The impact of Scotian Shelf Water "cross-over" on the plankton dynamics on Georges Bank: A 3-D experiment for the 1999 spring bloom

The 1999 March Sea WiFS images detected an intense phytoplankton bloom on the southern flank of Georges Bank (GB). The bloom covered a large portion of the southern flank between the 60 and 200 m isobaths, and later extended to and connected with an even larger patch near the Northeast Peak (NEP) and Browns Bank. A three-dimensional (3-D) model experiment was conducted to examine the cause of the bloom and the impact of Scotian Shelf Water on the spring phytoplankton bloom dynamics. The finite volume coastal ocean model (FVCOM) provided the hydrodynamic fields for Lagrangian particle trajectory, tracer and biological model experiments. Process-oriented modeling experiments showed that the formation and maintenance of the phytoplankton bloom on the southeastern flank of GB is related to the weak stratification caused by the transport of the colder but fresher Scotian Shelf Water across the Northeast Channel (NEC). With sufficient nutrients from the slope, the bloom could result from in situ growth of phytoplankton near the slope where the stabilizing salinity front is located. The model results suggest that the timing and location of the phytoplankton bloom on the southern flank of GB is sensitive to the spatial distribution of temperature and salinity on the bank, the flow fields across the NEC, and the location of the salinity front near the shelf break. (c) 2006 Elsevier Ltd. All rights reserved.