D. J. McGillicuddy1, Jr. and A. Bucklin2
1Woods Hole Oceanographic Institution, Woods HOle, MA 02543
2University of New Hampshire, Durham, NH 03824
Physical and biological controls on the springtime distributions of
Pseudocalanus moultoni and P. newmani on Georges Bank
are examined by assimilating observations into a coupled
physical-biological model. Monthly snapshots of abundance are
derived from U.S. GLOBEC Georges Bank broad-scale surveys during
1997. The forward problem is posed as an
advection-diffusion-reaction equation for the copepod concentration.
The adjoint method of data assimilation is used to invert for the
biological sources and sinks implied by the observed changes in
abundance between surveys and the flow during the intervening
period. Based on this analysis, the two species appear to have
distinct population centers in the late winter/early spring: P.
moultoni on the northwest flank of the Bank and P.
newmani on the Northeast Peak and the southern tip of Browns
Bank. As the growing season progresses, the clockwise circulation
around Georges Bank blends reproducing (but not interbreeding)
animals from the two source regions, causing their distributions to
overlap by early summer. The springtime evolution of
Pseudocalanus distributions in this region is driven by a
complex mixture of hydrodynamic transport and species-specific
population dynamics, including both growth and mortality.
Note: This talk is one of three that fit together as a sequence: Bucklin, McGillicuddy, and Li.
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