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.
| Language | English |
|---|---|
| Pages | 138-148 |
| Number of pages | 11 |
| Journal | Quaternary Science Reviews |
| Volume | 107 |
| Early online date | 10 Nov 2014 |
| DOIs | |
| Publication status | Published - 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
Cite this
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Influence of tropical easterlies in southern Africa's winter rainfall zone during the Holocene. / Chase, Brian M.; Lim, Sophak; Chevalier, Manuel; Boom, Arnoud; Carr, Andrew S.; Meadows, Michael E.; Reimer, Paula J.
In: Quaternary Science Reviews, Vol. 107, 01.01.2015, p. 138-148.Research output: Contribution to journal › Article
TY - JOUR
T1 - Influence of tropical easterlies in southern Africa's winter rainfall zone during the Holocene
AU - Chase, Brian M.
AU - Lim, Sophak
AU - Chevalier, Manuel
AU - Boom, Arnoud
AU - Carr, Andrew S.
AU - Meadows, Michael E.
AU - Reimer, Paula J.
PY - 2015/1/1
Y1 - 2015/1/1
N2 - 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.
AB - 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.
KW - Quatemary
KW - Holocene
KW - Southern Africa
KW - Rock hyrax midden
KW - Palaeoclimate
KW - delta C-13
KW - delta N-15
KW - Pollen
KW - Climate change
KW - LATE QUATERNARY PALEOENVIRONMENTS
KW - FECAL DEPOSITS HYRACEUM
KW - ROCK HYRAX MIDDENS
KW - ATMOSPHERIC CIRCULATION
KW - CLIMATE VARIABILITY
KW - VEGETATION HISTORY
KW - SOUTHWESTERN CAPE
KW - POLLEN ANALYSIS
KW - WESTERN CAPE
KW - SEA-ICE
U2 - 10.1016/j.quascirev.2014.10.011
DO - 10.1016/j.quascirev.2014.10.011
M3 - Article
VL - 107
SP - 138
EP - 148
JO - Quaternary Science Reviews
T2 - Quaternary Science Reviews
JF - Quaternary Science Reviews
SN - 0277-3791
ER -