Late Miocene to Pleistocene evolution of climate in Africa and the low-latitude Atlantic: overview of Leg 108 results

Abstract

Dust fluxes from Africa to the Atlantic were low during the final 3 m.y. of the Miocene and then increased markedly during the Pliocene and Pleistocene, suggesting major aridification of North Africa, possibly accompanied by an increase in the amplitude of aridity/humidity cycles. Other evidence also suggests increasing aridity and large oscillations during the Pliocene and Pleistocene, along with increased intensity of coastal trade winds. Northern Hemisphere ice sheets were not the major factor in the evolution of African climate. The apparent synchroneity of several major long-term changes in climate over Africa and the equatorial Atlantic with changes in the Southern Ocean and South Atlantic suggests long-term linkage in the response of these two regions. One plausible source of forcing is large-scale tectonic uplift, which occurred at unusually rapid rates during the latest Cenozoic in Southeast Asia, East Africa, and South America. Modeling experiments show that uplift causes large-scale rearrangements of atmospheric circulation, including the strength and position of the upper tropospheric jet streams and the lower tropospheric high- and low-pressure cells that control surface winds and moisture balances. -from Authors