Publication Date:
2022-05-26
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1992
Description:
This study concerns the barotropic interactions between a mesoscale eddy and a
straight monotonic bottom topography. Through simple to relatively complicated modeling
effort, some of the fundamental properties of the interaction are investigated.
In chapter two, the fundamental aspects of the interaction are examined using
a simple contour dynamics model. With the simplest model configuration of an ideal
vortex and a step topography, the basic dynamical features of the observed oceanic
eddy-topography interaction are qualitatively reproduced. The results consist of eddy-induced
cross-topography exchange, formation of topographic eddies, eddy propagation
and generation of topographic waves.
In chapter three, a more complicated primitive equation model is used to investigate
a mesoscale eddy interacting with an exponential continental shelf/slope topography
on both f and β-planes. The f-plane model recasts the important features of chapter
two. The roles of the eddy size and strength and the geometry of topography are studied.
It is seen that the multiple anticyclonic eddy-slope interactions strongly affect the total
cross-slope volume transport and the evolution of both the original anticyclone and the
topographic eddy. Since a cyclone is trapped at the slope and eventually moves on to the
slope, it is most effective in causing perturbation on the shelf and slope. The responses
on the shelf and slope are mainly wavelike with dispersion relation obeying that of the
free shelf-trapped wave modes. On the β-plane, the problem of an eddy colliding onto a
continental shelf/slope from a distance with straight or oblique incident angles is investigated.
It is found that the straight eddy incident is more effective in achieving large
onslope eddy penetration distance than the oblique eddy incident. The formation of a
dipole-like eddy pair consisting of the original anticyclone and the topographic cyclone
acts to suppress the eddy decay due to long Rossby wave radiation. A weak along-slope
current near the edge of the slope is found, which is part of a outer slope circulation cell
originated from the Rossby wave wake trailing the propagating eddy. Model-observation comparisons in_chapter four show favorable qualitative agreement
of the model results with some of the observed events in the eastern U.S. continental
margins and in the Gulf of Mexico. The model results give dynamical interpretations to
some observed features of the oceanic eddy-topography interactions and provide enlightening
insight into the problem.
Keywords:
Eddies
;
Ocean currents
;
Fluid dynamics
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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