Methane has been in the news for some time now as a source of climate alarm. The potential release of this powerful greenhouse gas from melting Arctic permafrost had considerable traction in the news over the last year.
The impact of methane on climate change is more than 20 times greater than carbon dioxide over a 100-year time frame, according to the US Environmental Protection Agency (EPA).
In July 2014, researchers from Stockholm University investigated plumes of methane rising from the floor of the East Siberian Arctic Ocean. The plumes themselves were not a surprise to the scientists, but their high concentration was unexpected.
Chief scientist Örjan Gustafsson speculates that the gas may be coming from collapsing methane hydrates – pockets of methane that are trapped in frozen water. Fears of methane release have most often focused on melting permafrost releasing the gas byproducts of rotting organic matter. Methane also leaks from vents and fissures in the seabed.
Methane hydrate pockets form under highly specific conditions of high water pressure and low temperature, where they generally remain stable. Gustafsson explains that a tongue of Atlantic water may have warmed up enough in recent years to start destabilizing the hydrates.
Methane hydrates have recently become the focus of efforts by India, Japan and Korea to develop as a source of future energy. There could potentially be more fossil fuel in them than there is in conventional reserves of coal, oil and gas. But if climate warming causes them to destabilize they could escape directly into the atmosphere.
If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we’re f’d.
—Jason Box, Geological Survey of Denmark and Greenland climatologist
Jason Box, a climatologist at the Geological Survey of Denmark and Greenland, was closely following the research expedition. He was moved to tweet that “If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we’re f’d.”
In August, researchers released a report describing the discovery of hundreds of methane plumes seeping from organic sediments along the US Atlantic coast. They also found patches of methane hydrate. This was quite unexpected for this particular environment and the scientists speculated that if the East Coast could harbour so many methane pits, there could be tens of thousands more awaiting discovery.
The Atlantic methane mostly dissolves in the ocean and doesn’t release to the atmosphere, but it still adds to the ocean’s carbon content. Some of the difficulties in predicting the behaviour of these phenomena include the rate at which the climate is changing in the Arctic, the unprecedented nature of the unfolding processes and the complex combinations of rapidly changing events. Peter Wadhams, internationally renowned Arctic expert and head of the Polar Ocean Physics Group at Cambridge University, points out that climate models need to represent very fine-scale processes to include all the possible effects. These effects include the break-up of sea ice due to unusually large waves that develop on newly ice-free Arctic water, and surface meltwater pools that melt all the way through ice sheets. Only with sophisticated models like this, he says, can we accurately see the possibilities of offshore permafrost melt – including methane hydrates.
Methane hydrate, also known as methane clathrate, is ice composed of crystalline cages called clathrates that trap methane gas molecules. Hydrates form when temperatures are cold enough and/or pressure is high enough, as in deep water. The source of the methane can be either thermogenic – created by deep-earth heating, or biogenic – created by microbial action in top layers of sediment and in soil. When clathrates melt, they release their trapped methane from the ground, or from bubble plumes when underwater. In the Arctic, clathrates also form on land both above and below the permafrost line.
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