Science Daily - 100s Of Methane Craters, 600+ Still Leaking Gas, Mapped On Arctic Ocean Floor

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Even though the craters were formed some 12,000 years ago, methane is still leaking profusely from the craters. Methane is a potent greenhouse gas, and of major concern in our warming climate. "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, first author of the study and professor at CAGE Centre for Arctic Gas Hydrate, Environment and Climate.

Today more than 600 gas flares are identified in and around these craters, releasing the greenhouse gas steadily into the water column.
"But that is nothing compared to the blow-outs of the greenhouse gas that followed the deglaciation. The amounts of methane that were released must have been quite impressive."

A few of these craters were first observed in the 1990s. But new technology shows that the craters cover a much larger area than previously thought and provides more detailed imaging for interpretation.

"We have focused on craters that are 300 meters to 1 kilometre wide, and have mapped approximately 100 craters of this size in the area. But there are also many hundred smaller ones, less than 300 meters wide that is" says Andreassen. In comparison, the huge blow-out craters on land on the Siberian peninsulas Yamal and Gydan are 50-90 meters wide, but similar processes may have been involved in their formation.

EDIT

https://www.sciencedaily.com/releases/2017/06/170601151803.htm

[OKIsItJustMe]

1. Massive craters formed by methane blow-outs from the Arctic sea floor

https://cage.uit.no/news/massive-craters-formed-methane-blow-outs-arctic-sea-floor/#more-3496

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Major methane venting events such as this appear to be rare, and may therefore easily be overlooked.

“Despite their infrequency, the impact of such blow-outs may still be greater than impact from slow and gradual seepage. It remains to be seen whether such abrupt and massive methane release could have reached the atmosphere. We do estimate that an area of hydrocarbon reserves twice the size of Russia was directly influenced by ice sheets during past glaciations. This means that a much larger area may have had similar abrupt gas releases in the overlapping time period “ says Andreassen

Another fact to consider is that there are reserves of hydrocarbons beneath the load of West Antarctica and Greenland ice sheets today.

“Our study provides the scientific community with a good past analogue for what may happen to future methane releases in front of contemporary, retreating ice sheets” concludes Andreassen.

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[OKIsItJustMe]

2. Domes of frozen methane may be warning signs for new blow-outs

https://www.eurekalert.org/pub_releases/2017-06/c-cf-dof060517.php

[font face=Serif][font size=5]Domes of frozen methane may be warning signs for new blow-outs[/font]

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"Every year we go back to the dome area with our research vessel, and every year I am anxious to see if one of these domes has become a crater," says lead author of the study Pavel Serov, PhD candidate at CAGE at UiT The Arctic University of Norway.

These domes are the present-day analogue to what scientists think preceded the craters found in the near-by area, which were recently reported in Science. The craters were formed as the ice sheet retreated from the Barents Sea during the deglaciation some 12.000 years ago.

At the time, 2km thick ice-cover loaded what now is the ocean floor with heavy weight. Under the ice sheet the methane became stored as hydrate, a solid form of frozen methane.

"We believe that one step before the craters are created, you get these domes. They are mounds of hydrates, technically we call them gas hydrate pingos. They are hydrate and methane saturated relics of the last ice-age. They haven't collapsed yet. And the reason is a matter of narrow margins" states Serov.

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