Methane escaping from Arctic seafloor

March 23, 2010 at 7:03 am Leave a comment

Arctic researchers were surprised to find vast amounts of methane — a powerful greenhouse gas — are leaking from the seabed off the East Siberian coast. This is the first time a study has found so much methane escaping into the atmosphere from the ocean.

Results of a five year study were published in the journal Science on March 5. It debunked the widely held view that the frozen arctic sea-floor prevented methane from escaping in large amounts. It turns out that the seabed permafrost is perforated, allowing the gas to leak out.

Natalia Shakhova, a leader researcher on the study from the University of Alaska Fairbanks, told ScienceDaily.com on March 5: “It was thought that seawater kept the East Siberian Arctic Shelf permafrost frozen. Nobody considered this huge area.”

Past studies of methane emissions have focused on the Siberian mainland. A 2005 study revealed that warming temperatures due to climate change was causing the soil to thaw across western Siberia, turning frozen peat bogs into shallow lakes. The melting of the huge Siberian peat bogs could release billions of tonnes of methane.

An August 2005 New Scientist article said Western Siberia’s peat bogs could hold up to a 25% of the world’s methane stored in land.

Scientists are concerned that business-as-usual carbon pollution may raise temperatures enough to release vast amounts of methane from the Arctic. This would trigger a climate “tipping point” and lead to runaway climate change.

But the East Siberian Arctic Shelf, covering about 2 million square kilometres, could be an even bigger methane source. The Science paper estimated the Arctic seabed emits about 7 teragrams a year — or about 7.7 million tonnes.

“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans”, said Shakova.

“Our concern is that the subsea permafrost has been showing signs of destabilisation already. If it further destabilises, the methane emissions may not be teragrams, it would be significantly larger.”

She told ScienceDaily.com: “The release to the atmosphere of only 1% of the methane assumed to be stored … might alter the current atmospheric burden of methane up to 3 to 4 times. The climatic consequences of this are hard to predict.”

Because this is the first study of its kind, nobody is sure if the methane emissions from the Arctic shelf are new. Shakova has called for followup studies to be made as soon as possible. However, it is clear that the Arctic is warming faster than elsewhere on the globe.

The Arctic Climate Impact Assessment (ACIA), an international research project of the Arctic Council and the International Arctic Science Committee, concluded that “five ACIA-designated models project that mean annual temperatures [in the East Siberia/Alaskan arctic region] will increase by 3 to 4 ºC by the late 21st century“.

Meanwhile, Wired.com reported on March 16 that researchers from the University of Bristol have found that methane levels may be building up underneath the Antarctic ice sheet. It means substantial melting of Antartica’s ice-sheet could also release big quantities of the powerful greenhouse gas.

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Entry filed under: Arctic, methane.

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