| Summary: | Can the buildup of anthropogenic CO2 in the atmosphere be reduced significantly by fertilizing the surface southern ocean waters with iron? There are many issues that need to be addressed in answering this question. Is iron scarcity indeed the dominant process limiting biological uptake of carbon, as has been suggested by Martin [e.g., Martin et al., 1990]? What is the role of zooplankton grazing and light supply? What would be the impact on southern ocean ecology of iron fertilization and its accompanying reduction of subsurface ocean oxygen levels? How does the environmental and economic cost of a fertilization effort compare with the cost of other mitigation strategies focussing, for example, on anthropogenic emissions? Addressing these highly complex issues will require a substantial investment ofresearch resources. It is important that we convince ourselves each step of the way that such expenditures are justified. An important contribution to the debate on this issue has recently been made by Broecker, who has concluded from a series of model studies that even if iron fertilization worked perfectly, the reduction in CO2 of the order of 50+_25 ppm that would result after 100 years of fertilization would not be significant [Broecker, 1990; Peng and Broecker, 1991]. This is for an atmospheric CO2 that would otherwise increase to 500 ppm over that time span, and represents a reduction of 34 % in the increase that would occur
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