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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 24, 2249, doi:10.1029/2003GL018458, 2003

Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emissions

Xin Jin

IGPP and Department of Atmospheric and Oceanic Sciences, UCLA, Los Angeles, California, USA


Nicolas Gruber

IGPP and Department of Atmospheric and Oceanic Sciences, UCLA, Los Angeles, California, USA


Abstract

Ocean iron fertilization is being considered as a strategy for mitigating the buildup of anthropogenic CO2 in the atmosphere. Assessment of this strategy requires consideration of its unintended consequences, such as an enhancement of ocean N2O emissions. This feedback could offset the radiative benefit from the atmospheric CO2 reduction significantly, because N2O is a much more powerful greenhouse gas than CO2 itself. Our model results show that the magnitude of this offsetting effect is substantial, but is highly dependent on the location and duration of fertilization. We find the largest offsets (of the order of 100%) when fertilization is undertaken in the tropics, particularly when it is of limited duration and size. Smaller, but still substantial effects are found when fertilization is undertaken elsewhere and over longer periods. These results suggest that any assessment of ocean fertilization as a mitigating option is incomplete without consideration of the N2O feedback.

Received 19 August 2003; accepted 4 November 2003; published 18 December 2003.

Index Terms: 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 4842 Oceanography: Biological and Chemical: Modeling; 4806 Oceanography: Biological and Chemical: Carbon cycling; 4808 Oceanography: Biological and Chemical: Chemical tracers; 3359 Meteorology and Atmospheric Dynamics: Radiative processes.

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Citation: Jin, X., and N. Gruber (2003), Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emissions, Geophys. Res. Lett., 30(24), 2249, doi:10.1029/2003GL018458.