My sense is that these are upper bound numbers because in the real world we would probably not fertilize the entire ocean south of 30 degrees, and the areas that were fertilized would probably not perform up to maximum possibilities. A researcher in California has a different take on the scheme: throw calcium bicarbonate Ca (HCO3) 2 * into the ocean—where it might help support … Pp. It can be stored in coral reefs which are carbon sinks. Nature. Some surfaces in the deep ocean are not well ventilated, so even though more organic carbon is being transported, more carbon is retained in those areas. Currently, CO2 levels are rising faster than any other time in known history. If we were to go down to a depth of 3,000 meters, we predicted that we would get a reduction in dissolution rate by about a factor of 2, based on the changing solubility (or ease of formation) of the hydrate. If we compared three years, 30 years, and 300 years, we found that previously sequestered carbon was leaking back out over much of the rest of the ocean, and by 300 years, there was significant leakage in the tropics. © 2020 National Academy of Sciences. The methane hydrate also dissolved, but at a rate about 10.5 times slower. Every U.S. citizen emits the equivalent of about 120 pounds of CO2 a day, and about a third of that goes rather quickly into the ocean. How can we put a value on the time-shifting of an emission? Mass bleaching will in future become annual, departing from the 4 to 7 years return-time of El Niño events. At present, we are also putting carbon into the atmosphere, which may create significant climate change. Not only is the entire claim that coral reefs are a CO2 sink completely incorrect, they are in fact a source of CO2 to the atmosphere even while they remove carbon from the ocean. Alendal, G., and H. Drange. FIGURE 1 Schematic representation of the concept of ocean fertilization. Critics of this approach—and I was a bit skeptical earlier—suggested that the dissolution might not be quite that easy. Register for a free account to start saving and receiving special member only perks. Source: Hanish, 1998. experiments, and we were fortunate to have access to modern, remotely operated vehicles (ROVs) to attempt this. Over time, massive accumulations of these skeletons made thick, carbon-rich deposits we call coral reefs. It was clearly time to carry out real, TABLE 1 The Evolving Chemistry of Surface Seawater under “Business as Usual”. Ocean carbon sequestration would only make sense if it diminishes the overall adverse consequences of releasing CO2 into the environment. 1997. Rather, as the liquid surface deformed microscopic cracks occurred, which were quickly annealed with hydrate, as both water and CO2 flowed into the cracks and combined to renew the skin with remarkable effectiveness. FIGURE 2 Amount of additional carbon stored in the ocean and amount of additional storage per year (net flux to the ocean) as computed at Lawrence Livermore National Laboratory for idealized iron fertilization south of 30 degrees using the POP ocean model. These specimens were squeezed at high pressure at Lawrence Livermore National Laboratory into dense solid units about the size of 35-millimeter film cassettes, placed in a specially designed pressure vessel under about 15.5 MPa methane pressure, and packed in ice. Copyright © 2020 Elsevier B.V. or its licensors or contributors. For stabilization at 2°C with a midrange climate sensitivity, we would have to add approximately one gigawatt of carbon-free primary power per day somewhere in the world. In the very long run, about 85 percent of all CO2 emissions will reside there (IPCC, 1990). If all of the CO2 we sequester eventually leaks back into the atmosphere, then all we are really doing is time-shifting emissions. A very large fraction of the emissions from the early part of the twentieth century are now in deep waters, well along on the exchange path between the upper ocean and the deep ocean; the oceanic fossil-fuel signal has reached a depth of >1,000 meters. Slowly, the CO2 dissolved into the water; the dissolution rate is given by the observed drop in pH. Many visitors come specifically to visit the reefs themselves, to swim over shimmering gardens of coral amongst hordes of fish, but many more are unknowing beneficiaries of the reefs as producers of sand, … Direct ocean carbon sequestration: observations of biological impacts during small-scale CO2 releases. captured locally at varying distances from the small CO2 source (Barry et al., in press). We were able to observe an apparent correlation between dissolution rate and current velocity. They are not. It reacts quickly with water to form carbonic acid and then with carbonate ion to add to the pool of dissolved bicarbonate in ocean waters. Many other issues have been raised, such as the enormous amount of fluids involved, suggesting a very large-scale engineering enterprise. If climate sensitivity is at the high end of the accepted range, nearly all of our energy would have to come from carbon-emission-free sources. Within a few hours, it was clear that both the methane and the carbon dioxide hydrates were dissolving. Journal of Geophyical Research 106(C1): 1085–1096. They are curious, and they come close up to our experiments, apparently unperturbed, for long periods of time. Towed pipe and droplet plume scenarios may offer the best approach in the near future. Although this has slowed global warming, it is also changing ocean chemistry. The ocean transports tracers along surfaces of constant density, controlled largely by temperature. The net flux starts out close to eight gigatons. Environmental Science and Technology 32: 20A–24A. This changes the CO2 under gas form to HCO3- (bicarbonate ion) dissolved in river water. 2) Determine how quickly CO2 can be stabilized to prevent extinction of coral reefs and flooding of low-lying coasts, based on quantity and quality (long-lived fraction) of soil carbon sequestration and global atmospheric CO2 input-output models. We measure the pH from a set of recording instruments, and we examine the physiological responses of the marine animals to the lower-pH plume that is formed. We use cookies to help provide and enhance our service and tailor content and ads. On geoengineering and the CO2 problem. That really begs the question, because we already do. The sketch that appears in the 1998 Environmental Science and Technology article shows blocks of dry ice being dropped into the surface ocean—a forbiddingly expensive idea. Thus, a bubble stream would quickly evolve into a pure nitrogen gas phase and a dense CO2 rich aqueous phase, which could be piped to great depth. and it’s leaking out 100 years or 200 years from now. Rehder, G., S. Kirby, W.B. We punched a small hole in the seafloor so the CO2 wouldn’t roll away and then inserted a pH electrode directly into the mass of liquid. We plan to conduct experiments on this process. For about the last five years, my laboratory group and our colleagues have been carrying out deep ocean experiments; they are difficult, but fun, and they raise all kinds of important questions. First, I applaud the use of colder water to reduce thermal stress. We’re putting CO2 in today. MyNAP members SAVE 10% off online. In addition, the progressive onset of ocean acidification will cause reduction of coral growth and retardation of the growth of high magnesium calcite-secreting coralline algae. In other parts of the ocean, CO2 slips back into the atmosphere much more quickly. This scheme formed the basis of a very fine modeling effort carried out by the Bergen group in Norway (Alendal and Drange, 2001; Drange et al., 2001). Asking How to Save Coral Reefs Leads to Better Understanding Carbon Sequestration By. What is the residence time of carbon in the ocean? So long time storage of carbon is present in coral reefs. Using one of our newer vehicles, we flew a small amount of CO2 to a depth of 3,600 meters. The volume of the oceanic “aquifer” is about 1021 liters. In other words, we use roughly a factor of three to account for the fact that this is not a permanent sequestration. This was excruciatingly difficult—painstaking, classical, hard work. With a zero discount rate, there is no time preference, and there is no point in ocean fertilization because future value would not be discounted. The ratio of both the solubility and the observed hydrate dissolution rates of CO2 to methane is about 10.5:1. Disposal scenarios that are the focus of current research include droplet plume and dense plume dissolution, dry ice and towed pipe dispersion, and isolation as a dense lake of CO2 on the sea floor. It is important to understand that ocean fertilization, insofar as it works and is environmentally and politically acceptable, might become part of a portfolio of responses. Denser surfaces outcrop at the colder poles. Growing concerns about climate change partly as a result of anthropogenic carbon dioxide emissions has prompted the research community to assess technologies and policies for sequestration. The 1998 President’s Council of Advisors on Science and Technology Energy R&D Panel recommended storing CO2 as a clathrate hydrate on the seafloor. When CO2 levels reached ∼340 ppm, sporadic but highly destructive mass bleaching occurred in most reefs world-wide, often associated with El Niño events. The result was almost precisely a factor of 2 slower than it was at 1,000 meters—as predicted by thermodynamic-equilibrium and saturated boundary-layer theory. The pros and cons of carbon dioxide dumping. • Fringing reefs: They follow the coastline, maintaining an active growth area offshore and an accumulation of dead coral inshore, forming a platform reef that over time turns into a lagoon. (5) This CO2 is eventually mixed up to the surface ocean. Since then, there have been numerous conferences to study the problem and discuss theoretical analyses. At high pressure and low temperature, CO2 will react with water to form an ice-like solid (CO2.6H2O), which is denser than seawater. In one simulation, organic carbon that sank into the deep ocean oxidized, thus consuming ambient dissolved oxygen in the water column. Although some researchers have raised concerns about possible negative effects of rising CO 2 on ocean surface pH, there are several lines of evidence demonstrating marine ecosystems are far more sensitive to fluxes of carbon dioxide from ocean depths and the biosphere’s response than from invasions of atmospheric CO 2. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. (1) Adding nutrients to the surface ocean can stimulate marine production of organic carbon. An analysis of the IS92A Intergovernmental Panel on Climate Change (IPCC) scenario shows that to stabilize climate at 2°C of warming, if climate sensitivity is at the low end of the accepted range, approximately 75 percent of all power production would have to come from sources free of carbon emissions by the end of this century. Once it is oxidized, we don’t know how long it would stay down before it cycles back up to the surface. (4) In the ocean interior, the organic carbon is oxidized to CO2. Climate change = ocean change. The North Pacific Ocean has the densest seawater exposed at northern latitudes. I worked on a highly idealized simulation of. Under IPCC “Business as Usual,” the pH of surface seawater drops by 0.4 pH units by 2100. Our current, de facto policy for disposing of carbon dioxide, both in the United States and internationally, is to dispose of it first in the atmosphere. We now have more than a hundred years of experience with this “technology,” and the numbers are very large. So maybe it's a good idea; maybe a terrible idea. It might be worth reducing emissions in the short term in anticipation of new energy technologies coming online in the long term. This aquifer covers 70 percent of the Earth’s surface, and the reaction with the alkalinity of surface ocean waters is the primary modifier of the increase of CO2 in the atmosphere. So there's a company called Cholera. Brewer. This means that for droplets initially about 1 cm in diameter, about 90 percent of the dissolution occurs within 30 minutes and within 200 meters of the release point. Drange, H., G. Alendal, and O.M. At today’s level of ∼387 ppm, allowing a lag-time of 10 years for sea temperatures to respond, most reefs world-wide are committed to an irreversible decline. Equilibrium of carbonic acid in sea water, from: http://www.coralscience.org/main/articles/biochemistry-2/how-reefs-grow. Science 284: 943–945. There is also some disagreement, although I think I know the answer, for how we should account for the sort of out-gas seen in de-gasing situations. Brewer, P.G., E.T. Share a link to this book page on your preferred social network or via email. Do you want to take a quick tour of the OpenBook's features? Buck, C. Lovera, L. Kuhnz, E.T. Using estimated rates of coral reef carbonate production, we compute that coral reefs release 0.02 to 0.08 Gt C as CO2 annually. Aya, I., K. Yamane, and H. Nariai. Caldeira, K., and G.H. We should look at the discount rate minus the emission cost because, if we have a 3-percent discount rate but the cost of carbon emissions rises at the rate of 3 percent, once again we would gain nothing. The idea of ocean sequestration is to put the CO2 into the ocean deliberately, thus avoiding most of the global warming. The explanation for this is the geological cycle of carbon, where the CO2 in the atmosphere is taken by rain water and slightly acidic rain dissolve the exposed rocks. Most (although certainly not all) coral reefs are in waters with low nutrient concentrations. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Dissolution rates of pure methane hydrate and carbon dioxide hydrate in undersaturated sea water at 1000m depth. And what are the environmental impacts? Although most of the CO 2 taken up by phytoplankton is recycled near the surface, a substantial fraction, perhaps 30 percent, sinks into the deeper waters before being converted back into CO 2 by marine bacteria. BUT my concern would be the possible stress of high nutrient loading. Geophysical Research Letters 28: 2637–2640. You're looking at OpenBook, NAP.edu's online reading room since 1999. A number of simulations have been done using general circulation models and schematic ocean models. We were able to show that the modeling done by the Norwegian group, and also laboratory pressure vessel studies in Japan (Aya et al., 1997), are probably correct. Peltzer, K. Osborne, P.J. Reefs will cease to be large-scale nursery grounds for fish and will cease to have most of their current value to humanity. If we add in Coral reefs, contributing another 111 million tons, … These sketches offer intuitive, but possibly confusing, images of how ocean carbon sequestration might work. A number of people have suggested that one solution to minimize costs is simply to take the CO2-nitrogen mixture resulting from combustion and inject it into the ocean without chemical separation (Saito et al., 2000). There are two reasons for leakage: (1) carbon placed in the deep ocean eventually mixes back up to the surface; and (2) along with the organic carbon, we sent nutrients down into the deep ocean, thus increasing the deep-ocean nutrient content at the expense of the surface ocean. We hope we will be able to make some objective evaluations about the feasibility and ethics of this option. Climatic Change 1: 59–68. Experimental determination of the fate of rising CO2 droplets in sea water. They suggest many possibilities for safe and effective oceanic disposal of CO2. CO 2 released in the ocean at a depth of about 800 meters (4.4°C) will dissolve at a rate of about 3 µmol/cm 2 /sec. The report also presents current efforts at enhanced oil recovery using carbon dioxide and demonstrating its utility. In addition, the ratio of added. The Norwegian study showed that, if the location and depth of release were carefully selected, the water masses labeled with this excess dissolved CO2 would be advected to the North Atlantic deep-water formation regions and transported into the abyssal flows. My work is focused on simulations of iron-based ocean fertilization. Ocean circulation then transports these CO2-modified surface waters to water mass conversion regions and subduction zones. The goal of fertilization is to remove carbon from the surface ocean, fix the CO2 as organic carbon, and then sink it into the deep ocean mostly by gravitational sinking of the total particles. Temperature-induced mass coral bleaching causing mortality on a wide geographic scale started when atmospheric CO 2 levels exceeded ∼320 ppm. 1990. The basic idea of iron-based ocean fertilization (see Figure 1) is to add iron to the upper ocean to stimulate biological activity and increase photosynthetic activity, and thus generate more organic carbon—removing it from the surface. The Calera Process: An Effective Means of CO2 Sequestration. In itself, it won’t solve the problem. The data were of remarkable quality. That is very close to the modeling result from the Bergen group. Show this book's table of contents, where you can jump to any chapter by name. saturated, molecular-boundary layer controlled by diffusion. FIGURE 1 Options for direct ocean disposal of CO2. CO3− in surface water drops by 55 percent from preindustrial values. Not a MyNAP member yet? Green Sea Ventures estimates that the cost of iron fertilization would be $7 to $7.50 per ton. About 20% of atmospheric carbon dioxide is absorbed by ocean waters. I don't know about the chemistry, physics and geology of deep-sea CO2 sequestration. Taking the range of discount rates that are typically used in business, we would have to sequester initially three gigatons of carbon, say at 0.33, in order to get one gigaton of carbon’s worth of sequestration value. ...or use these buttons to go back to the previous chapter or skip to the next one. Thus, the effectiveness of iron fertilization diminishes over time as the surface ocean runs out of macronutrients. 2001. Climate Change: The IPPC Scientific Assessment , edited by J.T. One advantage might be that it would give us time to invent new, carbon-emission-free energy technologies. Of the organic carbon that sinks to the deep ocean, some carbon can mix up from below, and some CO2 can come from the top. Higher velocities in the bulk fluid reduce the thickness of this layer and accelerate dissolution. Marchetti, C. 1977. Fossil fuel CO2 is now a major ion of seawater. Jump up to the previous page or down to the next one. At about 100 years, net additional storage (new storage minus leakage) is about one gigaton per year. Assuming that there are roughly 400,000,000,000 trees, each sequestering 50 pounds of CO2 a year, and assuming that we put out 28,431,741,000,000 pounds every year, trees alone should cover approximately 70% of the human contribution of greenhouse gases to the atmosphere (others besides CO2 having a negligible effect). On the basis of these results, we next asked how important the hydrate skin was in controlling the outcome of the experiment. It is essential that we know the effects of increased oceanic concentrations of CO2, even if we decide to put it into the atmosphere. The shrinkage rate of the solid diameter was 9×10−2 µm/sec. However, only about five or six years ago a number of us decided to initiate small-scale field experiments. When CO 2 levels reached ∼340 ppm, sporadic but highly destructive mass bleaching occurred in most reefs world-wide, often associated with El Niño events. We requested that the pilots fly to the release point, release a small quantity of liquid CO2, and follow this during upward transit over hundreds of meters, while the ROV takes images of the droplets with a precision of a tenth of a millimeter. Deep ocean waters are approximately 500-fold undersaturated with respect to dissolved CO2. The upper mixed layer equilibrates with the atmosphere roughly on a time scale of a year or so. Having thus made a water pocket inside the blob of CO2, we then locked the electrode in place and waited for half an hour. Geophysical Research Letters 27: 225–228. Geochimica et Cosmochimica Acta. It was performed under the auspices of DOE by the Lawrence Livermore National Laboratory under contract No. Carbon sequestration, the long-term storage of carbon in plants, soils, geologic formations, and the ocean. Or would they dissolve? 1998. By continuing you agree to the use of cookies. The regional partnership is injecting the CO2 into an oilfield located within Michigan's Northern Reef Trend, a series of highly-compartmentalized fields about 6,000 feet below the surface that were once ancient coral reefs. This is not simply a question of economics. If CO2 levels are allowed to reach 450 ppm (due to occur by 2030–2040 at the current rates), reefs will be in rapid and terminal decline world-wide from multiple synergies arising from mass bleaching, ocean acidification, and other environmental impacts. For our study, we took an ROV fitted with a high-definition TV camera and attempted direct imaging of the release, rise, and dissolution sequence. Orr, Jr. 1999. Clearly the deep ocean thermodynamic conditions of temperature and pressure favor hydrate formation, but it is also essential that chemical saturation occur. Past history shows that when CO2 rose sharply, this corresponded with mass extinctions of coral reefs. Start studying carbon. Marine sponges are sessile, benthic dwellers in the reef environment and harbor a high abundance of symbiotic microorganisms that can account for up to 40% of their body volume ().High-throughput sequencing of bacterial 16S ribosomal RNA genes has revealed the enormous diversity and stability of the sponge bacterial community, which is distinct from that of the surrounding environment … This experiment taught us something valuable about the lifetime of hydrates of all kinds in the ocean and provides a basis for making powerful, simple predictions based on saturated-boundary theory. Rising atmospheric CO2 is also increasing the absorption of CO2 by seawater, causing the ocean to become more acidic, with potentially disruptive effects on marine plankton and coral reefs. Numerical simulation can shed some fresh light on the idea of ocean fertilization. Others have proposed geochemical techniques, such as accelerating silicate or carbonate weathering. Houghton et al. Energy 22: 263–271. illustrating dissolution of a plume in the 800- to 600-meter depth zone probably represents the shallowest depth at which effective ocean CO2 sequestration should be considered. A colleague of mine, his postdoctoral students, and I are carrying out experiments with CO2-biological interactions right now. Threats to coral reefs: climate change. This work was supported by the Ocean Carbon Sequestration Research Program of the U.S. Department of Energy (DOE) Office of Biological and Environmental Research. How Gaia and Coral Reefs Regulate Ocean pH. A 1998 cover story in Environmental Science and Technology, a journal of the American Chemical Society, raised the question of whether we should actively dispose of CO2 in the oceans (Hanisch, 1998). One early discovery with this simulation was that, after only three years, CO2 would already begin to leak back into the atmosphere. However, when the organic carbon gets into the deep ocean, it is oxidized back to CO2, which can get mixed back up to the surface ocean and then can escape back into the atmosphere. Durham, L. Stern, E.T. This is likely to have been the path of great mass extinctions of the past, adding to the case that anthropogenic CO2 emissions could trigger the Earth’s sixth mass extinction. The argument is that this could have some adverse impacts on the marine environment, but at least we would avoid most of the climate change. We emplace about 20 liters of liquid CO2 in a small corral on the seafloor at 3,600 meters. All rights reserved. Brewer. To determine how ocean carbon sequestration would change allowable emissions, we can calculate the net benefits as functions of a discount rate and assume a price trajectory. We have already lowered surface ocean pH by about 0.1 pH units, and, if the Intergovernmental Panel on Climate Control “Business as Usual” scenario is followed, by the end of this century, we will have lowered carbonate ion concentrations in surface ocean waters by >50 percent (Brewer, 1997).