Holocene African droughts relate to eastern equatorial Atlantic cooling
- 1Deutsche Forschungsgemeinschaft (DFG) Research Center Ocean Margins, Bremen University, Leobener Strasse, 28359 Bremen, Germany
- 2Institut für Geowissenschaften, Universität Kiel, Ludewig-Meyn-Strasse 10, 24118 Kiel, Germany
- 3Deutsche Forschungsgemeinschaft (DFG) Research Center Ocean Margins, Bremen University, Leobener Strasse, 28359 Bremen, Germany
Abstract
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.
Footnotes
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↵*Current address: Department of Geological Sciences and Marine Science Institute, University of California–Santa Barbara, Santa Barbara, California 93106-9630, USA
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↵GSA Data Repository item 2005189, sample preparation and analysis of Mg/Ca, Figures DR1 and DR2, and Tables DR1 and DR2, is available online at www.geosociety.org/pubs/ft2005.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.
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- Accepted 19 August 2005.
- Received 17 May 2005.
- Revision received 18 August 2005.
- Geological Society of America
