Phys.Org - Are Antarctic Ice Sheets Serving (For Now) As Methane Hydrate Containment?

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(But) this is the first comprehensive study that shows that there is a third process that can create, contain and maintain large amounts of gas hydrates: ice sheets. " They are heavy, can exert enormous pressure on the ground below. And they are cold, of course. With enough supply of gas and water from below and favorable geological setting you will likely have enormous amounts of gas hydrates contained under modern ice sheets as well".


Pockmarks are scars on the ocean floor, an evidence of gas release. These likely appeared as the ice sheet retreated from the western part of Svalbard, and the area began to submerge in seawater again. They prove that release of methane followed the retreat of the ice sheet. Credit: Alexey Portnov/CAGE

The theory that this may be happening beneath the Antarctic ice sheet has been published previously in Nature. CAGE-study is a more comprehensive take on that idea, and shows same processes taking place in the Arctic. Scientists from CAGE have over time collected wide-ranging observational data offshore western Svalbard in the Arctic Ocean. This made it possible to create robust models for a scenario of subglacial evolution of gas hydrate reservoirs during and after Last Glacial Maximum, or last ice age in layman´s terms.

The results of the study indicate that even under conservative estimates of ice thickness a 500-meter thick gas hydrate stability zone existed beneath the ice sheet in the study area. This zone could have served as a methane sink-a reservoir containing immense amounts of the natural greenhouse gas. 1 m3 of gas hydrate contains almost 170 m3 of the greenhouse gas methane. During the last ice age the continental margin offshore western Svalbard, was land covered with ice, much as Greenland and Antarctica of today. But as the climate changed, the ice melted over a period of thousands of years, a rapid melt in geological terms.

The scientists have mapped over 1900 pockmarks - gas escape features - on what now is the seafloor in the study area. The age of these pockmarks has in previous studies been estimated as post-glacial, meaning that they appeared after the ice sheet had retreated. "Pockmarks are evidence of gas release from the ground. We infer that the gas hydrate zone was stable as long as the climate was cold and the ice sheet was stable. Abrupt climate warming caused sheets to melt, decreasing the pressure on the ground and increasing the temperature. This destabilized the hydrates. Methane was released into rising seawater and possibly the atmosphere." says Portnov.

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http://phys.org/news/2016-01-ice-sheets-vast-reservoirs-powerful.html