Last Glacial Maximum simulations over southern Africa using a variable-resolution global model: synoptic-scale verification

Abstract

Reconstructing the glacial maximum climates of the Cape south coast region of South Africa is important within the context of understanding the evolution of modern humans in this region. Simulating the Last Glacial Maximum (LGM) climate was also a focal period of the Paleoclimate Intercomparison Project Phase 3 (PIMP3), in order to test the ability of climate models to produce realistic simulations under radiative forcings very different to today’s. The purpose of this research is to reconstruct the paleoclimate of the Cape south coast region of South Africa using high resolution regional climate modelling. The model used for this purpose is a variable-resolution global atmospheric model, the conformal-cubic atmospheric model (CCAM), which has been developed by the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia. An ensemble of LGM simulations was constructed, through the downscaling of PMIP3 coupled model simulations over southern Africa. A multiple nudging was performed, where CCAM was first integrated globally at a quasi-uniform resolution, with subsequent high-resolution dowsnscaling to southern Africa. This paper describes the global CCAM simulations. The simulations provide new insights into the LGM climate over southern Africa, including evidence that winters during the LGM were significantly wetter than in the present-day climate.