Lots of interesting methane papers this week. In Nature Geoscience, Shakhova et al (2013) have published a substantial new study of the methane cycle on the Siberian continental margin of the Arctic Ocean. This paper will get a lot of attention, because it follows by a few months a paper from last summer, Whiteman et al (2013), which claimed a strong (and expensive) potential impact from Arctic methane on near-term climate evolution. That economic modeling study was based on an Arctic methane release scenario proposed in an earlier paper by Shakhova (2010). In PNAS, Miller et al (2013) find that the United States may be emitting 50-70% more methane than we thought. So where does this leave us?
The Context
Because methane is mostly well-mixed in the atmosphere, emissions from the Arctic or from the US must be seen within the context of the global sources of methane to the atmosphere. Estimates of methane emissions from the Arctic have risen, from land (Walter et al 2006) as well now as from the continental shelf off Siberia. Call it 20-30 Tg CH4 per year from both sources. The US is apparently emitting more than we thought we were, maybe 30 Tg CH4 per year. But these fluxes are relatively small compared to the global emission rate of about 600 Tg CH4 per year. The Arctic and US anthropogenic are each about 5% of the total. Changes in the atmospheric concentration scale more-or-less with changes in the chronic emission flux, so unless these sources suddenly increase by an order of magnitude or more, they won’t dominate the atmospheric concentration of methane, or its climate impact.
American Methane Emissions Higher Than Previously Thought
Miller et al (2013) combine measurements of methane concentrations in various locations through time with model reconstructions of wind fields, and “invert” the information to estimate how much methane was released to the air as it blew over the land. This is a well-established methodology, pushed to constrain US anthropogenic emissions by including measurements from aircraft and communications towers in addition to the ever-invaluable NOAA flask sample network, and incorporating socioeconomic and industrial data. The US appears to be emitting 50-70% more methane than the EPA thought we were, based on “bottom up” accounting (adding up all the known sources).
Is this bad news for global warming?
Not really, because the one real hard fact that we know about atmospheric methane is that it’s concentration isn’t rising very quickly. Methane is a short-lived gas in the atmosphere, so to make it rise, the emission flux has to continually increase. This is in contrast to CO2, which accumulates in the atmosphere / ocean system, meaning that steady (non-rising) emissions still lead to a rising atmospheric concentration. There is enough uncertainty in the methane budget that tweaks of a few percent here and there don’t upset the apple cart. Since the methane concentration wasn’t rising all that much, its sources, uncertain as they are, have been mostly balanced by sinks, also uncertain. If anything, the paper is good news for people concerned about global warming, because it gives us something to fix.
Methane from the Siberian continental shelf
The Siberian continental shelf is huge, comprising about 20% of the global area of continental shelf. Sea level dropped during the last glacial maximum, but there was no ice sheet in Siberia, so the surface was exposed to the really cold atmosphere, and the ground froze to a depth of ~1.5 km. When sea level rose, the permafrost layer came under attack by the relatively warm ocean water. The submerged permafrost has been melting for millennia, but warming of the waters on the continental shelf could accelerate the melting. In equilibrium there should be no permafrost underneath the ocean, because the ocean is unfrozen, and the sediment gets warmer with depth below that (the geothermal temperature gradient).
Ingredients of Shakhova et al (2013)
- There are lots of bubbles containing mostly methane coming up from the shallow sea floor in the East Siberian Arctic shelf. Bubbles like this have been seen elsewhere, off Spitzbergen for example (Shakhova et al (2013)). Most of the seep sites in the Siberian margin are relatively low flow but a few of them are much larger.
- The bubbles mostly dissolve in the water column, but when the methane flux gets really high the bubbles rise faster and reach the atmosphere better. When methane dissolves in the water column, some of it escapes to the atmosphere by evaporation before it gets oxidized to CO2. Storms seem to pull methane out of the water column, enhancing what oceanographers call “gas exchange” by making waves with whitecaps. Melting sea ice will also increase methane escape to the atmosphere by gas exchange. However, the concentration of methane in the water column is low enough that even with storms the gas exchange flux seems like it must be negligible compared with the bubble flux. In their calculation of the methane flux to the atmosphere, Shakhova et al focused on bubbles.
- Sediments that got flooded by rising sea level thousands of years ago are warmer than sediments still exposed to the colder atmosphere, down to a depth of ~50 meters. This information is not directly applied to the question of incremental melting by warming waters in the short-term future.
- The study derives an estimate of a total methane emission rate from the East Siberian Arctic shelf area based on the statistics of a very large number of observed bubble seeps.
Is the methane flux from the Arctic accelerating?
Shakhova et al (2013) argue that bottom water temperatures are increasing more than had been recognized, in particular in near-coastal (shallow) waters. Sea ice cover has certainly been decreasing. These factors will no doubt lead to an increase in methane flux to the atmosphere, but the question is how strong this increase will be and how fast. I’m not aware of any direct observation of methane emission increase itself. The intensity of this response is pretty much the issue of the dispute about the Arctic methane bomb (below).
What about the extremely high methane concentrations measured in Arctic airmasses?
Shakhova et al (2013) show shipboard measurements of methane concentrations in the air above the ESAS that are almost twice as high as the global average (which is already twice as high as preindustrial). Aircraft measurements published last year also showed plumes of high methane concentration over the Arctic ocean (Kort et al 2012), especially in the surface boundary layer. It’s not easy to interpret boundary-layer methane concentrations quantitatively, however, because the concentration in that layer depends on the thickness of the boundary layer and how isolated it is from the air above it. Certainly high methane concentrations indicate emission fluxes, but it’s not straightforward to know how significant that flux is in the global budget.
The more easily interpretable measurement is the time-averaged difference between Northern and Southern hemisphere methane concentrations. If Arctic methane were driving a substantial increase in the global atmospheric methane concentration, it would be detectable in this time-mean interhemispheric gradient. Northern hemisphere concentrations are a bit higher than they are in the Southern hemisphere (here), but the magnitude of the difference is small enough to support the conclusion from the methane budget that tropical wetlands, which don’t generate much interhemispheric gradient, are a dominant natural source (Kirschke et al 2013).
What about methane hydrates?
There are three possible sources of the methane in the bubbles rising out of the Siberian margin continental shelf:
- Decomposition (fermentation) of thawing organic carbon deposited with loess (windblown glacial flour) when the sediment was exposed to the atmosphere by low sea level during the last glacial time. Organic carbon deposits (called Yedoma) are the best-documented carbon reservoir in play in the Arctic.
- Methane gas that has been trapped by ice, now escaping. Shakhova et al (2013) figure that flaws in the permafrost called taliks, resulting from geologic faults or long-running rivers, might allow gas to escape through what would otherwise be impermeable ice. If there were a gas pocket of 50 Gt, it could conceivably escape quickly as a seal breached, but given that global gas reserves come to ~250 Gt, a 50 Gt gas bubble near the surface would be very large and obvious. There could be 50 Gt of small, disseminated bubbles distributed throughout the sediment column of the ESAS, but in that case I’m not sure where the short time scale for getting the gas to move comes from. I would think the gas would dribble out over the millennia as the permafrost melts.
- Decomposition (melting) of methane hydrates, a peculiar form of water ice cages that form in the presence of, and trap, methane.
Methane hydrate seems menacing as a source of gas that can spring aggressively from the solid phase like pop rocks (carbonated candies). But hydrate doesn’t just explode as soon as it crosses a temperature boundary. It takes heat to convert hydrate into fluid + gas, what is called latent heat, just like regular water ice. There could be a lot of hydrate in Arctic sediments (it’s not real well known how much there is), but there is also lot of carbon as organic matter frozen in the permafrost. Their time scales for mobilization are not really all that different, so I personally don’t see hydrates as scarier than frozen organic matter. I think it just seems scarier.
The other thing about hydrate is that at any given temperature, a minimum pressure is required for hydrate to be stable. If there is pure gas phase present, the dissolved methane concentration in the pore water, from Henry’s law, scales with pressure. At 0 degrees C, you need a pressure equivalent to ~250 meters of water depth to get enough dissolved methane for hydrate to form.
The scariest parts of the Siberian margin are the shallow parts, because this is where methane bubbles from the sea floor might reach the surface, and this is where the warming trend is observed most strongly. But methane hydrate can only form hundreds of meters below the sea floor in that setting, so thermodynamically, hydrate is not expected to be found at or near the sea floor. (Methane hydrate can be found close to the sediment surface in deeper water depth settings, as for example in the Gulf of Mexico or the Nankai trough). The implication is that it will take centuries or longer before heat diffusion through that sediment column can reach and destabilize methane hydrates.
Is there any way nature might evade this thermodynamic imperative?
If hydrate exists in near-surface sediments of the Siberian margin, it would be called “metastable”. Metastability in nature is common when forming a new phase for which a “seed” or starting crystal is needed, like cloud droplets freezing in the upper atmosphere. But for decomposition to form water and gas one would not generally expect a barrier to just melting when energy is available. Chuvilin et al (2011) monitored melting hydrate in the laboratory and observed some quirkiness.
But these experiments spanned 100 hours, while the sediment column has been warming for thousands of years, so the experiments do not really address the question. I have to think that if there were some impervious-to-melting hydrate, why then would it suddenly melt, all at once, in a few years? Actual samples of hydrate collected from shallow sediments on the Siberian shelf would be much more convincing.
What about that Arctic methane bomb?
Shakhova et al (2013) did not find or claim to have found a 50 Gt C reservoir of methane ready to erupt in a few years. That claim, which is the basis of the Whiteman et al (2013) $60 trillion Arctic methane bomb paper, remains as unsubstantiated as ever. The Siberian Arctic, and the Americans, each emit a few percent of global emissions. Significant, but not bombs, more like large firecrackers.
References
- N. Shakhova, I. Semiletov, I. Leifer, V. Sergienko, A. Salyuk, D. Kosmach, D. Chernykh, C. Stubbs, D. Nicolsky, V. Tumskoy, and . Gustafsson, "Ebullition and storm-induced methane release from the East Siberian Arctic Shelf", Nature Geoscience, vol. 7, pp. 64-70, 2013. http://dx.doi.org/10.1038/NGEO2007
- G. Whiteman, C. Hope, and P. Wadhams, "Vast costs of Arctic change", Nature, vol. 499, pp. 401-403, 2013. http://dx.doi.org/10.1038/499401a
- N.E. Shakhova, V.A. Alekseev, and I.P. Semiletov, "Predicted methane emission on the East Siberian shelf", Doklady Earth Sciences, vol. 430, pp. 190-193, 2010. http://dx.doi.org/10.1134/S1028334X10020091
- S.M. Miller, S.C. Wofsy, A.M. Michalak, E.A. Kort, A.E. Andrews, S.C. Biraud, E.J. Dlugokencky, J. Eluszkiewicz, M.L. Fischer, G. Janssens-Maenhout, B.R. Miller, J.B. Miller, S.A. Montzka, T. Nehrkorn, and C. Sweeney, "Anthropogenic emissions of methane in the United States", Proceedings of the National Academy of Sciences, vol. 110, pp. 20018-20022, 2013. http://dx.doi.org/10.1073/pnas.1314392110
- E.A. Kort, S.C. Wofsy, B.C. Daube, M. Diao, J.W. Elkins, R.S. Gao, E.J. Hintsa, D.F. Hurst, R. Jimenez, F.L. Moore, J.R. Spackman, and M.A. Zondlo, "Atmospheric observations of Arctic Ocean methane emissions up to 82° north", Nature Geoscience, vol. 5, pp. 318-321, 2012. http://dx.doi.org/10.1038/NGEO1452
- S. Kirschke, P. Bousquet, P. Ciais, M. Saunois, J.G. Canadell, E.J. Dlugokencky, P. Bergamaschi, D. Bergmann, D.R. Blake, L. Bruhwiler, P. Cameron-Smith, S. Castaldi, F. Chevallier, L. Feng, A. Fraser, M. Heimann, E.L. Hodson, S. Houweling, B. Josse, P.J. Fraser, P.B. Krummel, J. Lamarque, R.L. Langenfelds, C. Le Quéré, V. Naik, S. O'Doherty, P.I. Palmer, I. Pison, D. Plummer, B. Poulter, R.G. Prinn, M. Rigby, B. Ringeval, M. Santini, M. Schmidt, D.T. Shindell, I.J. Simpson, R. Spahni, L.P. Steele, S.A. Strode, K. Sudo, S. Szopa, G.R. van der Werf, A. Voulgarakis, M. van Weele, R.F. Weiss, J.E. Williams, and G. Zeng, "Three decades of global methane sources and sinks", Nature Geoscience, vol. 6, pp. 813-823, 2013. http://dx.doi.org/10.1038/NGEO1955
> if there were some impervious-to-melting hydrate
If there is — say some combination of other elements adding to produce a better structure for the ‘cage’ of water molecules that trap methane, say occurring naturally in pore spaces in sediment or leaf litter washed into the ocean — it ought to be discoverabe. Look for it in nature, look for it in theory.
I’ve speculated here before that any such form of hydrate would be commercially _very_ interesting, because it would be stable using lower pressure and higher temperature than currently used for liquefied methane gas.
Thanks for the update.
> the extremely high methane concentrations
> measured in Arctic airmasses
You mention shipboard and aircraft observations. What of satellite measurements? I was recently pointed to some breathless going-through-the-roof news at the pro-geoengineering arctic-news blog, and from there to a visualization of IASI data at methanetracker.org. Your post puts the implications of these measurements into helpful context. But how reliable are the measurements themselves, compared with other methods?
[Response: I’ve tried and failed to find a good reference to the IASI pictures that are going around. Many of them show obvious problems in the retrieval (i.e. huge jumps at the land/ocean or ocean/ice edge) and I have yet to see what the weighting kernel is or any ground truthing. This is unusual for a remotely-sensed product, and so I’m a little unclear as to what should be concluded. – gavin]
Is methane, and the CO2 it produces, the most likely source of carbon for past hyperthermals? If so, I presume this article means that it could happen again in response to anthropogenic warming but not in the small number of years that some fear – i.e. it would take thousands of years, and we won’t all be cooked to extinction by the end of the decade. Is that correct?
[Response: Methane is the “usual suspect” for those events, such as the Paleocene Eocene thermal maximum, because it is easier to explain the carbon isotopic spikes if the source is strongly isotopically labeled. However, that means we get the answer that there was less carbon released than if it had been, say, organic carbon (-20 o/oo rather than -60 o/oo). For the PETM in particular, the temperature proxies seem to require more warming than a ~1-2000 Gt C methane spike would generate (with the climate forcing agent being the CO2, as documented by its longevity). So I don’t know about methane in the deep past, but I do agree with your conclusion about our future. David]
Re David’s response to #3… I was just about to ask about the isotopic fingerprint. Your comment didn’t quite answer my question, which is whether or not a fingerprint is detectable to source the increasing atmospheric methane? I didn’t see any mention of it in the article above.
How would an ice-free arctic change the picture? A lot more energy is taken up by shallow seas if there is no ice floating on top, warming the sea. Have any model calculations been done to estimate the effects on the methane in the sea bed?
[Response: Yes, and in general the most important consideration is how far down in the sediment column any methane hydrate might be. If it’s hundreds of meters it will take a long time for a change in the overlying water to conduct down to where the hydrate is. David]
As usual, thanks for the perspective. I have to be honest – even with Real Climate’s grounding methane makes me nervous, and reading two nearly simultaneous studies that say we’ve been (relatively) dramatically underestimating the amount of release is unnerving. It seems from a lay perspective this area might deserve closer attention. Maybe we can get Congress to cough up some funding (snark)
I’m also wondering about local, acute effects of the Arctic methane. As stated, because methane is generally “well-mixed in the atmosphere,” then local emissions “must be seen within the context of the global sources,” I assume in order to accurately assess global impact. I’m wondering if the higher local concentrations have a local effect on temperature, and if this might be tied to Arctic temperature anomalies and contribute to local feedbacks. The other thing I’m wondering is if we underestimated the real surface warming since 1998, AND the oceans have warmed more than expected, AND we’ve underestimated at least some of methane release, might methane be a larger forcing factor than previously thought?
[Response: No, I don’t think so. I think the time constant is so long for warming that regional variations in forcing get pretty much smoothed out. I guess the footprint of the regional forcing from sulfate aerosols can be detected in temperature trends, but it’s subtle. David]
Is this methane data consistent with that used in the latest IPCC report?
Science 22 November 2013:
Vol. 342 no. 6161 pp. 964-966
DOI: 10.1126/science.1238920
Report
Constraints on the Late Holocene Anthropogenic Contribution to the Atmospheric Methane Budget
A very interesting site called methanetracker shows atmospheric methane over the Arctic.
Best viewed when choosing the layers from 650 mb / 11775 feet through 469 mb / 19819 feet
http://www.methanetracker.org/
Take note that there is plenty of methane coming from other shelves around the Arctic, in particular off Greenland.
Re: Miller et al’s finding that a bottom-up approach appears to underestimate U.S. methane emissions. Do other countries use similar methodologies and is it likely that methane inventories have been systematically underestimated across countries? I gather that there is speculation that natural gas extraction and distribution is the likely culprit, but my understanding is that Miller et al’s methodology doesn’t allow them to distinguish between potential sources (e.g. leakage at a wellhead vs. ruminant livestock).
>methanetracker
See Gavin’s inline reply to a question about the presentation at Methanetracker; it’s above (at 29 Nov 2013 at 5:09 AM )
Thanks for the excellent discussion of these important issues.
“unless these sources suddenly increase by an order of magnitude or more”
This seems to be the crucial question. As you point out, in theory, the methane coming from US fracking and mining is addressable (and should be a priority along with closing coal plant and moving quickly away from petroleum-based transportation systems).
The Arctic seabed methane rate of release, on the other hand, is likely to increase, as you point out. As you also point out, it is hard to know what kind of rate of increase to expect.
Some of the elements driving an increase in sea bottom warming and methane release include:
–increasingly ice free ocean allowing more waves;
–increasing (and increasingly intense?) Arctic storms creating more and bigger waves;
–increasingly ice free seas allowing more time for direct warming of the surface (to how deep?) directly from sunlight and from warmer air temps (although this may lead to greater stratification so could be a negative feedback?);
–increasingly warm waters running into the area from Siberian rivers;
–Atlantic currents becoming increasingly warm and making their way further into the Arctic (more an issue in the Svarlbard area than ESAS?)…
I’m sure I’m missing some others.
So there seem to many reasons to expect temperatures at the bottom of the ESAS and other parts of the Arctic Ocean to warm in the coming years and decades.
How fast that warming could affect the release of seabed methane? It would be nice to have some recent historical background. Do we know how much was coming from this area ten and more years ago? Hasn’t Semiletov said that those amounts were minimal pre-2000? (Sorry, I don’t have a link for this; I’ll see if I can track down the source of this recollection.)
[Response: I’m not aware of this; I’d be very interested if you can dig it up. But also very surprised to hear if methane fluxes were increasing that quickly. The permafrost has been melting for thousands of years. David]
Are there more specific measurements or estimates?
The crucial thing to know, it seems to me, is whether there is a doubling time and what that doubling time has been over the last few years/decades. It doesn’t really matter if relative current values are low relative to total global emissions if they are rising exponentially, especially if they are doubling in fewer than ten or so years.
One more point. I didn’t see any discussion of biological responses to these warming trends. Wouldn’t there be some such, and couldn’t that affect the rates of release (particularly if some kind of seabed worm starts burrowing deeper into the seabed, for example)?
[Response: There is talk of a “compost bomb” feedback in permafrost soils if the climate warms really quickly, and in places where there’s thermal insulation holding the carbon decomposition heat in. Luke and Cox (2011) Soil carbon and climate change: from the Jenkinson
effect to the compost-bomb instability. European Journal of Soil Science, February 2011, 62, 5–12 doi: 10.1111/j.1365-2389.2010.01312.x. But this doesn’t apply under the ocean. David]
Thanks again for treating these important issues.
An excellent review of methane hydrates. Do we have any data on the relative ages (isotopic methods)of the hydrates in drilled cores? Presumably, this would require some stringent procedures for sample and data collection. Perhaps, some of the compositional variations relate to age.(?)
Hank, the fact that the concentrations may not be exactly quantifiable doesn’t mean that we should not take such ancillary information into consideration.
Isn’t accelerating methane release in the Arctic likely to delplete atmospheric hydroxyl regionally, making it longer lived?
[Response: Most methane decomposition in the atmosphere is in the tropics, and there is a feedback on its own lifetime, but to get a big shift, you would need emissions orders of magnitude larger than we are discussing here. – gavin]
Sorry, I think my question was too vague. What I’m curious about is whether the buried methane that’s brought up through drilling (I would assume its fingerprint would be different than what is being released in the Arctic?) and then escapes has a detectable signal in the current atmosphere, or is it too small to accurately measure that change with the increase from other sources drowning it out? Also from some of the conversations after my question, sounds like there’s a compositional difference latitudinally, so maybe that actually answers my question?
[Response: Your question was not at all vague, I just don’t remember hearing much about the isotopic composition of methane in the atmosphere. I assume it’s close to -60 o/oo biogenic signature but I haven’t had time to look it up. There seems to be much more analysis of the latitudinal gradient, as you say. David]
Thanks for this overview. Arctic methane is a loose cannon.
We don’t know yet what an ice-free Arctic ocean will mean. What’s the effect of the giant cyclones that filled the Arctic? We have had a few, certainly we should expect more. Will it churn up clathrates? What are the anticipated bio changes to the Arctic waters? With increase summer algae, how much more methane does that mean? When sea level rise causes flooding to areas of permafrost, how much deeper will it thaw? How much more methane is released in deeper thaws? How much will increased Arctic methane affect temps locally? With increased temperatures, what are the increases in rate of permafrost melt? With increased temperature come greater atmospheric moisture, does that mean more rains on Greenland? There have been a few major rains on Greenland, with increased warming, will there be more? Is that modeled? How will albedo changes, increased rainfall and melt in Greenland affect ice degradation?
My point is that there are more ramifications of methane to the Arctic systems.
Thanks for the responses, David. On the Semiletov thing, I seem to have gotten that impression from this piece from CP a ways back: “Since 1994, Igor Semiletov of the Far-Eastern branch of the Russian Academy of Sciences “has led about 10 expeditions in the Laptev Sea but during the 1990s he did not detect any elevated levels of methane.”
http://thinkprogress.org/climate/2008/12/18/203494/arctic-research-center-the-underwater-permafrost-is-thawing-and-releasing-methane/
I don’t know whether Joe Romm got that from interviewing Igor Semiletov, or if it was something he derived from an article.
I think the point is that, even though, as you say, methane has been leaking from the seabed for millennia, it has not been doing so at levels high enough to make it into the atmosphere at significant levels until quite recently, apparently.
This level of change suggests a rapidly destabilizing situation to many, and hence the concern.
Again, thanks for your post and responses.
Here’s a fairly recent interview with Shakhova that may provide added information and perspectives for the discussion here: http://climatestate.com/2013/08/29/arctic-methane-outgassing-on-the-east-siberian-shelf-an-interview-with-dr-natalia-shakhova/
First, I would like to say how much I enjoyed this article and that I imagine that at a 50% confidence level, CL, the author’s positions are well-founded and well-reasoned. Unfortunately, at a 90% to 95% CL matters become much less certain, and risks generally increase non-linearly.
For example, Isaken et al (2011) quantify how as atmospheric methane concentrations increase, the global warming potential, GWP, of methane also increases (see references at end of post). Also note that any source increasing atmospheric methane concentrations, increase the GPW of all previously emitted methane remaining in the atmosphere. As an example of the possible extreme change in radiative forcing in a 50-year time horizon for Isaken et al (2011)’s 4 x CH4 (i.e. quadrupling the current atmospheric methane burden) case of additional emission of 0.80 GtCH4/yr is 2.2 Wm-2, and as the radiative forcing for the current methane emissions of 0.54 GtCH4/yr is 0.48 Wm-2, this give an updated GWP for methane, assuming the occurrence of Isaksen et al’s 4 x CH4 case in 2040, would be: 33 (per Shindell et al 2009, note that AR5 gives a value of 34) times (2.2/[0.8 + 0.48]) divided by (0.54/0.48) = 50.
As NOAA’s Mauna Loa measurement of atmospheric methane concentrations are only currently increasing at a rate of approximately 0.25% per year (or 12.5% change in 50-years); how could anyone be concerned that the change in atmospheric methane burden in 50-years could be 300% (as per Isaken et al (2011) case 4XCH4; which would require an additional 0.80 GtCH4/yr of methane emissions on top of the current rate of methane emissions of 0.54 GtCH4/yr)? At the high CL scenarios, I note the following possible additional sources (beyond or current emissions, and see list of references at the end of this post):
• RCP 8.5 50%CL (which does not consider such possible methane sources as the ESAS, the permafrost or from shale gas) assumes an approximately doubling (Meinshausen et.al. 2011) of the present atmospheric methane burden by 2100, or a 50% increase fifty years primarily due to increase emissions from marshlands and conventional anthropogenic sources.
• Methane emissions from permafrost degradation (see Schuur and Abbott (2011)).
• The Clathrate Gun Hypothesis postulated that methane hydrates can be destabilized due to geotechnical slope failures on the various continental slopes around the Arctic Ocean; which might take decades rather than millennia to accumulate meaningful methane emissions.
• Anthropogenic methane leaks associated with the development of international hydrofracking operations (including significantly that from China) will likely exceed the comparable leaks from USA hydrofracking operations, within one decade.
• The methanetrack.org website has shown significant increases in atmospheric methane concentrations over Antarctica this austral winter (which I believe are due to increases in methane emissions from the Southern Ocean seafloor due to increases in the temperature of bottom water temperatures), and if this trend continues, then the Southern Hemisphere could be a significant source of additional atmospheric methane (this century).
• Similarly, Eillott et al (2011), Reagan (2011) and Reagan and Moridis (2008), for the equivalent of RCP 8.5 50% CL methane emissions from global marine methane hydrates could be 0.3 GtCH4/yr by 2100.
• Significantly, the East Siberian Arctic Shelf, ESAS, has up to 1000 Gt of methane reserves, and it is highly believable that 1% of this (or up to 10 Gt) is in the form of free gas trapped underneath the currently degrading subsea permafrost cap, which could be released within the next few decades by a combination of increasing Arctic Ocean water temperatures, increased storm activity, and possible increases in seismic activity.
From the article: “Methane is a short-lived gas in the atmosphere …The bubbles mostly dissolve in the water column …”
Those two statements lead me to three questions. What are the contributions to atmospheric CO2 likely to be as the methane that makes it to the atmosphere dicomposes? What is the fate of the fate of the dissolved CO2 (how much of that will decompose, and at what rate)? Will dissolved CO2 in Arctic waters ultimately contribute to ocean acidification there? (High latitude are where acidification is most pronounced.)
[Response: Of course it depends on how much methane, how quick. Some scaling: if there were 5000 Gton C as hydrate globally, that’s about the right order of magnitude, if it oxidized in the ocean abruptly, to deplete the oxygen in the ocean. The impact on the total CO2 concentration would be about order 10%. The fate of the dissolved CO2 oxidation product of methane would be for some of it eventually to equilibrate with the atmosphere. The airborne fraction of new carbon added to the system drifts down from 15-25% after equilibration between the atmosphere and the ocean but before neutralization by the CaCO3 cycle and ultimate recovery by the silicate weathering CO2 thermostat. Presumably pretty the same atm/ocn equilibrium would be reached regardless of whether the CO2 started out in the ocean or the atmosphere. David]
That’s the same interview from last August, isn’t it? Has anyone been able to find a transcript and cites/pointers to supporting information?
Has anyone commented that the past claims of “shallow hydrates” would imply the presence about 50x as much methane in the shallow sediments — compared to methane in water or air or sediment not in clathrate form?
Seems to me we heard for a long time the “methane emergency … shallow hydrates” story repeated — and now the “shallow hydrates” term has dropped out of the claims (except for the copypasted repetition of old stories).
But if they’ve agreed nobody has been able to show hydrates above the stability zone, no shallow, metastable hypothetical hydrates found — that should revise the expected methane bomb down to 1/50th — 2 percent — of the claimed size.
How small does it have to get, before it falls within what’s already expected?
Guys, I’m not saying it’s not a problem.
I’m saying it seems an overblown, overhyped, issue that would direct a lot of money and effort into that particular kind of business and government’s projects in that area.
What are we missing here?
Gaia’s breath—global methane exhalations, Keith A. Kvenvolden, Bruce W. Rogers, Marine and Petroleum Geology,doi:10.1016/j.marpetgeo.2004.08.004
IPCC 7.4.1.1 Biogeochemistry and Budgets of Methane
From these it appears that prior to the research by Shakhova & Semilitov the CH4 flux from arctic marine geological sources was considered to be minimal.
Another paper was published last week, which discusses policy relevance of cutting methane emissions (as well as black carbon and other short-lived climate pollutants): Bowerman et al., “The role of short-lived climate pollutants in meeting temperature goals” Nature Climate Change 3, 1021 (2013). This paper reports an analysis that finds, “[Short-lived climate pollutant] emissions in any given decade only have a significant impact on peak temperature under circumstances in which CO2 emissions are falling. Immediate action on SLCPs might potentially ‘buy time’ for adaptation by reducing near-term warming; however early SLCP reductions, compared with reductions in a future decade, do not buy time to delay reductions in CO2.”
Hi wili, the interview is from April 2012. After this, of course, Shakhova and Semiletov went back out to the ESAS in August 2012, and possibly 1-3 other times.
In 2011, what they had found were bubbling areas that were as large as 100 m in diameter.
In 2012 — after the interview — what they found were bubbling areas as large as 1,000 m in diameter.
Their Nature paper discussed above is related to the 2011 expedition. (Correct me, please, if I am wrong.)
The Arctic shelves cover an extremely vast area. Methane is also being emitted from the shelves around Greenland, and there are no teams investigating this, that I know of.
Indeed, a great deal more funding should be made available to scientists willing to brave those unseemly elements, risking life and limb.
Further, we know that there are places were terrestrial permafrost is warming rapidly and at depths of as much as 30 meters.
Shakhova points out that the subsea permafrost is approaching equilibrium with its environment.
We already know that there are taliks (i.e., gas emission pathways) through the subsea permafrost.
These will only multiply and grow larger.
Hank wrote: “past claims of “shallow hydrates”” Who was making these past claims. The stability zones for methane hydrates have been well understood for a long time. So any such claim was either simply confused (something I confess to being on occasion), ill informed, or a kind of short hand for hydrates lying in stability zones beneath shallow waters.
The concern, as I understand it, is that pathways in the latter areas can bring undissolved methane up to the seabed surface, and from there it can make it way through the shallow water column into the ocean surface.
It seems to me that any such pathways, if they are small, would tend to reseal themselves from the cooling effect of the methane bubbles expanding into the ocean water (but this could be another place where I’m confused). But there are presumably other mechanisms counteracting this negative feedback, or we wouldn’t be getting even the amounts reported.
I’m not sure where you are getting your “50x” and “1/50” figures. Any clarity on this would be appreciated.
“I’m not saying it’s not a problem.” Well, we can certainly agree on that. Let’s all assume that we are all struggling together to figure out the exact nature of the problem.
Thanks for those links, Kevin.
Tenney and hank, I didn’t intend to imply that the interview was from the last few days. But since it is from after the period of the 2011 expedition that the recent Nature paper is about, it is relevant to understanding what they were seeing at that time, it seems to me. If anyone has a more recent interview, please do post it.
(Oracle reCaptcha adds: townships DoWori)
These are the references that I forgot to include at the end of post #20:
Bastviken, D., Tranvik, L.J., Downing, J.A., Crill, P.M., and Enrich-Prast, A. (2011), “Freshwater Methane Emissions Offset the Continental Carbon Sink”, Science, Vol 331, pp. 50.
Elliott, S., Maltrud, M., Reagan, M., Moridis, G., and Cameron-Smith, P., “Marine methane cycle simulations for the period of early global warming”, Journal of Geophysical Research, Vol. 116, G01010, doi: 10.1029/2010JG00 1300, 2011.
Isaksen, I. S. A., Gauss M., Myhre, G., Walter Anthony, K. M. and Ruppel, C., (2011), “Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions”, Global Biogeochem. Cycles, 25, GB2002, doi:10.1029/2010GB003845. (see: http://onlinelibrary.wiley.com/doi/10.1029/2010GB003845/abstract)
Meinshausen, M., Smith, S.J., Calvin, K., Daniel, J.S., Kainuma, M.L.T., Lamarque, J-F., Matsumoto, K., Montzka, S.A., Raper, S.C.B., Riahi, K., Thomson, A., Velders, G.J.M., and van Vuuren, D.P.P., (2011); “The RCP greenhouse gas concentrations and their extensions from 1765 to 2300”, Climatic Change, 109:213-241, doi: 10.1007/s10584-011 -0156-z.
Reagan, M.T. (PI), (2011), Interrelation of Global Climate and the Response of Oceanic Hydrate Accumulations, Lawrence Berkeley Laboratory: Task Report 10-1, January 31, 2011.
Reagan, M.T., and Moridis, G.J. (2008), “Dynamic response of oceanic hydrate deposits to ocean temperature change”, J. Geophys. Res., 113, 107, 486-513, doi: 10.1029/2008JC004938.
Schuur, E.A.G. and Abbott, B., (2011), “High risk of permafrost thaw”, Nature, 480, 32-33, Dec. 2011.
wili, I was just trying to give the chronology and point out that later expeditions found an order of magnitude greater amount of “bubbles” LOL
sources for wili:
“One litre of methane clathrate solid would therefore contain, on average, 168 litres of methane gas (at STP)” https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Methane_clathrate.html
Lots of other sources varying from 50x to that 168x; depends on which of several clathrate forms and how pure the sample, I’d guess.
and this search:
“arctic methane emergency” AND “shallow hydrate” AND “letter to world leaders”
OK, yeah, the AMEG folks do occasionally go over the top (or under the bottom?) sometimes. But these days it can be difficult in these matters to know who is an imbecile and who is just a bit ahead of their times.
In your response to my Nov 29th reply you said
“… to get a big shift, you would need emissions orders of magnitude larger than we are discussing here.” – gavin
Dr Natalia Shakhova and Dr. Igor Semitelov think that will happen. Here’s a paraphrase:
“The current atmosphere has about 5 Gigatonnes of methane. The East Siberian Arctic shelf has approximately hundreds to thousands of Gigatonnes.
Only one percent of that amount would double the atmosphere burden of methane. Not much effort would be needed to destabilize one percent of this carbon pool, because of
The state of the permafrost
The amount of methane involved
What divides this methane from the atmosphere is a very shallow water column and a weakening permafrost, losing its ability to seal.
It’s a matter of decades, at most a hundred years.
Many factors convince us that a runaway process might happen.
Igor Semitelov is convinced because he spent a lot of time over there, and where the ice should be about two meters thick it was forty centimeters thick. All of the processes that stabilize everything look anomalous, in the sea, the ice, the water column, and the currents under the ice. Because everything looks anomalous he thinks that the worst might happen.”
See Dr. Shakhova at http://youtu.be/_3gVZniFHA4
I recommend a Complex Systems perspective. We can no longer assume equilibrium. Positive feedbacks can push Earth’s climate rapidly to a new regime. Emissions orders of magnitude greater than what we’ve recently recorded are not only possible but probable, given the political/economic determination to monetize fossil fuel reserves over coming decades.
[Response: If this reservoir existed and was so poised to release methane as you speculate, then it would have done something during warmer conditions early in the Holocene, or in the last interglacial. There is no evidence that it did so. Waving hands and saying that we are no longer in equilibrium therefore anything can happen at any moment makes no logical or scientific sense. – gavin]
#22 Hank – Shakhova from the SKS interview:
As I’ve pointed out here before, and in other forums, the Russians have been researching the ESAS far longer than anyone else and much of their research has not been translated. Shakhova and Semilitov start from a different vantage point on the research history of the ESAS. Here for instance, you question the existence of shallow hydrates, they take it as already proven and move on.
[Response: Sorry, but that just isn’t very satisfactory. They need to be able to demonstrate that this is a real and widespread phenomena to other people. Curiously, the latest paper doesn’t mention ‘shallow hydrates’ at all, and none were reported in the sediment core they described. There are lots of other researchers on the Arctic continental shelf – including other Russians, USGS etc. No-one else has reported any shallow hydrates, and none of Shakhova’s papers provide any evidence for them either. – gavin]
# 33 – Gavin, one of the papers cited by Shakhova is Gas and Possible Gas Hydrates in the Permafrost of Bovanenkovo Gas Field, Yamal Peninsula, West Siberia by Evgeny M.Chuvilin, Vladimir S.Yakushev and Elena V.Perlova, Polarforschung 68: 215 – 219, 1998 (erschienen 2000) shows marine hydrates at depths of 60m to 120m.
The existence of hydrates outside the normal stability zone has a lot of research behind it. From the Experimental investigation of gas hydrate and ice formation in methane-saturated sediments E.M. Chuvilin, E.V. Kozlova, N.A. Makhonina (Faculty of Geology, Moscow State University, Russia) and V.S. Yakushev (Gazprom, VNIIGAZ, Russia) in Permafrost Phillips, Springman & Arenson (eds)2003 Swets & Zeitlinger, Lisse, ISBN 90 5809 582 7
Are all of these Russian researchers just wrong?
[Response: That there is a possibility of meta-stable hydrates has indeed been published, but that is not the same as showing that they are actually present to any extent, let alone that there is 50 Gt of them. I have repeatedly asked proponents of this idea to provide actually evidence of their presence on the ESAS as opposed to supposition. It has not (yet?) been forthcoming. – gavin]
As I’ve pointed out here before, and in other forums, the Russians have been researching the ESAS far longer than anyone else and much of their research has not been translated. Shakhova and Semilitov start from a different vantage point on the research history of the ESAS. Here for instance, you question the existence of shallow hydrates, they take it as already proven and move on.
Loads of Russian geologists believe in the abiogenic theory of petroleum formation and have been merrily publishing on this in Russian language journals for decades. Not saying that Shakova’s research isn’t high quality and interesting (or that geologists over there are inherently incompetent), but just because Russian geologists have been publishing stuff in Russian we shouldn’t automatically accept it.
Yep. I followed their cite on “shallow hydrates” and “metastable” — and you should look it up. The reference is not about undersea permafrost, nor about large amounts of material. See the August Unforced Variations thread; repeating the same would be pointless.
You said: “If this reservoir existed and was so poised to release methane as you speculate, then it would have done something during warmer conditions early in the Holocene, or in the last interglacial. There is no evidence that it did so. Waving hands and saying that we are no longer in equilibrium therefore anything can happen at any moment makes no logical or scientific sense.” – gavin
Recent warming may be exceeding earlier Holocene warming,
“… recent summer warming in the eastern Canadian Arctic is unprecedented in more than 44,000 years.”
Arctic Warming Unprecedented in Last 44,000 Years http://www.scientificamerican.com/article.cfm?id=arctic-warming-unprecedented-in-last-44000-years
More importantly, that earlier warming occurred over thousands of years. When greenhouse gasses rise in mere decades, slow moving processes which remove them can be overwhelmed.
An abrupt release can deplete hydroxyl regionally.
… hydroxyl depletion already is a big problem in the Arctic atmosphere …
http://arctic-news.blogspot.com/p/potential-for-methane-release.html
Faster acceleration, relative to earlier warming periods in the Holocene, can’t logically be ignored.
In my opinion, considering far-from-equilibrium possibilities of Climate Change isn’t unscientific. As I see it, a Climate Models without positive feedbacks are as useful as a “scientific model” of a matchstick that doesn’t include the head.
Granted we can’t quantify such complicated interactions. But we can acknowledge their existence and foresee the direction of error that they imply for Climate Models. Almost all of the feedbacks are positive.
Instead of describing our matchstick as just a piece of wood, we can at least say there’s a region whose response we can’t accurately quantify, but we do know that it’s self-feeding and has a huge amount of stored energy. We can admit that we don’t know exactly how much extra heat will set off a reaction out of our control, and that we’re heating it right now. Science is a tool within a larger context. Does logic require one to ignore the limitations of our tools?
Isn’t describing the position of Dr. Shakhova and Dr. Semiletov that runaway warming is at most a hundred years away as “anything can happen at any moment” a straw man argument?
[Response: Sea ice is still not at levels seen during the Early Holocene, and since we are discussing sea floor sediments the main reason given to be concerned is that the change of summer sea ice will warm the bottom sea water, we are clearly not there yet. The rate of warming has nothing to do with the arguments put forward – they are all based on absolute temperature thresholds, so the dismissal of orbitally driven causes is not appropriate. Please note, I am not arguing for Arctic changes to be ignored – they are large, serious and likely to increase – but this does not mean that anything goes. I see no basis for Dr. Shakhova and Dr. Semiletov’s argument that ‘runaway warming is at most a hundred years away’ – the statement is basically meaningless. If they mean a real transition to Venusian conditions, that is ridiculous, but if they only mean to imply that there are some amplifying feedbacks, then there is no argument (except on the terminology) – but the issue is whether they will be large or small. – gavin]
Re “anything can happen at any moment”, Dr. Shakhova did qualify her statement. I left out her qualifications in the interest of brevity. Here’s the relevant portion
56:06
And this is, I think it’s a matter of…
56:10
it’s not a matter of thousands of years, it’s a matter of decades.
56:14
I think, maybe, at most, hundred years but I think,
56:22
matter of decades.
56:25
It might potentially happen because, I would list many factors that might, that are very
56:37
convenient .. convincing for us.
56:40
So that might happen.
56:45
Not anytime.
56:48
Anytime sounds like it might happen today.
56:51
It might happen tomorrow.
56:53
The day after tomorrow.
For the full video and transcript see http://www.youtube.com/watch?v=m6pFDu7lLV4
Arstechnica story; This is from the last paragraph, with the cite:
You should not put the US and Arctic articles in the same sentence. It’s just a way of confusing the Arctic issue.
The US emission miscalculation is meaningless.
The Arctic ‘rate of change’ is devastating. You putting this together with the US miscalculation and saying that ‘Call it 20-30 Tg CH4 per year from both sources.’ is just BAD SCIENCE.
The arctic has just undergone a _doubling_ of methane emissions in 4 years, the reasons are very basic – darker water, less ice, more water saturation of methane, more bubble seems as more methane is exposed to warmth, and of course, more methane in the local atmosphere.
Stop confusing the issue.
[Response: The only person confusing things here is you. There is no evidence whatsoever of a doubling of CH4 in 4 years – the study is talking about a doubling of background level over what was estimated, not an actual increase in flux. – gavin]
[Response: I put them together in part to make the point that the emission fluxes from each paper are about the same. Why isn’t there an American Methane Emergency Group? David]
You can hear a fresh interview on the U.S. methane paper, with lead author Scot Miller from Harvard. He explains what they could and could not attribute to the fossil fuel industry, including tracking propane (which cows do not emit).
Radio Ecoshock interview 20 minutes December 1st.
http://www.ecoshock.org/downloads/climate2013/ES_ScotMiller_LoFi.mp3
Gavin #34, “That there is a possibility of meta-stable hydrates has indeed been published…”
Possibility? Their existence has been known for 25 years.
I can understand disagreements about the total size of meta-stable methane hydrates and/or their potential impact on climate, but what purpose is served by refusing to acknowledge their existence?
[Response: Interesting (link). However, the relevance to shallow hydrates in the ESAS is unclear. -gavin]
Philosophy (Logic and Reason) underpins the scientific method. Without it science wouldn’t be what it is today. So I’d like to take a philosophic view of this discussion on this subject. To begin I note the previous article: “Complex problems often cannot simply be answered with computer models. Experts form their views on a topic from the totality of their expertise – which includes knowledge of observational findings and model results, as well as their understanding of the methodological strengths and weaknesses of the various studies. Such expertise results from years of study of a topic..” […] ” It is important to identify relevant experts using objective criteria.” […] “Most of the experts thus expect a higher rise than the IPCC” https://www.realclimate.org/index.php/archives/2013/11/sea-level-rise-what-the-experts-expect/ The IPCC is noted as presenting ‘conservative’ future projection scenarios. Therefore, “speculation” outside the existing “consensus literature” is acceptable in that topic on RC.
In this article it’s said that ” If anything, the paper is good news for people concerned about global warming, because it gives us something to fix.” imho that’s a nonsequitur and a leading emotive assumption without any evidence to support the statement. Therefore, it is irrelevant in the discussion.
“Methane hydrate seems menacing as a source of gas” another emotive term is ‘menacing’. Seems n/a here.
“…so I personally don’t see hydrates as scarier than frozen organic matter. I think it just seems scarier.” More emotive framing of the topic. Hardly evidence based nor scientific. Again n/a here.
“The scariest parts of the Siberian margin are the shallow parts,…” More of the same. N/A here.
“Significant, but not bombs, more like large firecrackers.” I think the missing word at the end of this passage was “today” – and probably: “Tomorrow we don’t have enough evidence yet to know. Therefore, we don’t know today what could possibly happen in the future.”
@32 Ruth (keeping the SLR article in mind) quotes: “Many factors convince us that a runaway process might happen.” Igor Semitelov is convinced because he spent a lot of time over there, and where the ice should be about two meters thick it was forty centimeters thick. All of the processes that stabilize everything look anomalous..”
To whit Gavin responds: “Waving hands and saying that we are no longer in equilibrium therefore anything can happen at any moment makes no logical or scientific sense.” This is, imho, a complete re-framing the preceding tone and content of prior comments. There was no “waving hands” seen, only text. This is, imho, an emotive re-framing of what was being said. A strawman response, following on form the ‘tone’ of the article’s words by putting emotive hysterics into another’s mouth where it does not fit.
Also Gavin said: “IF this reservoir existed and was so poised to release methane as you speculate, then it would have done something during warmer conditions early in the Holocene, or in the last interglacial. There is no evidence that it did so.”
Well, an absence of evidence is not evidence of absence. Unless of course, there is substantive, well researched studies that show incontrovertible evidence that it was NOT so. Is there?
If not, therefore, no valid logical conclusion can be drawn. The matters rests in the “i do not know” category. Therefore this is not a matter that can be posited either way with any CL, and do so ” makes no logical or scientific sense”. imho.
Therefore, to admit one does not know, due to insubstantial evidence at this time, would be the most rational and logical position to take now, imho. Rather than use emotive terms, instead of being dismissive of others opinions and of others information and suggestions, and to see that it is quite acceptable and reasonable to present conjectures (as opposed to the incorrect semantics of the word ‘speculate’) seems to me to be a more positive, embracing, and open minded approach to take.
Furthermore, again given the theme of the previous article on SLR it appears rational and logical to actually contact Dr Natalia Shakhova and Dr. Igor Semitelov directly (go to the original source) and simply ask them exactly what their professional “opinion and conjecture” is at this time, and why is that so?
This to me would be a far more practical and effective use of one’s time than prejudging their position from the ‘published papers’ (ala the IPCC papers on SLR). It would seem to make more logical or scientific sense not to prejudge their current state of knowledge without doing so first. And then reporting back to those interested on this subject and also thanking them for their input as a simple courtesy before logging a phone call to Russia.
This at least is how Philosophy tends to inform all wise people from all professions since the Ancient Greeks. imho, only of course. I could be wrong, naturally. But that is my best suggestion given the current state of play I see before me.
Apologies for the length to those who struggle. It is not my fault the dialogues have become bogged down and unnecessarily complicated and working at cross purposes here. Unravelling mixed up balls of string takes time. It’s not easy nor simple. Easier to not get so entangled in the first place by following first principles as much as possible. As well as keeping one’s reactive ego and emotions in check.
“Sharing is Caring” Good luck with it.
Chris Masiero, you have been misinformed; I used Google to look for what you posted, and found that misinformation widely available, from unreliable sources.
#43 Sean: I think the scientists here are responding to the large amount of apocalyptic information that appeals directly to emotion out here in the blogosphere. What are they supposed to do, pretend that is not happening? Some anti-emotive reframing is exactly what is required. That is why I keep coming back to this site, it is one of the few places where scientific method seems to be followed.
#42 Gavin,”However, the relevance to shallow hydrates in the ESAS is unclear.”
Unclear? It seems pretty straightforward that if meta-stable hydrates exist in permafrost at shallow depth – then the ESAS is a likely place for them.
What is the history of estimates of arctic marine methane emissions? 20 years ago believed to be negligible. Three years ago, 8 Tg/yr. Today, 17 Tg/yr.
[Response: Still pretty small (3% of global emissions). – gavin]
The fact that the estimates have increased so dramatically is due to research – mainly concerning the ESAS by Shakhova and Semiletov.
[Response: I have nothing against research. – gavin]
We know shallow meta-stable methane hydrates exist outside of the Hydrate Stability Zone in the arctic permafrost.
We know that the vast majority of marine permafrost is in the ESAS.
We know the ESAS is very shallow.
We know that arctic marine methane emissions are far greater than once thought – including (perhaps especially) in the ESAS.
Is the relevance to shallow hydrates in the ESAS really that difficult to see?
[Response: Yes. Because no one has actually reported them there or even provided any convincing evidence for what the sources of methane are. So while I am not saying that it has been conclusively ruled out, the absence of any positive evidence for any meta-stable hydrates in the ESAS, let alone at the levels being speculated about, let alone supposedly being at some heretofore never seen threshold, means that people should not start talking about some huge emission as if it was ‘likely’ or that it could ‘happen any day now’. Neither of those claims follow from the (real) uncertainty and it is irresponsible to claim they do. – gavin]
Thanks for the discussion. I’m learning a lot.
Just so I am clear on the various positions: Gavin, are you accepting that there was very little methane coming from the ESAS but now there is something like 17 Tg coming from there every year? If so, what would you (or anyone else) attribute this increase to? What do you think the future trajectory of this increase might be and why?
Also, does everyone agree that it is now warmer than it was during the Holocene climate optimum (as has been recently widely reported; see RAG’s link above or ‘oogle relevant phrases)? If so, is the argument that the methane should have come out then relevant? (It seems to me that, even if we have not yet reached that temp for that region, there is no guarantee that the condition of the subsea materials is the same as it was 8000 years ago; in fact, it seems rather unlikely that it is. So again, the argument does not seem particularly germane.)
I think we can all agree that it would be nice to have clear evidence of large quantities of meta-stable hydrates in the ESAS (well, it would be actually nicer to know that this stuff was NOT there, of course).
Didn’t an international team go up to the region in the fall of 2012 to investigate just that? Is it only Shakhova and Semiletov and their teams who have ever done this kind of direct research in these areas?
Sorry for the many questions. And thanks again for the discussion.
One more point: Isn’t it possible that salinity levels, in particular, are different now in the ESAS than they were about 8000 years ago in the HCO, not long after most of the ice age ice sheet melted?
Wouldn’t that have an effect on how stable subsea permafrost and clathrates are/were?
Wili #47 – I don’t think it can be assumed that there is suddenly 17 Tg/yr where before there was little or none. Nobody was looking for it before.
*IF* it were the case that arctic methane had doubled and then doubled again in such a short period of time and continued to do so, we’d all be up the proverbial creek without a paddle.
Gavin #46- “let alone supposedly being at some heretofore never seen threshold”
The Russians have been writing about this ‘heretofore never seen threshold’ since the 1980’s. The scientific literature has detailed their existence in permafrost outside the HSZ since the 1990’s. And it’s not just the Russians, as Yakushev mentioned in the article I cited earlier, the Canadians have also seen meta-stable hydrates outside the HSZ: see Intrapermafrost gas hydrates from a deep core hole in the Mackenzie Delta, Northwest Territories, Canada, Dallimore and Collett, Geology, June, 1995, v. 23, p. 527-530.
“the absence of any positive evidence for any meta-stable hydrates in the ESAS”
These shallow hydrates have been detected in both the Pechora and the Laptev Seas. The Laptev drill site borders the ESAS. Given the geological history, why would these hydrates be unique to the Pechora and Laptev? Shall we just drop ESAS and say Siberian continental shelf? Then your argument that they’ve never been seen disappears.
“or even provided any convincing evidence for what the sources of methane are”
I’m not aware of any real debate. The near surface source is the marine permafrost. And of course there is also methane venting from unfrozen bottom sediments surrounding fault zones and paleo river beds.
[Response: I’m happy to read any references – but even Shakhova in the latest paper or in their 2012 paper do not claim the methane is from shallow meta-stable hydrates. Your absolute confidence that this is the source is not apparently shared by the researchers you’re championing (or perhaps they have not been able to convince the peer reviewers or editors that they can be conclusive on this?). There was none reported in the core they took in the Laptev sea for instance. I have also talked to a number of people – at USGS and elsewhere – that have also looked at sediments in the Siberian shelf and similar environments off Alaska etc. and they have not reported any widespread relict hydrates. Some people have even shown evidence that most of the CH4 is riverine in origin, not from the seabed at all (Bussmann, 2013). But my previous point still stands – there is no evidence that there was a massive methane release in the early Holocene when we know summer sea ice was less and – if you are correct – there should have been even more relict hydrate around. CH4 levels in the ice cores and the gradients between Greenland and Antarctica point clearly to tropical sources dominating the (small) observed Holocene variability. – gavin]