Holocene variability in climate and oceanic conditions in the winter rainfall zone of South Africa—inferred from a high resolution diatom record from Verlorenvlei |
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| Authors: | Kelly L Kirsten Thomas Kasper Hayley C Cawthra Paul Strobel Lynne J Quick Michael E Meadows Torsten Haberzettl |
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| Institution: | 1. Department of Environmental and Geographical Science, University of Cape Town, South Africa;2. Department of Physical Geography, Institute of Geography, Friedrich Schiller University Jena, Germany;3. Geophysics and Remote Sensing Unit, Council for Geoscience Western Cape regional office, South Africa
African Centre for Coastal Palaeoscience, Nelson Mandela University, South Africa;4. African Centre for Coastal Palaeoscience, Nelson Mandela University, South Africa;5. Physical Geography, Institute of Geography and Geology, University of Greifswald, Germany |
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| Abstract: | We present a diatom record from a well-dated 15.25 m composite sedimentary core from Verlorenvlei, a shallow coastal lake on the west coast of South Africa. We show that fluctuations in the diatom record occur in response to changes in sea level, ocean–atmosphere interactions and latitudinal shifts in the wind belts. During the early to mid-Holocene, the system primarily responds to sea level changes. A marine community that favours high nutrients is evident, particularly during 9200–8000, 7420–7000 and 6200–5600 cal a bp , corroborating periods of Benguela upwelling linked to fluctuations in the southeast trade winds. Increases in bioproductivity (%TOC, C/N) and fresher-water diatoms are associated with wetter conditions over the region and the northward migration of the southern westerly wind belt, most notably between 8000 and 7500 cal a bp and over the last 700 years. The latter trends are concomitant with changes in the extent of Antarctic sea ice and availability of moisture in southern South America. During the late Holocene, as sea levels stabilised to modern levels, climate variability is more strongly evident. The body of evidence further reveals the sensitivity of the region to high-latitude atmospheric mechanisms, but also showcases the significance of the southeast trade winds. |
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| Keywords: | Benguela upwelling climate dynamics palaeoceanography sea level changes southern westerly winds |
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