Thanks Andrew....maybe there's nevertheless something here..... First, to answer you, I think that Lovelock with his pipes idea also intended to promote coccolithophore growth - and thus DMS production - as well as pump down carbon, and I had always assumed that, whether intended or not, all the plans to increase PP at sea-surface would do this - but these are such blunt instruments & thus create all kinds of other problems.
.....So, what I was asking here was, rather: could there be a way to SELECTIVELY promote DMS without altering PP? In terms of your mentioning dust, Lovelock saw this and DMS feedbacks as interlinked (also methyl iodide, by the way), in his 'Modern Times' chapter of The Ages of Gaia (1988). In terms of what I'm now getting to, Lovelock mused in that same chapter: "The geophysiological system requires the production of dimethylsulfonio proprionate and the algae that make it. The difficult question is, How does this system become part of global climate regulation? The oceans become saltier when water freezes out as ice on the polar surfaces; this might lead to increased emission of dimethyl sulfide, increased cloudiness, and so a positive feedback on further cooling." But maybe locally the reverse is also true? Since the escape from salt stress through the use of betaines is the origin of the DMSP metabolism, in Lovelock's idea, then maybe some organisms like those mentioned below enjoy the ice bottom itself - and it seems that it is particularly around thin ice bottom..... A new source of dimethylsulfide (DMS) for the arctic atmosphere: ice diatoms by M Levasseur, M Gosselin, S Michaud Marine Biology (1994) We report the first evidence that pennate diatoms growing within the bottom layer of first-year ice in the Arctic produce significant amounts of particulate dimethylsulfoniopropionate (DMSP(p)) and dissolved DMSP+DMS. In 1992 in Resolute Passage, a tributary of Barrow Strait, DMSP(p) concentrations within the bottom layer of ice reached 1055 mg S m(-3) at the end of the vernal bloom, a value one order of magnitude higher than the maximum value reported in antarctic ice. Bottom-ice concentrations in DMSP(p) and DMSP(d)+DMS were significantly correlated with the abundance of the dominant pennate diatom Nitzschia frigida. Intracellular concentration in DMSP of ice algae was very low (0.001 pg cell(-1)) at the end of April when algae were light-limited and reached 1.17 pg cell(-1) in mid-May following an increase in light and algal growth. We calculate that the rapid release of the dissolved DMSP+DMS from the ice into surface waters following the ice break-up will generate a sea-to-air DMS flux of 0.7 mg S m(-2) d(-1), a pulse ten times higher than the mean arctic summer flux. We estimate that this 1-d pulse represents up to 5% of the annual DMS emission in the Arctic. Thus, maybe this could explain what John was mentioning? More broken up thin ice would be good for the diatoms growing on the thin ice bottom? Thus more DMS, more clouds, etc?....One could perhaps check this out with satellite data? In any case, the question arises for geoengineering: could one possibly promote this particular DMS-producer that enjoys the cold? Why does it like the thin ice bottom? I had once proposed 'prosthetic ice' - floats, that is - made for just the area where this ice- produced DMS is mostly coming from (according to the powerpoint I linked above) - down in the bering sea. Maybe to their albedo effect one could also get a DMS add on? Or could one just culture the Nitzschia and simply release them there? There's been plenty of talk about diatoms here before, but I don't remember its being from this DMS angle in particular..... But if Oliver has dealt with DMS engineering, maybe he could chime in? Cheers, Nathan On Nov 4, 7:09 pm, Andrew Lockley <andrew.lock...@gmail.com> wrote: > From recollection Oliver wingenter proposed DMS geoengineering. > > Aeolian dust deposition into the southern ocean in a cooler, drier > environment has been proposed as a limited runaway cooling feedback > mechanism at the start of an ice age. Whilst co2 drawdown by algae is a > given, my understanding is that the role of DMS in feedback is less well > understood. > > A > > On Nov 4, 2011 10:53 PM, "Nathan Currier" <natcurr...@gmail.com> wrote: > > > > > > > Hi, John - Could it be related to DMS production there? > > Although in the complex of things one could imagine it working the > > other way (i.e. in ice cores DMS, I believe, is ~5x higher during > > glacials) > > some models predict arctic DMS will actually increase a good deal as > > it warms..... > > > being familiar w/ Lovelock's ideas on the evolution w/ DMS and the > > cycling of S, > > where one might imagine melting ice leading to less saline water, > > leading to > > less DMS, it all seems counterintuitive.......but maybe it could > > somehow be a candidate? > > > But this makes me wonder: has DMS stimulation been proposed before, as > > a means of geoengineering the arctic > > climate?? After all, it is a potent climate modifier globally. The > > CLAW hypothesis, almost 25 years ago now, > > originally estimated that DMS' effect could be as big as the CO2 > > greenhouse in reverse..... > > w/ lots of debate since then..... > > > I've never thought of it much as an arctic > > tool - but the link to the powerpoint below ends w/ this estimate: > > > Use of a climate model to force ocean DMS model in Barents Sea (Gabric > > et al. 2005): > > - By the time of equivalent CO2 tripling (2080) > > zonal annual DMS flux increase: >80% > > zonal radiative forcing: -7.4 W/m2 > > >http://www.whoi.edu/fileserver.do?id=76944&pt=2&p=83808 > > > Of course, I'm sure it's complicated and could have many of the same > > issues as > > iron filings used to seed C pumping, but maybe it could work better, > > if algae added right at the surface > > could add to DMS production? > > > cheers, > > > Nathan > > > On Nov 3, 8:01 am, John Nissen <j...@cloudworld.co.uk> wrote: > > > Hi all, > > > > Peter Carter kindly sent me the URL for a JGR paper [1], while at the > > > Arctic methane workshop (Chiswick, 15-16th October) our sea ice expert, > > > Peter Wadhams, was supporting the PIOMAS model of sea ice volume [2], > > > with trend lines added here [3]. > > > > It is astonishing that the JGR paper seems to ignore the PIOMAS model of > > > sea ice volume, with a trend line for September pointing to zero volume > > > in 2015 with range 2013-2018 [4]. However the paper might help to > > > explain why models of sea ice extent have been absurdly optimistic about > > > the lifetime of the sea ice. It is interesting about the drift factor - > > > ice drifting more as it thins. Could this be the main reason why sea > > > ice extent appears to hold up while the volume is declining - the gaps > > > between bits of ice not showing up in the satellite data? Or perhaps > > > the ice becomes mushy and spreads out evenly to avoid gaps whilst > > > appearing to maintain or even increase its extent? > > > > What we really don't know is what the end game will look like, as sea > > > ice volume approaches zero. Will it just take a wind from the north to > > > blow the broken ice into warmer water and for it to melt away? Or will > > > polynias [5] start appearing all over the place and grow until there's > > > no ice left between them? > > > > However something we noticed at the workshop was a bounce affect: that > > > the year following a big retreat in extent tends to have less retreat > > > than average of the following years, and vice versa. It's as if, from > > > time to time, the extent is kicked out of the trend line but then > > > bounces back to the other side of the line the next year. I think this > > > could be shown to be statistically significant, although the effect was > > > only picked up by eyeballing the graph of sea ice extent (September > > > minimum?) since satellite records began in 1979. An explanation of > > > this effect could help our understanding or what's happening, and point > > > to ways that the sea ice retreat might be halted more effectively. > > > There seems to be some hitherto unrecognised negative feedback in the > > > system which could be exploited perhaps. > > > > One possible negative feedback could be how, as sea ice retreats, the > > > open water produces more thermal radiation than ice. Thus if there is > > > more open water one year, the water is cooled to cause less melt the > > > following year. Just an idea. But if this is happening, then we might > > > find a way to exploit the effect through creating/keeping more open > > > water at the end of the melt season or by letting more of the thermal > > > radiation escape into space (e.g. cloud removal?). > > > > An alternative explanation of the bounce could be some kind of "Arctic > > > oscillation", where the weather patterns occasionally move to an extreme > > > polarity in one year but then tend to recoil to the opposite polarity > > > the next year. > > > > But we must not rely on some unexplained, unconfirmed negative feedback > > > to slow the retreat over the next few years; instead we must assume that > > > positive feedback increases as the sea ice is replaced by open water, > > > and there could be a final burst of positive feedback when the sea ice > > > gets very thin and breaks up. (While the minimum sea ice extent has > > > remained around the 2007 level, each year since then, there has been > > > less positive feedback than would be expected from the volume trend.) > > > > Thus what remains clear is that we have to do our utmost to prevent the > > > sea ice disappearing even for one month of the year, because then we'll > > > be into unknown territory with the possibility of irreversible Arctic > > > warming with catastrophic consequences. Unless the PIOMAS trend to zero > > > volume from [4]is proved to be far too pessimistic by hard evidence, we > > > have to be prepared and ready to deploy cooling techniques on a large > > > scale in spring 2013, only 15 months away, if humanly possible, to halt > > > the sea ice retreat. This is a tremendous challenge. Can we rise to > > > it? We'll have to all pull together. And it may be necessary to use a > > > combination of techniques to maximise our chance of success. > > > > Cheers from Chiswick, > > > > John > > > > [1]http://www.agu.org/pubs/crossref/2011/2011JC007110.shtml > > > > [2] > > http://psc.apl.washington.edu/wordpress/research/projects/arctic-sea-... > > > > [3] > > http://neven1.typepad.com/blog/2011/10/piomas-september-2011-volume-r... > > > > [4]http://neven1.typepad.com/.a/6a0133f03a1e37970b0153920ddd12970b-pi > > > > [5]http://en.wikipedia.org/wiki/Polynya > > > > --- > > > > On 02/11/2011 20:34, PR CARTER wrote: > > > > >http://www.agu.org/pubs/crossref/2011/2011JC007110.shtml > > > -- > > You received this message because you are subscribed to the Google Groups > > "geoengineering" group.> To post to this group, send email to > geoengineering@googlegroups.com. > > To unsubscribe from this group, send email to > > geoengineering+unsubscr...@googlegroups.com.> For more options, visit this > group at > > http://groups.google.com/group/geoengineering?hl=en. > > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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