Climate

Melting Arctic Permafrost Could Release Millions of Gallons of Mercury Pollution

The tundra of Eurasia and North America contains twice as much mercury as the rest of the world combined.

Erosion on the shores of the Ninglick River is seen on July 3, 2015 in Newtok, Alaska. Newtok is one of several remote Alaskan villages that is being forced to relocate due to warming temperatures which is causing the melting of permafrost, widening of rivers, and the erosion of land and coastline. | Andrew Burton/Getty Images
Erosion on the shores of the Ninglick River is seen on July 3, 2015 in Newtok, Alaska. Newtok is one of several remote Alaskan villages that is being forced to relocate due to warming temperatures which is causing the melting of permafrost, widening of rivers, and the erosion of land and coastline. | Andrew Burton/Getty Images

Warming temperatures in the far north could thaw permafrost and release massive amounts of poisonous mercury into the environment.

In a study published in the journal Geophysical Research Letters, Kevin Schaefer, a research scientist at the National Snow and Ice Data Center at the University of Colorado in Boulder, and other researchers said the tundra of Eurasia and North America contains around 32 million gallons of mercury, or enough to fill 50 Olympic-sized swimming pools. That’s almost twice as much as the rest of the world combined according to previous estimates, the researchers claimed.

“If any portion of the mercury is released from thawing permafrost, it would have a negative but unknown impact on food resources and environments. Mercury is a neurotoxin,” Schaefer told Seeker.

With US and Chinese government funding, among other sources, the international team of researchers drilled and measured the mercury and carbon in 13 soil cores from 2004 and 2012 in Alaska. They then compared their findings with previously published data on 11,000 mercury samples in cores from permafrost and other soils around the globe and discovered that their findings were consistent.

Problem is, climate change is warming the Arctic region, melting ice, and thawing permafrost.

This diagram shows the modern mercury cycle with major reservoirs in white (gigagrams of mercury) and exchanges between reservoirs in black (gigagrams of mercury per year). Northern Hemisphere permafrost contains 863 gigagrams of mercury in the active layer, the layer of ground that is subject to annual thawing and freezing. About 793 gigagrams of mercury is found in Northern Hemisphere permafrost. | Schuster et al./GRL/AGU

Scientists have already sounded alarms about the release of carbon dioxide, methane, and other greenhouse gases as rising temperatures thaw out permafrost that covers almost 9 million square miles, or about a quarter of the Northern Hemisphere.

That’s occurring because permafrost traps the carbon that naturally occurs in the soil as plants grow, die, and decompose.  As the temperature decreases, the permafrost thaws and organic matter starts decaying and releasing the gases.

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The same goes for mercury. It too has been building up in the Arctic’s soil as the mosses, shrubs, and other plants of the tundra grow, die, rot, then freeze before they might migrate elsewhere. But rather than changing the climate, mercury emissions would harm people’s health.

“The microbes eat it,” Schaefer said. “The plankton eat the microbes. The fish eat the plankton. We eat the fish. It represents a health hazard.”

This image shows soil mercury content (in micrograms of mercury per square meter) in Northern Hemisphere permafrost zones for four soil layers: 0 to 30 centimeters, 0 to 100 centimeters, 0 to 300 centimeters, and permafrost. The permafrost map represents mercury bound to frozen organic matter below the active layer and above a depth of 300 centimeters. | Schuster et al./GRL/AGU

Humans have experience with mercury pollution. Mercury forces officials to post No Fishing signs along urban rivers. In the oceans, the substance is already making some fish unsafe to eat.

“Mercury is already a big concern in the high Arctic,” said Schaefer. “People who live off the land and fish in the oceans, they are already detecting mercury in the food. This is a really major impact.”

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Scientists predict that 30 to 90 percent of the permafrost could disappear by 2100 if climate trends and carbon emissions continue at current rates, the study said. Schaefer and his team were not sure whether mercury would be released at the same pace. It could take around 75 years for half of the mercury to move elsewhere as the permafrost’s vegetation decays, he said.

“It’s going to take centuries to leech out the mercury,” said Schaefer. “The question is, how much is going to come out and when? We don’t have those answers yet.”

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