Rapid changes in the hydroclimate of southeast Africa during the mid- to late-Holocene

Abstract

The nature and cause of past changes in rainfall over southeast Africa are widely debated and remain unresolved. Here we present a 5,700 year record of moisture balance in southeast Africa based on the high-resolution analysis of a sediment core from Lake Muzi, South Africa. Sediment composition and diatom assemblages document distinct fluctuations in lake level that reflect dramatic shifts in the balance between precipitation and evapotranspiration. The record reveals that climatic instability and episodic aridity were persistent features of the regional climate, with severe drought episodes recorded at 4600–4200, 3700–2600, 2100–1400 and 850–550 cal yr BP. We find correspondence between prominent periods of prolonged aridity at Lake Muzi and abrupt increases in El Niño frequency recorded in archives from the tropical Pacific, suggesting that changes in the El Niño-Southern Oscillation (ENSO) likely played an underlying role in driving hydroclimate fluctuations in southeast Africa during the mid-to late-Holocene. Periods of aridity may have been further conditioned by the influence of the subtropical Indian Ocean dipole (SIOD) and regional-scale circulation patterns that acted to modulate the local expression of El Niño. Our findings highlight the need to better understand the interplay between ENSO teleconnections, Indian Ocean sea surface temperatures and regional-scale drivers, and how these act to control rainfall in southeast Africa, particularly under a changing climate.