Permafrost: A whole other problem

Scientists map soils to see just how much melting the planet can handle. James Mitchell Crow reports.

Nobody knows how severe the effects of thawing permafrost will be. – Galen Rowell/Corbis

We do a reasonable job of measuring greenhouse gas released from manmade sources. But emissions from natural sources are harder to quantify, adding uncertainty to climate models.

“For me, the most problematic unknown is thawing permafrost,” says Bo Elberling from the University of Copenhagen in Denmark, who studies the greenhouse gases released from melting permafrost in northeast Greenland.

The biggest concern is that as the soil there thaws, bacteria awake from their cryogenic sleep and boot-up their metabolic activity, ready and able to digest the thousands of gigatonnes of organic matter – dead plant matter accumulated over the centuries – releasing CO2 as a by-product. But how big a problem is it?

Elberling and his team have just published the first long-term study monitoring CO2 release from melting permafrost in Nature Climate Change. Water is the crucial factor, they found. If the soil dries out, bacteria can access oxygen and could break down all the organic matter within a century. But if the soil stays wet, oxygen can’t penetrate and the carbon emissions will be negligible. Elberling’s best bet is that we’ll see a patchwork of both, depending on local geography and how well the soil drains.

Predicting how wet these soils will stay as the rainfall patterns change due to climate change is the next challenge, he says.

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