The Physical Oceanography of Georges Bank and Its Impact on Biology

The U.S. GLOBEC NW Atlantic/Georges Bank program was designed to investigate the underlying physical and biological processes that control the population dynamics of marine animals, with the specific target species being the pelagic early life stages of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) and the copepod zooplankton Calanus finmarchicus and Pseudocalanus spp. (GLOBEC, 1992). The resulting combination of broadscale, long-term and process-oriented field studies conducted between 1994-1999, together with numerical model studies, has produced unique data sets and new ideas with which to investigate specific processes and the integration of these processes into a new level of understanding of the physics and biology of the Bank. Developing this new paradigm for physical/biological processes that control the population dynamics of the target species is a central goal of the Phase IV synthesis effort.

The research proposed here has three primary objectives that all serve the broader Phase IV effort. First, we seek to more fairly understand the physical dynamics and interactions of several specific processes (e.g., those associated with the seasonal evolution of stratification on the Bank, the crucial flow field over the Northeast Peak, and cross-frontal exchange within the tidal mixing and northern flank fronts) that are thought to play critical roles in zooplankton and fish recruitment. Second, we propose to combine these observationally based process synthesis studies into model-based studies to provide our best descriptions of the Bank's physical environment and its variability on time scales from minutes to monthly to seasonal for the GLOBEC field years. These model studies will use the finite-volume coastal circulation model (FVCOM) developed by C. Chen for coupled physical/biological studies. The model solutions, generated by hindcast and data assimilation approaches, will be used to define and quantify key physical mechanisms and physical/biological interactions on the Bank. Third, we want to provide other Phase IV investigators with as complete a description and understanding of the basic physical processes affecting their observations as possible.

Our work has two long-term goals: (a) to refine and quantify the new physical paradigm and the physical/biological interactions that impact the target species, and (b) to develop with Franks, Chen et al. the FVCOM coupled physical/biological model system to understand the coupled physical/biological system on the Bank, including why one year might differ from another biologically. These goals are clearly related, since the proposed data synthesis work will guide model evaluation and refinement, and the model simulations (both process and seasonal prognostic) will provide process understanding and realistic property and flow fields that are essential for quantitative biological modeling.