Stager, Mayewski, Dixon — Climate of the Past
Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies
J. C. Stager1,2 , P. A. Mayewski2 , J. White1 , B. M. Chase3,4 , F. H. Neumann5,6 , M. E. Meadows7 , C. D. King1 , and D. A. Dixon2
1Natural Sciences, Paul Smith’s College, Paul Smiths, NY 12970, USA, 2Climate Change Institute, University of Maine, Orono, ME 04473, USA, 3Institut des Sciences de l’Evolution de Montpellier, D´epartement Pal´eoenvironnements et Pal´eoclimats (PAL), UMR5554, Universit´e Montpellier 2, Montpellier cedex 5, France, 4Department of Archaeology, History, Culture and Religion, University of Bergen, P.O. Box 7805, 5020, Bergen, Norway, 5Forschungsstelle f¨ur Pal¨aobotanik, Westf¨alische Wilhelms-Universit¨at M¨unster, 48143 M¨unster, Germany,6Bernard Price Institute for Palaeontological Research, University of the Witwatersrand Private Bag 3, Wits 2050, South Africa, 7Department of Environmental and Geographical Science, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
Clim. Past, 8, 877–887, 2012
www.clim-past.net/8/877/2012/
doi:10.5194/cp-8-877-2012
Abstract. The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures and ecosystems. Global climate models anticipate poleward retreat of the austral westerlies with future warming, but the available paleoclimate records that might test these models have been limited to South America and New Zealand, are not fully consistent with each other and 05 be complicated by influences from other climatic factors. Here we present the first highresolution diatom and sedimentological records from the winter rainfall region of South Africa, representing precipitation in the equatorward margin of the westerly wind belt during the last 1400 yr. Inferred rainfall was relatively high 1400–1200 cal yr BP, decreased until _950 cal yr BP, and rose notably through the Little Ice Age with pulses centred on 600, 530, 470, 330, 200, 90, and 20 cal yr BP. Synchronous fluctuations in Antarctic ice core chemistry strongly suggest that these variations were linked to changes in the westerlies. Equatorward drift of the westerlies during the wet periods 05 have influenced Atlantic meridional overturning circulation by restricting marine flow around the tip of Africa. Apparent inconsistencies among some aspects of records from South America, New Zealand and South Africa warn against the simplistic application of single records to the Southern Hemisphere as a whole. Nonetheless, these findings in general do support model projections of increasing aridity in the austral winter rainfall zones with future warming.