Mixing alone is likely to make very little difference to overall CO2 levels, and as such does not seem to be a viable approach. However, ocean mixing as a means of transporting nutrients may boost plankton growth if done correctly, and the manner in which it is done will affect CO2 transport. If the nutrient-rich water is more CO2 saturated than the atmosphere, then clearly it will lead to a temporary pulse of carbon into the atmosphere before the sequestration effect kicks in (I have a referenece for this if anyone needs it). If the lower level water is less saturated than the atmosphere, there will be an additional drawdown of CO2 by solution, in addition to the biological capture of dissolved CO2 in surface water by plankton. Whether or not the deep water has a surplus or not of CO2 relative to the atmosphere determines the likely mixing methods.
For a CO2-rich stream, you would want to dump the deep stream into the surface layer without much contact with the atmosphere, and possibly slightly below the surface itself. The system I've found from www.solarbee.com can lift 300 tph for a price of $70K per unit in this manner. These prices would obviously come down dramatically if a simpler and mass produced design was used. For a CO2-poor stream, you'd want to maximise contact with the atmosphere during the lift. This could be accomplished by using a bubble tube to lift the stream instead of an impeller. Alternitely, it may be worthwhile splashing or spraying the stream water into the ocean to maximise contact area. I know next to nothing about ocean biological chemistry, so the composition of suitable waters for nutrient mixing and the depth from which they may be obtained is best left to others. A 2009/1/16 dsw_s <[email protected]>: > > It sounds as though we need to distinguish between different areas of > ocean, and possibly different depths. Water that has been in the > depths for a thousand years, receiving organic material settling from > above, is obviously going to be supersaturated with CO2 relative to > air. Ventilating such water will put more CO2 into the air. Deep > water in areas of net downward motion, on the other hand, would > presumably be close to the amount of CO2 it had when it was > equilibrium with air a few decades or centuries ago. Ventilation of > that water would presumably take some additional CO2 out of the air, > by putting it in equilibrium with the higher current CO2 level. > > Oliver -- If you upload the paper you want me to read, I'll download > on the Files page. Or if you're referring to the one that you already > put there, I'll have a look at it now. > > I'm not doubting that we can mix water for relatively little energy > per cubic meter of water, nor that waves are a viable source of > energy. What I'm questioning is the amount of mixing needed to > sequester a climatically significant amount of carbon. If I'm > understanding correctly, the water would gain rather little CO2, > having been in equilibrium with air that differed by only a modest > factor from current levels. Meanwhile, the amount of carbon to be > dealt with is in the gigatons. Even if there's plenty of unsaturated > water waiting to be mixed, the amount of water that would have to be > moved seems likely to be bigger than what we can do mechanically. > > On Jan 15, 11:37 am, Greg Rau <[email protected]> wrote: >> I don't want to belabor this (perhaps we should >> continue off-line), but if you are advocating >> "sparging" the subsurface ocean with air this >> will proceed to strip the excess subsurface ocean >> CO2 into the atmosphere. Granted, the bubbles >> will also increase nutrient advection to the >> surface, but is the (presumed) ensuing enhanced >> bio CO2 fixation (and more importantly, organic C >> export back to the subsurface ocean) larger or >> smaller than the CO2 you've just injected into >> the atmosphere? My hunch is that sparging might >> be a good idea for avoiding an ice age, but not >> such a good idea for reducing global warming. >> Sparging would also reduce ocean acidity (elevate >> pH), to the extent that the induced ocean-->air >> CO2 transfer is permanent. Other viewpoints? >> Regards, >> Greg >> >> >Surely the effect detailed below will affect ALL plans to aid Ocean >> >mixing. The outgassing has nothing to do with the use of bubbles to >> >move the water - the bubbles can't possibly release more gas than a >> >comparable non-bubble technique. >> >> >A >> >> >2009/1/15 Mike MacCracken <[email protected]>: >> > > Andrew--Greg is right--and warming of ocean near surface would also >> > force >> >> CO2 out, so maybe do at high latitudes where it is cold and encourage >> >> marine >> >> life. >> >> >> Mike >> >> >> On 1/14/09 7:25 PM, "Andrew Lockley" <[email protected]> wrote: >> >> >>> Any outgassing of the deep ocean water when it rose to the surface >> >>> would only release gases added during the aeration process. Unless >> >>> the existing ocean water was supersaturated, then there shouldn't be >> >>> any additional outgassing. I don't have the expertise to advise >> >>> whether there are supersaturated CO2 layers in the ocean. >> >> >>> A >> >> >>> 2009/1/14 Greg Rau <[email protected]>: >> >>>> Perhaps I've missed something, but if you are advocating increased >> >>>> ventilation of the subsurface ocean, this water is not only nutrient >> >>>> rich, >> >>>> but is is also supersaturated in CO2 (relative to air). Natural ocean >> >>>> upwelling is a huge CO2 source for the atmosphere. So unless you can >> >>>> show >> >>>> that stimulation of biological CO2 fixation (via the nutrient >> >>>> upwelling) >> >>>> more than offsets the upwelled CO2 degassing to the atmosphere, what's >> >>>> the >> >>>> point? >> >>>> -Greg Rau >> >> >>>>> A simple way to achieve this would be to force air down into deep >> >>>>> pipes and allow it to bubble to the surface. The same principle is >> >>>>> used in fishtanks to create upwelling water and increase the surface >> >>>>> area for gaseous exchange. There's a tradeoff between little bubbles >> >>>>> (for gaseous exchange) and big bubbles (to force mixing). >> >> >>>>> Flow tubes would probably be necessary to create a defined upwelling >> >>>>> column of water. These tubes would provide a reasonably good mount >> >>>>> for a wind turbine or sea turbine, provided they could be anchored to >> >>>>> the sea bed. The most obvious engineering problem I can think of is >> >>>>> stability and resonances. >> >> >>>>> What do other people think? >> >> >>>>> A >> >> >>>>> 2009/1/13 John Nissen <[email protected]>: >> >> >>>>>> Hi all, >> >> >>>>>> Could there be a case for geoengineering to increase sea >> >>>>>> "ventilation" >> >>>>>> and >> >>>>>> thereby increase CO2 absorption by the sea? (I'm thinking of those >> >>>>>> millions >> >>>>>> of wave-powered tubes suggested by Chris Rapley and James Lovelock >> >>>>>> to >> >>>>>> bring >> >>>>>> deep cool water to the surface.) >> >> >>>>>> http:// www. >> >>>>>> >> >>>>>> guardian.co.uk/environment/2009/jan/12/sea-co2-climate-japan-environment >> >> >>>>>> --- >> >> >>>>>> Sea absorbing less CO2, scientists discover >> >> >>>>>> David Adam, environment correspondent >> >>>>>> The Guardian, Monday 12 January 2009 >> >>>>>> Article history >> >> >>>>>> Scientists have issued a new warning about climate change after >> >>>>>> discovering >> >>>>>> a sudden and dramatic collapse in the amount of carbon emissions >> > >>>>> absorbed by >> >>>>>> the Sea of Japan. >> >> >>>>>> The shift has alarmed experts, who blame global warming. >> >> >>>>>> The world's oceans soak up about 11bn tonnes of human carbon dioxide >> >>>>>> pollution each year, about a quarter of all produced, and even a >> >>>>>> slight >> >>>>>> weakening of this natural process would leave significantly more >> >>>>>> CO2 in >> >>>>>> the >> >>>>>> atmosphere. That would require countries to adopt much stricter >> >>>>>> emissions >> >>>>>> targets to prevent dangerous rises in temperature. >> >> >>>>>> Kitack Lee, an associate professor at Pohang University of Science >> >>>>>> and >> >>>>>> Technology, who led the research, says the discovery is the "very >> >>>>>> first >> >>>>>> observation that directly relates ocean CO2 uptake change to ocean >> >>>>>> warming". >> >> >>>>>> He says the warmer conditions disrupt a >> >>>>>>process known as "ventilation" - >> >>>>>> the >> >>>>>> way seawater flows and mixes and drags absorbed CO2 from surface >> >>>>>> waters >> >>>>>> to >> >>>>>> the depths. He warns that the effect is >> >>>>>>probably not confined to the Sea >> >>>>>> of >> >>>>>> Japan. It could also affect CO2 uptake in the Atlantic and Southern >> >>>>>> oceans. >> >> >>>>>> "Our result in the East Sea unequivocally demonstrated that oceanic >> >>>>>> uptake >> >>>>>> of CO2 has been directly affected by warming-induced weakening of >> >>>>>> vertical >> >>>>>> ventilation," he says. Korea argues that the Sea of Japan should be >> > >>>>> renamed >> >>>>>> the East Sea, because it says the former >> >>>>>>is a legacy of Japan's military >> >>>>>> expansion in the region. >> >> >>>>>> Lee adds: "In other words, the increase in atmospheric temperature >> >>>>>> due >> >>>>>> to >> >>>>>> global warming can profoundly influence the ocean ventilation, >> >>>>>> thereby >> >>>>>> decreasing the uptake rate of CO2." >> >> >>>>>> Working with Pavel Tishchenko of the Russian Pacific Oceanological >> >>>>>> Institute >> >>>>>> in Vladivostok, Lee and his colleague Geun-Ha Park used a cruise on >> >>>>>> the >> >>>>>> Professor Gagarinskiy, a Russian research vessel, last May to take >> >>>>>> seawater >> >>>>>> samples from 24 sites across the Sea of Japan. >> >> >>>>>> They compared the dissolved CO2 in the seawater with similar samples >> >>>>>> collected in 1992 and 1999. The results showed the amount of CO2 >> >>>>>> absorbed >> >>>>>> during 1999 to 2007 was half the level recorded from 1992 to 1999. >> >> >>>>>> Crucially, the study revealed that ocean mixing, a process required >> >>>>>> to >> >>>>>> deposit carbon in deep water, where it is more likely to stay, >> >>>>>> appears >> >>>>>> to >> >>>>>> have significantly weakened. >> >> >>>>>> Announcing their results in the journal Geophysical Research >> >>>>>> Letters, >> >>>>>> the >> >>>>>> scientists say: "The striking feature is that nearly all >> >>>>>> anthropogenic >> >>>>>> CO2 >> >>>>>> taken up in the recent period was confined to waters less than 300 >> >>>>>> metres in >> >>>>>> depth. The rapid and substantial reduction ... is surprising and is >> >>>>>> attributed to considerable weakening of overturning circulation." >> >> >>>>>> Corinne Le Quéré, an expert in ocean >> >>>>>>carbon storage at the University of >> >>>>>> East Anglia, said: "We don't think the >> >>>>>>ocean is just going to completely >> >>>>>> stop taking our carbon dioxide emissions, >> >>>>>>but if the effect weakens then >> >>>>>> it >> >>>>>> has real consequences for the atmosphere." >> >> >>>>>> --- >> >> >>>>>> Cheers, >> >> >>>>>> John > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
