A 25,000 year record of climate and vegetation change from the southwestern Cape coast, South Africa

Lynne J Quick,B Adriaan Grobler,Brian M Chase,Andrew S Carr,Michael E Meadows,Manuel Chevalier

doi:10.1017/qua.2021.31

Abstract

AbstractThe southwestern Cape of South Africa is a particularly dynamic region in terms of long-term climate change. We analysed fossil pollen from a 25,000 year sediment core taken from a near-coastal wetland at Pearly Beach that revealed that distinct changes in vegetation composition occurred along the southwestern Cape coast. From these changes, considerable variability in temperature and moisture availability are inferred. Consistent with indications from elsewhere in southwestern Africa, variability in Atlantic Meridional Overturning Circulation (AMOC) was identified as a strong determinant of regional climate change. At Pearly Beach, this resulted in phases of relatively drier conditions (~24–22.5 cal ka BP and ~22–18 cal ka BP) demarcated by brief phases of increased humidity from ~24.5–24 cal ka BP and 22.5–22 cal ka BP. During glacial Termination I (~19–11.7 ka), a marked increase in coastal thicket pollen from ~18.5 to 15.0 cal ka BP indicates a substantial increase in moisture availability, coincident, and likely associated with, a slowing AMOC and a buildup of heat in the southern Atlantic. With clear links to glacial and deglacial Earth system dynamics and perturbations, the Pearly Beach record represents an important new contribution to a growing body of data, providing insights into the patterns and mechanisms of southwestern African climate change.

Highlights

The southwestern Cape of South Africa is a dynamic region in terms of long-term climate change, as it is situated at the nexus of the three dominant climate systems in southern Africa: the South Atlantic anticyclone, the temperate westerlies, and the tropical easterlies (Tyson, 1986; Taljaard, 1996; Tyson and Preston-Whyte, 2000; Chase and Meadows, 2007)
We present new fossil pollen, microcharcoal, and sediment particle size data from a 25,000 year sediment core taken from a wetland at Pearly Beach, southwestern Cape coast of South Africa
The results reveal considerable variability in vegetation composition and, by inference, climate along the southwestern Cape coast since the onset of the last glacial maximum (LGM)

Summary

Introduction

The southwestern Cape of South Africa is a dynamic region in terms of long-term climate change, as it is situated at the nexus of the three dominant climate systems in southern Africa: the South Atlantic anticyclone, the temperate westerlies, and the tropical easterlies (Tyson, 1986; Taljaard, 1996; Tyson and Preston-Whyte, 2000; Chase and Meadows, 2007). While most of the subcontinent experiences summer rainfall as a result of perturbations in the tropical easterlies, the southwestern Cape presently receives the majority of its rainfall during the austral winter, when the southern westerly storm track migrates northward (Tyson, 1986; Taljaard, 1996; Tyson and Preston-Whyte, 2000). These spatially distinct precipitation patterns led to the classification of the winter rainfall zone (WRZ) (sensu Chase and Meadows, 2007; >66% of annual precipitation in winter), the summer rainfall zone (SRZ; >66% of annual precipitation in summer), and a transitional zone of limited seasonality between the WRZ and SRZ, the aseasonal or year-round rainfall zone (ARZ) (Fig. 1)

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