Hidden Gas Source Could Speed Global Warming

aolnews.com ^ | March 4, 2010 | Gregory Mone

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AOL News (March 4) -- Scientists have uncovered a powerful source of a leading greenhouse gas that is venting into the atmosphere at unprecedented rates. The permafrost beneath the East Siberian Arctic Shelf, a relatively shallow section of the Arctic Ocean, has been pumping 7.7 million tons of methane into the air each year -- roughly the amount released into the atmosphere by the rest of the world's oceans combined.

The researchers, who report their work in the March 5 issue of Science, caution that their findings in this previously unstudied region raise more questions than answers. The amount of methane released, though higher than expected, represents only a fraction of total global methane emissions.

But further warming could trigger added leakage of the greenhouse gas in the area, potentially leading to a positive feedback cycle. "The current global change might contribute to this process. It might accelerate this process," says University of Alaska Fairbanks scientist Natalia Shakhova. "The subsea permafrost is significantly more sensitive to further warming."

Jacques Descloitres, MODIS Land Rapid Response Team Scientists are concerned about the amount of methane being released from the East Siberian Arctic Shelf, an area that has not been studied until recently. Methane ranks third on the list of greenhouse gas culprits, after water vapor and carbon dioxide, but its concentration in the air has more than doubled in recent centuries. In the past, atmospheric methane levels have varied between .3 and .7 parts per million. Currently, the numbers are up to 1.85 parts per million -- a 400,000-year high. Above the East Siberian Arctic Shelf, this figure is even greater.

"They're measuring very high concentrations that aren't observed elsewhere," says University of Florida climate scientist Ted Schuur, who has studied climate change in the region. "Carbon is moving between different parts of the earth system every year," he explains. "The question for the future is whether we are losing some kind of balance and going into a new carbon state."

The study by Shakhova et al. does not answer that question, Schuur says, but it highlights the East Siberian Arctic Shelf as a potentially critical hot spot for further research. Though that's a paradoxical description: It is a barren, frozen and thoroughly unpleasant region where "warm" temperatures are those just below freezing.

Shakhova and her colleagues braved the conditions, conducting eight separate research trips to the area over several years, ultimately taking more than 5,000 measurements at sea. Schuur and other scientists had studied the release of methane from the permafrost on land, but no group had analyzed the region below the water.

This underwater source has been subject to massive change. At various points in Earth's history, it has been a frozen plain that effectively traps its methane stores. But that plain was flooded as the world warmed since the last ice age, and it now sits under seawater significantly warmer than the air in the surrounding region. So while the terrestrial permafrost has remained frozen, its subsea counterpart has thawed, sending its methane stores into the atmosphere.

Shakhova explains that while the rate of release the scientists measured on the East Siberian Arctic Shelf is already high, relative to the rest of the world's oceans, it could still increase further. Several major rivers flow into that sea, and increased temperatures in the area could lead to more runoff.

This warmer river water could raise the temperature of the sea further, driving the release of still more methane. Shakhova estimates that even if just 1 percent of the methane stored in the permafrost were released into the air, it could triple atmospheric levels of the gas.

The broader implications of the findings are hard to gauge -- Shakhova said it is too early to tell how her research could affect the projections of the Intergovernmental Panel on Climate Change. But she and other scientists will be monitoring that icy hot spot for years to come.

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