3 March, 2010 ESSC Brown Bag/Climate Dynamics Seminar
11:15 am, 529 Walker

Mechanisms of Terrestrial Climate Variability in Tropical Africa During the Early Pleistocene

Clayton Magill
Geosciences, Penn State

Abstract: Discrepancies between marine and terrestrial climate reconstructions have led to conflicting views on the mechanisms that control hydrologic variability in the tropics. Millennial-scale precipitation variability in monsoonal Africa during the late Pleistocene has been linked to equatorial sea-surface conditions, however, little is known about the consequences of weakening zonal (Walker) circulation on regional moisture balance. Here, we will present a record of equatorial African monsoon intensity and ecological succession during the development of modern Walker circulation (1.95 to 1.79 million years ago), derived from the hydrogen and carbon isotopic composition of terrestrial biomarkers. We conclude that prior to the intensification of Walker circulation, climate variability in equatorial Africa must have been determined by the changes in African monsoon strength that were driven by low-latitude precessional (23 kyr) forcing. The high frequency of equatorial climate changes, as compared to coeval glacial-interglacial cycles of about 41 kyr, may have impacted the speciation and dispersal of hominids.