The drivers of late Quaternary climate variability in eastern South Africa

The scarcity of continuous, terrestrial, palaeoenvironmental records in eastern South Africa leaves the evolution of late Quaternary climate and its driving mechanisms uncertain. Here we use a ~ 7-m long core from Mfabeni peatland (KwaZulu-Natal, South Africa) to reconstruct climate variability for the last 32 thousand years (ka BP). We infer past vegetation and hydrological variability using stable carbon (𝛿13Cwax) and hydrogen isotopes (𝛿Dwax) of plant-wax n-alkanes and use Paq to reconstruct water table changes. Our results indicate that late Quaternary climate in eastern South Africa did not respond directly to orbital forcing nor to changes in sea surface temperatures (SSTs) in the western Indian Ocean. The arid conditions evidenced at Mfabeni during the Last Glacial Maximum (LGM) are a consequence of both low SSTs and an equatorward displacement of the southern hemisphere westerlies due to increased Antarctic sea ice extent. The increased humidity at Mfabeni between 19–14 ka BP likely resulted from decreased Antarctic sea ice which led to a southward retreat of the westerlies and increased the influence of the moisture-bearing tropical easterlies. Between 14–5 ka BP, when the westerlies were in their southernmost position, local insolation became the dominant control, leading to stronger atmospheric convection and an enhanced tropical easterly monsoon. Generally drier conditions persisted during the past c. 5 kyrs, but were overlain by high amplitude, millennial-scale environmental variability, probably resulting from an equatorward return of the southern hemisphere westerlies and heightened ENSO activity. Our findings stress the influence of the southern hemisphere westerlies in driving climatological and environmental changes in eastern South Africa.