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 geoch emical cycling is driven by a Michaelis - Menten type production kinet ics. 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 m echanism of lysocline - sediment interaction. Principal variables are SIGMACO2, alkalinity. phosphate, oxygen, and silicate. The carbon vari ables are defined for C-12, C-13, and C-14 separately. In addition to these carbon isotopes, 39A and deltaO-18 of dissolved oxygen are predi cted. The model predicts realistic global patterns of tracer distribut ion. In the equatorial eastern Pacific, however, the structures are ex aggerated due to a strong upwelling which is a common feature of coars e resolution models of the general circulation of the ocean.