Baroclinic Eddy Interaction with Isolated Topography

Abstract

Point vortex and finite-difference methods are used to study baroclinic eddies advected into weak and strong encounters with topography. It is argued that weak interactions often scatter radially symmetric eddies into generalized hetons. The dipole moments so generated within the eddy result in eddy propagations at various angles to the current. Strong interactions can result in the complete separation of the upper- and lower-layer circulations. Subsequent evolution in this case depends on many factors, although strong topographic obstacles (i.e., seamounts) permit a reorganization of the centers into a coherent structure. Weaker topography, confined to the deep ocean, can disrupt the lower center, although the upper center typically survives. Disassociation of the centers with both retaining their integrity is also possible. Heton generation can occur for eddies with weak lower-layer expressions, demonstrating a potentially strong control of shallow eddy propagation by deep sea bathymetry. Analytical and numerical estimates of the induced propagation speeds are sizable, arguing topographic scattering is a potentially powerful mechanism influencing eddy propagation.