U.S. GLOBEC: Process Studies of Physical-Biological Interactions and Larval Fish on Georges Bank

Peter J.S. Franks (UCSD/Scripps) and
Changsheng Chen (Univ. of Georgia)

1. understand the interactions of tidal forcing, wind forcing and surface heat flux in determining the physical and biological dynamics of tidal fronts and banks on diel and seasonal time scales,
2. explore the details of boundary-layer dynamics, the influence of stratification, and the effects of biological behavior on cross-frontal exchange and patchiness in tidal fronts,
3. understand how large-scale winter storms, and patchiness of temperature, turbulence and food affect the growth and retention of larval cod and haddock on Georges Bank,
4. understand the influence of the shelf-break front on physical and biological exchanges and dynamics on Georges Bank.

These objectives will be achieved using a hierarchy of two- and three-dimensional models, incorporating data gathered during phases I and II of the U.S. GLOBEC Georges Bank study. The model architecture is based on the primitive- equation/turbulence-closure/ecosystem model developed in previous work. These models will use both idealized and realistic topography and forcings, including isolated banks and a realistic regional model of the Gulf of Maine and Georges Bank.

Previous work has shown this model architecture capable of accurately reproducing the tidally forced physical and biological dynamics on Georges Bank. This work must now be expanded to include surface heat flux and wind stress forcings over diel and seasonal time scales, and the influence of the shelf-slope front. The effects of these forcings on the target species of larval cod and haddock will be studied by coupling a metabolic model of larval fish to the physical-ecosystem model. The larval fish model incorporates temperature, food and turbulence dependence of growth.

The proposed research will make several important contributions to the oceanographic community:

1. the modelling analyses will significantly increase our understanding of the temporal and spatial dynamics of physical-biological couplings on Georges Bank and other regions of strong bathymetry, strong tidal forcing, and variable surface wind stress and heat flux,
2. the models are novel in the oceanographic community, and will be used in aiding the interpretation of data collected during Phases I and II of the U.S. GLOBEC Georges Bank Study, and in the planning of the 1999 field process study of tidal fronts on Georges Bank, and future field experiments,
3. the combination of physical and biological models will lead to significant increases in our understanding of the factors influencing planktonic production and the growth and recruitment of larval cod and haddock on Georges Bank.