Methane escaping from Arctic seafloor

Issue 

Arctic researchers have found 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 March 5 Science journal. 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 lead 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 August New Scientist said western Siberia's peat bogs could hold up to 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 likely 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 million tonnes a year.

"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 ... would be significantly larger."

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 follow-up 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 3-4ºC by the late 21st century".

Meanwhile, Wired.com reported on March 16 that researchers from the University of Bristol found methane levels may be building up underneath the Antarctic ice sheet. This would mean substantial melting of Antarctica's ice-sheet could also release big quantities of the powerful greenhouse gas.

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