The subject of localized topographic circulation has received much attention in the past, in particular Taylor columns have been extensively studied and several observations indicate their existence in the real ocean. In contrast, we study here the closed circulation created above a large scale seamount, in the absence of a mean flow, by the interaction of the eddy field with the topography. This study is based on the mean state theory of Dewar (1998) which relies in part on the downgradient diffusion of potential vorticity (PV) by eddies. Using a multilayered eddy resolving quasigeostrophic model, the eddy parameterization is directly confirmed through computation of eddy PV fluxes. The critic raised by Cummins (2000) about a spurious source of angular momentum above the anomalous topography due to the parameterization is seen to depend on the geometry of the basin. In the present case, the rectangular domain can maintain a pressure gradient torque which closes the angular momentum balance. The time variability of the circulation is characterized and interpreted in the light of the mean state theory result that bottom friction and eddy diffusivity control the circulation. A very low frequency mode internal to the topographic circulation is unraveled which is related to eddy diffusivity and PV homogenization . Interactions with higher frequency basin modes are also seen to provoke the sheddings of the circulation away from its topographic anchor. The combination of these two modes leads to different regimes. In the unstable regime, the circulation is destabilized by perturbations and shed away. In the stable regime, the circulation is stronger and remains above the topography anomaly. An anticyclonic wave with azimuthal mode number one is also observed in the numerical simulation, that is similar to observations. The observation in the Argentine Basin of a strong anticyclone above the Zapiola Drift is the main motivation for the present study. Results from the present study are compared to observations of the Zapiola Anticyclone, as well as its numerical simulation with the primitive equations model SPEM. / A Dissertation Submitted to the Department of Oceanography in Partial FulfiLlment of
the Requirements for the Degree of Doctor of Philosophy. / Summer Semester, 2005. / June 16, 2005. / Diffusion, Time Variability, Potential Vorticity, Quasigeostrophy, Eddies, Topographic Circulation / Includes bibliographical references. / William K. Dewar, Professor Directing Dissertation; Christopher Hunter, Outside Committee Member; Allan J. Clarke, Committee Member; Nancy Marcus, Committee Member; Doron Nof, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_175937 |
| Contributors | Bigorre, Sebastien (authoraut), Dewar, William K. (professor directing dissertation), Hunter, Christopher (outside committee member), Clarke, Allan J. (committee member), Marcus, Nancy (committee member), Nof, Doron (committee member), Department of Earth, Ocean and Atmospheric Sciences (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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