Dunne, John, Robert Armstrong, Curtis Deutsch, Anand Gnanadesikan, Nicolas Gruber, Jorge Sarmiento, Pananjady Swathi

Princeton University, Program in Atmospheric and Oceanic Sciences and NOAA/Geophysical Fluid Dynamics Laboratory, E-mail: jpd@gfdl.noaa.gov

Empirical and predictive models for the particle export ratio

We utilize a global compilation of field observations of the ratio of particulate organic matter export to primary production (pe-ratio) to calibrate new empirical and predictive models. Our empirical model captures 64% of the variance using only sea surface temperature and chlorophyll concentration. We describe a simple ecosystem model of the allocation and recycling of new production that includes small and large phytoplankton, as well as explicit ballast driven sinking and remineralization of particulate organic matter. A key feature of this model is a representation of grazing that reproduces the observed allometric behavior of phytoplankton community composition. When calibrated using our compilation of field observations, this model captures 62% of the variance in the pe-ratio when driven by biomass and temperature. This model has been incorporated into an ocean general circulation model, and is able to reproduce major patterns in primary production as interpreted from satellite-based estimates. However, important differences exist, pointing primarily to deficiencies in the ocean circulation model, but also to deficiencies in the chosen biological representation of ocean ecosystems and the satellite-based chlorophyll and primary productivity algorithms.