A 6000-year high-resolution composite record of El Niño-related drought in subtropical southeast Africa

Abstract

El Niño–Southern Oscillation (ENSO) extremes have a major impact on global temperature and rainfall patterns, triggering severe droughts and floods in many regions of the world. Paleoclimate records reveal significant changes in ENSO activity at centennial and millennial scales, but uncertainty remains regarding the exact nature of these variations during the Holocene and how they impacted climate patterns across different regions. Here we present a highly resolved sedimentary record from Lake Bhangazi North on the subtropical east coast of South Africa, where modern-day rainfall variability is profoundly influenced by ENSO through teleconnections mediated by the Walker Circulation. Stratigraphic and inorganic geochemical proxies at Lake Bhangazi North provide evidence for significant fluctuations in the local hydrological regime, characterised by extended intervals of aridity. Our findings corroborate independent sedimentary evidence from nearby sites at Lake Muzi and Mkhuze Delta, allowing for the generation of a composite proxy record of drought for the region. This record provides compelling evidence for the occurrence of several major drought events at ∼5100–4200, 3600–2700, 1900–1700 and ∼990 cal yr BP. The timing of these distinctive events exhibits striking correspondence with the ENSO proxy sedimentary record from Laguna Pallcacocha, Ecuador. We propose that El Niño, impacting moisture convergence over the subtropical eastern region of South Africa, was the primary driver of drought in the region over the mid-to-late Holocene. This hypothesis is further supported by stalagmite records from northwest Madagascar that reveal pronounced shifts towards wetter conditions coincident with major drought events in our study area, consistent with the modern rainfall anomaly pattern associated with ENSO. Our findings suggest that major aridity phases observed in records from the east coast of South Africa likely reflect large-scale shifts in regional moisture transport across subtropical southeastern Africa, driven by fluctuations in ENSO conditions.