Orbital forcing of climate over South Africa: A 200,000-year rainfall record from the Pretoria saltpan

Abstract

Late Pleistocene variations in rainfall in subtropical Southern Africa are estimated from sediments preserved in the Pretoria saltpan, a 200,000 year-old closed-basin crater lake on the interior plateau of South Africa. This record is one of the few long and continuous palaeoclimate records from the Southern hemisphere subtropics, as such it provides a fundamental test of the role of the orbital forcing on the global subtropical climate. The authors show that South African summer rainfall covaried with changes in southern hemisphere summer insolation resulting from orbital precession. As predicted by orbital precession geometry, this South African record is out of phase with North African palaeomonsoon indices; the amplitude of the rainfall response to insolation forcing agrees with climate model estimates. These results document the importance of direct orbital insolation forcing on both subtropical North and South African climate as well as the predicted antiphase sensitivity to precessional insolation forcing.