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Holocene African droughts relate to eastern equatorial Atlantic cooling

¹ Deutsche Forschungsgemeinschaft (DFG) Research Center Ocean Margins, Bremen University, Leobener Strasse, 28359 Bremen, Germany
² Institut für Geowissenschaften, Universität Kiel, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany
³ Deutsche Forschungsgemeinschaft (DFG) Research Center Ocean Margins, Bremen University, Leobener Strasse, 28359 Bremen, Germany

Here we present evidence that the Holocene African monsoon system (AMS) varied in response to the eastern equatorial Atlantic sea-surface temperature (SST). Several short-term episodes of decreased moisture availability as a result of low eastern equatorial Atlantic SST are suggested by planktonic foraminiferal Mg/Ca ratios. These episodes promoted a weakening of the AMS and thus determined the timing and intensity of arid periods. Local sea-surface salinities also reveal regional patterns of precipitation in equatorial western Africa. The high eastern equatorial Atlantic SSTs occur in concert with seasonally increased insolation at low latitudes, suggesting a strong response of African monsoonal precipitation to oceanic conditions at low latitudes.

Key Words: eastern equatorial Atlantic • Mg/Ca • sea-surface temperature • African monsoon • aridity • lake levels

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