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Illustration showing methane chimney from sea floor to surface (USGS)
Illustration showing methane chimney from sea floor to surface (USGS)
A team of scientists confirms that sea-bottom and surface waters of the East Siberian Arctic Shelf are “supersaturated” with Methane (CH4) gas and “out-gassing” this potent GHG to the Atmosphere.
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A variable quantity known as the “venting flux” was calculated for the ESAS and found to be nearly equal to that amount from the entire World Ocean. Previous calculations by climate scientists estimated that “remobilization” of only a small fraction of of this trapped methane could potentially trigger “abrupt climate warming”.
A research team confirms “extensive out-gassing of methane to the atmosphere” over the Eastern Siberian Arctic Shelf, and confirm its source to be venting from sea-bed sediments. Though acknowledging their findings do not seriously alter climate change predictions, the team also asserts that the sub-sea permafrost layer is failing and advise more urgent investigation.
Large quantities of carbon (C) and methane (CH4)–typically in the form of methyl hydrate (or methyl clathrate)–are trapped in ocean sediments the world over. The source of this trapped methane is commonly through organic decay or from primary production (food-making by planktonic lifeforms, known as autotrophs). Through natural erosion of sediments, shifting of the ocean floor covering, and/or from pressure cracking, bubbles of the gas often escape and rise up through the water column. In the deeper seas and oceans, this natural gas venting to the atmosphere (“out-gassing”) is largely constrained due to the fact that, as the gas rises through the water column, much of it combines with oxygen and forms other, less potent molecules. Also, in colder seas, sub-sea permafrost acts as a “lid” to contain much of the buried carbon.
However, in shallower, warmer seas like the ESAS, where the average depth is only 45 meters, a far larger quantity of this potent GHG is released into the atmosphere, through the dual processes of diffusion and ebullition (pressure conversion of a liquid to a vapor). In the latter process, this transport is in the form of bubbles of methane gas rising up through the water column, and bursting at the surface.
The ESAS is the largest shallow sea in the world. However, this sea is more turgid that other shallow seas and receives less sunlight penetration, which usually means there is less abundance of planktonic life forms, which directly or indirectly produce much of the methane. Despite this, the ESAS generates a methane flux ten times that of the deeper ocean, according to the research findings. Clearly then, something more is going on in this undersea environment.
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The Permian–Triassic extinction event (the Great Dying) may have been caused by release of methane from clathrates. 96% of marine species were wiped out. Chart based on data reported by Rohde & Muller (2005)
The Permian–Triassic extinction event (the Great Dying) may have been caused by release of methane from clathrates. 96% of marine species were wiped out. Chart based on data reported by Rohde & Muller (2005)
Many climatologist are concerned that Arctic warming–which is greater than predicted by several degrees C so far this century–will accelerate the thawing of sub-sea permafrost and thus also the release of CH4. Methane, though shorter-lived in the atmosphere than CO2, is a far more potent GHG than CO2, in terms of its heat-trapping capability. Its build-up will increase atmosphere and surface heating, and some of this heat will be down-transported through the water column, resulting in more thawing of permafrost, more methane release, etc. This is known as a positive feedback cycle. Such self-reinforcing feedback loops, it is asserted, are the major driving force for “abrupt climate change” predictions and “runaway greenhouse effect” scenarios.
The team calculated an annual out-gassing from the ESAS at 7.98 Tg (Tera grams, or trillions of grams). This is an amount roughly equivalent to the CH4 emissions estimate for the entire world ocean. In some “hot spots”, the venting was 8300% greater than the background methane estimates.
While advocating a revision of the current, estimated global CH4 flux, the team also acknowledges in their paper that this current estimate is “not alarmingly altering the contemporary global CH4 budget.” However, the report’s authors go on to state: “These finding do not change our view of the vulnerability of the large, sub-sea permafrost carbon reservoir on the ESAS; the permafrost ‘lid’ is clearly perforated, and sedimentary CH4 is escaping to the atmosphere.”
Features known as polynyas (open areas of ocean surrounded by sea ice, where much ocean-air exchange happens) and sea-ice breaks provide the mechanical means for transporting large quantities of the gas between ocean and atmosphere.
The key questions are: As Arctic sea temperatures warm, how will this impact the permafrost lid in its default function of containing trapped CH4? And, will a tipping point be reach in this failure of the permafrost “lid”?
The annual average temperature of the ESAS sub-sea permafrost, typically falling between -1.8° C and 1° C, is still 12° to 17° C warmer than that over on-land permafrost. A combination of bottom up geothermal and top-down seawater heat fluxes is believed to be permitting partial thawing and failure of the sub-sea permafrost, allowing greater permeability of gases.
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Global atmospheric methane chart 2006-2009 showing Methane concentration in the upper troposphere
Global atmospheric methane chart 2006-2009 showing Methane concentration in the upper troposphere
The study was the joint project of the International Arctic Research Center, University of Alaska at Fairbanks, Russian Academy of Sciences, The Pacific Oceanological Institute, and Stockholm University. The purpose of the study was to achieve an integrated assessment of the entire ESAS in order to determine the total venting flux of CH4 to the atmosphere.
The team tested their hypothesis during a half dozen field campaigns undertaken between 2003 and 2008, and in addition, one helicopter survey and one over-ice winter expedition. In making their assessment, the research team utilized results from over 5100 at-sea observations.
The published reference for this article: Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf, Shakhova et al, Science, 5 March, 2010
Michael R.
Mr. Arnold
Thanks for all the stats! Much of climate modeling and subsequent prediction depends entirely on the starting variables used.
Despite predictions, the global average temperature has risen “only” .6 degree C (or just over 1 degree F), for the past two centuries (lower/slower than predicted), and, the percentage of CO2 absorbed by the world’s oceans (despite sea surface temp. increases and acidification, etc.) has remained virtually the same for the past two centuries. There is probably some unknown, or under-estimated, carbon sink operating here.
I mention this only to emphasize that climate science is highly complex, consisting of a multitude of interacting and interdependent variables, and that, to prevent a “climate backlash” in the public sector (which can impede environmental progress and reinforce political inertia) we need to do due diligence (with the numbers), state the uncertainties/complexities clearly, and keep ourselves honest about what we do not know.
Of course, I accept the reality of climate change, and that human activity is accelerating the forcing of certain components of the climate system–particularly in the Arctic. I embrace movements to curb CO2/GHG emissions, adopt renewable energies, and protect resources and ecosystems.
But there are also many natural phenomena that are at work in this system, some counter-veiling (like vulcanism, atmospheric negative feedback loops, oceanic carbon sinks, solar activity {sun spot minima} and Milankovitch cycling).
Climate models are invaluable tools for climate prediction, and for giving us fair warning of growing impacts, but they also over-simplify and create the illusion that we understand the total system in all its intricacies (enough to make dire, existential predictions). We don’t.
Still, it is good that we have the knowledge that we do have. It is something to build on.
Brad Arnold
Ecosystems go into quick decline when warming reaches a certain threshold. Leemans and Eickhout (2004) found that more ecosystems collapse as warming speeds up:
If the warming is 0.1 °C per decade, 5 percent of ecosystems will collapse.
If the warming is 0.3 °C per decade, 15 percent of ecosystems will collapse.
If the rate exceeds 0.4 °C per decade, all ecosystems will be quickly destroyed.
Here is what Climate Code Red says:
–Human emissions have so far produced a global average temperature increase of 0.8 degree C.
–There is another 0.6 degree C. to come due to “thermal inertia”, or lags in the system, taking the total long-term global warming induced by human emissions so far to 1.4 degree C.
–If human total emissions continue as they are to 2030 (and don’t increase 60% as projected) this would likely add more than 0.4 degrees C. to the system in the next two decades, taking the long-term effect by 2030 to at least 1.7 degrees C. (A 0.3 degree C. increase is predicted for the period 2004-2014 alone by Smith, Cusack et al, 2007).
–Then add the 0.3 degree C. albedo flip effect from the now imminent loss of the Arctic sea ice, and the rise in the system by 2030 is at least 2 degree. C, assuming very optimistically that emissions don’t increase at all above their present annual rate! When we consider the potential permafrost releases and the effect of carbon sinks losing capacity, we are on the road to a hellish future, not for what we will do, but WHAT WE HAVE ALREADY DONE.
To summarize, climate models do not currently include increased natural methane emissions, and still a 0.3 degree C. increase is predicted for the period 2004-2014 by Smith, Cusack et al, 2007. If the rate exceeds 0.4 °C per decade, all ecosystems will be quickly destroyed.
“The alternative (to geoengineering) is the acceptance of a massive natural cull of humanity and a return to an Earth that freely regulates itself but in the hot state.” –Dr James Lovelock, August 2008