Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Numerical ocean model study of the Agulhas Bank and the cool ridge
Includes bibliographical references (p. [147]-158).
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Oceanography
2015
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613270944251904 |
|---|---|
| access_status_str | Open Access |
| author | Chang, Nicolette |
| author2 | Shillington, Frank |
| author_browse | Chang, Nicolette Shillington, Frank |
| author_facet | Shillington, Frank Chang, Nicolette |
| author_sort | Chang, Nicolette |
| collection | Thesis |
| description | Includes bibliographical references (p. [147]-158). |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/12426 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:28.738Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2015 |
| publishDateRange | 2015 |
| publishDateSort | 2015 |
| publisher | Department of Oceanography |
| publisherStr | Department of Oceanography |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/12426 Numerical ocean model study of the Agulhas Bank and the cool ridge Chang, Nicolette Shillington, Frank Penven, Pierrick Oceanography Includes bibliographical references (p. [147]-158). Includes abstract. The oceanic structure and circulation of the Agulhas Bank, the very wide continental shelf area off South Africa, has been explored in this thesis. The Agulhas Bank is a complex ocean region influenced by shelf processes as well as a nearby western boundary current, the Agulhas Current on its eastern margin and the Benguela Upwelling system on its western margin. In addition, a cold water feature, known as the cool ridge, has been observed on the Eastern Agulhas Bank. A consistent dynamical description is not available but it is commonly observed as a south-westerly flow of cold water in the upper water column, roughly following the 100m isobath and extending seawards off the coast. The formation of the cool ridge has also been investigated in this thesis by means of a numerical ocean model. Previous studies on the Agulhas Bank have been limited temporally and / or spatially. Thus, the Agulhas Bank as a whole has been inadequately sampled to provide a comprehensive representation. In order to remedy these deficiencies, the Regional Ocean Modeling System (ROMS) was used to study the Agulhas Bank dynamics. A large-scale model of the surrounding oceans, the SAfE (South African Experiment) configuration of the ROMS model, was used to force a one-way embedded finer-resolution model over the Agulhas Bank. This produced, 8 years of model data at an approximate horizontal resolution of 8km and 32 vertical terrain-following levels. Two main experiments were performed to understand the nature of the Agulhas Bank. Firstly, the "Reference Experiment" derived a seasonal ocean climatology of the Agulhas Bank. Secondly, the "No Agulhas Experiment" was carried out in an approach in which the Agulhas Current was removed from the shelf edge. A comparison of these two experiments yielded the influence of the Agulhas Current on the Agulhas Bank. The ROMS model was able to reproduce the main observed seasonal structure and circulation of the Agulhas Bank as well as the cool ridge. The Agulhas Bank showed marked seasonality, with its two-layer structure being significantly influenced by the Agulhas Current. The direct influence of the Agulhas Current on the Bank occurs on the Outer Agulhas Bank by the Agulhas Current itself or an Agulhas Current filament. Ekman veering by the interaction of the Agulhas Current with the bottom topography on the slope of the eastern Agulhas Bank advect cool water vertically onto the Bank. This strengthens the thermocline from below, in contrast to surface warming by solar insolation in summer and the Agulhas Current in winter. Cold waters, upwelled over the shelf edge, indirectly affect the greater Agulhas Bank by their advection by the predominantly westward mean currents. The most significant influence of the cold shelf-upwelled waters are in bringing cold waters to shallower depths over most of the Agulhas Bank. This may influence the waters that upwell at the coast, which on the eastern Agulhas Bank (without the Agulhas Current) are trapped under a thick warm surface layer. 2015-02-10T13:42:41Z 2015-02-10T13:42:41Z 2008 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/12426 eng application/pdf Department of Oceanography Faculty of Science University of Cape Town |
| spellingShingle | Oceanography Chang, Nicolette Numerical ocean model study of the Agulhas Bank and the cool ridge |
| thesis_degree_str | Doctoral |
| title | Numerical ocean model study of the Agulhas Bank and the cool ridge |
| title_full | Numerical ocean model study of the Agulhas Bank and the cool ridge |
| title_fullStr | Numerical ocean model study of the Agulhas Bank and the cool ridge |
| title_full_unstemmed | Numerical ocean model study of the Agulhas Bank and the cool ridge |
| title_short | Numerical ocean model study of the Agulhas Bank and the cool ridge |
| title_sort | numerical ocean model study of the agulhas bank and the cool ridge |
| topic | Oceanography |
| url | http://hdl.handle.net/11427/12426 |
| work_keys_str_mv | AT changnicolette numericaloceanmodelstudyoftheagulhasbankandthecoolridge |