Abstract. A size-structured ecosystem model is coupled to a 3-dimensional, high-resolution circulation model to investigate the seasonal and interannual variability of physical and biological states and their driving mechanisms at the shelfbreak front of the Middle Atlantic Bight (MAB). Simulated surface chlorophyll fields compare favorably to the satellite observations and capture the shelfbreak biomass enhancement, which is one of the essential biological features of the region. The domain-wide upper water column nutrient content peaks in late winter-early spring. The phytoplankton spring bloom starts 1–2 months later, followed by a zooplankton bloom in early summer. Seasonal and interannual variability in hindcast shelfbreak nutrient supply is controlled by three processes: (1) local mixing that deepens the mixed layer and injects deep ocean nutrients into the upper water column; (2) alongshore nutrient transport by the shelfbreak jet and associated currents; and (3) nutrient upwelling associated with shelfbreak bottom boundary layer convergence. Interannual variability of physical and biological processes are highlighted by cross-shelf nutrient budget diagnostics for spring 2004 and 2007, which show not only complex vertical structure of various dynamical terms, but also significant variations in magnitude between the two years.
Seasonal and interannual variability of the marine bacterioplankton community throughout the water column over ten years
