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Scientists say they have found evidence that frozen methane deposits in the Arctic Ocean have started to be released over a large area of the continental slope off the East Siberian coast, the Guardian can reveal. The slope sediments in the Arctic contain a huge quantity of frozen methane and other gases — known as hydrates. Methane has a warming effect 80 times stronger than carbon dioxide over 20 years. The United States Geological Survey has previously listed Arctic hydrate destabilisation as one of four most serious scenarios for abrupt climate change. Scientists estimate 1, gigatonnes of carbon are locked up in subsea hydrates frozen methane and other gases under Arctic submarine permafrost, some of which could be vulnerable to global heating.

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If large volumes were released, this could rapidly destabilise the climate because methane is a potent greenhouse gas with a warming effect 80 times stronger than carbon dioxide over a year period. Such concerns led the United States Geological Here to list Arctic hydrate destabilisation as one of four most serious scenarios for abrupt climate change. However, several studies suggest such fears are exaggerated.

There are many uncertainties: at what temperature will hydrates destabilise and, if they do, how fast will it happen; and will the gas bubbles reach the surface and be released into the atmosphere or simply dissolve in the oceans? These and other questions are now the subject of intense research on the shelf and slopes of the Laptev Sea and other areas of the Arctic.

The scientists — who are part of a multi-year International The Carbon Of The Greenhouse Gas Problem Study Expedition — stressed their findings were preliminary. Methane seeps detected in the past were found to be historic, but the expedition believes these are new based here an earlier study Greennouse movement of the subsea permafrost between the early s and Carnon scale of methane Carbno will not be confirmed until they return, analyse the data and have their studies published in a peer-reviewed journal.

But the discovery of potentially destabilised slope frozen methane raises concerns about the potential impact on the speed of global heating. With the Arctic temperature now rising more than twice as fast as the global average, the question of when — or even whether — they will be released into the atmosphere has been a matter of considerable uncertainty in climate computer models. The member team on the Akademik Keldysh believe they are the first to observationally confirm the methane release is already under way across a wide area of the slope about km offshore. At six monitoring points over a slope area km in length and 10km wide, they saw clouds of bubbles released from sediment. At one location on the Laptev Sea slope at a depth of about metres they found methane concentrations of up to 1, nanomoles per litre, which is times higher than would be expected if the sea and the atmosphere were in The Carbon Of The Greenhouse Gas Problem.

Potentially they can have serious climate consequences, but we need more study before we can confirm that. The most likely cause of the instability is an intrusion of warm Atlantic currents into the east Arctic. The latest discovery potentially marks the third source of methane emissions from the region.

Semiletov, who has been studying this area for two decades, has previously reported the gas is being released from the shelf of the Arctic — the biggest of any sea. For the second year in a row, his team have found crater-like pockmarks in the shallower parts of the Laptev Sea and East Siberian Sea that are discharging bubble jets of methane, which is reaching the sea surface at levels tens to hundreds of times higher than normal.

This is similar to the craters and sinkholes reported from The Carbon Of The Greenhouse Gas Problem Siberian tundra earlier this autumn. Temperatures in Siberia were 5C higher than average from January to June this year, an anomaly that was made at least times more likely by human-caused emissions of carbon dioxide and methane. The reference to a tipping point was revised to better convey the nature of this concern.

Quick guide Methane and the Arctic Show Hide Management And Management are methane hydrates considered 'sleeping giants' for the climate? That sounds scary.

8 feet of sea-level rise

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