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Abstract

In this talk, we present the current status and future plans for the biological-physical coupled modeling study in the Gulf of Maine and Georges Bank region. The food web model (Nitrogen-Phytoplankton-Zooplankton-Detritus, NPZD model) has been coupled on-line with the hydrodynamics model (FVCOM) and the whole year simulation for 1995 has been completed. The copepod population dynamics model (for Pseudocalanus sp.) has also been tested using a stage with mean age approach. The models were used to examine the local and remote forcings that affect nitrogen cycling/fluxes and phytoplankton bloom dynamics, as well as their impact on biological productivities in the Gulf of Maine/Georges Bank region. Specifically the impact of NAO related slope water intrusion on the seasonal nitrogen and phytoplankton dynamics was examined by initializing the model with different nitrogen concentrations in the deep waters. The NPZD model captures the spatio-temporal distribution of nitrogen and phytoplankton reasonably well. The model results suggest that high productivity on Georges Bank during summer is mainly supported by internal nitrogen recycling and tidal pumping processes along the tidal mixing front; and variation of nitrogen concentration in deep water (potentially associated with NAO) may not drive the interannual variability of phytoplankton productivity. Some critical issues regarding the application of coupled models in the Gulf of Maine/Georges Bank region were discussed, including the vital rates for copepod population dynamics model and the sensitivity of NPZD model to stratification and boundary conditions.