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A Guide to Information on Greenhouse Gases and Ozone Depletion
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FROM VOLUME 9, NUMBER 12, DECEMBER 1996

NEWS...
OCEAN FERTILIZATION

Item #d96dec62

Spectacular results in a major ocean field experiment have oceanographers looking forward to follow-up experiments, and have renewed controversy over a geoengineering scheme. Last summer, in "IronEx II," iron was added to areas of the tropical Pacific Ocean, triggering a massive bloom of phytoplankton that removed CO₂ from the air. The results confirm that lack of iron is a controlling factor in this part of the carbon cycle, and support the hypothesis that iron reaching the oceans in the form of windblown dust accounts for the reduced levels of CO₂ during the ice ages that kept the planet cool. Stimulation of plankton also increased emissions of dimethyl sulfide (DMS), a gas which oxidizes in the atmosphere to form sulfate particles. These particles further contribute to cooling, by shielding the Earth from solar heating and by enhancing the formation of clouds. (See New Scientist, p. 4, Oct. 12, 1996; Chem. Eng. News, p. 10, Oct. 14; and papers in Prof. Pubs./Ocean Fertilization, this Global Climate Change Digest issue--Dec. 1996.)

The next experimental phase will investigate the mechanism in the Southern Ocean, where its impact on atmospheric CO₂ is likely to be the most permanent, because carbon incorporated into phytoplankton would be carried to the ocean floor and locked away for centuries. (See Chem. Eng. News, pp. 40-41, Nov. 4, 1996.) According to British oceanographer Andrew Watson, putting iron in the Southern Ocean could theoretically reduce atmospheric CO₂ by 17 percent within a century.

Another line of research has shown that ocean bacteria also need iron, and stimulating bacteria with iron would also remove CO₂ from the atmosphere. (See Science News, p. 197, Sep. 28, and papers in Prof. Pubs./Ocean Fertilization, this Global Climate Change Digest issue--Dec. 1996.)

Ever since the iron fertilization theory was proposed a few years ago, some have grasped at the concept as a solution to global warming, while others are leery of this and other geoengineering schemes, particularly because of possible unintended consequences. The controversy is discussed thoroughly in The New York Times (pp. C1, C6, Nov. 12, 1996).