Dataset: Model Results for the BATS Region

The overall goal of the proposed research is to investigate the role of mesoscale dynamics and upper ocean processes on biogeochemical fluxes in the Sargasso Sea. The general approach is to use a three-dimensional coupled physical and biological model together with in situ observations and a full complement of remotely sensed information (altimetry, ocean color, scatterometry and AVHRR) to study the biological and chemical ramifications of spatially and temporally intermittent physical processes. The coupled model system will be configured in a "Topex/Poseidon (T/P) Diamond" surrounding the U.S. JGOFS Bermuda Atlantic Time Series Study (BATS) site.  This implementation will make it possible to prescribe the necessary physical model boundary conditions directly from T/P altimetry. Assimilation of additional data available in the interior (from moorings, BATS hydrography, and ERS altimetry) will facilitate the construction of optimal estimates of the three dimensional structure of the water column as it evolves. These space-time continuous representations of oceanic fields will constitute a novel basis for interpretation of SeaWiFS and OCTS imagery by providing the ability to analyze ocean color variations in the context of the underlying circulation patterns.

A nitrogen based planktonic ecosystem model which has been incorporated into the circulation model will serve as a vehicle for the analysis of the biogeochemical response to physical forcing.  The specific process of interest here is the role of mesoscale eddies in nutrient supply to the upper ocean.  Recent modeling studies (McGillicuddy et al., 1995; McGillicuddy and Robinson, 1997) indicate substantial nutrient flux associated with the formation of cyclonic eddies and subsequent intensification caused by interaction with adjacent features.  Long term simulations in the Sargasso Sea based on statistically realistic mesoscale flow fields suggest that this eddy upwelling mechanism is the dominant mode of nutrient transport in the annual budget for the region.  Data driven coupled physical-biological simulations of the type proposed here will be used to test this hypothesis and thus should help to reconcile the longstanding controversy concerning nutrient supply in the oligotrophic waters of the open ocean. In addition, these hindcast simulations will be used to conduct a retrospective analysis of the BATS data to help differentiate between spatial and temporal variability in the time series record. The possibility of using this interdisciplinary model system in a nowcast/forecast mode to contribute to optimal resource deployment in future observational activities will be evaluated.