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William Calvin

Mar 5, 2013
03:36

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There is no slot on the template for discussing Pro and Con, nor is there space for known objections. So I will start the comments with a FAQ featuring some of the questions that have arisen in the four years that I have been presenting this to knowledgeable audiences. Q: Won't it pollute? A: Perhaps not as proposed here, using local algae and nutrients, but the usual considerations would apply should we want to introduce exotic or modified algal species to achieve even higher rates of sinking fossil carbon. Note that this "plowing under" has few of the characteristics of algae-based fuel proposals. They are concerned with algal species with rich oil content, notoriously fickle about temperature and packing density. They want to harvest them, not bury them.

William Calvin

Mar 5, 2013
03:03

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Q: Won't anoxic "dead zones" form? A: Shallow continental shelf sites should be avoided because hypoxia will occur from the decomposition of the downwelled organic carbon in a restricted volume. Fish kills occur when anoxia develops more quickly than fish can find their way out of the increasingly hypoxic zone; however, a maintained hypoxic zone will mostly repel fish that stray into it. Plumes serve to quickly spread out the oxidation targets.

William Calvin

Mar 5, 2013
03:34

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Q: We don't know what will happen. A: The novelty here is minimal, even less than for iron fertilization. Fertilizing and sinking surface waters merely mimics, albeit in new locations or new seasons, those frequently studied natural processes seen on a large scale in winter mixing and in ocean up- and down-welling. To some extent, their history at a candidate site can be studied in cores of the ocean floor. There is also prehistorical precedent. The 80 ppm drawdown of atmospheric CO₂ in the last four ice ages is thought to have occurred via new greenery on the exposed Continental Shelf and by enhanced ocean productivity triggered by a major reduction in the Antarctic offshore downwelling that re-sinks some of the nutrient-rich waters brought to the surface by the circumpolar winds:
Toggweiler JR, Murnane R, Carson S, Gnanadesikan A, Sarmiento JL (2003) Representation of the carbon cycle in box models and GCMs, 2, Organic pump. Global Biogeochem Cycles 17:1027, doi:10.1029/2001GB001841

William Calvin

Mar 5, 2013
03:57

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Q: Won't this just move the ocean acidification problem into the depths? A: Since the depths are 98% of ocean volume, there is a fifty-fold dilution of the acidity. If counteracting out-of-control emissions were to continue for a century, depth acidification might be more of a problem.

William Calvin

Mar 5, 2013
03:28

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Q: Won't pumping just bring up water with higher CO₂ than in the surface waters? A: A depth difference of, say, 80 μmol/kg means that upwelling a cubic meter of seawater brings up an unwanted 0.96 g of inorganic carbon. However, pumping down the same volume sinks 1 gC of potential CO₂ as DOC, even without fertilization enhancements. Push-pull pumping can overcome the well-known problems of up-only pumping.

William Calvin

Mar 5, 2013
03:24

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Q: To sink it all, aren’t you going to run out of phosphate, what currently limits the global ocean productivity to a fraction of its potential capacity? A: River outflows are the main source of near-surface phosphates. Rivers in higher latitudes, where the SST is low enough for the algae to thrive (say, the Rhine, Hudson, St. Lawrence, and north-flowing rivers) would continue to supply enough PO4 locally. Up-pump pipes could also be sited to bring up AABW bottom waters from the southern oceans that are currently rich in phosphate.

William Calvin

Mar 6, 2013
02:53

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Q: Is that really permanent storage of the excess CO2? A: No, but once below the winter thermocline, it takes about 1,000 years to begin resurfacing. After that, the 600 GtC is likely to be spread out over more than 6,000 years. So re-emissions are delayed and then come up at 0.1 GtC/yr, an amount that could be handled by forest management if advanced technologies were not available. It's like an annuity: big deposit up front (600 GtC over 20yr), then a delay, then steady payouts.

Guy Dauncey

Mar 14, 2013
02:09

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Some people may react by saying that this is ridiculous, or impossible. But it's no more impossible than the first trip to the Moon, and we'd be blind fools not to engage in trials, as William is suggesting. The scenarios that are suggested in the opening paragraphs are scarily possible; the Arctic is already burping methane both the melted waters and from the permafrost. This needs to be trialled, in addition to the 1001 other solutions.

Robert Tulip

Jun 15, 2013
07:51

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I would like to see this proposal combined with the Offshore Membranes Enclosures for Growing Algae (OMEGA) project designed by NASA Ames Research Center. My sketches at rtulip.net illustrate how we can use tide and wave power to augment the effectiveness of this CO2 drawdown method.

2013geoengineeringjudges 2013geoengineeringjudges

Jul 5, 2013
11:05

Judge


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Thank you for the proposal. Please find below an integrated set of comments and additional comments on your proposal from two reviewers. Integrated Comments In general, the concept of push pull pumping is perceived to be novel. The key difficulties with your proposal involve questions about ocean biogeochemistry that would need to be addressed as the proposal moves forward. First, the rate of CO2 dissolution in ocean water would seem to be far too small to have the impact on atmospheric CO2 that is envisioned in the proposal. Can this be addressed by increasing the area of these plantations? Or are there solutions to enhance gas exchange rates by large enough magnitudes to make what is proposed feasible? Would such solutions facilitate the achieving of more modest objectives? Another basic difficulty relates to the fact that deeper ocean is rich in CO2. For this reason it is hard see how increasing vertical mixing between shallow and deep waters will achieve the goals. What would seem to be required for the idea to work is to improve the efficiency of the biological pump, not just to increase vertical mixing to bring more nutrients to the surface. These points really need to be addressed for the proposal to be considered feasible. Another important issue is the depth to which carbon needs to be moved in order to be sequestered, and so prevent the long-term release of CO2 back into the atmosphere. Are there modifications that can be made to address this problem? Furthermore, the proposed activity would increase ocean acidification. Are there solutions to neutralize this effect that could be part of the proposal? Another set of issues raised has to do with the engineering viability of aspects of the solution such as freely floating off-shore windmills. Is this really practical? Questions that arose in reviewer discussions concerned whether introducing organisms such as zooplankton could improve the effectiveness of what is being proposed, and whether harvesting the biomass production for biofuels might also be part of the solution. One possible context within which these suggestions by the reviewers might be addressed in the proposal could be to consider the energy costs of constructing and maintaining these plantations. Presumably fossil energy will have to be used to an extent in the scheme that is being proposed, and biofuels harvested from the process could substitute some part of this. A viewpoint on these questions could strengthen the proposal, but only after the critical questions about biogeochemistry that have been raised by the reviewers have been addressed. We encourage you to address these comments by the reviewers as best as you can while revising the proposal during the next phase of the contest. Reviewer 1: This proposal misses a couple of points which would prevent it having much, if any, impact on the atmospheric CO2 concentration.   The first issue is gas exchange, the process of CO2 dissolving in ocean water, which is pretty slow.  A typical gas exchange "piston velocity" is 3-5 meters per day, meaning that under usual wind/wave conditions, the CO2 concentration of this much water would equilibrate with the atmosphere if it were unbuffered.  Let's assume that the surface seawater is completely depleted in CO2.  The equilibrium CO2 concentration is about, generously, 20 micromolar.  Taking these numbers and the author's claim of Lake Michigan area (3E10 m2), I get an uptake rate of about 0.01 Gton C per year.  Another "reality check": the global gas exchange flux with the ocean is about 100 Gton C per year over an area of 3.5E14 m2.  Taking half of that (for the ingassing part) and scaling down to Lake Michigan cuts it to 0.1 Gton C per year.  Either way it's small unless it's enhanced by bubblers, which the author did not mention.  The gas exchange problem is exacerbated by the fast time scale for pushing the water back down in the water column.  The second difficulty is the fact that deep waters of the ocean are high in CO2, which came from the same plankton that brought the nutrients.  Seawater when it subducts has some unused nutrients in it, called "preformed" nutrients, and let's say that it's also close to atmospheric equilibrium with CO2.  In order for the water to be pulled below equilibrium with atmospheric CO2, the nutrient concentration has to be brought down below the "pre-formed" concentration.  If all you do is bring deep water up and let plankton bloom, but don't insist that they actually deplete the nutrients completely, surface pCO2 values would be higher in the patch than outside, and you'd be releasing CO2 to the atmosphere.   The idea would sequester carbon through the initial spike period, but the atmosphere and ocean would eventually equilibrate, preserving the "long tail" of the fossil fuel lifetime in the atmosphere.   Reviewer 2: The scale of the problem could be limited to just the current rate of emissions and projected into the future. Here I refer this proposal and others in the MIT program to a novel presentation in the text by Spiro, et al. (2012) Environmental Chemistry (Sec. 11.7). He reviews an article by Pacala and Socolow, Science 2004 on how to practically control “wedges” of increased carbon dioxide production to prevent a doubling in the atmosphere over the next fifty years. The bottom line is that massive energy conservation implementation alone could reduce almost half of the projected increase, followed by massive installation of renewable wind and photovoltaic capacity (in this proposal referred to as a “second Manhattan project”). An analysis presented subsequently by McKinsey and Company, 2009 suggest 35% reduction of current levels and 70% reduction by 2030 at < 1% of GDP and current defense budget. This would leave only 480 ppmv carbon dioxide in the atmosphere with < 2 deg C of atmospheric heating. Deep sea removal of carbon dioxide is not practical unless the carbon is carried below the seasonal thermocline of liquid phase retention (500 meters), or major thermocline for long term organic carbon removal as either dominant DOC or POC (1000 meters). Before “pumping down” fixed carbon, biomass should be processed first for sustainable hydrocarbon production, thus offsetting fossil fuel emissions. The release of carbon dioxide from the ocean as concentrations decrease in the atmosphere is not of the same time scale because the carbonic acid system is not strictly reversible due to kinetics of carbon dioxide hydration. Besides, the excess gas will be rapidly consumed by the surface ocean biosphere for potential benthic export. Any attempt at carbon dioxide clean up should preferentially focus on the current rise of emission rates. To implement the reciprocal pumping mechanism, reference should be made to the implementation of OTEC and preferred locations of cool nutrient rich waters at reasonable depths. Freely floating windmills with long tethers will be physically challenged enough off shore. The diagram refers to a wave pump, while the text refers to a wind pump that is currently designed to generate electrical power that could be used for pumping as well or hydrogen as a fuel cell reactant. I am not sure the numbers keep full account of new production, net of respiration. The large area of the pump “plantations” required to “sink the carbon soup” could be more confined if integrated as aquaculture in the large scale production facilities. Including zooplankton would have the benefit of producing larger sinking POC. Certainly the cost of construction and maintenance of such plantations will be considerable and not carbon neutral. Water at the shelf break will not naturally “be carried over a cliff”, rather a potential of relatively shallow nutrient rich cold pool water to be pumped up for aquaculture. As such one could exploit systems off shelf sewage disposal already implemented. The actions taken will require international approaches that include value added carbon taxes for atmospheric disposal as waste space, besides traded commodity credits. So should this Second Manhattan Project be waged using saved defense money on a War against Climate Change, the real global terror?

William Calvin

Jul 6, 2013
07:35

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[Reviewer One’s: "This proposal misses a couple of points which would prevent it having much, if any, impact on the atmospheric CO2 concentration." • The slow rate that air CO2 dissolves into seawater. “Either way it's small unless it's enhanced by bubblers, which the author did not mention.”] Slow uptake is indeed a potential limitation which I only briefly addressed: "Sufficient wave action to bury air bubbles may be needed to move enough CO₂ into surface waters to maintain high productivity." And later at "Windmills... can optionally create compressed air to aerate surface waters or hypoxic depths." Slow air-water transfer needs to be addressed in the site selection phase of the Second Manhattan Project (“2ndMP”) by real experts, not by me within a 2,000-word limit. The whitewater of the high southern latitudes might be needed, or the calmer “Pacific” might suffice. • Another basic difficulty relates to the fact that deeper ocean is rich in CO2. For this reason it is hard see how increasing vertical mixing between shallow and deep waters will achieve the goals. Mixing is what this proposal avoids. The push-pull process is not mixing; rather, it is organized convection (or bulk flow, as we physiologists call it). One pulls up nutrient-rich deep water in one pipe and then pushes new DOC, POC, and cells down another pipe. The resulting plume is at a different depth than intake pipes, so layer mixing on the millennial time scale is avoided. (The usual two compartment models can mislead when there are plumes in moving water.) Apropos the unwanted CO2 pulled up: see my Comment #5 in the seven-part FAQ. “Q: Won't pumping just bring up water with higher CO₂ than in the surface waters? A: A depth difference of, say, 80 μmol/kg means that upwelling a cubic meter of seawater brings up an unwanted 0.96 g of inorganic carbon. However, pumping down the same volume sinks 1 gC of potential CO₂ as DOC, even without fertilization enhancements. Push-pull pumping can overcome the well-known problems of up-only pumping.” • What would seem to be required for the idea to work is to improve the efficiency of the biological pump, not just to increase vertical mixing to bring more nutrients to the surface. Enhancing the biological pump is exactly what the push aspect of push-pull achieves by piping DOC as well as POC into the slowly circulating depths. It took me awhile to realize that sinking living cells might be a minor aspect of what push-pull pipes can achieve. • Are free-floating windmills practical? Perhaps, but note that I said, after introducing windmills, "But there are a number of ways to achieve wind-or-wave-powered pumps, both up and down, such as Isaacs’ buoyed one-way pipes and Salter’s elevated ring to capture wave tops and create a hydrostatic pressure head for pushing surface waters into the depths." Both look to be cheaper than windmills. There are serious windmill designs out there, for offshore electricity production, which could be simplified for pumps and compressed air. The multi-spoked base that they need to control tipping in the wind could be enclosed by skirts to concentrate production, another issue for the 2ndMP chemostat experts. • Combine with biofuel plantations? I cannot agree with Reviewer Two’s prescription: “Before 'pumping down' fixed carbon, biomass should be processed first for sustainable hydrocarbon production, thus offsetting fossil fuel emissions.” The push-pull cleanup would certainly stimulate the technology useful for subsequent commercial development, in the manner of the US space program. The serious problem with doing commercial first is what the time frame now requires: effective reduction in extreme weather within several decades. Grow-your-solution incremental (what I too would have suggested thirty years ago) will no longer do the job quickly enough. • Questions that arose in reviewer discussions concerned whether introducing organisms such as zooplankton could improve the effectiveness of what is being proposed, and whether harvesting the biomass production for biofuels might also be part of the solution. I have considered such but, for strategic reasons, I have avoided including them here, on the premise that exotic (or genetic-mod) phytoplankton may not be needed if local sunken nutrients suffice with the local algae. Unnecessarily introducing agricultural-pollution issues at this point could delay climate solutions that must be big, quick, and sure-fire. Reviewer Two's "Any attempt at carbon dioxide clean up should preferentially focus on the current rise of emission rates." That has been the plan for decades and it has yet to work. Note that reducing emissions (a rate) only slows the CO2 buildup (a quantity), leaving nature's slow processes to do the cleanup. There are many worthwhile ways of reducing emissions but none is likely to do the job in the time frame of an emergency cleanup, which is what I am addressing here. There are hazards to providing a specific mechanistic example, and so I warned, "What follows is an idealized example of how we might implement the equivalent of plowing under a cover crop." I do not expect the product of the 2ndMP to look much like my idealized example. What I wish to get across with it is that we still have a chance at executing a big-quick-secure CO2 cleanup by exploring variations on this theme.

William Calvin

Jul 17, 2013
12:24

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A note to those concerned about the numbers: 1) Engaging in a quick ballpark check on the numbers by using a two-compartment equilibrium model has led a number of people astray. The water is flowing a la Heraclites but the pumps are tethered. Pumping up creates a plume of nutrients at the surface; pumping DOC, POC, and new greenery down creates a slower plume (at a different depth than any downstream up-pump’s intake). The laminar plume has a high surface-to-volume ratio and is surrounded by water with the usual oxygen content. The plumes are only 20 years long, only 1 percent of recirculation time. Thus input and output will not mix as in two-box models unless the project is continued for many millennia. 2) Similarly it is often observed that pumping up will bring up unwanted CO2, but push-pull pumping means that much more potential CO2 is pushed down than brought up, overcoming the objection.

Hank Roberts

Jul 17, 2013
06:00

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Amateur reader question -- would this attract the krill harvesters? Finance is attracted to projects where they can make a killing -- make money fast. Will this look like you're making a harvestable, profitable product and just sinking it, to those with the short-term-profit viewpoint? And if there's a harvestable product will the whales also come to feed there? (Which -- since whale poop is a good fertilizer -- would be a benefit, perhaps) Just guessing here

2013geoengineeringjudges 2013geoengineeringjudges

Jul 31, 2013
02:54

Judge


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To reduce the atmospheric CO2 concentration and thereby reduce CO2-induced global warming, this proposal envisions pulling excess nutrients up to the surface layer from up to a kilometer depth, using sunlight to power biomass growth in order to draw down and tie up CO2 present in the upper ocean before subsequently sinking the biomass to the ocean depths. The intention is that lower upper ocean CO2 concentration would lead to ocean uptake of CO2 from the atmosphere in areas where the biomass is being grown. (Furthermore, due to the natural redistribution of excess CO2 among fast reservoirs that would result from reducing the atmospheric CO2 concentration, this would also lead to uptake of CO2 from the terrestrial biosphere and other areas of the upper ocean). There are several fundamental problems that the proposal needs to overcome: (a) bringing up nutrient-rich water from depth brings up water supersaturated in CO2 that would normally be released to the atmosphere, especially as the water warms at the surface; (b) as the biomass grows and pulls down the upper ocean CO2, the transfer of CO2 from the atmosphere to the ocean can be slow compared to what would be required to implement such an approach to draw down atmospheric CO2 [it might seem that, once started, CO2 replenishment of CO2 taken up by the increased biological activity could come from bringing CO2-rich deep water to the surface at the right rate, but the goal is to be pulling CO2 from the atmosphere]; (c) it requires energy to pull up and push down the waters, and doing so on a reliable basis from wind power may prove difficult, which would disrupt the important timing of the various steps; and (d) the benefit to offset the cost is, in essence, postulated to come from reducing the rate of climate change rather than generating revenue by selling the biomass as a fuel that would reduce the pace of fossil fuel extraction as a source of energy, and this would require a very large implementation to actually limit the pace of climate change, and the effectiveness of such a large effort would furthermore be limited by difficulties such as raised in (a) and (b) above. Whether clever engineering could work out these problems was not clear to the expert reviewers as it was to the proposer. Members of the Climate CoLab community are also invited to read a more comprehensive set of “Comments by Expert Reviewers on the Geoengineering Proposals” at http://climatecolab.org/resources/-/wiki/Main/Comments+by+Expert+Reviewers+on+the+Geoengineering+Proposals

William Calvin

Aug 1, 2013
02:08

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Both the revised proposal and my Comment on the reviewers' first expert comments showed that "problems" a) and b) were not the problems that they first appear to be. Apropos c), I would add that wave-based pumping ought to be less fickle than the local winds as waves are generated by winds over a far larger area ("reach"). Problem d) is essentially a promotion of a different class of climate actions, useful but slow, not a critique of this one.

Dennis Peterson

Aug 1, 2013
03:41

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As long as you're pulling water from the deep ocean anyway, would it be feasible to use an OTEC as the energy source? It extracts energy from the temperature difference between shallow and deep water. Lockheed is working on a 10MW plant in Hawaii, and planning to expand to 100MW. http://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion

Hank Roberts

Aug 24, 2013
05:59

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I asked a knowledgeable friend why Dr. Calvin's proposal could be lagging so far behind other -- in my opinion less promising -- proposals. His answer was -- because this one can be done -- right now. He thought the vaguely possible notions attract more votes than the do-it-right-now option, because voting for this means admitting it's really needed -- right now. Another, different thought -- while sinking artificial plankton blooms to the deep right away makes sense, there's another path that would take that carbon out of circulation. Let the whales eat some of it. All but the "Right Whales" sink when they die. Most end up in the abyssal depths. Before that, they poop out iron fertilizer. ""The planet's largest animals are also a part of the ecology of the very deep ocean, providing a rich habitat of food and shelter for deep sea animals for many years after their death" http://www.sciencedaily.com/releases/2013/03/130318104953.htm http://www.sciencedaily.com/releases/2010/12/101206161828.htm Boosting plankton with this proposal would attract the plankton feeders, I think, if continued for a while in a single location. How they'd find it would be interesting science in itself. That would include whale sharks, which also (typical of all sharks) sink when they die: "The largest-ever study of whale shark migrations, nine years in the making, shows that the hundreds of school bus-sized animals that feed in a plankton-saturated stretch off the Mexican coast .... the waters of Mexico's Quintana Roo state, on the northeastern Yucatan Peninsula, draw far more animals than other spots and attract an estimated 800 or more in a given season." http://news.nationalgeographic.com/news/2013/08/130821-whale-shark-satellite-tracking-migration-gulf-mexico-science/ --------------- We should be doing this proposal. There's nothing else immediately doable; this is. And it would be easy to study, easy to document, and easy to tweak, move around, tune up.

William Calvin

Aug 26, 2013
08:47

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Thanks, Hank. Apropos "I asked a knowledgeable friend why Dr. Calvin's proposal could be lagging so far behind other -- in my opinion less promising -- proposals. His answer was -- because this one can be done -- right now. He thought the vaguely possible notions attract more votes than the do-it-right-now option, because voting for this means admitting it's really needed -- right now." I had not considered that before, and it has been troubling me all day. I did spend some time several years ago working through the psychology of denial to see how it might apply to climate inaction in general. (A talk of mine on the subject is on the landing page at WilliamCalvin.org). But I came away from that analysis wondering why people should spend millions of dollars trying to discredit the scientists, blow smoke, and confuse the issues. Denial usually works on a personal level; they usually don't form ad hoc clubs to promote it. We usually blame the fossil fuel industries, and indeed there are a number of books analyzing their contributions. But why should business types such as the US Chambers of Commerce promote denial? They are the biggest lobbying shop in town, having outgrown K Street to build their headquarters directly across from the White House. Do they have reasons other than just funding from the usual suspects? Having myself whitewashed the basement walls prior to selling our house, I recalled that some civic booster groups have been known to paper over problems in order to attract new industries to their community-- or at least out-of-town buyers for properties where the owner wants to move elsewhere for good reasons known to the locals as well. You might expect some of that to happen in regions identified as vulnerable to climate trends--say the eastern third of North Carolina exposed to sea level rise. Remember the efforts to get the state to use outdated 20th-C estimates of SLR in granting building permits? The middle of the country and the deep south are identified as being particularly vulnerable to heat waves, deluge and drought. The Red State politicians are particularly big on denial. Is this a case of "a little knowledge is a dangerous thing"? Perhaps their leaders want to get out, but hope to sell to buyers less knowledgeable about climate risks than they are. For a parallel to this scale of denial, one has to look back at the political climate before World War Two and the difficulty that FDR had in preparing the US for a newly dangerous world over the objections of people that sounded a lot like the climate deniers and postponers of today.

Mark Roest

Aug 29, 2013
01:31

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There are wind turbine designs which are not yet in use (due to lack of funds for their inventors) which are relatively light in weight and low in cost. There is also a pair of structural geometries which would greatly reduce the cost of floats, big tubes, towers and cross-members, well-tested and effective. I suggest bringing a lot of followers of R. Buckminster Fuller together with the ocean ecology community to do the initial scoping and design, with people who understand the structural geometries, and some physicists who understand vortices and mixing better than most (e.g. Gunter Pauli and his friends). You may be able to reduce total investment requirements by an order of magnitude. There will also soon be superior batteries for buffering the variable production of electricity from wind turbines to meet relatively steady-state requirements for mixing and pumping. I can make introductions, and I know the structural geometries very well. It would definitely be great to make this into a recovery system for whale populations, by design. Orca management may be an issue to address, in such a program. It also may make sense to combine this project with the one that would create and sequester calcium carbonate by putting limestone and water in contact with CO2-rich exhaust plumes from fossil fuel power plants.

Chris Vivian

Aug 30, 2013
01:30

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In my view here are a number of issues with the proposal: 1. While I can see the induced upwelling working in terms of causing phytoplankton blooms, I don’t see how you can capture and sink more than a very small fraction of that generated biomass in a wide open ocean system due to:  - Algal blooms generated by fertilization take some time to get started - some 2-5 days in the case of ocean iron fertilisation blooms– and then take a further period of time to build up to a peak – up to 14 days or so in the case of ocean iron fertilisation blooms. i.e. you cannot continuously pump nutrients up and immediately pump algae etc down.  - Throughout those periods of time, the blooms and the associated water masses will be being dispersed and moved around. Thus, positioning the downwelling devices to capture that bloom material and sink it is likely to be very challenging, not least since you aim to tether the devices to the seabed! 2. Given the periods of time mentioned in 1 above, it does not seem likely that only little of the pulled up DIC will be released. 3. The assumption of 50g algae (dry weight) grown each day under each square meter of sunlit surface seems very high and is stated to come from algaculture, presumably of macroalgae, not from measurements on phytoplankton blooms. Assuming a bit less than half of that is carbon, say 22g, then that is some 10-20 times more than the primary productivity of blooms measured in iron fertilization experiments. 4. In your description of the project you refer to the 240 times larger amounts of organic carbon from feces and decomposition that are dissolved in surface waters and will never sink out”. Where does that figure come from? 5. You refer to countries being able to implement your concept on their own continental shelves without endless international conferences. However, the UN Convention on the Law of the Sea covers all marine waters and it is only really within territorial waters (out to 12 miles) that a country has, subject to certain freedoms such as innocent passage of vessels, a relatively free hand. 6. As said by one of the expert reviewers, water at the shelf break will not naturally “be carried over cliff and into the slower-moving deep ocean”. This shows a lack of knowledge about water movements in the ocean. 7. The oxygen problem with fertilisation of surface water lies in the mid-depths of the ocean where oceanographers have found that such zones are expanding. 8. Your reply to the question ‘Won’t this just move the ocean acidification problem into the depths’ misses the point entirely. The deep ocean is already more acid than the surface layers and ocean fertilisation will exacerbate that at least to a small extent i.e. there will be no 50 times dilution of the acidity from the sunk bloom material. 9. There are a number of other potential effects of your proposal that need to be considered including: - Reduced light penetration due to the blooms at the surface - Increased production of methane and nitrous oxide at depth when the bloom material decomposes. - Reduction in stratification due to the induced upwelling - Increased flux of carbon to the deep sea and its seabed and ecological consequences for biota in those environments.

William Calvin

Aug 31, 2013
11:29

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Thanks you very much, chrisvivian , for taking the time to critique so usefully. I see that I only have an hour or so to reply before the contest ends, so my replies will be incomplete. 1. Those are indeed issues for plantation layout and will differ with the ocean current direction and its variability. Some are only issues for the startup transients, not for the steady-state operation. 2. I have made no assumptions about up-pumped DIC and its equilibration with atmospheric CO2 concentration. I'd welcome an analysis of that. I have only said that the rate of down-pumping of living dells plus DOC is likely to be larger than it, even without fertilization. 3. You are correct that the 50g dry weight comes from macroalgae, but it is a 1996 estimate; see refs in Calvin (2012b) in the refs. 4. Again, refs in Calvin (2012b). 5. I did not attempt, within the 2000-word limit, to spell out the details of sea law, only state that it is a lot simpler to get something started in ones own waters before going the international law route. 6. You missed how I qualified that. I am indeed aware of the density issues that control whether the "Continental Shelf Pump" waters (refs in Calvin 2012b) sink or continue at the same depth upon reaching the shelf falloff. 7. Pass. 8. The 50x dilution applies to the added influx. But you are of course correct that the pre-existing must also be considered. 9. You are correct. Those are indeed issues for the experts of the Second Manhattan Project. I don't claim to have solved the problem, only to have outlined our task and the ballpark in which we are now forced to play, given that we have already passed earlier exit possibilities.
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