Oceanic Uptake of Anthropogenic CO₂: TheMajor Uncertainties

The recent notes by Broecker [1991] and by Smith and Mackenzie [1991] rightfully point out that many oceanographers do not have a clear grasp of the relationship between the oceanic biological pump and anthropogenic CO2 transient. This misunderstanding has unfortunately led some scientists to make misleading claims as to the importance of the biological pump in the anthropogenic transient. It is remarkable that someone who contributed as much to our understanding of the oceanic carbon cycle as Revelle could have incorrectly stated that the biological pump takes up anthropogenic CO2 [Revelle, 1990]. However, both notes go too far when they dismiss the biological pump as being of minimal relevance to global change, with a particular indictment by Broecker of the Joint Global Ocean Flux Study (JGOFS) as having been guilty of "tarnishing the integrity of global change research" by "hitching their wagons to the greenhouse star." The following brief overview of issues that are important in estimating oceanic uptake of anthropogenic CO2, and where the biological pump fits into them, is offered as an attempt o strike a more balanced point of view. Sarmiento and Siegenthaler [ 1991] give a more detailed discussion.