May 27, 2009

Study Finds Arctic Thawing A “˜Slow Motion Time Bomb’

"A slow-motion time bomb." That's what one ecologist calls the looming threat of trapped greenhouse gases in the melting Arctic.

Ted Schuur, an ecologist from the University of Florida, says the impact of thawing Arctic soil would allow bacteria to slowly break down organic matter and release carbon into the atmosphere, further exacerbating global warming.

However, plants will also began to grow more as a result of thawing, which causes researchers to question how much these shrubs will be able to compensate for the increased release of carbon.

In a study published in Thursday's edition of the journal Nature, Schuur and colleagues suggest that plant growth resulting from Arctic thawing could initially be able to keep up with the rising rates of carbon dioxide release.

However, as thawing continues, the permafrost will release massive amount of carbon which the plants will no longer be able to compensate for after time.

"At first, with the plants offsetting the carbon dioxide, it will appear that everything is fine, but actually this conceals the initial destabilization of permafrost carbon," said Schuur.

"But it doesn't last, because there is so much carbon in the permafrost that eventually the plants can't keep up."

Equipped with hand-built, automated chambers, researchers trapped and measured the carbon dioxide emissions in Alaska from 2004 to 2006.

"Tundra sites that had thawed for the past 15 years gained net carbon, as increasingly verdant plant growth was greater than the permafrost's carbon losses. However, radiocarbon dating of carbon dioxide showed that old carbon from the permafrost was already being released in higher amounts due to thaw "“ signifying that all was not well with the permafrost carbon even in that time period," researchers found.

While the majority of the 13 million square kilometers, or roughly 5 million square miles, of permafrost in Alaska, Canada, Siberia and parts of Europe remain frozen, Schuur says that thawing is already under way around the southern edges and is expected to continue to grow during this century.

He noted that while man-made emissions can be slowed, the growth of emissions from thawing permafrost will be difficult, if not impossible to stop once it begins.

"It is not an option to be putting insulation on top of the tundra," he said. "If we address our own emissions, either by reducing deforestation or controlling emissions from fossil fuels, that's the key to minimizing the changes in the permafrost carbon pool."


Image Caption: In this photo from February 2006, research team member Christian Trucco makes a wintertime measurement of ecosystem carbon flux in Eight Mile Lake near Denali National Park in Alaska. The black suitcase contains an infrared gas analyzer to measure carbon dioxide exchange between tundra and the air. When the small clear chambers are placed on the snow/tundra surface, the carbon dioxide in the chamber increases slowly over 10 minutes because of microbial release of carbon dioxide from decomposing soil organic matter. Even during the winter when the plants are not active, there is a slow release of carbon by microbes that is significant once it is added up over the long winter period. Credit: Emily Tissier/University of Florida


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