Ocean-Basin Scale Modeling of Plankton Dynamics in the NorthAtlantic and Eastern North Pacific

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The objective of this effort is to construct ocean-basin scale models of plankton dynamics in the North Atlantic and the North Pacific in support of the overall objectives of the U.S. Global Ocean Flux Study sponsored by NSF and NASA. These new physical-biological models will utilize historical data on the climatological mixed layer depth , historical data on the large scale, wind-driven Ekman flux at the base of the mixed layer, and the GEOSECS nutrient chemistry data in the North Atlantic and North Pacific. These ocean-basin scale models will study how seasonal mixed layer deepening and shallowing, along with wind-driven Ekman upwelling and downwelling, interacts with the vertical gradient of dissolved nutrients to determine the total amount of limiting nutrient available to the plankton ecosystem. This in turn determines the biological productivity of the ocean. Maps will be produced by the model of the monthly and annual primary production in the North Atlantic and eastern North Pacific basins. Estimates will be made of the interannual variability in primary production due to interseasonal fluctuations in the large scale wind stress over the North Atlantic. %%% The models will incorporate details on the physiological growth rate of the phytoplankton, enabling resolution of regional variations in chlorophyll content of the plant population. This will enable direct comparison of model predictions of the phytoplankton distribution to ocean-basin scale composites of historical CZCS images of surface chlorophyll. These basin- wide models will be validated by comparison to plankton abundance and productivity data published in the literature, and historical CZCS imagery. New data forthcoming from the GOFS field program and new ocean color imagery may or may not become available for assimilation into these models within the time frame of this proposal (1988-1991). However, this modeling effort can help provide an essential link between general theory and observations planned by GOFS investigators.