts, mercury gets embedded in permafrost when the atmosphere binds with organic material in the soil, getting buried by sediment and freezing in permafrost where it could remain trapped for thousands of years. Only changes such as permafrost thaw, like the one possibly due to  climate change, will release the mercury.

In the course of over eight years, beginning 2004, researchers drilled 13 permafrost soil cores from several Alaskan sites, and measured the mercury and carbon levels. Each site had varied soil types and was selected to represent every part of the Northern Hemisphere as closely as possible.

"This discovery is a game-changer," says Paul Schuster, the lead author of the study. "We've quantified a pool of mercury that had not been done previously, and the results have profound implications for better understanding the global mercury cycle."

Experts point out that permafrost made up a large proportion of land north of the equator and in this study the researchers found that it also holds the largest amount of mercury concentrations in the world.

''As permafrost thaws in the future, some portion of this mercury will get released into the environment, with unknown impact to people and our food supplies,'' said Kevin Schaefer, a scientist with the National Snow and Ice Data Center in Boulder, Colorado, and a co-author of the study.

The scientists took cores from permafrost across Alaska and measured mercury levels. They then extrapolated to calculate how much mercury there is in permafrost across the globe, where it covers large portions of Canada, Russia and other northern countries.