Extratropical forcing of Sahel aridity during Heinrich stadials

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 delta(13)C 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 degrees 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. 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.