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Eolian Evidence for Spatial Variability of Late Quaternary Climates in Tropical Africa1

Published online by Cambridge University Press:  20 January 2017

Edward M. Pokras  and
Alan C. Mix
Edward M. Pokras
Affiliation:
Lamont-Doherty Geological Observatory, Columbia University, Palisades, New York 10964
Alan C. Mix
Affiliation:
Lamont-Doherty Geological Observatory, Columbia University, Palisades, New York 10964
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Abstract

Study of the eolian fraction of late Quaternary sediments from the tropical Atlantic reveals that two modes of long-term climate variability have existed in tropical Africa during the last 150,000 yr. Tropical northwest Africa (i.e., the southwestern Sahara and Sahel) was driest during glaciations and stades, but wetter than at present during interglaciations and interstades. This may be a response to ice sheets at higher latitudes, via equatorward displacement of the westerlies and the subtropical high. In contrast, central equatorial Africa (southeast of the Sahara) was most arid during interstades and times of ice growth, and most humid during deglaciation. Wet periods in this area correspond to insolation maxima in northern hemisphere summer. A 23,000-yr precessional rhythm is suggested, supporting a direct link between African Monsoon intensity and orbitally modulated insolation. The late Holocene is the only time observed when both areas are arid during an interglacial episode. This may reflect, in part, anthropogenic disturbance of late Holocene climates.

Type
Research Article
Information
Quaternary Research , Volume 24 , Issue 2 , July 1985 , pp. 137 - 149
Copyright
University of Washington

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Footnotes

1

Lamont-Doherty Geological Observatory, Contribution No. 3808.

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