The Azimuth Project
Arctic methane deposits (Rev #5)

Contents

Idea

The cold Arctic regions contain large amounts of the greenhouse gas methane deposited in forms which are currently stable due to the low temperature. It is hypothesized that a small but significant warming of the Arctic regions could destabilize these deposits and lead to large releases of methane into the atmosphere.

Details

The Arctic currently (in geological time) has large stores of methane in three dominant forms:

  1. Conventional gas deposits (e.g. trapped by shale rock, etc).

  2. Stored as methane clathrates (essentially methane molecules trapped in ice crystals) on the seabed.

  3. Locked in permafrost (essentially similar chemistry to methane clathrates above but stored several metres down into frozen soil).

The conventional gas deposits have the high stability of gas deposits elsewhere. The last two are believed to be relatively stable at historical Arctic temperatures, but may be destabilised by a small but significant warming of the Arctic regions. It is believed that 0.5 megatonnes of methane is currently being released from the Arctic per year. However it is believed plausible that up to 50 Gt of methane could be released into the atmosphere very quickly should the storage become destabilised:

  • N. Shakhova, I. Semiletov, A. Salyuk, D. Kosmach, and N. Bel’cheva, Methane release on the Arctic East Siberian shelf, Geophysical Research Abstracts, 9 (2007), 01071.

It should be noted that apparently modeling and measurements of methane in the atmosphere is less advanced than modeling carbon dixoide. In addition, there is debate about whether a sudden destabilisation of Arctic methane reserves is possible or only gradual release.

Methane clathrates

Here’s a picture by W. F. Kuhs, showing what methane clathrate looks like at the atomic scale:

The green thing in the middle is methane, trapped in a cage of water molecules. Click for more details, or see:

Increasing atmospheric methane

This is a good review of discussion up to 2009 concerning the rise in atmospheric methane, some of which may be caused by the release of methane from the Arctic:

  • Amanda Leigh Mascarelli, A sleeping giant?, Nature Reports Climate Change, 5 March 2009.

Mascarelli writes:

Between 1974 and 2000, methane emissions increased by 58 per cent in the part of northern Siberia where Walter’s team have focused their research. In a paper in Nature, they attributed this increase to melting permafrost, which forms ponds and lakes on the land surface. What’s more, they found that a positive feedback had kicked in: Pleistocene-age carbon was being released as methane, which was triggering the loss of even more ancient carbon from the permafrost. Walter and her colleagues reckon that ancient carbon stored here would boost current levels of atmospheric methane ten-fold if it were to escape. All in all, Walter and colleagues warn, Siberia’s still-frozen, ice age-era carbon could be a ‘methane time bomb’. Scientists are hesitant to speculate on whether and when this time bomb will be detonated. But, says Walter, “Yedoma is warming and thawing now. Acceleration should occur during the next century.”

A sign that this acceleration may have already begun comes from scientists who closely monitor concentrations of the gas in the atmosphere. Having remained stable for a decade, atmospheric levels of methane suddenly spiked in 2007:

It’s not yet clear where the extra emissions came from and why methane levels increased uniformly across the globe. But there may be an explanation for the rise in emissions in the Northern Hemisphere, at least. Says Matthew Rigby, a postdoctoral researcher at the Massachusetts Institute of Technology in Cambridge and lead author of a recent study analyzing the trend, “If I had to put my money on it, I’d put it on increased emissions from the northern wetlands.” This, however, invites the question, why are northern wetlands releasing more methane? “Some are worried it may be the start of permafrost melting,” says Rigby. “We can’t rule that out.”

At the time, Ed Dlugokencky and James White (a geochemist at the University of Colorado, Boulder) tried to argue that this rise was just some sort of glitch:

Ed Dlugokencky, an atmospheric chemist with the US National Oceanographic and Atmospheric Administration in Boulder, Colorado, who oversees their atmospheric-methane measurement program, says indications are that global methane levels remained high in 2008, but he expects to see a return to previous levels over the long term. “If I had to make a prediction about what’s going to happen in the future based on the last three decades of observations, I would say that there’s a reasonable chance methane will continue to stay flat or even decrease before we see the effects of a warming climate on methane sources,” says Dlugokencky. White agrees and says it’s too early to tell whether this is a blip on the radar or a true signal that change is afoot. “I think we’re going to need to see two to three years or more with increased methane in order to make a strong statement that we’re beginning to see permafrost degradation resulting in methane increase,” says White.

However, the rise in methane concentrations continued in 2008 and 2009, as discussed here:

And in fact, Dlugokencky was one of the ones to observe this:

The new figures will be revealed this morning at a major two-day conference on greenhouse gases in the atmosphere, taking place at the Royal Society in London. They will be disclosed in a presentation by Professor Euan Nisbet, of Royal Holloway College of the University of London, and Dr Ed Dlugokencky of the Earth System Research Laboratory in Boulder, Colorado, which is run by the US National Oceanic and Atmospheric Administration (NOAA).

Both men are leading experts on CH4 in the atmosphere, and Dr Dlugokencky in particular, who is in charge of NOAA’s global network of methane monitoring stations, is sometimes referred to as “the keeper of the world’s methane”. In a presentation on “Global atmospheric methane in 2010: budget, changes and dangers”, the two scientists will reveal that, after a decade of near-zero growth, “globally averaged atmospheric methane increased by [approximately] 7ppb (parts per billion) per year during 2007 and 2008.”

They go on: “During the first half of 2009, globally averaged atmospheric CH4 was [approximately] 7ppb greater than it was in 2008, suggesting that the increase will continue in 2009. There is the potential for increased CH4 emissions from strong positive climate feedbacks in the Arctic where there are unstable stores of carbon in permafrost … so the causes of these recent increases must be understood.

(Emphasis ours.) It would be interesting to know the latest figures on atmospheric methane concentrations. This website lists references:

but the latest new measurements listed here seem to date back to around 2009.

References

Wikipedia has information about Arctic methane:

See also:

For more on the carbon stored in permafrost, see:

category: carbon

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