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

Abstract

[1] Ocean iron fertilization is being considered as a strategy for mitigating the buildup of anthropogenic CO 2 in the atmosphere. Assessment of this strategy requires consideration of its unintended consequences, such as an enhancement of ocean N 2 O emissions. This feedback could offset the radiative benefit from the atmospheric CO 2 reduction significantly, because N 2 O is a much more powerful greenhouse gas than CO 2 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 N 2 O feedback.

Top-down constraints on global N<sub>2</sub>O emissions at optimal resolution: application of a new dimension reduction technique

“…Recent work also suggests that the indirect N 2 O flux could be 2.6-9 times larger than is presently accounted for in bottom-up estimates (Griffis et al, 2013;Turner et al, 2015b), which would imply an underestimate of the agricultural contribution to the overall N 2 O budget. Nonagricultural soils and oceans are thought to contribute an additional 7.4-11 Tg N yr −1 (Saikawa et al, 2013) and 1.2-6.8 Tg N yr −1 (Nevison et al, 1995;Jin and Gruber, 2003;Manizza et al, 2012), respectively, to the global N 2 O source. Industrial, transportation, and biomass burning emissions also exist but are thought to be relatively minor, totaling 1.2-1.8 Tg N yr −1 (Prather et al, 2001).…”

Ocean Iron Fertilization Experiments: Past–Present–Future with Introduction to Korean Iron Fertilization Experiment in the Southern Ocean (KIFES) Project

“…During the SOIREE experiment, a significant increase in N 2 O production was observed in the pycnocline after iron addition (Law and Ling, 2001). This phenomenon was also illustrated in a modeling study of long-term and large-scale OIF (Jin and Gruber, 2003). Complicating the story, however, excess N 2 O 15 was not found after iron addition during EIFEX, the second-longest experiment (~39 days) (Walter et al, 2005).…”

Dossier « Adaptation aux changements climatiques » – La géo-ingénierie : réduction, adaptation et scénario du désespoir

“…La première vise une fertilisation des océans par un épandage à large échelle de sulfate de fer (Jin et Gruber, 2003 ;Jin et al, 2008). Il en résulte-rait une croissance significative du phytoplancton marin consommateur de CO 2 .…”