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Greening vs. Gassing in the Arctic

Scientists have long debated how the global climate might be affected by thawing of the Arctic’s permanently frozen soils, known as permafrost. As permafrost melts, bacteria break down the organic matter in the soil, releasing greenhouse gases. But at the same time, plants flourish with access to warmer, deeper soils, taking in carbon dioxide. The overall affect on the climate was assumed to be the balance between the gassing and greening.

A new study in this week’s Nature [subscription], suggests that initially, after 15 years of thaw, plants grow faster and take in more carbon than is released by the melting tundra, making the ecosystem an overall carbon sink. But after a few decades, the balance shifts and the ecosystem becomes a source of carbon.

“The plants are growing faster, but after a few decades the rate of carbon loss from the soils is so high the plants can’t keep up,” says Edward Schuur from the University of Florida in Gainesville, who led the research. When Schuur extrapolated the findings to the entire Arctic region, they suggested a release of around a billion tonnes of carbon every year — of the same order of magnitude as emissions from current deforestation of the tropics. Burning of fossil fuels releases about 8.5 billion tonnes of CO2 a year.

It’s estimated that permafrost soils store about twice as much carbon than is currently present in the atmosphere, so the stores of carbon in permafrost are unlikely to run out any time soon. “It’s a slow-motion time bomb,” says Schuur.

Read the full story over on Nature News.

Anjali Nayar is an intern reporter with Nature News.


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    Dougo said:

    And don’t forget albedo. As the snowy tundra is replaced by darker shrubs and trees, the landscape becomes darker and warmer.

    Previous work by Bala et al. has shown that the carbon uptake from new forests is more than offset by loss of albedo, add to that the “gassing” and the net effect is clearly a positive-feedback trend toward warming.

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    Autumn Lovell said:

    An important observation to all those who are following this development. We have to assume that no matter how fast we act, some of the effects of gassing will be felt. This means that all of our global climate advancements need to take into account the additional carbon that will be emitted from the ice melting. If we are expecting an additional billion tonnes of year from permafrost melt, then we need to have an environmental plan in place to counter that effect BEFORE it happens! Isn’t it time to stop playing catch up and start being pro-active? Now that we have some scientific evidence to illustrate the problem, lets get some legislation that will really do something about it.

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