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Ironing away a greenhouse wrinkle.

Ironing away a greenhouse wrinkle

An unusual strategy for slowing global greenhouse warming -- fertilizing the Antarctic Ocean with iron -- has received mixed reviews from scientists exploring its feasibility. While one group suggests that fertilization won't do the trick, others say their initial research indicates it might appreciably slow carbon dioxide buildup in the atmosphere, although they caution that scientists must still address many basic questions about the strategy, including its potential to alter the ocean ecosystem.

Oceanographers at the Moss Landing (Calif.) Marine Laboratories suggested last year that the Antarctic Ocean's unusually low concentrations of single-celled plants called phytoplankton result from an iron deficiency that keeps these organisms from making full use of the rich supplies of available nutrients. If so, the team theorized, fertilizing the waters with iron could enhance phytoplankton photosynthesis -- an effect that would pull large amounts of carbon dioxide from the atmosphere, helping to counteract the buildup of this greenhouse gas.

Now a thumbs-down response comes from Tsung-Hung Peng of the Oak Ridge (Tenn.) National Laboratory and Wallace S. Broecker of Columbia University's Lamont-Doherty Geological Observatory in Palisades, N.Y. Using a computer model of the world's oceans, these researchers found that currents bring water to the region too slowly for the fertilization scheme to make a significant difference. If their model is correct, a century's worth of iron fertilization would reduce the global concentration of atmospheric carbon dioxide to a level only 5 to 15 percent below what it would be without fertilization, they say. "Even if iron fertilization worked perfectly, it would not significantly reduce the atmospheric [CO.sub.2] content," they assert in the Jan. 17 NATURE.

Jorge L. Sarmiento, a mathematical modeler at Princeton (N.J.) University, argues that a 15 percent reduction would represent a significant effect, dramatically slowing the rise in carbon dioxide. What's more, he told SCIENCE NEWS, his computer simulations indicate that fertilization would lower carbon dioxide levels by about double the amount calculated by Peng and Broecker.

Nonetheless, he says, "it's very unlikely that iron fertilization will have practical applications." For one thing, oceanographers don't know whether an iron deficiency really limits the Antarctic phytoplankton population; indeed, that theory runs counter to traditional thinking about the region's ecology. And even if the strategy could lower carbon dioxide levels, its cost might be prohibitive; once begun, the treatments would have to continue forever. Moreover, scientists express concern that fertilization could disrupt aquatic ecosystems -- a threat that hasn't escaped environmentalists, who vehemently oppose the strategy. Environmentalists and other critics also worry that the fertilization prospect might derail crucial attempts to control the world's use of fossil fuels, the source of most carbon dioxide pollution.

"This is not to be viewed as a fix-it or cure-all to the [CO.sub.2] problem," says Oskar R. Zaborsky, director of the National Research Council's board on biology. Even if fertilization worked, he says, it could not replace other actions such as energy conservation.

He says scientists are proceeding with caution on the iron question: "No one is suggesting initiating a treatment process at this time." Researchers are planning ship-board and laboratory experiments and are even discussing a small-scale field study in which they would fertilize about 400 square kilometers of the Antarctic Ocean. Ecologists and biologists say an experiment of this size would not harm the aquatic system, Zaborsky adds.
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Title Annotation:fertilizing the Antarctic Ocean with iron to slow global warming
Publication:Science News
Date:Jan 26, 1991
Words:558
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