Tuesday, June 6, 2017

Domes of Frozen Methane May Be Warning Signs for New Blow-Outs #Science

Frequently we hear of Carbon Dioxide as the primary greenhouse gas but the really Big Kahuna is the methane frozen in enormous deposits under the ocean and under the ice.  The last major blowout of methane is postulated to have been a prime cause behind the Snowball Earth in which the planet froze from pole to pole.

500m wide and 10m high, the methane domes on the Arctic Ocean floor are containing huge amounts of methane.

Illustration: Pavel Serov/CAGE Credit: Pavel Serov/CAGE

Several methane domes, some 500m wide, have been mapped on the Arctic Ocean floor. They may be signs of soon-to-happen methane expulsions that have previously created massive craters in a near-by area.

The results are published in PNAS.

"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.

Phys.org:  Domes of frozen methane may be warning signs for new blow-outs

There you see how the methane originated.

However unstable these domes on the Arctic Ocean floor may be, they are still more stable than the pingos found in sub- sea permafrost in Canadian and Russian Arctic.

"The gas hydrate pingos in permafrost are formed because of the low temperatures. But the water-depth that supports gas hydrates in sub-sea permafrost is only 40 to 50 meters. There is no significant pressure there to keep them in check. Sub-seabed permafrost is deteriorating constantly and quickly" notes Serov.

Even though they are more stable than the permafrost pingos, the Barents Sea domes are on the limit of their existence.

"A relatively small change in the water temperature can destabilise these hydrates fairly quickly. We were actually very lucky to observe them at this point. And we will probably be able to observe significant changes to these domes during our lifetime."

- PO

Seeing those changes in my lifetime is improbable but I have studied the problem and its consequences for some while.  There is frequent babble about tipping points but whatever tip happened came some while ago and is shown by the steadily increasing temperature with a new record ever year.

Whether there's any literal tipping point for the release of the methane is unclear and the article was surprisingly cautious on the matter since there are craters observed commonly in the North which have been strongly hypothesized to have been caused by methane blowouts.  Some may be aware of a man-made methane blowout in California which may, even now, not yet be sealed but the contribution of man toward the problem is incontrovertible in that context, at least.

People will almost certainly survive global warming in general when coastal cities have often become major sources of filth which tow their rubbish into the ocean to dump it and frequently spew open sewage into the sea.  Flooding them when the poles melt is of little concern and, besides, they have failed egregiously to maintain their infrastructure and flooding those obsolete cities gives an excellent opportunity to build ones free of the governance of the Law of Evolutionary Potential which has no play in construction of a new city.

However, almost nothing survives the situation of a Snowball Earth and that's the real game you play but that one is no more than Russian roulette since you win or you die and that game is considered suicidally stupid played individually with a gun but is considered political expediency when played collectively for the planet.

The interested student is almost implored to pursue the original article to pursue the matter beyond Ithaka.

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