Climate Science

Testing the Waters

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Science  16 Jan 2004:
Vol. 303, Issue 5656, pp. 287
DOI: 10.1126/science.303.5656.287a

Iron fertilization of the surface ocean layer has been considered as a possible strategy for reducing the burden of atmospheric CO2; this would mitigate greenhouse gas buildup and global warming. The idea is that CO2 would be removed from the atmosphere by sequestering it as new ocean production in “high nutrient—low chlorophyll” regions, where biological production is limited by the scarcity of iron. This approach might have other consequences, however, including the increased production and atmospheric concentration of N2O, another powerful greenhouse gas.

Using a suite of three-dimensional, coupled physical-biogeochemical models and an oceanic N2O cycle module, Jin and Gruber assess how excess production caused by iron fertilization would affect atmospheric N2O. They find that additional N2O production could offset 100% of the effect of CO2 removal when fertilization of limited duration and size is undertaken in the tropics, and that smaller but still substantial offsets can be expected when fertilization is undertaken elsewhere over longer periods. These results indicate that ocean fertilization with iron, in order to reduce atmospheric CO2, may be less efficacious than has been hoped. — HJS

Geophys. Res. Lett. 30, 10.1029/2003GL018458 (2003).

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