NOTE - the source images for these videos have been changed with effect from October 2012. This means I will need to recompile and update all of the videos from scratch. I aim to do this by the end of the month but am unwell at present - so can't do right now.
There's been a flurry of activity on the 'net about methane and the Arctic recently. This seems to be related to the AGU poster by Semilitov & Shakhova and new research from them due for publication this year. The ever-excellent Realclimate have posted two articles by Dr David Archer, here and here. Neven's Sea-Ice blog (also excellent) addresses the issue here.
I'm busy reading up on the subject. In the meantime Dr Leonid Yurganov has been kind enough to give permission for me to put some of his satellite images into videos. The images are derived from NASA's Atmospheric Infra-red Sounder (AIRS), info and data. Version 5 of the retrieval algorithm is used. The images are available here and Dr Yurganov's email is 'yurganov at umbc.edu'. Those interested may want to read Dr Yurganov's presentation to a London symposium on Arctic methane (pdf - right click and 'save as'), it's informative and well worth spending time on.
There are 12 videos each covering the full set of data for one month. Due to the large intra-annual variability this seemed the best approach. I'll be referring to these in due course but for now they're posted so that anyone who's interested can make use of them. They're done as links because the Blogger video interface is too small (and I can't be bothered manually editing all the html entries).
Bear in mind that these show methane at 400mbar height so any large surface fluxes will be mixed unless plumed up into the atmosphere. For example the AIRS website has a graphic of a plume of methane at 200mbar implying signifcantly higher concentrations at the surface. That page also states AIRS is most sensitive around 200mbar with an accuracy of 1.2 to 1.5%.
These videos will be updated regularly. However I can only update by deleting the original and replacing it with a new version, the new version will have a different URL. The links here will be updated accordingly.
Most recent update - August 2012 updated on 8/9/12.
I'm still not sure what to think of arctic seabed methane emissions. I am at least slightly reassured by two papers: Arctic methane sources: Isotopic evidence for atmospheric inputs and Dynamic autoinoculation and the microbial ecology of a deep water hydrocarbon irruption.
The latter is an examination of model results showing how ocean bacteria ate the Deepwater Horizon hydrocarbons. I've seen estimates that 200,000 tons of methane were released - yet it never reached the atmosphere. This paper offers a model that explains why.
The first paper is along the same lines; it shows how large methane 'bubbles' off Svalbard can be seen at depth in ships sonar, but the bubbles never make it to the surface. Oxidation or methanotrophs at work. This in relatively shallow water as opposed to the much deeper depths of the Deepwater Horizon spill.
Each of these indicates that ol' mother earth ain't quite defenseless. She still has a couple of tricks up her sleeve.
On the other hand, I'm not sure what to think about this: Norway - Spitsbergen, Zeppelinfjell (NO0042G) - GC-FID - methane - air
Yes, I've read the Fisher paper on isotopic evidence - my take on that is that emissions from the ESS aren't significant (yet).
I've noticed from the AIRS images that CH4 seems to be at a peak in January/February, precisely when the Arctic is coldest. Which seemed odd to me, as then emissions should be at a minimum. However further reading revealed a paper that stated Arctic CH4 was at a minimum in the summer due to chemical reactions. I think that the maximum in the winter is because the CH4 + OH reaction is muted by the cold.
In a similar way I suspect that microbial activity will be significantly limited in the Arctic as compared to the Gulf of Mexico by cooler temperatures. Even in summer under open water the peak temperatures are of the order of 5degC much colder than in the GOM.
I'll be posting on this subject but have to read and think quite a bit more before I do.
I'm now some what confused by the methane issue too. Methane is mentioned in all the literature I have read on climate change and always as an impending problem
But after reading the Real Climate piece;
I was quietly reassured but now realise that it was only considering ocean sediments. Now Climate progress has done a fairly long piece and things look more uncertain.
Unfortunately I lack the time, and perhaps the intelligence, to get a fuller understanding so I'm looking forward to your planned pieces here.
Just noticed that Real Climate has a piece and a link to an online Methane model;
In the 'worst case scenario' post it's actually about total Arctic methane emissions.
I'm more concerned about permafrost and wetland emissions than the ocean clathrates. I'll post again soon.
> bubbles never make it to the
> surface. Oxidation or
> methanotrophs at work.
Bubbles of methane gas are dissolving into the seawater as they rise -- it's still methane but the gas goes into solution. Well documented; one such: http://www.ooi.washington.edu/story/Bubbles+from+the+Seafloor
Hank, the point is that the methane is not reaching the atmosphere. Nor is it building up in the oceans. If it was simply dissolving into the seawater and there existed no natural process to remove it, we'd have a methane sea :)
Instead what we see (sic) is that even for a large methane spill (Deepwater Horizon), there exist natural mechanisms for dealing with it.
Now a 50GT burp in the middle of the arctic night might be a different story.
> if ... there were no natural
> process to remove it ,
> we'd have a methane sea :)
Big assumption there.
What we actually do have is -- uncertainty, but no sign of a massive change yet.
Not getting this PDF posted above, is it still at the link?
> Those interested may want to
> read Dr Yurganov's presentation
> to a London symposium on Arctic
> methane (pdf - right click and
> 'save as')
Sorry, it's dead.
I know it's frowned upon but I can't help feeling I should delete some of my pages and this is one.
Post a Comment