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The variability of Lagrangian transport in the southern Benguela Current upwelling system
This study analyses the physical mechanisms that impact Lagrangian pathways and transport in the southern Benguela upwelling system (SBUS),an environment in which currents are key components of many important ecological processes, including the dispersal of marine larvae. Physical advection by curre...
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| Format: | Thesis |
| Language: | English |
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Department of Oceanography
2020
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| _version_ | 1867613296011509760 |
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| access_status_str | Open Access |
| author | Ragoasha, Moagabo Natalie |
| author2 | Reason, Christopher |
| author_browse | Ragoasha, Moagabo Natalie Reason, Christopher |
| author_facet | Reason, Christopher Ragoasha, Moagabo Natalie |
| author_sort | Ragoasha, Moagabo Natalie |
| collection | Thesis |
| description | This study analyses the physical mechanisms that impact Lagrangian pathways and transport in the southern Benguela upwelling system (SBUS),an environment in which currents are key components of many important ecological processes, including the dispersal of marine larvae. Physical advection by currents is an important mechanism for egg and larvae transport success in the SBUS since the spawning areas and recruitment areas are separated by a long distance. High-resolution numerical model simulations of the SBUS coupled with particle tracking experiments are used to investigate Lagrangian pathways between the Cape Peninsula (34◦S) and St Helena Bay(32◦S) and how they are linked to the oceanic circulation. Transport success, given by the ratio of the number of particles that reach St Helena Bay over the total number of particles released, is used quantify the alongshore connectivity between the two regions. We have identified and quantified the following physical drivers: (i) Benguela Jet, (ii) offshore Ekman transport,(iii) inner shelf poleward current, (iv) mesoscale eddies to be responsible for the spatial and temporal variability of the alongshore connectivity. The Benguela Jet was found to be the dominant driver of the connectivity at both seasonal and interannual timescales. Moreover, the presence of anti-cyclonic eddies near the shelf-edge negatively impact transport success by advecting particles into the open ocean. The opposite occurs with shelf-edge eddies as they transport particles onshore onto the shelf and the Benguela Jet contributing to positive transport success anomalies. These findings will provide a valuable information for the future studies on the role of the physical drivers that impact transport of larvae and eggs. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/32411 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:51.607Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| 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:11427/32411 The variability of Lagrangian transport in the southern Benguela Current upwelling system Ragoasha, Moagabo Natalie Reason, Christopher Herbette, Steven Veitch, Jenny Cambon, Gildas Roy, Claude Oceanography This study analyses the physical mechanisms that impact Lagrangian pathways and transport in the southern Benguela upwelling system (SBUS),an environment in which currents are key components of many important ecological processes, including the dispersal of marine larvae. Physical advection by currents is an important mechanism for egg and larvae transport success in the SBUS since the spawning areas and recruitment areas are separated by a long distance. High-resolution numerical model simulations of the SBUS coupled with particle tracking experiments are used to investigate Lagrangian pathways between the Cape Peninsula (34◦S) and St Helena Bay(32◦S) and how they are linked to the oceanic circulation. Transport success, given by the ratio of the number of particles that reach St Helena Bay over the total number of particles released, is used quantify the alongshore connectivity between the two regions. We have identified and quantified the following physical drivers: (i) Benguela Jet, (ii) offshore Ekman transport,(iii) inner shelf poleward current, (iv) mesoscale eddies to be responsible for the spatial and temporal variability of the alongshore connectivity. The Benguela Jet was found to be the dominant driver of the connectivity at both seasonal and interannual timescales. Moreover, the presence of anti-cyclonic eddies near the shelf-edge negatively impact transport success by advecting particles into the open ocean. The opposite occurs with shelf-edge eddies as they transport particles onshore onto the shelf and the Benguela Jet contributing to positive transport success anomalies. These findings will provide a valuable information for the future studies on the role of the physical drivers that impact transport of larvae and eggs. 2020-11-19T12:03:50Z 2020-11-19T12:03:50Z 2020 2020-11-19T08:43:28Z Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/32411 eng application/pdf Department of Oceanography Faculty of Science |
| spellingShingle | Oceanography Ragoasha, Moagabo Natalie The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| thesis_degree_str | Doctoral |
| title | The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| title_full | The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| title_fullStr | The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| title_full_unstemmed | The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| title_short | The variability of Lagrangian transport in the southern Benguela Current upwelling system |
| title_sort | variability of lagrangian transport in the southern benguela current upwelling system |
| topic | Oceanography |
| url | http://hdl.handle.net/11427/32411 |
| work_keys_str_mv | AT ragoashamoagabonatalie thevariabilityoflagrangiantransportinthesouthernbenguelacurrentupwellingsystem AT ragoashamoagabonatalie variabilityoflagrangiantransportinthesouthernbenguelacurrentupwellingsystem |