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 2016
Eddies in the ocean move westwards. Those shed by western boundary currents
must then interact with continental shelf-slope topography at the western boundary.
The presence of other eddies and mean lows complicates this simple picture,
yet satellite images show that mesoscale eddies translating near the shelfbreak routinely
affect the continental shelves of the Mid-Atlantic Bight, the Gulf of Mexico
etc. The consequent cross-shelfbreak transports are currently of unknown importance
to shelf budgets of heat, salt and volume.
Thus motivated, this thesis uses idealized continuously stratified numerical experiments
to explore eddy-slope interactions under four questions:
1. Can the continental slope prevent an eddy from reaching the shelfbreak?
2. What is the structure of the eddy-driven offshore low?
3. How is the continental shelf affected by an eddy at the shelfbreak?
4. Given surface observations, can one estimate the volume of water transported
across the shelfbreak?
The experiments show that the efficiency of Rossby wave radiation from the
eddy controls whether it can cross isobaths: by radiating energy the eddy becomes
shallow enough to move into shallower water. For wide continental slopes, relative
to an eddy diameter, a slope can prevent an anticyclone from reaching the
shelfbreak by shutting down such radiation. For narrow continental slopes, the interaction
repeatedly produces dipoles, whose cyclonic halves contain shelf-slope
water stacked over eddy water. The formation of such cyclones is explained. Then,
the structure of shelf lows forced by the eddy are studied: their vertical structures
are rationalized and scalings derived for their cross-isobath scales; for example, the
extent to which the eddy influences the shelf. A recipe for estimating cross-isobath
transports based on eddy surface properties is put forward. Finally, the findings
are tested against observations in the Middle Atlantic Bight of the northeastern
I acknowledge high-performance computing support from Yellowstone
(ark:/85065/d7wd3xhc) provided by NCAR’s Computational and Information Systems
Laboratory, sponsored by the National Science Foundation. The research presented here
was funded by National Science Foundation grants OCE-1059632 and OCE-1433953. Funding
support from the Academic Programs Oice, WHOI is also gratefully acknowledged.
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