Have we already pulled the trigger on the methane gun? As Arctic warms, surprisingly large and uncontrollable releases of methane (much more potent than CO2) are growing from massive shallow seabed deposits and permafrost
1. Wikipedia, Clathrate gun hypothesis (emphasis added):
The clathrate gun hypothesis is the popular name given to the hypothesis that rises in sea temperatures (and/or falls in sea level) can trigger the sudden release of methane from methane clathrate compounds buried in seabeds and permafrost which, because the methane itself is a powerful greenhouse gas, leads to further temperature rise and further methane clathrate destabilization – in effect initiating a runaway process as irreversible, once started, as the firing of a gun. …
2. Skeptical Science, Wakening the Kraken, April 23, 2011:
a major study in Science that found the vast East Siberian Arctic Shelf methane stores appeared to be destabilizing and venting. The normally staid National Science Foundation issued a press release warning “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.”
Now there is a new Geophysical Research Letters study on a paleoclimate analog that may be relevant to humanity today, “Methane and environmental change during the Paleocene‐Eocene thermal maximum (PETM): Modeling the PETM onset as a two‐stage event.” …
We know that in the past there have been sudden changes in global warming associated with releases of greenhouse gases. These rapid, massive releases were characterised by unusualdeficiency in carbon isotope 13 (∂13C ) and massive extinction of animals, most recently at the time of the Paleocene-Eocene Thermal Maximum (PETM), about 55.8 million years ago. …
The description of Stage 2: Very rapid and massive release of carbon deficient in ∂13C, does put one in mind of the Methane Gun hypothesis. It postulates that methane clathrate at shallow depth begins melting and through the feed-back process accelerate atmospheric and oceanic warming, melting even larger and deeper clathrate deposits. The result: A relatively sudden massive venting of methane – the firing of the Methane Gun. Recent discovery by Davy et al (2010) of kilometer-wide (ten 8-11 kilometer and about 1,000 1-kilometer-wide features) eruption craters on the Chatham Rise seafloor off New Zealand adds further ammunition to the Methane Gun hypothesis.
It has been known for many years that methane is being emitted from Siberian swamplands hitherto covered by permafrost, trapping an estimated 1,000 billion tons of methane. Permafrost on land is now seasonally melting and with each season melting it at greater depth, ensuring that each year methane venting from this source increases.
Methane clathrate has accumulated over the East Siberian continental shelf where it is covered by sediment and seawater up to 50 meters deep. An estimated 1,400 billion tons of methane is stored in these deposits. By comparison, total human greenhouse gas emissions (including CO2) since 1750 amount to some 350 billion tons.
Significant methane release can occur when on-shore permafrost is thawed by a warmer atmosphere (unlikely to occur in significance on less than a century timescale) and undersea clathrate at relatively shallow depths is melted by warming water. This is now occurring. In both cases, methane gas bubbles to the surface with little or no oxidation, entering the atmosphere as CH4 – a powerful greenhouse gas which increases local, then Arctic atmospheric and ocean temperature, resulting in progressively deeper and larger deposits of clathrate melting.
Methane released from deeper deposits such as those found off Svalbard has to pass through a much higher water column (>300 meters) before reaching the surface. As it does so, it oxidises to CO2, dissolving in seawater or reaching the atmosphere as CO2 which causes far slower warming, but can nevertheless contribute to ocean acidification.
A significant release of methane due to melting of the vast deposits trapped by permafrost and clathrate in the Arctic would result in massive loss of oxygen, particularly in the Arctic ocean but also in the atmosphere. Resulting hypoxic conditions would cause large extinctions, especially of water breathing animals, which is what we find at the PETM.
Shakhova et al (2010) reports that the continental shelf of East Central Siberia (ECS), with an area of over 2 million km2, is emitting more methane than all other ocean sources combined. She calculates that methane venting from the ECS is now in the order of 8 million tons per annum and increasing. This equates to ~200 million tons/annum of CO2, more than the combined CO2 emissions of Scandinavia and the Benelux countries in 2007. This methane is likely sourced from non-hydrate methane previously kept in place by thin and now melting permafrost at the sea bed, melting clathrates, or some combination of both.
Release of ECS methane is already contributing to Arctic amplification resulting in temperature increase exceeding twice the global average. The rate of release from the tundra alone is predicted to reach 1.5 billion tons of carbon per annum before 2030, contributing to accelerated climate change, perhaps resulting in sustained decadal doubling of ice loss causing collapse of the Greenland Ice Sheet (Hansen et al, 2011). This would result in a possible sea level rise of ~5 meters before 2100, according to Hansen et al.
Evidence supports the theory that sudden and massive releases of greenhouse gases, including methane, caused decade-scale climate changes – with consequent species extinctions – culminating in the Holocene Thermal Optimum.
In summary, immense quantities of methane clathrate have been identified in the Arctic. Were a fraction of these to melt, the result would be massive release of carbon, initially as CH4 causing deeper clathrate to melt and oxidise, adding CO2 to the atmosphere. Were this to occur, it would greatly worsen global warming.
While natural global warming during the ice ages was initiated by increased solar radiation caused by cyclic changes to Earth’s orbital parameters, there is no evident mechanism for correcting Anthropogenic Global Warming over the next several centuries. The latter has already begun producing methane and CO2 in the Arctic, starting a feedback process which may lead to uncontrollable, very dangerous global warming, akin to that which occurred at the PETM.
This extremis we ignore – to our peril.
– Agnostic & Daniel Bailey
Methane release from the not-so-perma-frost is the most dangerous amplifying feedback in the entire carbon cycle (see “NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100“).
It is worth noting that no climate model currently incorporates the amplifying feedback from methane released by a defrosting tundra. Indeed the NSIDC/NOAA study I wrote about in February on methane release by the land-based permafrost itself doesn’t even incorporate the carbon released by the permafrost carbon feedback into its warming model!
4. Doc alert: Siberian methane (Jan 14, 2011)
5. Joe Romm, Climate Progress, Paleoclimate data suggests CO2 “may have at least twice the effect on global temperatures than currently projected by computer models”, January 13, 2011
Methane release from the not-so-perma-frost is the most dangerous amplifying feedback in the entire carbon cycle. The permafrost permamelt contains a staggering “1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere,” much of which would be released as methane. Methane is is 25 times as potent a heat-trapping gas as CO2 over a 100 year time horizon, but 72 times as potent over 20 years! The carbon is locked in a freezer in the part of the planet warming up the fastest (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“). Half the land-based permafrost would vanish by mid-century on our current emissions path (see “Tundra, Part 2: The point of no return” and below). No climate model currently incorporates the amplifying feedback from methane released by a defrosting tundra.
6. Joe Romm, Climate Progress, Science stunner: Vast East Siberian Arctic Shelf methane stores destabilizing and venting, Science: Vast East Siberian Arctic Shelf methane stores destabilizing and venting: NSF issues world a wake-up call: “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.” March 4, 2010
Methane release from the not-so-perma-frost is the most dangerous amplifying feedback in the entire carbon cycle. Research published in Friday’s journal Science finds a key “lid” on “the large sub-sea permafrost carbon reservoir” near Eastern Siberia “is clearly perforated, and sedimentary CH4 [methane] is escaping to the atmosphere.”
… the situation in the ESAS is far, far more dicey, as NSF explains:
The East Siberian Arctic Shelf, in addition to holding large stores of frozen methane, is more of a concern because it is so shallow. In deep water, methane gas oxidizes into carbon dioxide before it reaches the surface. In the shallows of the East Siberian Arctic Shelf, methane simply doesn’t have enough time to oxidize, which means more of it escapes into the atmosphere. That, combined with the sheer amount of methane in the region, could add a previously uncalculated variable to climate models.
“The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to 3 to 4 times,” Shakhova said. “The climatic consequences of this are hard to predict.”
And we also know that a key trigger for accelerated warming in the Arctic region is the loss of sea ice.
A 2008 study by leading tundra experts found “Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss.” The lead author is David Lawrence of the National Center for Atmospheric Research (NCAR), whom I interviewed for my book and interviewed again via e-mail in 2008. The study’s ominous conclusion:
We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends. The accelerated warming signal penetrates up to 1500 km inland….
In other words, a continuation of the recent trend in sea ice loss may triple Arctic warming, causing large emissions in carbon dioxide and methane from the tundra this century.
Oh, and the Arctic warming could lead to another feedback according to a 2008 Science article: “Continuation of current trends in shrub and tree expansion could further amplify this atmospheric heating 2-7 times.” The point is that if you convert a white landscape to a boreal forest, the surface suddenly starts collecting a lot more solar energy (see “Tundra 3: Forests and fires foster feedbacks“).
“Our concern is that the subsea permafrost has been showing signs of destabilization already,” she said. “If it further destabilizes, the methane emissions may not be teragrams, it would be significantly larger.”
NSF explains:
“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans,” said Shakhova, a researcher at UAF’s International Arctic Research Center. “Subsea permafrost is losing its ability to be an impermeable cap.”
Shakhova notes that the Earth’s geological record indicates that atmospheric methane concentrations have varied between about .3 to .4 parts per million during cold periods to .6 to .7 parts per million during warm periods. Current average methane concentrations in the Arctic average about 1.85 parts per million, the highest in 400,000 years, she said. Concentrations above the East Siberian Arctic Shelf are even higher.
The East Siberian Arctic Shelf is a relative frontier in methane studies. The shelf is shallow, 50 meters (164 feet) or less in depth, which means it has been alternately submerged or terrestrial, depending on sea levels throughout Earth’s history. During the Earth’s coldest periods, it is a frozen arctic coastal plain, and does not release methane. As the Earth warms and sea level rises, it is inundated with seawater, which is 12-15 degrees warmer than the average air temperature.
“It was thought that seawater kept the East Siberian Arctic Shelf permafrost frozen,” Shakhova said. “Nobody considered this huge area.”
The hardest of the hard core climate geeks (and we all know who we are) probably recognize the name Natalia Shakhova. She’s a Research Assistant Professor working with the International Arctic Research Center at the University of Alaska Fairbanks and is probably best know to people of our ilk for her work involving Siberian methane deposits. She gave a presentation at a US Dept. of Defense symposium and workshop last November, and it (and others from the event) are online.
Dr. Shakhova’s presentation is titled “Methane Release from the East Siberian Arctic Shelf (ESAS) and the Potential for Abrupt Climate Changes”, and you can download it in PDF format from the event’s site.
Based on that title and the things I write about here (and by “write about” you can substitute “obsess over”, if you’re feeling a need for unflinching accuracy), you’ve probably figured out that this is yet another unsettling collection of data about methane. A couple of tidbits to show that such a conclusion would be accurate, even without the benefit of context (emphasis in the original):
[Slide 34]
Interpretation of acoustical data recorded with deployed multibeam sonar allowed moderate quantification of bottom fluxes as high as 44 g/m2/d (Leifer et al., in preparation). Prorating these numbers to the areas of hot spots (210×103 km2) adds 3.5Gt to annual methane release from the ESAS. This is enough to trigger abrupt climate change (Archer, 2005).
[Slide 38, one bullet taken from the conclusion]
Considering the significance of the ESAS methane reservoir and enhancing mechanism of its destabilization, this region should be considered the most potential in terms of possible climate change caused by abrupt release of methane.
Methane (CH4) deserves attention it is such a highly potent greenhouse gas — 25-33 times more powerful than carbon dioxide (CO2) over a 100-year time-horizon, but as much as 100 time more potent over 20 years, according to the latest research!
Last year I reported on a major study in Science that found the vast East Siberian Arctic Shelf methane stores appeared to be destabilizing and venting. The normally staid National Science Foundation issued a press release warning “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.” …
Most deposits of methane clathrate are in sediments too deep to respond rapidly, and modelling by Archer (2007) suggests the methane forcing should remain a minor component of the overall greenhouse effect.[10] Clathrate deposits destabilize from the deepest part of their stability zone, which is typically hundreds of metres below the seabed. A sustained increase in sea temperature will warm its way through the sediment eventually, and cause the deepest, most marginal clathrate to start to break down; but it will typically take of the order of a thousand years or more for the temperature signal to get through.[10]
One exception, however, may be in clathrates associated with the Arctic ocean, where clathrates can exist in shallower water stabilized by lower temperatures rather than higher pressures; these may potentially be marginally stable much closer to the surface of the sea-bed, stabilized by a frozen ‘lid’ of permafrost preventing methane escape. Recent research carried out in 2008 in the Siberian Arctic has shown millions of tons of methane being released, apparently through perforations in the seabed permafrost,[11] with concentrations in some regions reaching up to 100 times normal.[12][13] The excess methane has been detected in localized hotspots in the outfall of the Lena River and the border between the Laptev Sea and the East Siberian Sea. Some melting may be the result of geological heating, but more thawing is believed to be due to the greatly increased volumes of meltwater being discharged from the Siberian rivers flowing north.[14] Current methane release has previously been estimated at 0.5 Mt per year.[15]Shakhova et al. (2008) estimate that not less than 1,400 Gt of carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and 5–10% of that area is subject to puncturing by open taliks. They conclude that “release of up to 50 Gt of predicted amount of hydrate storage [is] highly possible for abrupt release at any time”. That would increase the methane content of the planet’s atmosphere by a factor of twelve,[16][17] equivalent in greenhouse effect to a doubling in the current level of CO2.
In 2008 the United States Department of Energy National Laboratory system[18] and the United States Geological Survey’s Climate Change Science Program both identified potential clathrate destabilization in the Arctic as one of four most serious scenarios for abrupt climate change, which have been singled out for priority research. The USCCSP released a report in late December 2008 estimating the gravity of this risk.
The East Siberian Arctic Shelf is a methane-rich area that encompasses more than 2 million square kilometers of seafloor in the Arctic Ocean. It is more than three times as large as the nearby Siberian wetlands, which have been considered the primary Northern Hemisphere source of atmospheric methane. Shakhova’s research results show that the East Siberian Arctic Shelf is already a significant methane source, releasing 7 teragrams of methane yearly, which is as much as is emitted from the rest of the ocean. A teragram is equal to about 1.1 million tons.
Scientists learned last year that the permafrost permamelt contains a staggering “1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere,” much of which would be released as methane. Methane is is 25 times as potent a heat-trapping gas as CO2 over a 100 year time horizon, but 72 times as potent over 20 years!
The carbon is locked in a freezer in the part of the planet warming up the fastest (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“). Half the land-based permafrost would vanish by mid-century on our current emissions path (see “Tundra, Part 2: The point of no return” and below). No climate model currently incorporates the amplifying feedback from methane released by a defrosting tundra.
The new Science study, led by University of Alaska’s International Arctic Research Centre and the Russian Academy of Sciences, is “Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf” (subs. req’d). The must-read National Science Foundation press release (click here), warns “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.” The NSF is normally a very staid organization. If they are worried, everybody should be.
It is increasingly clear that if the world strays significantly above 450 ppm atmospheric concentrations of carbon dioxide for any length of time, we will find it unimaginably difficult to stop short of 800 to 1000 ppm. …
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