tag:blogger.com,1999:blog-1367053740188758246.post6500887670699825197..comments2023-06-21T00:39:34.443-07:00Comments on Dosbat: Arctic Methane: What can AIRS tell us. Part 2.Chris Reynoldshttp://www.blogger.com/profile/16843133350978717556noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-1367053740188758246.post-83665981251933932992012-02-17T11:33:59.916-08:002012-02-17T11:33:59.916-08:00Kevin,
I think the biggest issue, as the C13/C12 ...Kevin,<br /><br />I think the biggest issue, as the C13/C12 ratio suggests is that the NH has more wetlands, including tundra, which emit CH4. However in Yurganov's London Presentation (see my most recent post on methane by clicking on the methane tag at the bottom of this post) he notes an interesting Antarctic methane anomaly, who's origin is not known.Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-51297777885279245882012-02-17T11:26:40.900-08:002012-02-17T11:26:40.900-08:00Anonymous (& Kevin),
Before I start rambling ...Anonymous (& Kevin),<br /><br />Before I start rambling (always a danger with me), to quickly answer the question: <br /><br />AIRS shows that the atmospheric concentration around the Arctic climbs in winter, this is because emissions continue during the winter (although at a reduced rate) but oxidation (hence destruction) of methane slows markedly during the winter, due to cold. AIRS shows prominent increased Arctic methane in winter as compared to mid lattitudes. So I think most of the increased atmospheric concentration in the Arctic is due to reduced destruction of methane during the winter.<br /><br />It would be interesting to examine this - using monthly means averaged over lattitude bands. However the sources of methane data I've come across all seem to be daily and are of a complex format, so getting the data into Excel isn't trivial, and I've not got the motivation together to tackle the problem - it's a big hassle.<br /><br />Methane levels are higher over the Arctic and NH mid lattitudes than other lattitude bands. See <a href="http://cdiac.ornl.gov/trends/otheratg/blake/methane/methane.html" rel="nofollow">here</a> (second graphic down). Kevin's source shows a difference of perhaps 100ppb, this seems to be suported by the preceding link. It would be interesting to see if there's a change with time in lattitudinal concentration - maybe I should boot myself up the arse and deal with the data.<br /><br />Also the ratio of Carbon13/Carbon12 isotopes in methane shows a strong lattitudinal bias, with the Arctic having a much lower ratio than other lattitudes, see <a href="http://farm8.staticflickr.com/7003/6517656241_6991c0214c_o.jpg" rel="nofollow">here</a> (my own calculation - note that there are only a few stations in the SH so I'd only take the NH graphs as reliable).<br /><br />The lower C12/C13 ratio shows that much of the source in the Arctic is biological. That graph suggests that there is a role for the Arctic in the recent increase of methane, this is supported by research I've read. The graph also shows a similarly high annual range toward the end of the last period of rise; methane had been stable between about 1998 and 2006. Dlugokencky (2003), <a href="http://165.91.85.82/class/atmo689-gs/lectureweek4/2003GL018126.pdf" rel="nofollow">PDF</a>, finds that the early part of this period of stability was due to a reduction of emissions from north of 50degN. So that finding tallies with the C13/C12 ratio I've graphed. <br /><br />So I wouldn't agree that the Arctic is a low emitter, for it's area it bats above it's weight. (That's another calculation I could do if I got to grips with the concentration data)Chris Reynoldshttps://www.blogger.com/profile/16843133350978717556noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-49626039132454209162012-02-16T17:05:09.295-08:002012-02-16T17:05:09.295-08:00@Anonymous: I think the premise of your question ...@Anonymous: I think the premise of your question is wrong. The historical <a href="http://cdiac.ornl.gov/trends/atm_meth/graphics/eth_comp.gif" rel="nofollow">ice core record does not show a significant difference</a> between arctic (Greenland) and antarctic methane levels. The graph is from <b><i>Historic CH4 Records from Antarctic and Greenland Ice Cores, Antarctic Firn Data, and Archived Air Samples from Cape Grim, Tasmania</i></b>, Etheridge et al, 2002.<br /><br />During the austral winter Antarctica has a far higher incidence of polar stratospheric clouds compared to the arctic and should, if I understand the chemistry correctly, lead to a reduction in atmospheric methane. I'm guessing here, but I suspect that might account for any observed difference.Kevin O'Neillhttps://www.blogger.com/profile/06692943768484857724noreply@blogger.comtag:blogger.com,1999:blog-1367053740188758246.post-57800516128809346342012-02-16T13:03:29.736-08:002012-02-16T13:03:29.736-08:00Could you please answer a simple question?
Methane...Could you please answer a simple question?<br />Methane emissions at the Antarctic are low, and the CH4 concentration is very low (the lowest globally ?). <br />Methane emissions for the Arctic are also supposedly low. Why then does the CH4 concentration seem to be so high (the highest globally?) over the Arctic circle?Anonymousnoreply@blogger.com