Weakened ENSO-precipitation teleconnection over southern Africa during the Last Interglacial: A modeling perspective

Abstract

Precipitation in southern Africa has major impacts on local socio-economic development owing to the strong dependency on rain-fed agriculture, and its interannual variability is controlled by the El Niño-Southern Oscillation (ENSO). To help comprehend their linkage in a warmer future, here we investigate how the ENSO-southern African precipitation teleconnection in austral summer may vary during the Last Interglacial (LIG; ∼130–115 ka BP). Based on the model outputs from Paleoclimate Modeling Intercomparison Project Phase 4, we demonstrated that southern African precipitation in austral summer was negatively correlated with ENSO during the LIG (e.g., reduced precipitation during an El Niño event), similar to modern conditions, but the linkage was weakened by ∼42 % relative to the preindustrial in terms of the regression coefficient. The weakened ENSO-precipitation teleconnection was forced primarily by the El Niño-driven anomalous low-level cyclone over southern Africa during the LIG, which was also observed in the moisture flux pattern. The abnormal cyclone was associated with anomalous ascents and increased regional precipitation, supported by moisture budget analysis, which hence dampened the negative linkage between ENSO and precipitation seen in the present day. The anomalous atmospheric circulations might be linked to the dampened ENSO variability during the LIG by inducing a weakened Gill-type response in the central Pacific and associated secondary forcings in the Atlantic. Our results may help obtain a deeper comprehension of ENSO-southern African precipitation teleconnection in the orbitally induced warmer climate.