Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios

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dc.contributor.advisorCompton, John Sen_ZA
dc.contributor.authorVon Koslowski, Rebeccaen_ZA
dc.date.accessioned2017-10-04T14:24:55Z
dc.date.available2017-10-04T14:24:55Z
dc.date.issued2017en_ZA
dc.description.abstractVariations in the global climate over time have long been associated with changes in the meridional overturning circulation of the oceans. It is now commonly believed that, during the Last Glacial Maximum (LGM), the transport of North Atlantic Deep Water (NADW) to the southeast Atlantic Ocean was reduced. A popular method to trace these ambient changes is the stable isotope systematics of neodymium (given as εNd). In this study εNd data were measured on mixed planktic and bulk foraminifera from two gravity cores, GeoB8336-6 and GeoB8342-6, retrieved from the Cape Basin at water depths of 3524 and 3521 meters from the western continental slope of South Africa. The samples were prepared following the protocol presented by the Cambridge group (Tachikawa, Piotrowski, & Bayon, 2014). Planktic and bulk foraminifera samples taken from the same core depth interval had the same εNd ratios within error, which suggests that bulk foraminifera may provide a quick way to reconstruct ambient bottom water values. However, more research is needed to further support these findings. While the Holocene samples' εNd ratios (εNd(N36/6a) -10.7±0.3 and εNd(N42/6a mean) -10.2±0.4) lie within the range of modern Eastern NADW (εNd(modern ENADW) -10.9±1.2), glacial samples yield significantly more radiogenic εNd ratios (εNd(N42/6b) -7.7/ εNd(N36/6b) -8.1). This indicates the greater influence of southern-sourced water masses and thus provides further evidence for a reduction of NADW during the last glacial. MIS3 samples show ratios that lie in between those observed in the LGM and Holocene, and it is hypothesized that ocean circulation during MIS3 was comparable to that during the transition from the LGM to the Holocene (Termination I).en_ZA
dc.identifier.apacitationVon Koslowski, R. (2017). <i>Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios</i>. (Thesis). University of Cape Town ,Faculty of Science ,Marine Research (MA-RE) Institute. Retrieved from http://hdl.handle.net/11427/25524en_ZA
dc.identifier.chicagocitationVon Koslowski, Rebecca. <i>"Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios."</i> Thesis., University of Cape Town ,Faculty of Science ,Marine Research (MA-RE) Institute, 2017. http://hdl.handle.net/11427/25524en_ZA
dc.identifier.citationVon Koslowski, R. 2017. Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Von Koslowski, Rebecca AB - Variations in the global climate over time have long been associated with changes in the meridional overturning circulation of the oceans. It is now commonly believed that, during the Last Glacial Maximum (LGM), the transport of North Atlantic Deep Water (NADW) to the southeast Atlantic Ocean was reduced. A popular method to trace these ambient changes is the stable isotope systematics of neodymium (given as εNd). In this study εNd data were measured on mixed planktic and bulk foraminifera from two gravity cores, GeoB8336-6 and GeoB8342-6, retrieved from the Cape Basin at water depths of 3524 and 3521 meters from the western continental slope of South Africa. The samples were prepared following the protocol presented by the Cambridge group (Tachikawa, Piotrowski, & Bayon, 2014). Planktic and bulk foraminifera samples taken from the same core depth interval had the same εNd ratios within error, which suggests that bulk foraminifera may provide a quick way to reconstruct ambient bottom water values. However, more research is needed to further support these findings. While the Holocene samples' εNd ratios (εNd(N36/6a) -10.7±0.3 and εNd(N42/6a mean) -10.2±0.4) lie within the range of modern Eastern NADW (εNd(modern ENADW) -10.9±1.2), glacial samples yield significantly more radiogenic εNd ratios (εNd(N42/6b) -7.7/ εNd(N36/6b) -8.1). This indicates the greater influence of southern-sourced water masses and thus provides further evidence for a reduction of NADW during the last glacial. MIS3 samples show ratios that lie in between those observed in the LGM and Holocene, and it is hypothesized that ocean circulation during MIS3 was comparable to that during the transition from the LGM to the Holocene (Termination I). DA - 2017 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2017 T1 - Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios TI - Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios UR - http://hdl.handle.net/11427/25524 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/25524
dc.identifier.vancouvercitationVon Koslowski R. Glacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratios. [Thesis]. University of Cape Town ,Faculty of Science ,Marine Research (MA-RE) Institute, 2017 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/25524en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentMarine Research (MA-RE) Instituteen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherApplied Marine Scienceen_ZA
dc.titleGlacial-interglacial variations of the water masses in the southeast Atlantic Ocean derived from foraminiferal neodymium isotope ratiosen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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