Late Holocene precipitation variability in the summer rainfall region of South Africa

The late Holocene history of the South African summer rainfall zone offers insights into the effects of climate on ecosystems and human societies, as well as into the accuracy of model projections of the future. However, some important aspects of this region's climatic history remain unresolved. Here we present new high-resolution diatom records representing hydrological fluctuations at Lake Sibaya, KwaZulu-Natal, during the last 1800 years. The cores were dated with 14C, 210Pb, 137Cs, and exotic pollen, and were sampled at increments of 1–22 years. A low stand ending ∼AD 150 was followed by additional decadal to century-scale droughts, most notably ∼AD 1540–1760, and several periods of markedly wetter conditions ∼AD 220–290, AD 790–830, AD 1470–1540, and AD 1760–1860. The Medieval Climate Anomaly was generally wetter than average and the Little Ice Age was generally drier, but hydroclimate during both intervals was highly variable. These records confirm that local tree ring and stalagmite gray scale series represent rainfall variability, but they also show that widely cited stable isotope series from Makapansgat do not represent past climate as clearly. Because many interpretations of the climatic history of southern Africa have been influenced by those isotope data, we re-examine late Holocene precipitation variability in the summer rainfall zone, and also address model projections of future precipitation in the region.

► The first high-resolution diatom record from South Africa's summer rainfall zone is presented. ► Precipitation varied markedly during the late Holocene, starting with major drought ca 1800 BP. ► The MCA and LIA intervals were wetter and drier than average, respectively, but not consistently. ► Stable isotope data from Cold Air Cave do not represent rainfall as clearly as speleothem gray scale. ► Complexity of rainfall history revealed in these records could make future projections difficult.