GLOBAL OCEAN PHOSPHATE AND OXYGEN SIMULATIONS

We examine the role of dissolved organic matter (DOM) and the stoichiometric ratios of organic matter remineralization in determining the magnitude and distribution of remineralization of organic matter in the oceanic water column, and the impact of this remineralization on tracer distributions. Our aim is to improve the parameterization of relevant processes in ocean general circulation models by bringing the models into closer agreement with new observational constraints that suggest substantial differences from previous work (lower DOM levels and higher -O-2/P ratios). We used phosphate and apparent oxygen utilization (AOU) to analyze the effect of the remineralization profile on water column tracer distributions. The primary impact of DOM cycling is to modify the distribution of remineralization over that obtained from a model with particle cycling only. Changing the oxygen-to-phosphorus stoichiometric ratio modifies the magnitude of oxygen utilization, but preserves its basic distribution. We find that even a small amount of DOM is sufficient to prevent the problem of nutrient trapping. Improved phosphate and AOU simulations are obtained when the amount of DOM is reduced and the deep ocean -O-2/P ratio is increased in accord with recent. observations of these properties.