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AGU: Geophysical Research Letters

 

Keywords

  • sea surface temperature
  • Heinrich stadial
  • Sahel

Index Terms

  • Global Change: Abrupt/rapid climate change
  • Geographic Location: Africa
  • Paleoceanography: Sea surface temperature
  • Oceanography: Biological and Chemical: Stable isotopes
  • Atmospheric Processes: Paleoclimatology

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L20707, 4 PP., 2009
doi:10.1029/2009GL039687

Extratropical forcing of Sahel aridity during Heinrich stadials

E. M. Niedermeyer

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Matthias Prange

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Department of Geosciences, University of Bremen, Bremen, Germany

Stefan Mulitza

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Gesine Mollenhauer

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Department of Geosciences, University of Bremen, Bremen, Germany

Alfred Wegener Institute, Bremerhaven, Germany

Enno Schefuß

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Michael Schulz

Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Department of Geosciences, University of Bremen, Bremen, Germany

In order to investigate a possible link between tropical Northeast (NE) Atlantic sea-surface temperature (SST), Atlantic meridional overturning circulation (AMOC), and drought in the Sahel during the past 44 thousand years (kyr) we used alkenone paleothermometry and δ 13C of C. wuellerstorfi of a marine sediment core from the continental slope off Senegal. Our data show periods of low SST and reduced AMOC that coincided with drought in the Sahel during North Atlantic Heinrich stadials (HS). The coldest period was HS1 (ca. 15–18 kyr before present, BP) when SST decreased by more than 2°C. Moreover, the SST off Senegal lagged variations in Sahel aridity, which is in agreement with results from a freshwater hosing experiment. We conclude that variations in tropical NE Atlantic SST were not the initial trigger of millennial-scale Sahel droughts of the past 44 kyr. Instead, it is thought that these droughts were induced by substantial coolings of the extratropical North Atlantic.

Received 19 June 2009; accepted 23 September 2009; published 28 October 2009.

Citation: Niedermeyer, E. M., M. Prange, S. Mulitza, G. Mollenhauer, E. Schefuß, and M. Schulz (2009), Extratropical forcing of Sahel aridity during Heinrich stadials, Geophys. Res. Lett., 36, L20707, doi:10.1029/2009GL039687.

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