A LATITUDE-DEPTH, CIRCULATION BIOGEOCHEMICAL OCEAN MODEL FOR PALEOCLIMATE STUDIES - DEVELOPMENT AND SENSITIVITIES

We extend a zonally-averaged, global ocean circulation model to includ e a simple description of the cycles of organic carbon and CaCO3. The circulation in the model is first calibrated so that basin mean vertic al profiles of temperature, salinity and radiocarbon agree closely wit h data for the modern oceans. Then, the capability of the model to rep roduce the observed large-scale distribution of five biogeochemical tr acers (phosphate, oxygen, total dissolved inorganic carbon (DIC), alka linity (ALK) and delta(13)C of DIC) is investigated. If organic carbon is transported only as fast-sinking particles with a remineralization profile constrained from sediment trap data, large PO4 excesses and a noxia are simulated in subsurface waters in the equatorial Pacific and Indian Oceans. As in 3-dimensional models, these features disappear i f a significant fraction (sigma) of organic carbon is allowed to be ex ported away from production sites as labile dissolved organic carbon ( DOCiota). With sigma = 0.5 and an ocean mean DOCiota of 10 mmol m(-3) the latitude-depth distributions of PO4 and apparent O-2 utilization i n the different basins are in agreement with climatological data. The basin mean vertical profiles of DIC, ALK and delta(13)C(DIC) compare f avourably with observations in the modern oceans. The model predicts a global new production of 6.3-10.8 GtC yr(-1), a rate consistent with data- and model-based estimates.