Generation of mid-ocean eddies : the local baroclinic instability hypothesis

dc.contributor.author Arbic, Brian K.
dc.date.accessioned 2010-11-12T21:27:01Z
dc.date.available 2010-11-12T21:27:01Z
dc.date.issued 2000-08
dc.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 August 2000 en_US
dc.description.abstract The plausibility of local baroclinic instability as a generation mechanism for midocean mesoscale eddies is examined with a two-layer, quasi-geostrophic (QG) model forced by an imposed, horizontally homogeneous, vertically sheared mean flow and dissipated through bottom Ekman friction, Explanations are sought for two observed features of mid-ocean eddies: 1) substantial energy is retained in the baroclinic mode and in the associated deformation radius (Rd) scale, and 2) the ratio of eddy to mean kinetic energy is much larger than one, The tendency of QG to cascade energy into the barotropic mode and into scales larger than Rd can be counteracted when stratification is surface-trapped, for then the baroclinic mode is weakly damped, and hence enhanced, Numerical experiments are performed with both surface-trapped and uniform stratification to quantify this, Experiments with equal Ekman frictions in the two layers are also performed for purposes of contrast, Interpretation is aided with an inequality derived from the energy and enstrophy equations, The inequality forbids the simultaneous retention of substantial energy in the baroclinic mode and in scales near Rd when Ekman friction is symmetric, but points towards surface-trapped stratification and bottomtrapped friction as an environment in which both of these can be achieved, The dissertation also contains a systematic study of geostrophic turbulence forced by nonzonal flows, Narrow zonal jets emerge when shear-induced mean potential vorticity (PV) gradients are small compared to the planetary gradient (β), and energy is a strong function of the angle shear presents to the east-west direction, When shear-induced PV gradients are comparable to β, and the mean shear has a westward component, fields of monopolar vortices form and persist, Energy is asymmetric between fields of cyclones and anticyclones, Such asymmetry was commonly thought not to occur in QG, but is shown here to be introduced by the nonzonal basic state, In both jet and vortex regimes, eddy energy can be much larger than mean kinetic energy, contrary to the expectation that β stabilizes weak shear flows, en_US
dc.description.sponsorship My first three years here were funded by an Office of Naval Research/National Defense Science and Engineering Graduate Fellowship administered by Jeff Jarocz at the American Society for Engineering Education. During the last three years, most of my support has come the National Science Foundation via grant OCE-9617848, with some additional support coming from the Office of Naval Research via grant N00014-95-1-0824. en_US
dc.format.mimetype application/pdf
dc.identifier.citation Arbic, B. K. (2000). Generation of mid-ocean eddies : the local baroclinic instability hypothesis [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server. https://doi.org/10.1575/1912/4085
dc.identifier.doi 10.1575/1912/4085
dc.identifier.uri https://hdl.handle.net/1912/4085
dc.language.iso en_US en_US
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en_US
dc.relation.ispartofseries WHOI Theses en_US
dc.subject Eddies en_US
dc.subject Vortex-motion en_US
dc.subject Baroclinicity en_US
dc.subject Ocean-atmosphere interaction en_US
dc.subject Dynamic meteorology en_US
dc.title Generation of mid-ocean eddies : the local baroclinic instability hypothesis en_US
dc.type Thesis en_US
dspace.entity.type Publication
relation.isAuthorOfPublication 7739b52b-8194-46c9-85f2-4bc4448a016f
relation.isAuthorOfPublication.latestForDiscovery 7739b52b-8194-46c9-85f2-4bc4448a016f
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