Abstract:
The degree to which a baroclinic deep ocean could be responsible for the mean flow
on the shallow continental shelf is examined using steady, boundary forced models
which incorporate bottom friction. One set of models, for a vertically well mixed shelf,
includes the horizontal advection of density. The second set of models comprises a
three-layer model without and a two-layer model with interfacial friction.
It is found that near bottom flow has a short cross isobath scale due to the steep
continental slope and consequently that the deep oceans lower water column could
not be responsible for the observed mean flow. The cross isobath scale of flow in
the upper deep ocean is predominantly determined by the oceans velocity profile. In
a barotropic or near barotropic flow the upper water column follows the near bottom
flow and therefore has little influence on the shelf. A surface intensified deep ocean flow
is able to cross isobaths until it encounters the bottom. If deep ocean flow is confined
to a surface layer thinner than the depth at the shelf break it could be responsible
for the observed flow. The depth scale for velocity and density over the slope in the
Mid-Atlantic Bight is generally larger than the shelf break depth and consequently
it is concluded that the steep continental slope "insulates" this particular shelf from
baroclinic deep ocean influence and therefore that the observed shelf flow is not of
oceanic origin.
Using oxygen isotope data, Chapman et al. (1986) found that the Scotian shelf is
the major source of Mid-Atlantic Bight shelf water. Their barotropic modeling results
are extended to show that a baroclinic deep ocean also acts to hold shelf water on the
shelf.
