Abstract:
A two-layer linear analytic model is used to study the
response of the mid-latitude ocean to the seasonal variation
of the windstress. The most important component of the response
is a barotropic quasi-steady Sverdrup balance.
A meridional ridge such as the Antilles Arc is modeled
as an infinitely thin meridional barrier that blocks the lower
layer but does not protrude into the
upper layer. It is found
that such a barrier has little effect on the upper layer flow
across the barrier. This result is obtained provided the frequency
of the motion is low enough so that free short Rossby
waves are essentially nondivergent. In this case there is
little coupling between the layers for energy propagating to
the east away from the barrier.
A study of the dynamics of flow over a sloping bottom
is made and the results are used to determine the effect on
seasonal oscillations of eastern boundary slopes and triangular
ridges. It is found that the presence of a slope at the
eastern boundary has little effect. A meridional ridge that
does not reach the interface may cause substantial scattering
of free Rossby waves, but unless the ridge is steep its
effect on the quasi-steady Sverdrup balance is minimal.
However, if the ridge height is a substantial fraction of the
lower layer depth and the width is comparable to the scale
of free short Rossby waves, the ridge will tend to block flow
in the lower layer, acting like the infinitely thin barrier.
The theory suggests that the Antilles Arc should have the
effect of a thin barrier, while the Mid-Atlantic Ridge should
have little effect on the response of the ocean to seasonal
wind variations.
