Gas hydrate breakdown unlikely to cause clathrate gun - report
post by morganism · 2017-02-19T22:47:20.680Z · LW · GW · Legacy · 5 commentsThis is a link post for http://onlinelibrary.wiley.com/doi/10.1002/2016RG000534/full
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comment by [deleted] · 2017-02-19T22:57:25.407Z · LW(p) · GW(p)
The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir... Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.
The relevant parts from the abstract.
Replies from: morganism↑ comment by morganism · 2017-02-23T04:01:41.671Z · LW(p) · GW(p)
Well, last year, they found significant gas columns breaking the surface in the Leptev sea, and the Ridiculously Resilent Ridge is still there, going on 4 years now, of a stationary high....
'The area of spread of methane mega-emissions has significantly increased in comparison with the data obtained in the period from 2011 to 2014,' he said. 'These observations may indicate that the rate of degradation of underwater permafrost has increased.'
Dr Semiletov and his team are paying special attention to clarify the role of the submarine permafrost degradation as a factor in emissions of the main greenhouse gases - carbon dioxide and methane - in the atmosphere.
The team are examining how the ice plug that has hitherto prevented the exit of huge reserves of gas hydrates has today 'sprung a leak'. This shows in taliks - unfrozen surface surrounded by permafrost - through which powerful emissions of methane reach the atmosphere.
Scientists are eager to determine the quantity of methane buried in those vast areas of the Siberian Arctic shelf and the impact it can have on the sensitive polar climate system.
Five years ago the professor has claimed: 'We found more than 100 fountains, some more than a kilometre across....These are methane fields on a scale not seen before. The emissions went directly into the atmosphere... Earlier we found torch or fountain-like structures like this.."
there are a bunch of on ship blog posts from the folks on the Leptev expeditions that show a LOT of methane getting to the surface.
comment by morganism · 2017-03-23T21:50:29.079Z · LW(p) · GW(p)
Methane Hydrate: Killer cause of Earth's greatest mass extinction
http://www.sciencedirect.com/science/article/pii/S1871174X16300488
"The most significant marker of this event is the negative δ13C shift and rebound recorded in marine carbonates with a duration ranging from 2000 to 19 000 years depending on localities and sedimentation rates. Leading causes for the event are Siberian trap volcanism and the emission of greenhouse gases with consequent global warming. Measurements of gases vaulted in calcite of end Permian brachiopods and whole rock document significant differences in normal atmospheric equilibrium concentration in gases between modern and end Permian seawaters. The gas composition of the end Permian brachiopod-inclusions reflects dramatically higher seawater carbon dioxide and methane contents leading up to the biotic event. Initial global warming of 8–11 °C sourced by isotopically light carbon dioxide from volcanic emissions triggered the release of isotopically lighter methane from permafrost and shelf sediment methane hydrates. Consequently, the huge quantities of methane emitted into the atmosphere and the oceans accelerated global warming and marked the negative δ13C spike observed in marine carbonates, documenting the onset of the mass extinction period. The rapidity of the methane hydrate emission lasting from several years to thousands of years was tempered by the equally rapid oxidation of the atmospheric and oceanic methane that gradually reduced its warming potential but not before global warming had reached levels lethal to most life on land and in the oceans."
the OP article points out that breakdown is not easily accelerated, but once you hit a tipping point, is likely over.
Replies from: morganism↑ comment by morganism · 2017-03-23T22:01:06.290Z · LW(p) · GW(p)
and Siberian Times just reports the tundra pingos are multiplying
"The summer was abnormally hot for the Yamal peninsula, with the air temperature reaching 35C.
This heat impacted on the depth of seasonal thawing which grew both deeper spread wider than in the past, so causing the formation of new lakes and a noticeable change in the regional tundra landscape.
Scientists are simultaneously observing the sudden formation of the large craters, evidently caused by eruptions or explosions of methane gas which has melted below the surface.
On Yamal, the main theory is that the craters were formed by pingos - dome-shaped mounds over a core of ice - erupting under pressure of methane gas released by the thawing of permafrost caused by climate change.
The Yamal craters, some tiny but others large, were created by natural gas filling vacant space in ice humps, eventually triggering eruptions, according to leading authority Professor Vasily Bogoyavlensky, of Moscow's Oil and Gas Research Institute.
Recently there were accounts of a 'big bang' triggering the formation of a crater on the Taimyr Peninsula. However, there was no pingo on this spot before the eruption in 2013. The noise could be heard up to 100 km away and one resident saw a 'glow in the sky' after the explosion, it was revealed. "
comment by morganism · 2017-02-19T23:58:12.251Z · LW(p) · GW(p)
From a review article:
"The review pays particular attention to gas hydrates beneath the Arctic Ocean, where some studies have observed elevated rates of methane transfer between the ocean and the atmosphere. As noted by the authors, the methane being emitted to the atmosphere in the Arctic Ocean has not been directly traced to the breakdown of gas hydrate in response to recent climate change, nor as a consequence of longer-term warming since the end of the last Ice Age.
"After so many years spent determining where gas hydrates are breaking down and measuring methane flux at the sea-air interface, we suggest that conclusive evidence for release of hydrate-related methane to the atmosphere is lacking."
Professor Kessler explains that, "Even where we do see slightly elevated emissions of methane at the sea-air interface, our research shows that this methane is rarely attributable to gas hydrate degradation."
The review summarizes how much gas hydrate exists and where it occurs; identifies the technical challenges associated with determining whether atmospheric methane originates with gas hydrate breakdown; and examines the assumptions of the Intergovernmental Panels on Climate Change, which have typically attributed a small amount of annual atmospheric methane emissions to gas hydrate sources.
The review also systematically evaluates different environments to assess the susceptibility of gas hydrates at each location to warming climate and addresses the potential environmental impact of an accidental gas release associated with a hypothetical well producing methane from gas hydrate deposits."
topic thread over at Arctic Sea Ice forum
http://forum.arctic-sea-ice.net/index.php?topic=12.msg102955#new