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Retreating Ice Sheets Spurred Massive Methane Expulsions from Arctic Sea Floor

Posted by feww on June 2, 2017

Ice sheets provided perfect conditions for subglacial gas hydrate formation, but…

A new study published in Science shows that hundreds of massive, kilometer-wide craters, were formed on the Arctic ocean floor following substantial methane blowouts about 12,000 years ago.

Abstract

Widespread methane release from thawing Arctic gas hydrates is a major concern, yet the processes, sources, and fluxes involved remain unconstrained. We present geophysical data documenting a cluster of kilometer-wide craters and mounds from the Barents Sea floor associated with large-scale methane expulsion. Combined with ice sheet/gas hydrate modeling, our results indicate that during glaciation, natural gas migrated from underlying hydrocarbon reservoirs and was sequestered extensively as subglacial gas hydrates. Upon ice sheet retreat, methane from this hydrate reservoir concentrated in massive mounds before being abruptly released to form craters. We propose that these processes were likely widespread across past glaciated petroleum provinces and that they also provide an analog for the potential future destabilization of subglacial gas hydrate reservoirs beneath contemporary ice sheets.

The giant craters were formed about 12,000 years ago, but are still seeping large quantities of methane and other gases. Illustration: Andreia Plaza Faverola. Source: CAGE

The craters were formed about 12,000 years ago; however, methane is still leaking profusely from them.

“The crater area was covered by a thick ice sheet during the last ice age, much as West Antarctica is today. As climate warmed, and the ice sheet collapsed, enormous amounts of methane were abruptly released. This created massive craters that are still actively seeping methane” says Karin Andreassen, the study lead author and professor at CAGE Center for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Norway.

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