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- Title
The Squeezing of Eddies through Gaps.
- Authors
Simmons, Harper Lightfoot; Nof, Doron
- Abstract
The islands of the Lesser Antilles present a porous meridional barrier to North Brazil Current (NBC) rings. To better understand if, when, and how a NBC ring could be squeezed into the Caribbean Sea through such a gappy barrier, the encounter of a westward drifting eddy with a porous meridional wall is considered. First an eddy encountering a single aperture is modeled. To do so, both an analytical model and a reduced-gravity primitive equations numerical model are used. This was followed by numerical experiments that explored eddy collisions with barriers containing many gaps. In all of these models, the collisions were forced by either β or a steady advection through the gap(s). Using integrated constraints, an analytical solution was constructed for a zero potential vorticity lens passing through a single gap on a β plane. The solution involves a small parameter ε, the ratio of the short timescale associated with the f-plane adjustment, and the long encounter timescale due to β. It is found that, throughout the encounter, the lens remains axisymmetric and is drained by wall jets. Ultimately, the lens diameter adapts to the gap width so that the eddy loses contact with the walls and drifts slowly into the interior of the western basin. Numerical simulations are in good agreement with this theory. Numerical experiments also revealed that, just like a lens forced by β, an intense advected lens remained axisymmetric as it was slowly drained by wall jets. These intense lenses were “stiff” in the sense that they were not distorted by the strain resulting from the convergence of the advecting flow as it passed through the gap. Because of the stiffness of the eddy, it “stalled” and traveled through the gap more slowly than the underlying fluid. By contrast, weak lenses were “slaves” in the sense that they were squeezed through the gap with the advecting flow. No wall jets were present in ...
- Subjects
BRAZIL; TIDAL currents; EDDIES; BARRIER islands
- Publication
Journal of Physical Oceanography, 2002, Vol 32, Issue 1, p314
- ISSN
0022-3670
- Publication type
Article
- DOI
10.1175/1520-0485(2002)032<0314:TSOETG>2.0.CO;2