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Apocalypse4Real

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Antarctic Methane Concentrations
« on: February 28, 2013, 03:07:53 PM »
Over the last couple of weeks, higher levels of methane have started to appear over Antarctica.

I have updated the METOP 2/B images through February 26, 2013 pm. They reveal that there is a significant area of high methane concentration over Antarctica.

See: https://sites.google.com/site/a4r2013metop2iasich4co2/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb
« Last Edit: April 21, 2013, 07:13:24 PM by Apocalypse4Real »

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #1 on: February 28, 2013, 04:02:42 PM »
A4R,

Thanks of this update.  Historically, natural methane emissions (from hydrate decomposition) have been coming from the Antarctic Peninsula for some years now (as it is warming so quickly), and your figures makes it look like these new emissions are also down wind of the Antarctic Peninsula.  Maybe in a few years this will start happening in the Amundsen Sea Embayment as the glacier retreat exposing hydrate bearing sediment.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #2 on: March 03, 2013, 02:08:33 PM »
A4R,

As I noted yesterday in my "Collapse Main Period 2060 to 2100" thread, I am now concerned that the Antarctic methane emissions that you identified could possibly be coming from a degradation of the Weddell Sea Embayment, WSE, ice sheet (due to a pulse of warm Circumpolar Deep Water, CDW) exposing methane hydrates in the seafloor.  It this is true, then this would be much more serious than methane emissions from the Antarctic Peninsula, due to the amount of ice sheet mass around the WSE, which is enough to raise sea levels by about 0.34 m, by themselves (and the loss of the WSE ice sheets would help destabilize adjoining ice features in both the WAIS and the EAIS).
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sg_smith

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Re: Antarctic Methane Concentrations
« Reply #3 on: April 07, 2013, 01:22:33 PM »

I have been looking at the temperature anomalies shown on arctic news site on march 22, and  comparing  them  with the methane anomalies.  I think it is interesting that the methane anomalies are coming from and or near the area with the coldest (-10) degrees.  I thought they would be from the warmest areas  :).

Cheers

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #4 on: April 14, 2013, 07:28:21 PM »
For those who have not visited A4R's website recently, he has posted methane concentrations including for Antarctica thru March 31, 2013 at the following site:

https://sites.google.com/site/a4r2013metop2iasich4co2/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb

Looking at the pattern of methane atmospheric concentration around the Antarctic it appears to me that it is occurring in an area where the warm Circumpolar Deep Water, CDW, has recently migrated southward where it may have encountered (and thermally destabilized) ocean sediment containing methane hydrates.
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Donna

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Re: Antarctic Methane Concentrations
« Reply #5 on: April 15, 2013, 12:10:48 AM »
For those who have not visited A4R's website recently, he has posted methane concentrations including for Antarctica thru March 31, 2013 at the following site:

https://sites.google.com/site/a4r2013metop2iasich4co2/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb

Looking at the pattern of methane atmospheric concentration around the Antarctic it appears to me that it is occurring in an area where the warm Circumpolar Deep Water, CDW, has recently migrated southward where it may have encountered (and thermally destabilized) ocean sediment containing methane hydrates.
 

AbruptSLR - A4R wrote the following on the Arctic Methane Release thread -   

Quote
I have started posting the METOP2 IASI CH4 for April to June 2013  on a new website due to space constraints.

See: https://sites.google.com/site/a4r2013metop2ch4aprjun/
 

Sorry but I don't know how to link to a particular comment  :-\

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #6 on: April 15, 2013, 12:22:46 AM »
Donna,

Thank you. 

The April atmospheric methane concentrations in portions of the Antarctic look higher than those currently in the Arctic, per this link: 

https://sites.google.com/site/a4r2013metop2ch4aprjun/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb
 
 
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Donna

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Re: Antarctic Methane Concentrations
« Reply #7 on: April 15, 2013, 04:22:17 AM »
The April atmospheric methane concentrations in portions of the Antarctic look higher than those currently in the Arctic, per this link: 

https://sites.google.com/site/a4r2013metop2ch4aprjun/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb
 
 

Indeed they do. If the highs listed are from there then they are higher than the alarming levels in Svalbard in January.  I wish this site - http://www.esrl.noaa.gov/gmd/dv/iadv/graph.php?code=HBA&program=ccgg&type=ts  were up to date. 

I wonder if this has caught the attention of Dr. Leonid Yurganov, though I know his work in the past has been in the arctic.  If you learn of a site with more exact levels or more information please share.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #8 on: April 15, 2013, 05:07:31 PM »
For convenience I have posted the Antarctic atmospheric methane concentration figure linked by Donna, from the Halley Research Station, run by the British Antarctic Survey; which is located on the Brunt Ice Shelf floating on the Weddell Sea.  Although this data ends in Dec 2011, it indicates a troubling trend of increasing methane concentration in the Antarctic atmosphere.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #9 on: April 15, 2013, 06:51:37 PM »
Donna,

Here is a link to slightly newer atmospheric methane concentration data (from the South Pole Station, see attached figure) from a different part of the website that you referenced in your post at:

http://www.esrl.noaa.gov/gmd/dv/iadv/graph.php?code=SPO&program=ccgg&type=ts

This graph shows a similar trend at that from the Halley Station, but as the South Pole is further from the Southern Ocean the data trend is less pronounced.
« Last Edit: May 17, 2013, 12:15:52 AM by AbruptSLR »
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Apocalypse4Real

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Re: Antarctic Methane Concentrations
« Reply #10 on: April 20, 2013, 01:13:25 AM »
Donna and Abrupt SLR,

Dr Yurganov is aware of what I am posting. We have had a brief discussion of the observations.

I'll add more over the weekend, work has been crazy and I am behind on posting. I'll keep you apprised and may add a couple of Google Earth images with an Antarctic perspective to give us a better way of viewing the concentrations.

A4R

Donna

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Re: Antarctic Methane Concentrations
« Reply #11 on: April 20, 2013, 04:43:03 AM »
Donna and Abrupt SLR,

Dr Yurganov is aware of what I am posting. We have had a brief discussion of the observations.

I'll add more over the weekend, work has been crazy and I am behind on posting. I'll keep you apprised and may add a couple of Google Earth images with an Antarctic perspective to give us a better way of viewing the concentrations.

A4R
 

Wow! This is fantastic. Thank you so much A4R!  Really looking forward to your posts when you have time.

Apocalypse4Real

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Re: Antarctic Methane Concentrations
« Reply #12 on: April 21, 2013, 07:12:11 PM »
To demonstrate the Antarctic methane concentrations, attached is the April 12 2013 pm 586 mb CH4 concentrations, which were as high as 2163 ppbv.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #13 on: April 21, 2013, 07:22:29 PM »
A4R,

Thanks for your great posts on Antarctic Atmospheric Methane Concentrations. 

The attached figure shows the bathymetry of the Southern Ocean; which, indicates that the submerged Kerguelen Plateau has a depth of about -700m, which indicates that any methane hydrates present there would be directly exposed to the measured recent increases in water temperatures of the circumpolar deep water, CDW; which could be contributing to the decomposition of the methane hydrates and consequently contributing to plumes of methane gas emissions measured to be occurring in this area.

Furthermore, this post refers to images on A4R's website before April 20, 2013 which show the high methane concentrations over the Southern Ocean; while A4R's posted image immediately above shows areas of very high atmospheric methane concentration over the East Antarctic Ice Sheet, EAIS, itself; for which I have no idea how this methane got to where it is indicated unless the coriolis effect drove circumpolar offshore winds on to the EAIS, carrying the methane with it.
« Last Edit: April 23, 2013, 01:17:47 AM by AbruptSLR »
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Apocalypse4Real

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Re: Antarctic Methane Concentrations
« Reply #14 on: April 22, 2013, 01:41:35 PM »
Abrupt SLR,

I'll post more images later, I am buried in the last week before finals, then finals/graduation  next week. There is alot more to add, but no time at the moment.

A4R.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #15 on: May 07, 2013, 05:01:29 PM »
I thought that I would post this accompanying methane hydrate stability graph including the influence of saltwater on hydrate stability.  To me this chart clearly indicates that natural gas hydrates in marine sediment in the Southern Ocean at depths shallower than about 350m (such as in the Kerguelen Plateau, shown in my earlier post, or most of the continental shelf) are subject to decomposition as the CDW warms above its historical values.  This curve also indicates to me that most of any hydrates below the Antarctic Ice Sheet, AIS, at depths deeper than about 350m are probably relatively stable even if the ice sheet above then thins due to ice mass loss.
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Omar

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Re: Antarctic Methane Concentrations
« Reply #16 on: May 14, 2013, 04:46:57 PM »
At first I thought the methane was coming from subsea clathrates, but if it was from subsea clathrates and then transported inland, it would have appeared on 800hPa - 1000hPa mapping. Maybe IASI can't detect methane effectively at those pressures... That's a question for Yurganov (AFR, could you ask him?).

Anyway, I'm no scientist and have no scientific background, but I've been following daily the methane levels in Antarctica  for the last couple of months and it seems to be coming from East Antarctica itself. After reading http://www.dailykos.com/story/2013/04/10/1200602/-The-Antarctic-Half-of-the-Global-Thermohaline-Circulation-Is-Faltering, I thought the methane release could have happened on subsea clathrates and winds could have pushed the methane inland, but it seems odd for methane to flow against the wind direction consistently for two months, and, most importantly, there's no methane whatsoever detected at sea level 800hPa+...

The detected methane really seems to be consistent starting at around 650hPa to 670hPa. At the current temperatures in Antarctica of -58F and dewpoint of -64F the elevation would be approximately 1600 to 1900 meters; and the highest levels of methane are found at 586 hPa / around 3000 meters.

What I'm about to say sounds like nosense even to a noob like me, but could it be possible that there are deep fractures in the East Antarctic Ice Sheet that are causing extensive methane venting? After all, the area where the methane is being detected seems to follow pretty much the elevation of the area.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #17 on: May 14, 2013, 05:29:55 PM »
Omar,

While would be better for A4R to respond about the accuracy of Yurganov's methane readings, I will make the following observations:

- Regarding the elevations that you posted for the methane concentration readings, per the attached image, ice sheets are present in the EAIS almost every where between el 1600 and 1900m (also note how thick the ice is in the EAIS which has bearing on the probability of any crevasses extending all the way to the bed elevation (see the next point).

- As methane hydrates are stable at the pressure/temperature levels present in Antarctica, it would not matter whether there are crevasses in the ice sheets, as no significant amount of methane gas could vent from them as the stable hydrates are the only likely source of methane (unless you think that large fields of free gas are venting).

-  I suspect that due to the constant circumpolar winds, that the normally low pressures in the South Pole area must trap methane gas over Antarctica, where the very low temperatures probably slows the rate of chemical reduction of the methane to CO2.  Thus this high methane concentration over Antarctica may not be due to high rates of active venting but rather due to a slow accumulation of methane from adjoining areas at a rate that is faster than either the rates of dissipation and chemical reduction.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #18 on: May 14, 2013, 06:06:28 PM »
I thought that I should provide the attached image illustrating the "Clathrate Gun" mechanism for continental slope instability for releasing methane from methane hydrates from the sea floor.  Such a mechanism makes is more likely, in my opinion, for the atmospheric methane shown by A4R, to come (gradually from multiple ventings) from marine sources, rather than from the Antarctic continent.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #19 on: May 16, 2013, 12:25:07 AM »
I think that looking at the attached image of the wind pattern for May 16 2013 from http://www.weather-forecast.com/maps/Antarctica
I can imagine how it might be possible for methane gas from destabilized offshore hydrates could drift over the continent and then become trapped (much like the hydroclorofluorocarbon molecules that degraded the Antactic ozone layer).

Also see A4R's latest methane concentration posts at:

https://sites.google.com/site/a4r2013metop2ch4aprjun/home/2011-airs-ch4-359-hpa-vs-iasi-ch4-970-600-mb
« Last Edit: May 16, 2013, 12:32:20 AM by AbruptSLR »
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Omar

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Re: Antarctic Methane Concentrations
« Reply #20 on: May 16, 2013, 04:11:11 PM »
Thank you! I really hope you're right and the instrument is no good under 1500 meters.

Actually not only I agree with your arguments, but your rationale is exactly where I started. Based on melting maps, my initial hypothesis was that the methane was coming somewhere around Prydz Bay, so I started looking at 10 or more of the IASI graphs at different pressures every day for the last couple of months looking at the methane, at winds, reading papers, etc. trying to pinpoint the source, but IASI just won't show methane nowhere near the coast.

Every day since the beginning of the release, the lowest altitude readable graphs of methane from Antarctica (where the instrument actually picked up methane) have way less methane that the area at 3000 meters, and they aren't close to the coast either.

I'm convinced that at this point either IASI can't see the methane coming up from under 1000 meters (which has huge implications since IASI is pretty much the only instrument available to the community), or the methane is being generated at high altitudes.

Let me show you the inconsistency coming from the instrument readings:

I may be completely off, but this is what I'm using to convert hPa to elevation: http://www.csgnetwork.com/densaltcalc.html

and I'm taking the temperature and dew point from the amundsen station from here: http://www.timeanddate.com/weather/antarctica/south-pole

To look at the levels of methane for yesterday, this is the IASI page for 12-24: http://www.osdpd.noaa.gov/IASI/html/M2/RP/mrm_t2.html

Now here's the thing that has been puzzling me (and trust me, it's been like this every day since beginnings of February):

Methane at 586hPa / 3158.5 meters (2190ppb today!): http://www.osdpd.noaa.gov/IASI/img/t2/D1/mr_ch4.080.gif

Methane at 695hPa / 1475.3 meters: http://www.osdpd.noaa.gov/IASI/img/t2/D1/mr_ch4.085.gif

You can see better the contour of Antarctica as picked up by IASI here: http://www.osdpd.noaa.gov/IASI/img/t2/D1/mr_ch4.005.gif

And even though it's of no relevance, I've been looking at the ground altitude here (same Mercator projection as IASI, makes it easier to place markers by eyeballing it): http://www.daftlogic.com/sandbox-google-maps-find-altitude.htm . I place a lot of markers roughly on the places where the yellow methane emissions are to compare if the elevation matches the hPa. I've found that the elevation on the ground actually matches the elevation by IASI. Again, it doesn't mean anything because methane could be close to the ground regardless of the source.

Your arguments make all the sense in the world and actually I've been trying to prove that is coming from the sea from February, but the instrument just won't help.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #21 on: May 16, 2013, 05:15:59 PM »
Omar,

As I have no meterological training, I can make no expert comments on your methodology or on the IASI accuracy; but I will say that in the in the two attached IASI images for 416mb and 487mb that it appears to me that the concentrated methane is near the coast by the Amery Ice Shelf in the Australian sector; where in my opinion it could by been blown by the offshore circumpolar winds from points to the west (i.e. from the Weddell gyre area that I have noted is recently entraining warm CDW from the ACC (Antarctic Circumpolar Current) and bringing a warm stream of CDW in contact with the continental shelf in the Queen Maud Land (or Norwegian sector), which is another possible source of degrading marine methane hydrates.  If the methane leaks from the ocean are low volume it is possible that the IASI reading only show the high concentrations at higher altitudes where it is colder (thus slowing the chemical process that reduces methane to CO2, thus allowing the methane concentrations to accumulate and to remain high for long periods of time.  Again these are only my thoughts.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #22 on: May 16, 2013, 05:35:38 PM »
To help clarify my point about warm CDW water entering the Weddell Gyre from the north and then traveling along the coast of the Queen Maud Land, please see the attached figure from the following website for the Andrex project that is actively monitoring this behavior:

http://www.noc.soton.ac.uk/ooc/PROJECTS/andrex/

The caption for the figure from the Andrex website is:

"Schematic of the circulation in the Weddell Sea (in black). The red arrows represent the escape route from the Weddell Sea. The white arrows are the eastern branches of the Weddell Gyre."

Furthermore, if it is not clear, in the image the white arrows should indicate warm CDW entrained in the eastern end of the Weddell Gyre from the ACC to the north.
« Last Edit: May 16, 2013, 06:10:20 PM by AbruptSLR »
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #23 on: May 17, 2013, 12:29:13 AM »
As a continuation of the Methane Concentration readings that I posted in this thread on April 15, 2013, I attached NOAA's South Pole flask readings for January 2013 from:

http://www.esrl.noaa.gov/gmd/dv/iadv/graph.php?code=SPO&program=ccgg&type=ts%5dhttp://www.esrl.noaa.gov/gmd/dv/iadv/graph.php?code=SPO&program=ccgg&type=ts

This data does not show any significant changes (only the normal seasonal drift).
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #24 on: May 26, 2013, 03:30:42 PM »
The first attached image from NOAA on May 25, 2013 of atmospheric methane concentration at 469 mb; which shows a continuingly (and disturbingly) high concentration trend as indicated by the second image from Sam Carana (who belongs to a controversial group concerned about the risks of abrupt methane releases).  As I find it difficult to image a biological source for this pattern of Antarctic atmospheric methane concentration; I continue to suspect a marine sediment methane hydrate source (triggered by the local warming of the marine by warm CDW coming south from the ACC on the eastern side of the Weddell Gyre).
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #25 on: June 01, 2013, 01:42:42 AM »
The attached image indicates that the high atmospheric methane concentrations at 586mb over the Antarctic are continuing and are some of the highest concentrations in the world.
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Pmt111500

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Re: Antarctic Methane Concentrations
« Reply #26 on: June 01, 2013, 07:03:04 AM »
The only biological source I can come up with could be that some huge algal bloom has died and entered in to deep circulation on a particularly deoxygenized spot. What I'd like to see if this is a yearly or rarer occurrence, something like the H2S releases on Namibian coasts that have been going on as long as there have been measurements. That is a huge difference from the rest of the antarctic coast, though.
« Last Edit: June 01, 2013, 07:18:05 AM by Pmt111500 »
Cooling the outside by heat pump.

AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #27 on: June 01, 2013, 09:04:13 PM »
Pmt11500,

While I am an engineer and not a scientist, and while I agree that it would be good for researchers to track-down any possible biological source for this anomalous methane emission; I am still of the opinion (as stated earlier) that it seems most likely to me that these methane emissions come from the decomposition of marine methane hydrates subjected to seafloor slope instabilities associated with the introduction of relatively warm circumpolar deepwater, CDW, down from the north along the eastern leg of the Weddell Gyre.  I believe that methane emissions frequently come from the breakdown of biological sources beneath fresh water, I believe that CO2 is emitted from the breakdown of biological sources beneath saltwater; as has been indicated by paleo-evidence when increased historical circumpolar wind velocities have increase upwelling around Antarctica which have caused abrupt emissions of biological CO2 in the past.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #28 on: June 04, 2013, 01:02:31 AM »
The following abstract indicates that not is a jet of warm CDW current is directed southward from the main ACC (located further to the north); which passes near the Kerguelen Plateau (off the Antarctic coast), and has jets near the bottom that actively cause mixing that could help promote the decomposition of methane hydrates in the local seafloor:

Waterman, Stephanie, Alberto C. Naveira Garabato, Kurt L. Polzin, 2013: Internal Waves and Turbulence in the Antarctic Circumpolar Current. J. Phys. Oceanogr., 43, 259–282.
doi: http://dx.doi.org/10.1175/JPO-D-11-0194.1


"Abstract:  This study reports on observations of turbulent dissipation and internal wave-scale flow properties in a standing meander of the Antarctic Circumpolar Current (ACC) north of the Kerguelen Plateau. The authors characterize the intensity and spatial distribution of the observed turbulent dissipation and the derived turbulent mixing, and consider underpinning mechanisms in the context of the internal wave field and the processes governing the waves’ generation and evolution.
The turbulent dissipation rate and the derived diapycnal diffusivity are highly variable with systematic depth dependence. The dissipation rate is generally enhanced in the upper 1000–1500 m of the water column, and both the dissipation rate and diapycnal diffusivity are enhanced in some places near the seafloor, commonly in regions of rough topography and in the vicinity of strong bottom flows associated with the ACC jets. Turbulent dissipation is high in regions where internal wave energy is high, consistent with the idea that interior dissipation is related to a breaking internal wave field. Elevated turbulence occurs in association with downward-propagating near-inertial waves within 1–2 km of the surface, as well as with upward-propagating, relatively high-frequency waves within 1–2 km of the seafloor. While an interpretation of these near-bottom waves as lee waves generated by ACC jets flowing over small-scale topographic roughness is supported by the qualitative match between the spatial patterns in predicted lee wave radiation and observed near-bottom dissipation, the observed dissipation is found to be only a small percentage of the energy flux predicted by theory. The mismatch suggests an alternative fate to local dissipation for a significant fraction of the radiated energy."
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #29 on: June 13, 2013, 03:15:31 PM »
You can see from the first attached NOAA image of atmospheric methane concentrations, that the values over East Antarctica (here taken at 525 mb) continue to be the highest values in the atmosphere.

Furthermore, the second image shows a deep AABW current near the Kerguelen Plateau (off the East Antarctic coast), circa 2010.  This Antarctic Bottom Water, AABW, current probably originates near the Moscow University Ice Shelf and Totten Glacier, and as discussed elsewhere (the "EAIS" thread, etc), fresh meltwater from the Moscow University Ice Shelf and Totten is reducing the AABW production that feeds into this deep current; which implies that the branch of this AABW current that is shown in the image to travel westard along the coastline south of the Kerguelen Plateau, probably currently has less cold AABW than previously and probably has more warm CDW (than previously).  This double hit of less cold and more warm deep water, maybe resulting in more methane hydrate decomposition that could be steadily supplying small abouts of methane to the atmosphere over the East Antarctic; where the very cold temperatures would slow the chemical reduction of the methane, thus allowing it to accumulate in the high concentrations indicated in the first image.

This concentration of methane ove the East Antarctic is significant because it can contribute to the reduction of the local atmospheric pressure which will result in high circumpolar wind velocities (slowly migrating southward); which accelerates upwelling of warm CDW which results in less AABW and more icemelt.
« Last Edit: June 14, 2013, 02:25:57 AM by AbruptSLR »
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Re: Antarctic Methane Concentrations
« Reply #30 on: June 17, 2013, 03:11:10 AM »
The attached image from Purkey and Johnson 2013, supports my prior statement that the bottom water in the Kerguelen Plateau area is introducing a large amount of heat to the seafloor; where this heat can help to destabilize methane hydrates in the seafloor, particularly around the continental shelf/slope areas.
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Re: Antarctic Methane Concentrations
« Reply #31 on: June 17, 2013, 08:18:51 AM »
ASLR, in your post #27 you source the AABW to the Moscow University ice shelf and Totten Glacier. I believe the source is probably further east for AABW in the South Australian Basin. The warming and mixing with the CDW probably also occurs at it's source although the PMEL article linked below doesn't specifically address the warming that Purkey focuses on. The heating and potential methane releases may be linked to the changes taking place in the Ross sea?                                                       
  Decadal ventilation and mixing of Indian Ocean waters

Fine, R.A., W.M. Smethie, Jr., J.L. Bullister, M. Rhein, D.-H. Min, M.J. Warner, A. Poisson, and R.F. Weiss

Deep-Sea Res. I, 55, doi: 10.1016/j.dsr.2007.10.002, 20–37 (2008)

Chlorofluorocarbon (CFC) and hydrographic data from the World Ocean Circulation Experiment (WOCE) Indian Ocean expedition are used to evaluate contributions to decadal ventilation of water masses. At a given density, CFCderived ages increase and concentrations decrease from the south to north, with lowest concentrations and oldest ages in Bay of Bengal. Average ages for thermocline water are 0–40 years, and for intermediate water they are less than 10 years to more than 40 years. As compared with the marginal seas or throughflow, the most significant source of CFCs for the Indian Ocean south of 12°N is the Southern Hemisphere. A simple calculation is used to show this is the case even at intermediate levels due to differences in gas solubilities and mixing of Antarctic Intermediate Water and Red Sea Water. Bottom water in the Australia–Antarctic Basin is higher in CFC concentrations than that to the west in the Enderby Basin, due to the shorter distance of this water to the Adelie Land coast and Ross Sea sources. However, by 40°S, CFC concentrations in the bottom water of the Crozet Basin originating from the Weddell Sea are similar to those in the South Australia Basin. Independent observations, which show that bottom water undergoes elevated mixing between the Australia–Antarctic Basin and before entering the subtropics, are consistent with high CFC dilutions (3–14-fold) and a substantial concentration decrease (factor of 5) south to north of the Southeast Indian Ridge. CFC-bearing bottom waters with ages 30 years or more are transported into the subtropical South Indian Ocean by three western boundary currents, and highest concentrations are observed in the westernmost current. During WOCE, CFC-bearing bottom water reaches to about 301S in the Perth Basin, and to 201S in the Mascarene Basin. Comparing subtropical bottom water-CFC concentrations with those of the South Pacific and Atlantic oceans, at comparable latitudes, Indian Ocean bottom water- CFC concentrations are lower, consistent with its high dissipation rates from tidal mixing and current fluctuations as shown elsewhere. Thus, the generally high dilutions and low CFC concentrations in bottom water of the Indian Ocean are due to distance to the water mass source regions and the relative effectiveness of mixing. While it is not surprising that at thermocline, intermediate, and bottom levels, the significant ventilation sources on decadal time scales are all from the south, the CFCs show how local sources and mixing within the ocean affect the ventilation.

« Last Edit: June 17, 2013, 10:17:25 AM by Bruce Steele »

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Re: Antarctic Methane Concentrations
« Reply #32 on: June 17, 2013, 12:14:43 PM »
...  where the very cold temperatures would slow the chemical reduction of the methane, thus allowing it to accumulate in the high concentrations indicated in the first image.


A tiny, persnickety correction.  Methane is oxidized by hydroxyl radicals, not reduced.  The radicals are formed from sunlight and water vapor.  Methane in the atmosphere in polar regions tends to hit maximum in the dead of winter, due to absence of sunlight, and perhaps also colder temps slowing the chemical reaction.  This is a bit counter-intuitive, since release of methane from thawing permafrost and warming waters surely is at a maximum in the summer melt time.

But this is a small matter.  AbruptSLR's contributions to this forum are exceptional, extraordinary, and a bit intimidating in both quantity and sophistication. 

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Re: Antarctic Methane Concentrations
« Reply #33 on: June 17, 2013, 11:35:30 PM »
Bruce,

You are right that in my post #27 the sources of the AABW is further to the east as I believe that the image indicates two sources (from Adelie Land and the Ross Sea).  What I was thinking was that the fresh meltwater from the Moscow University Ice Shelf (and a little from Totten) is probably reducing the AABW production from Adelie Land; but I now see that the fresh meltwater from the Getz Ice Shelf maybe reducing the AABW from the Ross Sea (and the reduction of both sources of AABW would then result in seafloor warming near the Kerguelen Plateau.  However, I have to admit that as the methane concentration is located over the Antarctic mainland that methane hydrate could be decomposing due to seafloor warming from any location of reduced AABW (including the Weddell Sea or the Cape Darnley polynya); it is just that Purkey and Johnson 2013 show the greatest warming near the Kerguelen Plateau.  See various images for orientation and the following summaries related to AABW production from Adelie Land and the Cape Darnely polynya.


Antarctic Bottom Water from the Adélie and George V Land coast, East Antarctica (140–149°E)
By G. D. Williams; S. Aoki; S. S. Jacobs, S. R. Rintoul, T. Tamura, N. L. Bindoff
Article first published online: 30 APR 2010
DOI: 10.1029/2009JC005812
We report on observations of dense shelf water overflows and Antarctic Bottom Water (AABW) formation along the continental margin of the Adélie and George V Land coast between 140°E and 149°E. Vertical sections and bottom layer water mass properties sampled during two RVIB Nathaniel B Palmer hydrographic surveys (NBP00–08, December 2000/January 2001 and NBP04–08, October 2004) describe the spreading of cold, dense shelf water on the continental slope and rise from two independent source regions. The primary source region is the Adélie Depression, exporting high-salinity dense shelf water through the Adélie Sill at 143°E. An additional eastern source region of lower-salinity dense shelf water from the Mertz Depression is identified for the first time from bottom layer properties northwest of the Mertz Sill and Mertz Bank (146°E–148°E) that extend as far as the Buffon Channel (144.75°E) in summer. Regional analysis of satellite-derived ice production estimates over the entire region from 1992 to 2005 suggests that up to 40% of the total ice production for the region occurs over the Mertz Depression and therefore this area is likely to make a significant contribution to the total dense shelf water export. Concurrent time series from bottom-mounted Microcats and ADCP instruments from the Mertz Polynya Experiment (April 1998 to May 1999) near the Adélie Sill and on the upper continental slope (1150 m) and lower continental rise (3250 m) to the north describe the seasonal variability in downslope events and their interaction with the ambient water masses. The critical density for shelf water to produce AABW is examined and found to be 27.85 kg m−3 from the Adélie Depression and as low as 27.80 kg m−3 from the Mertz Depression. This study suggests previous dense shelf water export estimates based on the flow through the Adélie Sill alone are conservative and that other regions around East Antarctica with similar ice production to the Mertz Depression could be contributing to the total AABW in the Australian-Antarctic Basin.


Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya
by: Kay I. Ohshima, Yasushi Fukamachi, Guy D. Williams, Sohey Nihashi, Fabien Roquet, Yujiro Kitade, Takeshi Tamura, Daisuke Hirano, Laura Herraiz-Borreguero, Iain Field, Mark Hindell, Shigeru Aoki & Masaaki Wakatsuchi
Nature Geoscience, Volume:6, Pages:235–240 (2013), doi:10.1038/ngeo1738
Abstract:
The formation of Antarctic Bottom Water—the cold, dense water that occupies the abyssal layer of the global ocean—is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65°–69° E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3–0.7×106 m3 s−1 of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic Bottom Water. The transformation of this water mass, which we term Cape Darnley Bottom Water, accounts for 6–13% of the circumpolar total.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #34 on: June 17, 2013, 11:49:31 PM »
SteveMDFP,

Thank you for the correction, about oxidation, and also the kind words.  I do what I can in the little spare time that I have.  However, I will note that we are just beginning the Austral Winter now and according to the attached image from NOAA for June 16, 2013 at 525mb (which is typical of other similar altitudes) the concentration over the Antarctic mainland is now decreasing from what it has been from January 2013 up until a couple of weeks ago.  This implies to me that the source of methane is decreasing now.

Best,
ASLR
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Re: Antarctic Methane Concentrations
« Reply #35 on: June 18, 2013, 12:30:46 AM »
Bruce,

I thought that you might like to look at the attached pdf about the Cape Darnely polynya being the second greatest source of AABW production after the Ross Sea area.

Best,
ASLR
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Re: Antarctic Methane Concentrations
« Reply #36 on: June 18, 2013, 03:37:15 AM »
ASLR,  The polynya is new to me but that just shows my rather meager knowledge. Do you know of papers that describe fresh water influence on frazil ice production. Salinity is important to it's production and it would be interesting to see how freshening of the surface waters at the "great polynyas" has changed over the last few decades and maybe make some projections of further freshening on frazil ice production . Is this process or mixing with fresh water after the saline cold water is ejected from the surface the primary reason for the slowdown in bottom water formation?
http://onlinelibrary.wiley.com/doi/10.1029/93JC01905/abstract

I will do some more research on my own and thanks for giving me a much better idea about how the Southern oceans work.

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Re: Antarctic Methane Concentrations
« Reply #37 on: June 18, 2013, 04:48:52 PM »
ASLR, this paper was in the references of the PDF you linked. It shows a strengthening of the Ross Sea polynya. I think the processes responsible for the slowdown  in bottom water formation and the reasons for it's warming are important to better understand if they are contributing to methane increases. I have been interested in how the slowdown changes ventilation of the deep oceans because shoaling of the hypoxic boundary has large influences on biology.

http://rkwok.jpl.nasa.gov/publications/Drucker.2011.GRL.pdf

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Re: Antarctic Methane Concentrations
« Reply #38 on: June 18, 2013, 07:09:33 PM »
Bruce,

With the caveat that I am an engineer and not a scientist; it is clear that the various factors that affect AABW production are more complex that my previously stated rule of thumb that generally more ice shelf meltwater reduces AABW; as you correctly point-out that in certain situations and ice shelf / ocean interactions AABW production could be increased (say if the geometry of the associated ice shelf changes by calving in interaction with bathemytry in a way that helps to  carry the AABW away via a deep channel/trough to the deep ocean, etc.

The attached two images are from:

Modelling Amery Ice Shelf/Ocean Interaction
by:Ben Galton-Fenzi
bkgalton@utas.edu.au
Antarctic Climate and Ecosystems CRC, Hobart, Australia
Simon Marsland(CSIRO), John Hunter (ACE CRC),
Richard Coleman (UTas)
WAIS/FRISP meeting: 27 Sept 2009, Pack Forest

The first attached image shows the ice shelf - ocean interaction including tidal action, advection, ice shelf water (ISW), frazil ice production, marine ice accretion and the influence of frazil ice on turbulent kinetic energy (TKE) which affect current mixing/stratification/circulation and thus can reduce AABW production as indicated in both the second image and in the following quote from Galton-Fenzi 2009:
"1. Frazil destabilises cool ISW plume, enhancing mixing with waters that melt base.
2. Frazil enhances the basal accretion of marine ice."

The influence of the frazil ice is also discussed in the following source:


"Observations of thermohaline convection adjacent to Brunt Ice ShelfBy: Ilker Fer , Keith Makinson and Keith Nicholls
Our observations provide direct evidence for enhanced dissipation rates associated with the conditional thermohaline convection mechanism proposed by Foldvik and Kvinge (1974). The ice crystal formation at depth and its ascent to the surface will influence the local sea ice budget and contribute to underwater ice production. Upwelling of the water associated with the convection might supply nutrients from the bottom layer toward the euphotic zone and enhance the primary production. The formation of ice crystals in suspension is probably a characteristic feature of the ice shelves producing ISW in the Southern Ocean and constitute an additional source of TKE production which might increase mixing substantially with consequences for the regional stratification and circulation."

Again, I agree that predicting the actual affect on AABW production is complex and requires the use of a computer model; but on average I believe that this information (especially the second figure) supports the rule of thumb that without ISW and the ice shelf - ocean interaction the AABW production would be higher (in general).

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Re: Antarctic Methane Concentrations
« Reply #39 on: June 20, 2013, 07:28:41 PM »
I provide this post to emphasize the importance of the atmospheric methane concentration currently measured over Antarctica.  In this regard, the following extract comes from:

Atmospheric science: Tug of war on the jet stream,
by: Judith Perlwitz, Nature Climate Change Volume:1, pp:29–31 (2011) doi:10.1038/nclimate1065

http://www.nature.com/nclimate/journal/v1/n1/full/nclimate1065.html?WT.ec_id=NCLIMATE-201104

"Recovery of the ozone hole and increasing greenhouse-gas concentrations have opposite effects on the jet stream. New model experiments indicate that they will cancel each other out over coming decades, leaving storm tracks at a stand still.
Over about the past 30 years, depletion of the ozone layer over Antarctica has had a greater effect on climate in the Southern Hemisphere than rising greenhouse-gas concentrations, causing a polewards shift of wind and precipitation patterns. Since about 2000, the so-called ozone hole has stopped enlarging and it is expected to close completely sometime after the middle of the century, in response to a ban on the production and use of ozone-depleting substances under the Montreal Protocol. This raises the question of whether wind and precipitation patterns will revert to their pre-ozone-hole conditions as the ozone layer recovers. Two new studies — one by Polvani and colleagues1 in Geophysical Research Letters and the other by McLandress and colleagues2 in Journal of Climate — show that as the ozone hole closes, increasing greenhouse-gas concentrations will counter the effects of ozone recovery, preventing atmospheric circulation from returning to 'normal'."
The  caption for the first attached image is:
"The locations of the westerly jet stream and the southern boundary of the Hadley cell, along with the storm tracks and subtropical dry zones associated with them, are affected by increasing greenhouse-gas concentrations and the recovery of the Antarctic ozone hole. Ozone-hole recovery causes them to shift towards the Equator (blue arrow) and increasing greenhouse-gas concentrations drive them towards the South Pole (red arrow). Polvani et al. and McLandress et al. explored the impact of these two anthropogenic climate forcings on atmospheric circulation and hydrological features over the twenty-first century using climate models. Both studies found that the location of circulation and precipitation patterns will not change during Southern Hemisphere summertime because the two forcings will cancel each other out."
The second attached image shows the relationship of the Hadley, Ferrel and the Polar, atmospheric cells.
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AbruptSLR

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Re: Antarctic Methane Concentrations
« Reply #40 on: June 21, 2013, 12:53:50 AM »
While I did not state it in my last post, as the GHG concentration over the South Pole increases, the Westerlies (and the Antarctic Polar Jet Stream) migrate southward.

Also, I thought the attached image from April 2013 would help to locate the position of the concentrated atmospheric methane over Antarctica.
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Re: Antarctic Methane Concentrations
« Reply #41 on: June 21, 2013, 01:35:08 AM »
ASLR, "the AABW overflows entrain on average about an equal amount of warmer( >0c ) Circumpolar Deep Water." Orsi et al 1999 . So the largest driver of  the slowdown of AABW is probably the warmer Upper Circumpolar Deep Water that it is coming in contact with and mixing with AABW on it's descent. I know the CDW  is warming but are there projections for the rate of warming to increase? I keep thinking the heat that has been documented entering depths ( to 2000 meters ) must take awhile to feed into the CDW. It just seems like the 900 lb. Gorilla.   

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Re: Antarctic Methane Concentrations
« Reply #42 on: June 21, 2013, 02:45:36 AM »
Bruce,

I agree that both the increase in the temperature of the CDW and the increase in the volume of the CDW (note that according to Purkey & Johnson as the AABW volume is decreasing the CDW volume is increasing) will be critical for ice mass (VAF) from Antarctica.  While I do not have time to dig-up specific trends:

(a) the first attached image (from RealClimate) shows how during the El Nino hiatus period more heat content has been going into the deep ocean and I have seen projections that upto half of this deep ocean heat content will telecommunicate into the Southern Ocean.
and (b) the second image shows the trend of increasingly positive Southern Annular Mode (SAM) that is increasing the wind velocity around the Southern Ocean and thus both increasing the velocity of the ACC and more importantly increasing the volume of warm CDW near the ocean-ice interface around Antarctica.  Also, note that as the ozone hole is shrinking and the ozone hole is more effective in inducing positive values of SAM than is GHG, one might expect that the values of SAM should be becoming less positive; and I suspect the fact that the values of SAM are still trending toward more positive values, may indicate how effective the high atmospheric methane concentrations over Antarctica are at making values of SAM more positive.  See also the write-up below regarding the second image:

"The Southern Annular Mode (SAM), which is defined by changes in the westerly winds that are driven by temperature contrasts between the tropics and southern polar areas. The annular modes generally take a circular pattern (‘annular’ means ring-shaped) and see-saw between positive and negative phases for weeks or months. In the SAM’s positive mode, the ring is stronger and further south, inhibiting Antarctic air outbreaks. In the negative mode, a weaker, more variable vortex allows Antarctic air to spill north more easily.
The Southern Annular Mode has steadily trended positive in recent decades. Computer models indicate this trend is related to ozone depletion above Antarctica and increases in greenhouse gases." (the attached second image is courtesy Jianping Li, China Institute for Atmospheric Physics.)
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Re: Antarctic Methane Concentrations
« Reply #43 on: June 21, 2013, 04:48:51 PM »
I have discussed the upwelling of warm CDW in many different threads, but I will continue this discussion in this thread because I believe that some of the methane hydrate decomposition is occurring along the Queen Maud Coast where Purkey & Johnson have identified a current of warm CDW has recently entered the eastern side of the Weddell Gyre (coming from the north), from which location it then travels westward along the Queen Maud Coast (and from there I have speculated that some of this current then enters the Filchner Trough where it then continues on to accelerate basal ice melting from the FRIS, particularly near the grounding line).  In this regards, the first attached image comes from the following website, together with the associated summary statement below:
http://dimes.ucsd.edu/
"Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean, DIMES, is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.
The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.
Schematic representation of Southern Ocean meridional overturning circulation. The isopycnal upwelling of Upper and Lower Circumpolar Deep Water (UCDW and LCDW, with sources in the North Atlantic) is supported by mean geostrophic mass fluxes below the level of topographic obstacles to the ACC and by mesoscale eddy-driven mass fluxes at mid-depth. The upwelled water changes density through air-sea-ice interaction. It then returns northward in the wind-driven Ekman layer to form Antarctic Intermediate Water (AAIW), and as Antarctic Bottom Water (AABW) in mean geostrophic flows. The magnitude of interior diapycnal mixing and the rate of along-isopycnal mixing are open for investigation and are the DIMES objectives."
The second attached figure provides an alternate representation of this upwelling of the warm CDW and clarifying that much (but not all) of this upwelling system is driving by the circumpolar winds that are partially sustained by the high atmospheric methane over Antarctica.
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Re: Antarctic Methane Concentrations
« Reply #44 on: June 21, 2013, 05:47:24 PM »
To many the following comment goes without saying, but at the risk of stating the obvious, I would like to note the following with regard to the second attached image for my reply #42 at 2:45am on June 21, 2013, of the trend of the Southern Annular Mode, SAM: 
As SAM is an oscillation it fuctuates about the indicated nonlinear trend line (the trend line is nonlinear because of the nonlinear influence of both the ozone hole and the GHG on promoting a positive SAM trend); but also the strength and latitude of the circumpolar winds (implied by the SAM index value) is strongly influence by interactions with the ESNO index. For example the highest (most positive) SAM value shown is for the 1997-1998 season which is as the period of the last strong El Nino event when much of the damage was done to the ice shelves in the ASE by warm CDW (caused by upwelling), and which also temporarily accelerated ice mass loss (VAF) from both PIG and TG.  Thus when the current El Nino hiatus period ends, we may well experience the return of exceptionally positive SAM values (particularly if continued venting of methane into the Antarctic atmosphere continues to drive up the SAM trend line).
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Re: Antarctic Methane Concentrations
« Reply #45 on: June 24, 2013, 08:16:10 PM »
I thought a glimpse at the recent readings of three elements in the Antarctic GHG and climate changes to come might be of interest. What follows first is the CH4 levels for June 22, 2013 am at 469 mb, with a possible high concentration of 2142 ppbv.

Second are the CO2 levels for June 22 2013 am at 469 mb and possibly up to 423.6 ppm.

The final images are the Antarctic surface temperature anomalies for June 22, 2013
« Last Edit: June 24, 2013, 08:23:37 PM by Apocalypse4Real »

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Re: Antarctic Methane Concentrations
« Reply #46 on: June 24, 2013, 08:18:19 PM »
Now the CO2 readings, from the same perspective. The highest possible reading is 423.6 ppm.

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Re: Antarctic Methane Concentrations
« Reply #47 on: June 24, 2013, 08:20:45 PM »
The final images are the Antarctic surface temperature anomalies for June 22, 2013.

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Re: Antarctic Methane Concentrations
« Reply #48 on: July 03, 2013, 04:54:18 PM »
In the way of a status report, the attached image (at 585 mb) indicates that the anomolously high atmospheric methane concentrations over Antarctica are continuing (although at concentrations that are a little bit lower than during the immediately past Austal Fall).
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Re: Antarctic Methane Concentrations
« Reply #49 on: July 11, 2013, 07:54:25 PM »
I would like to complement both Omar Cabrera and A4R on their excellent 3D methane tracker at the new website:

http://methanetracker.org

Omar Cabrera's reviews of the new website can be found at the You Tube links:

Video 1:
Video 2:

In the second You Tube video, Omar repeats his doubts that the recent high Antarctic atmospheric methane concentrations have their origins in marine methane hydrates, and expresses his believe that Albert Kallio's theory that heat from the asthenosphere may be decomposing methane hydrate beneath the EAIS, thus allowing this postulated release of methane to seep through the ice sheet directly into the atmosphere.

While I am very impressed by the 3D tool that Omar is creating at the methanetracker site; I respectfully, state my disagreement with Albert Kallio's theory, cited above.

It is my opinion that the Antarctic case is similar to that for the Arctic case (only shifted by 6 months to match the Austral seasons); where marine methane hydrate decomposition releases more methane as the seawater over the continental shelves warm-up by the end of summer (around February in the Antarctic), thereafter the atmospheric methane concentration increases due to the chemical reactions in the atmosphere as described below:

Antarctic atmospheric methane concentrations decrease from Austral Spring thru Summer, as the methane gets oxidized and converted to other gases.  Similarly, Antarctic atmospheric methane concentrations increase from Austral Fall thru Winter, as the cold temperatures limit chemical reactions between CO₂ and CH4.  The annual cycle is due to reactions with hydroxyl radicals, which is the dominant methane sink: The hydroxyl radical is produced in the atmosphere by sunlight, which explains the cycle. Hydroxyl oxidizes methane in a complicated network of reactions ending in CO2 and H₂O, as described at the following Wikipedia site:

http://en.wikipedia.org/wiki/Atmospheric_methane#Removal_proc

After gassing out from the Antarctic continental shelves, CH4 accumulates in the atmosphere during the Antarctic night but as the Sun returns to the Antarctic, UV + Hydroxil Radical convert atmospheric CH4 into CO2, H2O. See the following Wikipedia site:

 http://en.wikipedia.org/wiki/Hydroxyl_radical

In support of my position, I post the attached image from NOAA's website for 586mb on July 9th, 2013, showing that the Antarctic atmospheric methane concentration is now decreasing (it peaked in May); which makes sense if the cold slowed hydroxyl radicals are finally oxidizing the methane release from the oceans in the Austral Fall; while it makes no sense at all for the Albert Kallio theory based on heat from the asthenosphere, which theoretically should happen year round (not seasonally).  See also, my earlier posts in this thread on this topic.
« Last Edit: July 11, 2013, 08:36:31 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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