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A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012
The Antarctic Circumpolar Current (ACC) within the Southern Ocean (SO) is the primary driver for global interoceanic exchanges. These exchanges form the foundation for the Meridional Overturning Circulation (MOC), a deep density driven circulation, which extends throughout the global oceans. The fro...
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| Format: | Thesis |
| Language: | English |
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Department of Oceanography
2015
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| _version_ | 1867613183479382016 |
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| access_status_str | Open Access |
| author | Jacobs, Christopher Richard |
| author2 | Ansorge, Isabelle Jane |
| author_browse | Ansorge, Isabelle Jane Jacobs, Christopher Richard |
| author_facet | Ansorge, Isabelle Jane Jacobs, Christopher Richard |
| author_sort | Jacobs, Christopher Richard |
| collection | Thesis |
| description | The Antarctic Circumpolar Current (ACC) within the Southern Ocean (SO) is the primary driver for global interoceanic exchanges. These exchanges form the foundation for the Meridional Overturning Circulation (MOC), a deep density driven circulation, which extends throughout the global oceans. The fronts of the ACC, consisting of several branches, separate zones of distinct water masses, thus identifying the location of the fronts and understanding their dynamics is of global importance. The GoodHope programme, is a repeat annual transect between South Africa and Antarctica, monitoring the exchanges within the Southeast Atlantic sector of the Southern Ocean. This is achieved through high resolution Expendable Bathythermograph (XBT) sampling. In this study XBT data over an eight year period (2004 – 2012) were investigated and analysed. One aim is to illustrate the variability of the fronts associated with the ACC using in-situ data from 21 transects during this eight year period. The Sub-tropical Front (STF) and Northern branch of the Sub-Antarctic Front (SAF-N) are seen to be the most variable with frontal latitudinal shifts ranging from 2-4° and 1-2° respectively. One cause of this high variability is the interaction of mesoscale features, particularly in the form of eddies and Agulhas rings. The southernmost fronts of the ACC, namely the Southern Antarctic Circumpolar front(sACCf), consisting of a Northern and Southern branch of the sACCf (sACCf-N and sACCf-S) and Southern Boundary (SBdy), also display high variability due to seasonality brought on by ice melt. The central fronts of the ACC, the Middle and Southern branches of the SAF (M-SAF and S-SAF)and Northern, Middle and Southern branches of the Polar Front (PF-N, PF-M and PF-S) remain throughout the eight year observations fairly constant, with shifts observed to be less than 1° of latitude. Grouping the Good Hope transects into austral summer periods, illustrates the di-pentadal nature of the STF, whereby the shifts are in response to mesoscale interactions. Comparing the mean position of the fronts and their position observed during a single winter cruise in July 2012, an overall Northward shift was observed with most of the fronts with significant shifts occurring in the SAF-N and PF-N. This is due to the outcrop of different water masses occurring further South ward and Northward respectively. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/15495 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:06.010Z |
| 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:11427/15495 A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 Jacobs, Christopher Richard Ansorge, Isabelle Jane Oceanography The Antarctic Circumpolar Current (ACC) within the Southern Ocean (SO) is the primary driver for global interoceanic exchanges. These exchanges form the foundation for the Meridional Overturning Circulation (MOC), a deep density driven circulation, which extends throughout the global oceans. The fronts of the ACC, consisting of several branches, separate zones of distinct water masses, thus identifying the location of the fronts and understanding their dynamics is of global importance. The GoodHope programme, is a repeat annual transect between South Africa and Antarctica, monitoring the exchanges within the Southeast Atlantic sector of the Southern Ocean. This is achieved through high resolution Expendable Bathythermograph (XBT) sampling. In this study XBT data over an eight year period (2004 – 2012) were investigated and analysed. One aim is to illustrate the variability of the fronts associated with the ACC using in-situ data from 21 transects during this eight year period. The Sub-tropical Front (STF) and Northern branch of the Sub-Antarctic Front (SAF-N) are seen to be the most variable with frontal latitudinal shifts ranging from 2-4° and 1-2° respectively. One cause of this high variability is the interaction of mesoscale features, particularly in the form of eddies and Agulhas rings. The southernmost fronts of the ACC, namely the Southern Antarctic Circumpolar front(sACCf), consisting of a Northern and Southern branch of the sACCf (sACCf-N and sACCf-S) and Southern Boundary (SBdy), also display high variability due to seasonality brought on by ice melt. The central fronts of the ACC, the Middle and Southern branches of the SAF (M-SAF and S-SAF)and Northern, Middle and Southern branches of the Polar Front (PF-N, PF-M and PF-S) remain throughout the eight year observations fairly constant, with shifts observed to be less than 1° of latitude. Grouping the Good Hope transects into austral summer periods, illustrates the di-pentadal nature of the STF, whereby the shifts are in response to mesoscale interactions. Comparing the mean position of the fronts and their position observed during a single winter cruise in July 2012, an overall Northward shift was observed with most of the fronts with significant shifts occurring in the SAF-N and PF-N. This is due to the outcrop of different water masses occurring further South ward and Northward respectively. 2015-12-01T09:25:38Z 2015-12-01T09:25:38Z 2015 Master Thesis Masters MSc http://hdl.handle.net/11427/15495 eng application/pdf Department of Oceanography Faculty of Science University of Cape Town |
| spellingShingle | Oceanography Jacobs, Christopher Richard A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| thesis_degree_str | Master's |
| title | A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| title_full | A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| title_fullStr | A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| title_full_unstemmed | A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| title_short | A description of the hydrography between Cape Town and Antarctica along the GoodHope Transect between 2004-2012 |
| title_sort | description of the hydrography between cape town and antarctica along the goodhope transect between 2004 2012 |
| topic | Oceanography |
| url | http://hdl.handle.net/11427/15495 |
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