A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region

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dc.contributor.advisorShillington, Franken_ZA
dc.contributor.advisorRae, Christopher Duncombeen_ZA
dc.contributor.authorWhittle, Christo Peteren_ZA
dc.date.accessioned2014-08-13T19:44:16Z
dc.date.available2014-08-13T19:44:16Z
dc.date.issued2000en_ZA
dc.descriptionBibliography: leaves 111-126.en_ZA
dc.description.abstractAn anomalous leakage of Agulhas Current water into the south-east Atlantic Ocean, exhibiting a mushroom-like shape, was observed during routine observations of A VHRR satellite imagery in early December 1996. The development of this anomaly was followed on the sea surface temperature (SST) imagery and it was tentatively identified as a consequence of filament interaction between the Agulhas retroflection and an occluding Agulhas ring. This interpretation prompted a cruise onboard the FR.S Africana with the objective of conducting a hydrographic survey of the Agulhas ring and the associated filament near Cape Town. A descriptive analysis, gleaned from A VHRR satellite imagery and in situ data, of the hydrographic characteristics of a vortex dipole, surveyed during this cruise, is presented in this thesis. An analysis of water mass properties and geostrophic flow patterns determined that an Agulhas ring and a cyclonic eddy, containing Benguela Current water in its core, constituted a dipole vortex in the south-eastern Atlantic Ocean. During the period of the hydrographic survey, the secondary vortex exhibited an anticlockwise rotation of 8. 6°/day around the Agulhas ring A warm filament, originating from the western Agulhas Bank, was entrained between the two counter-rotating eddies, thus resulting in the mixing of Agulhas Bank water into the South Atlantic Ocean. Satellite altimetry and A VHRR imagery were used to "backtrack" the vortex dipole to its origin at the Agulhas retroflectiOn. By combining interpretations from the altimetry and A VHRR imagery, it was possible to describe the complex interactions the dipole displayed with the retroflection and the Agulhas Bank as it franslated in a north-westerly direction. The mushroom configuration, identified earlier on SST imagery, betrayed the presence of an adjacent pair of circulatory features of opposing spm. As the dipole translated northward, it interacted with the Agulhas Bank and the cyclone was strained, becoming a filament as it was forced between the Agulhas ring and the Agulhas Bank. West of Cape Town the dipole was re-established when the cyclone redeveloped, changing the orientation of the dipole so that a filament was drawn directly from the Agulhas Bank.en_ZA
dc.identifier.apacitationWhittle, C. P. (2000). <i>A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/6445en_ZA
dc.identifier.chicagocitationWhittle, Christo Peter. <i>"A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Oceanography, 2000. http://hdl.handle.net/11427/6445en_ZA
dc.identifier.citationWhittle, C. 2000. A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Whittle, Christo Peter AB - An anomalous leakage of Agulhas Current water into the south-east Atlantic Ocean, exhibiting a mushroom-like shape, was observed during routine observations of A VHRR satellite imagery in early December 1996. The development of this anomaly was followed on the sea surface temperature (SST) imagery and it was tentatively identified as a consequence of filament interaction between the Agulhas retroflection and an occluding Agulhas ring. This interpretation prompted a cruise onboard the FR.S Africana with the objective of conducting a hydrographic survey of the Agulhas ring and the associated filament near Cape Town. A descriptive analysis, gleaned from A VHRR satellite imagery and in situ data, of the hydrographic characteristics of a vortex dipole, surveyed during this cruise, is presented in this thesis. An analysis of water mass properties and geostrophic flow patterns determined that an Agulhas ring and a cyclonic eddy, containing Benguela Current water in its core, constituted a dipole vortex in the south-eastern Atlantic Ocean. During the period of the hydrographic survey, the secondary vortex exhibited an anticlockwise rotation of 8. 6°/day around the Agulhas ring A warm filament, originating from the western Agulhas Bank, was entrained between the two counter-rotating eddies, thus resulting in the mixing of Agulhas Bank water into the South Atlantic Ocean. Satellite altimetry and A VHRR imagery were used to "backtrack" the vortex dipole to its origin at the Agulhas retroflectiOn. By combining interpretations from the altimetry and A VHRR imagery, it was possible to describe the complex interactions the dipole displayed with the retroflection and the Agulhas Bank as it franslated in a north-westerly direction. The mushroom configuration, identified earlier on SST imagery, betrayed the presence of an adjacent pair of circulatory features of opposing spm. As the dipole translated northward, it interacted with the Agulhas Bank and the cyclone was strained, becoming a filament as it was forced between the Agulhas ring and the Agulhas Bank. West of Cape Town the dipole was re-established when the cyclone redeveloped, changing the orientation of the dipole so that a filament was drawn directly from the Agulhas Bank. DA - 2000 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2000 T1 - A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region TI - A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region UR - http://hdl.handle.net/11427/6445 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6445
dc.identifier.vancouvercitationWhittle CP. A descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection region. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Oceanography, 2000 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6445en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Oceanographyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherOceanographyen_ZA
dc.titleA descriptive analysis of the genesis and translation of a dipole vortex from the Agulhas retroflection regionen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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