FUTURE OCEAN UPTAKE OF CO2 - INTERACTION BETWEEN OCEAN CIRCULATION AND BIOLOGY

We discuss the potential variations of the biological pump that can be expected from a change in the oceanic circulation in the ongoing glob al warming. The biogeochemical model is based on the assumption of a p erfect stoichiometric composition (Redfield ratios) of organic materia l. Upwelling nutrients are transformed into organic particles that sin k to the deep ocean according to observed profiles. The physical circu lation model is driven by the warming pattern as derived from scenario computations of a fully coupled ocean-atmosphere model. The amplitude of the warming is determined from the varying concentration of atmosp heric CO2. The model predicts a pronounced weakening of the thermohali ne overturning. This is connected with a reduction of the transient up take capacity of the ocean. It yields also a more effective removal of organic material from the surface which partly compensates the physic al effects of solubility. Both effects are rather marginal for the evo lution of atmospheric pCO(2). Running climate models and carbon cycle models separately seems to be justified.