Influence of tropical easterlies in southern Africa's winter rainfall zone during the Holocene

Brian M. Chase*, Sophak Lim, Manuel Chevalier, Arnoud Boom, Andrew S. Carr, Michael E. Meadows, Paula J. Reimer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)

Abstract

South Africa's southwestern Cape occupies a critical transition zone between Southern Hemisphere temperate (winter) and tropical (summer) moisture-bearing systems. In the recent geological past, it has been proposed that the relative influence of these systems may have changed substantially, but little reliable evidence regarding regional hydroclimates and rainfall seasonality exists to refine or substantiate the understanding of long-term dynamics. In this paper we present a mid-to late Holocene multi-proxy record of environmental change from a rock hyrax midden from Katbakkies Pass, located along the modern boundary between the winter and summer rainfall zones. Derived from stable carbon and nitrogen isotopes, fossil pollen and microcharcoal, these data provide a high resolution record of changes in humidity, and insight into changes in rainfall seasonality. Whereas previous work concluded that the site had generally experienced only subtle environmental change during the Holocene, our records indicate that significant, abrupt changes have occurred in the region over the last 7000 years. Contrary to expectations based on the site's location, these data indicate that the primary determinant of changes in humidity is summer rather than winter rainfall variability, and its influence on drought season intensity and/or length. These findings are consistent with independent records of upwelling along the southern and western coasts, which indicate that periods of increased humidity are related to increased tropical easterly flow. This substantially refines our understanding of the nature of temperate and tropical circulation system dynamics in SW Africa, and how changes in their relative dominance have impacted regional environments during the Holocene. 

Original languageEnglish
Pages (from-to)138-148
Number of pages11
JournalQuaternary Science Reviews
Volume107
Early online date10 Nov 2014
DOIs
Publication statusPublished - 01 Jan 2015

Keywords

  • Quatemary
  • Holocene
  • Southern Africa
  • Rock hyrax midden
  • Palaeoclimate
  • delta C-13
  • delta N-15
  • Pollen
  • Climate change
  • LATE QUATERNARY PALEOENVIRONMENTS
  • FECAL DEPOSITS HYRACEUM
  • ROCK HYRAX MIDDENS
  • ATMOSPHERIC CIRCULATION
  • CLIMATE VARIABILITY
  • VEGETATION HISTORY
  • SOUTHWESTERN CAPE
  • POLLEN ANALYSIS
  • WESTERN CAPE
  • SEA-ICE

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