The methane time-bomb

In September 2008, The Independent newspaper reported how preliminary scientific findings suggested that massive deposits of sub-sea methane were bubbling to the surface as the Arctic region becomes warmer and its ice retreats.

In January 2010, The Guardian reported that the amount of methane seeping from Arctic permafrost rose by almost one-third in just five years.

Alarming development
The move is seen as extremely worrying, because it could be a positive feedback mechanism, where the more the Arctic melts the more methane is released. As methane is 20 times more potent than carbon dioxide, its release into the atmosphere causes much greater rates of climate change and warming and hence more methane release. So you could get the runaway greenhouse effect.

The scientists had been sailing the entire length of Russia’s northern coast discovered intense concentrations of methane – sometimes at up to 100 times background levels – over several areas covering thousands of square miles of the Siberian continental shelf. They saw areas of sea foaming with gas bubbling up through “methane chimneys” rising from the sea floor. This could mean that the sub-sea layer of permafrost, which has acted like a “lid” to prevent the gas from escaping, have melted away to allow methane to rise from underground deposits.

Orjan Gustafsson of Stockholm University in Sweden, one of the leaders of the expedition, said in an email. "Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface. These ‘methane chimneys’ were documented on echo sounder and with seismic [instruments] ... Nobody knows how many more such areas exist on the extensive East Siberian continental shelves."

He continued: "The conventional thought has been that the permafrost 'lid' on the sub-sea sediments on the Siberian shelf should cap and hold the massive reservoirs of shallow methane deposits in place. The growing evidence for release of methane in this inaccessible region may suggest that the permafrost lid is starting to get perforated and thus leak methane... The permafrost now has small holes. We have found elevated levels of methane above the water surface and even more in the water just below. It is obvious that the source is the seabed."

Record levels
In January 2010, scientists recorded a massive spike in the amount of methane seeping from Arctic permafrost, rising by almost one-third in just five years, correlating the rise to sharply rising temperatures. The study, published in the journal Science, shows that methane emissions from the Arctic increased by 31% from 2003-07. The increase represents about 1 million extra tons of methane each year. Paul Palmer, a scientist at Edinburgh University who worked on the study, said: "High latitude wetlands are currently only a small source of methane but for these emissions to increase by a third in just five years is very significant. It shows that even a relatively small amount of warming can cause a large increase in the amount of methane emissions."

Global warming is occuring twice as fast in the Arctic than anywhere else on Earth. Some regions have already warmed by 2.5C, and temperatures there are projected to increase by more than 10C by 2100 if carbon emissions continue to rise at current rates. The change in the Arctic is enough to explain a recent increase in global methane levels in the atmosphere, Palmer said. Global levels have risen steadily since 2007, after a decade or so of holding steady.

The findings are part of a wider study of methane emissions from global wetlands, such as paddy fields, marshes and bogs. To identify where methane was released, the researchers combined methane levels in the atmosphere with surface temperature changes. They did not measure methane emissions directly, but used satellite measurements of variations in groundwater depth, which alter the way bacteria break down organic matter to release or consume methane. They found that just over half of all methane emissions came from the tropics, with some 20m tonnes released from the Amazon river basin each year, and 26m tonnes from the Congo basin. Rice paddy fields across China and south and south-east Asia produced just under one-third of global methane, some 33m tonnes. Just 2% of global methane comes from Arctic latitudes, the study found, though the region showed the largest increases. The 31% rise in methane emissions there from 2003-07 was enough to help lift the global average increase to 7%.

The study follows repeated warnings that even modest levels of global warming could trigger huge increases in methane release from permafrost. Phillipe Ciais, a researcher with the Laboratory for Climate Sciences and the Environment in Gif-sur-Yvette, France, told a scientific meeting in Copenhagen last March that billions of tonnes could be released by just a 2C average global rise. Although methane is present in much lower quantities in the atmosphere than carbon dioxide, its potency makes it responsible for about one-fifth of man-made global warming. About two-thirds of global methane comes from man-made sources, and levels have more than doubled since the industrial revolution.

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