Production and export in a global ocean ecosystem model

The Hadley Centre Ocean Carbon Cycle (HadOCC) model is a coupled physical-b iogeochemical model of the ocean carbon cycle. It features an explicit repr esentation of the marine ecosystem, which is assumed to be limited by nitro gen availability. The biogeochemical compartments are dissolved nutrient, t otal CO2, total alkalinity, phytoplankton, zooplankton and detritus. The re sults of the standard simulation are presented. The annual primary producti on predicted by the model (47.7 Gt C yr(-1)) compares well to the estimates made by Longhurst et al. (1995, J. Plankton Res., 17, 1245) and Antoine et al. (1996, Global Biogeochem. Cycles, 10, 57). The HadOCC model finds high production in the sub-polar North Pacific and North Atlantic Oceans, and a round the Antarctic convergence, and low production in the sub-tropical gyr es. However in disagreement with the observations of Longhurst et al. and A ntoine et al., the model predicts very high production in the eastern equat orial Pacific Ocean. The export flux of carbon in the model agrees well wit h data from deep-water sediment traps. In order to examine the factors cont rolling production in the ocean, additional simulations have been run. A nu trient-restoring simulation confirms that the areas with the highest primar y production are those with the greatest nutrient supply. A reduced wind-st ress experiment demonstrates that the high production found in the equatori al Pacific is driven by excessive upwelling of nutrient-rich water. Three f urther simulations show that nutrient supply at high latitudes, and hence p roduction there, is sensitive to the parameters and climatological forcings of the mixed layer submodel. Crown Copyright (C) 2001 Published by Elsevie r Science Ltd. All rights reserved.