ON THE RELATIONSHIP BETWEEN ANTARCTIC SEA ICE AND SOUTH-WESTERN AFRICAN CLIMATE

The typical Fynbos vegetation of the Cape region of South-western Africa is brought about by the local Mediterranean (winter rainfall) climate and its associated sharp seasonal precipitation contrasts. The winter-rain realm is bordered by hyper-arid deserts which may rapidly expand in response to future global warming, such as during the last warm period 125.000 years ago. It is therefore essential to understand the mechanisms that drive the winter rainfall in such a restricted area. Here, we correlate variations in South-western African humidity with changes in Antarctic sea-ice extent. New records of Antarctic sea-ice extent compared to existing palaeoclimate records of South-western Africa reveal a coherent signal during the last 50 kyr BP, with enhanced continental humidity during periods of increased sea-ice presence. We propose that greater glacial Antarctic sea-ice extent causes an equator-ward shift of oceanic and atmospheric frontal zones, causing a northward shift of the belt of Southern Westerlies, leading to an expansion of the winter-rain region and thus, increased precipitation over South-western Africa. This relationship implies enhanced desertification in South-western Africa in response to retreating sea-ice edge in the Atlantic sector of the Southern Ocean if global warming continues.