Li, X.1, D. McGillicuddy1
1AOPE Department, Woods Hole Oceanographic
Institution, Woods Hole, MA 02543
An adjoint data assimilation approach is used to explore the
physical and biological controls on Calanus finmarchicus C2 to C5
copepodites in the Georges Bank region. Monthly climatological
distributions of Calanus finmarchicus from the GLOBEC Georges Bank
Broad-Scale Surveys are assimilated into a coupled
physical-biological model. The model is run over the observational
period between January and June. The inversion quantifies the
supply stock of these Calanus finmarchicus copepodites to Georges
Bank, the biological sources/sinks, and physical advective/diffusive
transports of these animals near the Georges Bank region. Results
show that the Scotian Shelf and Gulf of Maine are important source
regions of C4 and C5 in late winter. Wilkinson Basin provides a
continuous source of Calanus finmarchicus to Georges Bank during
spring and early summer. The adjacent Georges Basin is a region of
both source and sink. Generally, both biological gains/losses and
physical advection are important for the observed distributions.
Large seasonal and spatial variabilities are present in all the
fields of the convergence of the advective/diffusive flux, as well
as growth and mortality. During spring and early summer, biological
production is the major contributor to the observed high abundance
on the Bank. The decline of C2 and C3 abundances in May is a
combined balance among biological processes and advection. The
disappearance of C2 to C4 from the crest of the Bank in June is
mainly a result of biological losses, while disappearance of C5 from
the crest results from both biological loss and advection.
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