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Climate engineering by artificial ocean upwelling: Channelling the sorcerer's apprentice

Author(s): Oschlies A, Pahlow M, Yool A, Matear RJ

Published: February, 2010

Publisher: Geophysical Research Letters

DOI: 10.1029/2009GL041961

Tags: Ocean Fertilization, Environmental Side-Effects, Climate Modelling

URL: http://www.agu.org/pubs/crossref/2010/2009GL041961.shtml

Abstract: Recent suggestions to reduce the accumulation of anthropogenic carbon dioxide in the atmosphere have included ocean fertilization by artificial upwelling. Our coupled carbon-climate model simulations suggest that artificial upwelling may, under most optimistic assumptions, be able to sequester atmospheric CO2 at a rate of about 0.9 PgC/yr. However, the model predicts that about 80% of the carbon sequestered is stored on land, as a result of reduced respiration at lower air temperatures brought about by upwelling of cold waters. This remote and distributed carbon sequestration would make monitoring and verification particularly challenging. A second caveat predicted by our simulations is that whenever artificial upwelling is stopped, simulated surface temperatures and atmospheric CO2 concentrations rise quickly and for decades to centuries to levels even somewhat higher than experienced in a world that never engaged in artificial upwelling.


Low efficiency of nutrient translocation for enhancing oceanic uptake of carbon dioxide

Author(s): Yool A, Shepherd JG, Bryden HL, Oschlies A

Published: August, 2009

Publisher: Journal of Geophysical Research

DOI: 10.1029/2008JC004792

Tags: Ocean Fertilization

URL: http://www.agu.org/pubs/crossref/2009/2008JC004792.shtml

Abstract: Anthropogenic emissions of carbon dioxide (CO2) are steadily increasing the concentration of this greenhouse gas in the Earth's atmosphere. The possible long-term consequences of this elevated concentration have led to proposals for a number of large-scale geoengineering schemes that aim to enhance or augment natural sinks for CO2. One such scheme proposes deploying a large number of floating “pipes” in the ocean that act to translocate nutrient-rich seawater from below the mixed layer to the ocean's surface: the nutrient supplied should enhance the growth of phytoplankton and consequently the export of organic carbon to the deep ocean via the biological pump. Here we examine the practical consequences of this scheme in a global ocean general circulation model that includes a nitrogen-based ecosystem and the biogeochemical cycle of carbon. While primary production is generally enhanced by the modeled pipes, as expected, the effect on the uptake of CO2 from the atmosphere is much smaller, may be negative, and shows considerable spatiotemporal variability.


Ocean fertilization: a potential means of geoengineering?

Author(s): Lampitt RS, Achterberg EP, Anderson TR, Hughes JA, Iglesias-Rodriguez MD, Kelly-Gerreyn BA, Lucas MI, Popova EE, Sanders RJ, Shepherd JG, Smythe-Wright D, Yool A

Published: November, 2008

Publisher: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

DOI: 10.1098/rsta.2008.0139

Tags: Ocean Fertilization

URL: http://rsta.royalsocietypublishing.org/content/366/1882/3919.abstract

Abstract: The oceans sequester carbon from the atmosphere partly as a result of biological productivity. Over much of the ocean surface, this productivity is limited by essential nutrients and we discuss whether it is likely that sequestration can be enhanced by supplying limiting nutrients. Various methods of supply have been suggested and we discuss the efficacy of each and the potential side effects that may develop as a result. Our conclusion is that these methods have the potential to enhance sequestration but that the current level of knowledge from the observations and modelling carried out to date does not provide a sound foundation on which to make clear predictions or recommendations. For ocean fertilization to become a viable option to sequester CO2, we need more extensive and targeted fieldwork and better mathematical models of ocean biogeochemical processes. Models are needed both to interpret field observations and to make reliable predictions about the side effects of large-scale fertilization. They would also be an essential tool with which to verify that sequestration has effectively taken place. There is considerable urgency to address climate change mitigation and this demands that new fieldwork plans are developed rapidly. In contrast to previous experiments, these must focus on the specific objective which is to assess the possibilities of CO2 sequestration through fertilization.


Geo-engineering might cause, not cure, problems

Author(s): Shepherd JG, Iglesias-Rodriguez MD, Yool A

Published: October, 2007

Publisher: Nature

DOI: 10.1038/449781a

Tags: Environmental Side-Effects, Ocean Fertilization

URL: http://www.nature.com/nature/journal/v449/n7164/full/449781a.html

Abstract: James E. Lovelock and Chris G. Rapley, in their Correspondence ‘Ocean pipes could help the Earth to cure itself ’ (Nature 449, 403; 2007) propose a variant on some well-publicized schemes to remove carbon dioxide from the atmosphere, by fertilizing the surface waters of the ocean (see also Nature doi:10.1038/news070924-8; 2007). All such schemes suffer from a major problem, because simply enhancing the growth of phytoplankton is not enough. It is the sinking flux of particulate organic carbon into the deep ocean — and ideally into the sediments (usually a small fraction of the total primary production) — that must be enhanced for sequestration to be effective.


Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms

Author(s): Orr JC, Fabry VJ, Aumont O, Bopp L, Doney SC, Feely RA, Gnanadesikan A, Gruber N, Ishida A, Joos F, Key RM, Lindsay K, Maier-Reimer E, Matear RJ, Monfray P, Najjar RG, Mouchet A, Plattner GK, Rodgers KB, Sabine CL, Sarmiento JL, Schlitzer R, Slater RD, Totterdell IJ, Weirig MF, Yamanaka Y, Yool A

Published: September, 2005

Publisher: Nature

DOI: 10.1038/nature04095

Tags: Ocean Acidification

URL: http://www.nature.com/nature/journal/v437/n7059/full/nature04095.html

Abstract: Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a ‘business-as-usual’ scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.


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