Global Models of Chemical Fluxes in the Oceans

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Chemical fluxes from the ocean's surface into the deep sea vary over the ocean in response to the supply of nutrients, the availability of light, and the dispersion of newly-produced material by local turbulence and sinking. Funding is requested to continue the development of global scale models which integrate biological and chemical components into three- dimensional ocean general circulation models (GCM's) that simulate the major features on the ocean's physical forcing. Towards this end we have already developed a series of component models describing the upper ocean ecology and water column transformations, and carried out a first series of three-dimensional simulations in which these components have been included separately in ocean GCM's. Our Atlantic Ocean GCM model of upper ocean ecology, while reproducing the gross features of ocean biology, such as the spring bloom, low productivity in the subtropical gyre, and high productivity in the equatorial region, has numerous problems, some of which can be traced to the GCM, and others of which are due to the ecology model. We propose to carry out a series of new experiments with higher resolution, more realistic GCM's; and to work on the continued development of our ecosystem model, with the inclusion of 2 size classes of phytoplankton and zooplankton being our first priority. We also propose to enter a new phase in our work of working closely with JGOFS investigators in analyzing the results of the North Atlantic Bloom Experiment, and planning future studies such as the Pacific Equatorial Experiment. Our world ocean GCM model of water column transformations shows an improved fit to observations when the formation and regeneration of dissolved organic matter is included in addition to particulate organic matter. In addition to continuing our effort to improve our understanding of the production and regeneration of dissolved organic matter in the water column (a process which will be greatly helped by additional measurements), we propose to proceed on development of a more detailed model of particle dynamics which makes use of the ecosystem approach we have employed in the upper ocean and the observational constraints obtained by reactive trace metals radioisotopes. We also propose to complete an ongoing reanalysis of Redfield ratios which thus far suggests that as much as 1/4 of the organic nitrogen sinking below 1000 m may be getting denitrified.