Geochemical cycles in an ocean general circulation model. Preindustrial tracer distributions

A state‐of‐the‐art report is given of the Hamburg model of the oceanic carbon cycle. The model advects geochemical tracers important to the carbon cycle by the currents of a general circulation model. The geochemical cycling is driven by a Michaelis‐Menten type production kinetics. The model is an extension of the Bacastow and Maier‐Reimer (1990) model. It is based on a more realistic current field and includes a mechanism of lysocline‐sediment interaction. Principal variables are ∑CO 2 , alkalinity, phosphate, oxygen, and silicate. The carbon variables are defined for 12 C, 13 C, and 14 C separately. In addition to these carbon isotopes, 39 A and δ 18 O of dissolved oxygen are predicted. The model predicts realistic global patterns of tracer distribution. In the equatorial eastern Pacific, however, the structures are exaggerated due to a strong upwelling which is a common feature of coarse resolution models of the general circulation of the ocean.