Methane—a potent greenhouse gas that could be released in vast quantities as climate change melts Arctic permafrost—has received quite a bit of media attention in the last month. But the coverage has caused a bit of confusion about where the methane is coming from—land or sea—and which source has scientists most worried.
The first round of stories, in early December, followed the publication in the journal Nature of an analysis by forty-one scientists associated with the Permafrost Carbon Network, which found that the amount of organic carbon stored in the perennially frozen ground is 1.7-5.2 times larger than previous estimates. If released, they said, the resultant carbon dioxide and methane could play a much larger role in climate change than deforestation:
“We calculate that permafrost thaw will release the same order of magnitude of carbon as deforestation if current rates of deforestation continue,” the group wrote. “But because these emissions include significant quantities of methane, the overall effect on climate could be 2.5 times larger.”
Methane has about twenty-five times more global-warming potential than carbon dioxide over a 100-year period, and although the scientists acknowledged that it “remains highly uncertain” how much the greenhouse gases emanating from the Arctic will actually accelerate climate change, they stressed that thawing permafrost is “cause for serious concern.” Journalists such as the Associated Press’s Seth Borenstein and Time’s Bryan Walsh did a good job conveying that message, but the Knight Science Journalism Tracker’s Charlie Petit pointed out that they stumbled over one important detail.
Both reporters referred to methane and carbon dioxide being “trapped” in Arctic permafrost, but that’s not quite accurate (Borenstein explained this in the bottom half of his piece; Walsh didn’t). What’s trapped in the permafrost—on land, at least—is organic carbon in the form of ancient, frozen plant and animal matter. As the permafrost thaws, microbes decompose the plant and animal matter and produce methane and/or carbon dioxide depending on local conditions, such as the amount of oxygen present.
This seemingly nitpicking detail is important, because in areas along the Arctic seafloor, methane is trapped in the permafrost in the form of methane hydrates (also referred to as methane clathrates)—basically, methane-laced ice that forms only under high pressures and low temperatures. The second pulse of news stories about Arctic-methane this month focused on this type of deposit, which is found in relatively shallow waters along the coasts of Siberia, Canada, and Alaska.
It resulted from a scoop that Steve Connor—science editor at The Independent, a British paper—picked up while attending the American Geophysical Union’s annual meeting in December to receive an award for outstanding news reporting. The news was that the head of a Russian research team who had been studying the seabed along Russia’s northern coast had spotted “dramatic and unprecedented plumes of methane … bubbling to the surface.”
The team had published a study in 2010 describing significant “methane venting” in the area—which results when permafrost along the seafloor thaws due to the global-warming abetted retreat of insulating sea ice along the surface—but new data the group collected over the summer suggested it had underestimated the amount being vented. This methane also has the potential to accelerate climate change, but critics quickly started poking holes in Connor’s article.
The Knight Science Journalism Tracker’s Petit, who was also at the geophysical union’s meeting to receive an award (for sustained achievement in science journalism), wrote a post explaining how Connor broke away from the press pack at the meeting, and complimenting him for so doing. But “speaking of bubbling methane,” Petit observed, “I am bubbling with methane questions that this story raises.”
First and foremost, Petit wanted to know more about the source of gas. “One or two sentences on what this methane is and whether it is distinct from the kind feared from thawing, terrestrial permafrost would have answered the question,” he wrote.
I found the comments after Justin Gilles' piece interesting. e.g. John U. Harkness said:
I didn't notice the increases at first - until I set the timespan to 2010-2011. Provisional data show there is a substantial increase in methane levels in the past few months. Looks worrying to me - Barrow seems to be the nearest station to the East Siberian Arctic Shelf, from where seabed methane may be being released.
Do read the rest of John Harkness' comment. He has other interesting points. But who will take him seriously? He doesn't seem to be a mainline climate scientist. He is possibly just someone that cares and takes the time to find out.
It's a pity that Justin Gilles did not address these points. The interesting question is why they were missed. Is it a case of waiting until some paper with a theoretical framework (or a computer model) has been peer reviewed and published?
As one leading empirical climate scientist said this to me recently:
Help!
#1 Posted by Geoff Beacon, CJR on Thu 22 Dec 2011 at 05:05 PM
"Both reporters referred to methane and carbon dioxide being “trapped” in Arctic permafrost, but that’s not quite accurate (Borenstein explained this in the bottom half of his piece; Walsh didn’t). What’s trapped in the permafrost—on land, at least—is organic carbon in the form of ancient, frozen plant and animal matter."
It is in fact accurate. There are 4 sources of CH4 in the Arctic, namely:
Yedoma – thaw of Pleistocene ice av. 2% CH4
Clathrate – thaw of methane filled ice lattice
Bacterial – resumption of biota decay
Gaseous – contained sub-surface in sediments by permafrost capping.
Yedoma is a Pleistocene permafrost containing 2-3% carbon by mass which is estimated to cover over 1 million square kilometers of Siberia. The area is becoming increasingly threatened by rising temperature which has the capacity to thaw yedoma in summer, particularly deposits near the surface. This will releasing CH4 directly into the atmosphere where it oxidizes over an 8-12 year period.
Bacterial action on biota (animal and vegetable material) can – and will – resume when surface permafrost thaws permitting seasonal or longer term establishment of an “active” zone. As the atmosphere warms, permafrost retreats and the active zone becomes deeper, permitting bacterial action on biota to resume, resulting in emission of CH4. It is predicted that by 2100, continuous and discontinuous permafrost will have thawed to a depth of 3 metres, enabling increasing bacterial action on the very extensive biota deposits found in Siberia.
#2 Posted by Mike Pope, CJR on Thu 22 Dec 2011 at 06:43 PM
Thanks for the compliments, Geoff. No I am not a scientist, just a concerned citizen.
A caveat on the Barrow readings is that they are preliminary.
One thing that seems to be overlooked here is that there are not only frozen clathrates beneath the sea. These formations cap large, pressurized pools of free methane.
The continuously bubbling and expanding 'torches' and 'plumes' that Semiletov witnessed suggest that the clathrate is in fact melting, and that the process is continuous and self-reinforcing, probably accelerated by sea water pouring down to displace the melted hydrates, thereby further melting what is there. How long would it take for such a process to essentially 'drill' down into ever deeper levels, eventually hitting the large pools of free methane below?
Here's hoping that this is not what is happening and that there is some other, cyclical or self-limiting process going on here.
#3 Posted by John U. Harkness, CJR on Fri 23 Dec 2011 at 02:07 AM
John
Discussion continues on RealClimate.
Sorry I got your middle inittial wrong there.
#4 Posted by Geoff Beacon, CJR on Fri 23 Dec 2011 at 06:59 AM