We applied the modern analog technique to foraminiferal counts from three equatorial Atlantic gravity cores to estimate paleothermocline depths in the eastern and western tropical Atlantic during the past 250 kyr. The eastern equatorial core GeoB 1105-4 is characterized by variations in the 23-kyr cycle, whereas the western sediment cores show a dominant periodicity at the 41-kyr band. The phase relationships with respect to insolation and ice volume suggest that thermocline fluctuations in the east are primarily driven by the intensity of the monsoon due to variations in low-latitude insolation. In contrast, changes of the thermocline depth in the western tropical Atlantic, which lead global ice volume at the 41-kyr band by 3-4 kyr, seem to depend on the strength of the SE trade winds in response to the meridional temperature gradients in the South Atlantic.
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