Arctic seabed methane stores destabilizing, venting

From up north, we have some more troubling news. Actually very troubling. Catastophic release of methane hydrates is a prime suspect in a few events dramatic enough to show in the earth’s geological records, coarse and obscured as that record may be. (Our actions today will be featured prominently in that record for anyone looking back a million years from now.) It has been a worry for many years that humanity is running the risk of triggering such a release again, which would truly pile disaster on top of calamity.

New research coming out in Science today indicates that this most dire of feedbacks may well be underway already. Below is the text of a press release I received about it last night.

Fairbanks, Alaska–A section of the Arctic Ocean seafloor that holds vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas, according to the findings of an international research team led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov.

The research results, published in the March 5 edition of the journal Science, show that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is leaking large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.

“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.”

Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. It is released from previously frozen soils in two ways. When the organic material–which contains carbon–stored in permafrost thaws, it begins to decompose and, under oxygen-free conditions, gradually release methane. Methane can also be stored in the seabed as methane gas or methane hydrates and then released as subsea permafrost thaws. These releases can be larger and more abrupt than those that result from decomposition.

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: 7 teragrams yearly, which is equal to the amount of methane emitted from the rest of the ocean. A teragram is equal to about 1.1 million tons.

“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.”

Shakhova notes that 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 or less in depth, which means it has been alternately submerged or terrestrial, depending on sea levels throughout Earth’s history. During Earth’s coldest periods, it is a frozen arctic coastal plain, and does not release methane. As the planet warms and sea levels rise, 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.”

Earlier studies in Siberia focused on methane escaping from thawing terrestrial permafrost. Semiletov’s work during the 1990s showed, among other things, that the amount of methane being emitted from terrestrial sources decreased at higher latitudes. But those studies stopped at the coast. Starting in the fall of 2003, Shakhova, Semiletov and the rest of their team took the studies offshore. From 2003 through 2008, they took annual research cruises throughout the shelf and sampled seawater at various depths and the air 10 meters above the ocean. In September 2006, they flew a helicopter over the same area, taking air samples at up to 2,000 meters in the atmosphere. In April 2007, they conducted a winter expedition on the sea ice.

They found that more than 80 percent of the deep water and greater than half of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached at least 250 times that of background levels in the summer and 1,400 times higher in the winter.

They found corresponding results in the air directly above the ocean surface. Methane levels were elevated overall and the seascape was dotted with more than 100 hotspots. This, combined with winter expedition results that found methane gas trapped under and in the sea ice, showed the team that the methane was not only being dissolved in the water, it was bubbling out into the atmosphere.

These findings were further confirmed when Shakhova and her colleagues sampled methane levels at higher elevations. Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline. When they flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated arctic levels.

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.”
Shakhova, Semiletov and collaborators from 12 institutions in five countries plan to continue their studies in the region, tracking the source of the methane emissions and drilling into the seafloor in an effort to estimate how much methane is stored there.

Shakhova and Semiletov hold joint appointments with the Pacific Oceanological Institute, part of the Far Eastern Branch of the Russian Academy of Sciences. Their collaborators on this paper include Anatoly Salyuk, Vladimir Joussupov and Denis Kosmach, all of the Pacific Oceanological Institute, and Orjan Gustafsson of Stockholm University.

58 thoughts on “Arctic seabed methane stores destabilizing, venting

  1. Maxwell,

    The ice cores and the “closure times” of the bubbles they contain are easily calibrated and dated using various methods (you can read up on this, just Google it) Scientists can use interannual banding by physically counting layers, they can compare them with ocean core sediments from nearby, they can use the oxygen isotope ratios (16-18), they can look for confirmation markers such as volcanic residue to calibrate parts of a core to the exact year, they can radiodate gaseous inclusions, they can model ice flows quite well and on….. I’ve just looked up for you the extremes of this snow-firn-ice transformation process. In the interior of the East Antarctic ice sheet, with little accumulation and no melt, it’s 3500 years. On Alaska’s Seward glacier, with about coastal precipitation, it’s achieved in 3-5 years.

    This is all VERY well established stuff and is not where any of the uncertainty lies – as I said, if you were genuinely skeptical and interested in this, it is discoverable in about 45 seconds and is simply not a source of contention. However….

    Your statement: “I still think that in a strict sense of the word ‘proxy’, since scientists are not measuring the actual atmosphere of the past, still works” is DEAD WRONG and THAT is the main point I was trying to get across to you. You were questioning the accuracy of the methane (and other) graphs and claiming them as ‘proxies’ which is a non-trivial error. I’ll say it again, they are NOT proxies. You ARE, indeed “measuring the actual atmosphere of the past” directly. That is the exquisite beauty of this.

    As a comparison, to make it absolutely clear. Pretend you found a beautiful piece of Baltic amber while strolling along a lonely shoreline. You polished it up and found inside a perfectly preserved honey bee, pollen sacs overflowing, lying alongside a couple of prehistoric ants. You date the amber to 5.8 million years, with a known error of +/- 60,000 years. You do not turn around and say, “well, I suspect that living in the forests of this area during the very late Miocene were a number of thriving insect communities, because I have found a proxy for insects”… No. You’ve found the insects themselves! As perfectly formed as the day they were sealed off for eternity. In EXACTLY the same way, we can directly measure samples of the atmospheres of ages past using AMS and be certain of its various constituents, literally down to the atom. Clear?

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  2. Matt,

    that’s a nice analogy, but I still disagree with you. I don’t think you’re wrong. I just don’t agree. I hope I am making that difference clear.

    And I’m sure these cores are calibrated to something, but how do they know the time resolution is constant looking up to down in a piece of ice? When it’s not constant, how do they decide the rate of change of time where the ice isn’t as easy to ‘read’ as other places? At some point, like in any other research endeavour, someone has to make a judgment call. Where do they do so with ice cores?

    Joseph,

    the equilibrium amount of methane in the atmosphere is set by two constraints. First is the concentration of hydroxide ions that oxidize methane to water and CO2. Second is the sources of methane. Right now, you and I agree that it is likely that humans have thrown the sources of methane part of this equation into overdrive.

    But if we stopped producing methane today, it would be interesting to see how long it took to oxidize away the ‘excess’ methane. If there are enough hydroxide ions, then I would gamble it would take 14 years before we got to a point where the ‘natural’ sources were putting enough methane into the atmosphere to find an equilibrium.

    But without such sources, yes the concentration of methane would tend toward zero. Because it’s modeled as an exponential, it wouldn’t ever get to zero probably, but it would be exceedingly smaller than it is today, given enough water in the atmosphere to make the necessary ions to oxidize it.

    So I don’t understand your point other than maybe a physical model where methane production stops in a day may be unphysical. But even if methane productions decreases over the course of fifty years, the atmospheric concentrations are still going to fall rather rapidly assuming enough hydroxide ions, which seems like a sound assumption here. They might even rise and fall too rapidly for ice cores to resolve such ‘spikes’.

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  3. But if we stopped producing methane today, it would be interesting to see how long it took to oxidize away the ‘excess’ methane. If there are enough hydroxide ions, then I would gamble it would take 14 years before we got to a point where the ‘natural’ sources were putting enough methane into the atmosphere to find an equilibrium.

    OK. Let’s do the math. Let’s take the Wikipedia half-life figure of 7 years as correct. Let’s also assume the ‘equilibrium’ concentration (without human-caused emissions) is 650 ppb in the current interglacial period.

    Now, the concentration has increased to 1750 ppb by some unknown mechanism. The question is: How long does it take to get back down to equilibrium? Well, in theory, it never quite reaches equilibrium, but let’s figure out when it reaches 660 ppb.

    The excess concentration at time T in years (we start out with T = 0) is given by:

    M = (1750-650) e-0.099 T

    Does that make sense? e-0.099×7 is 0.5 — that’s the half-life.

    So now we solve the following for T:

    (660-650) = (1750-650) e-0.099 T

    The result is:

    T = 47 years

    So, maxwell, I think you were right on the first estimate you gave, but not on your subsequent calculations.

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  4. They might even rise and fall too rapidly for ice cores to resolve such ‘spikes’.

    I understand your point, but I don’t believe you’re right. Again, the Vostok methane reconstruction has 458 data points. It’s not sufficient that the hypothetical spikes are short lived relative to the resolution of the reconstruction. They would also need to be exceedingly rare.

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  5. Joseph,

    I think I see the point your making.

    I think you’re right. It would take about 50 years.

    Thanks for clearing that up.

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  6. Maxwell, I can’t make it ANY clearer, I don’t think you understand what a proxy is. You need to read up a bit more. It doesn’t become a proxy just because you misunderstand and decide to call it one. Scientists literally ARE measuring ancient atmospheres. And I don’t understand where your problem with dating things comes from – that is an undisputed and unremarkable part of this work. As I said, please read up so you can fill in this gap in your knowledge. Then point out to me, if you care to, where the Vostok data and dating processes (for example) demonstrates the uncertainty you allege and quantify for me their maximum error (you might also want to email the research team themselves to let them know they overlooked these glaring uncertainties)

    Otherwise, please just admit that, indeed, you didn’t quite understand where the methane graph came from but now you do and are happy to agree with it.

    Matt

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  7. Upper layers of an ice core have individually countable layers, like tree rings. So that’s pretty damn accurate. I believe some of the antarctic cores have up to 160,000 discernible layers. Below that, other (typically isotopic) means of dating are used, with an accuracy usually better than 1%.

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