The toxic threat in thawing permafrost

The toxic threat in thawing permafrost

Christian Elliott writes:

Covering nearly the same area as Norway, the Hudson Bay Lowlands in northern Ontario and Manitoba is home to the southernmost continuous expanse of permafrost in North America. Compared with many marine waterways this far south, Hudson Bay stays frozen late into the summer, its ice-covered surface reflecting sunlight and keeping the surrounding area cold.

The influence of Hudson Bay on the weather is crazy, says Adam Kirkwood, a graduate student at Carleton University in Ottawa, Ontario. “It can be sunny and 20 °C one day in August, and then half an hour later there’s a wicked wind coming in from the bay—it’s 5 °, and you’re putting on all your layers, and you’re still freezing cold. And when it’s neither of those two things,” he says, “it’s very, very buggy.”

Trapped in all that permafrost is 30 billion tonnes of carbon. It’s an unfathomable amount, says Kirkwood. With global warming, the permafrost is thawing, threatening to release a “carbon bomb” of heat-trapping methane gas to the atmosphere. But there’s something else lurking in the permafrost, too. Something that has the potential to be more immediately dangerous to the people and wildlife living in the area: mercury.

Wildfires and volcanoes belch mercury and since the Industrial Revolution so, too, do coal-burning power plants and factories. Warm air currents carry mercury in its inorganic heavy metal form to the Arctic where it settles into the soil and vegetation before being safely locked away in the deeply frozen permafrost.

In its inorganic form, mercury is less threatening to people. But as the permafrost thaws, says Kirkwood, mercury is finding its way into the soil and into the regions’ many ponds, rivers, and lakes. Once there, microbes can convert inorganic mercury into the form to be concerned about: neurotoxic methylmercury. [Continue reading…]

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