Preprints
https://doi.org/10.5194/cp-2020-130
https://doi.org/10.5194/cp-2020-130

  26 Oct 2020

26 Oct 2020

Review status: this preprint is currently under review for the journal CP.

Holocene sea level and environmental change at the southern Cape – an 8.5 kyr multi-proxy paleoclimate record from lake Voёlvlei, South Africa

Paul Strobel1, Marcel Bliedtner1, Andrew S. Carr2, Peter Frenzel3, Björn Klaes4, Gary Salazar5, Julian Struck1, Sönke Szidat5, Roland Zech1, and Torsten Haberzettl6 Paul Strobel et al.
  • 1Physical Geography, Institute of Geography, Friedrich Schiller University Jena, Jena, Germany
  • 2School of Geography, Geology and the Environment, University of Leicester, Leicester, UK
  • 3Institute of Geosciences, Friedrich Schiller University Jena, Jena, Germany
  • 4Department of Geology, University of Trier, Trier, Germany
  • 5Department of Chemistry and Biochemistry and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 6Physical Geography, Institute of Geography and Geology, University of Greifswald, Greifswald, Germany

Abstract. South Africa is a key region for paleoclimate studies reconstructing and understanding past changes in atmospheric circulation, i.e., temperate Westerlies and tropical Easterlies. However, due to the scarcity of natural archives, the environmental evolution during the late Quaternary remains highly debated. Many archives that are available are peri-coastal lakes and wetlands and sea level changes during the Holocene often overprinted the paleoenvironmental signals in these archives. This study presents a new record from the coastal wetland Voёlvlei, which is an intermittent lake situated in the year-round rainfall zone (YRZ) of South Africa at the southern Cape coast. It presents an ideal archive to investigate both sea level and environmental changes. A 13 m-long sediment core was retrieved from Voёlvlei and analysed using a multi-proxy approach. The chronology reveals a basal age of 8,440+200/−250 cal BP. Paleoecological and elemental analyses indicate marine intrusions from 8,440 to 7,000 cal BP with a salinity optimum at 7,030+150/−190 cal BP. Since 6,000 cal BP, silting up has been causing an intermittent freshwater lake.

Inferred from changes in allochthonous input, δ13Cn-alkane and δ2Hn-alkane increasing moisture is observed from 8,440+200/−250 cal BP. The δ2Hn-alkane record provides new evidence in contribution of different precipitation sources throughout the record with contributions from both Westerlies and Easterlies from 8,440 to 7,070 cal BP. Westerlies dominate from 7,070 to 6,420 cal BP followed by a distinct shift to an Easterly-dominance at 6,420 cal BP. An overall trend to a Westerly-lasting until 2,060 cal BP is followed by a trend towards an Easterlies-dominance, but both phases show several climatic spikes. Those spikes are also evident in other regional studies highlighting that the source and seasonality of precipitation has a mayor role for the hydrological balance. By comparing the Voёlvlei record with other regional studies, a similar trend in the overall moisture evolution along the southern Cape coast is inferred during the past 8.500 yrs.

Paul Strobel et al.

 
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Paul Strobel et al.

Paul Strobel et al.

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Short summary
This study presents a multi-proxy record from lake Voёlvlei and provides new insights in the sea level and paleoclimate history of the past 8.5 ka at South Africa’s southern Cape coast. Our results show that sea level changes at the southern coast are in good agreement with the western coast of South Africa. In terms of climate, our record provides valuable insights in changing sources of precipitation at the Southern Cape coast, i.e. Westerly- and Easterly-derived precipitation contribution.