Spring Bloom on the Central Georges Bank in 1999: Its Origin and Fate

Ji, R.1, C. Davis1, C. Chen2, R. Beardsley1 and G. Cowles2
1Woods Hole Oceanographic Institution, Woods Hole, MA 02543
2School for Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, MA 02744

The possible sources and transport time scales of water parcels on the central portion of Georges Bank (inside 60-m isobath) have been estimated to examine the origin and fate of the spring phytoplankton bloom in that region. An "off-line" Lagrange particle trajectory approach was used in this study. The hydrodynamic flow field was interpreted from hourly model outputs of FVCOM (Finite Volume Coastal Ocean Model), which was driven by the realistic meteorological forcing from MM5 model output, with inclusion of SST and observed current velocity data assimilation. Particle trajectory results show that the "blooming" water in the southern part of the central Bank during February and March was mainly from the northern and northwestern edge of the Bank and was relatively older than the "non-blooming" water in the north. The water parcels on the central Bank had average exposure time (time spent inside 60-m isobath) of about 20 days, and tended to leave south- or southwest-ward. Moreover, particle trajectory results also suggested that the phytoplankton bloom on the central Bank has a limited potential contribution as a food source for the zooplankton population in the deeper flank areas.

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