Oceanography, Climate and Vegetation development of tropical Africa during the last glacial: Palynology and geochemistry of marine sediments of ODP Site 1078 (off Angola)

Abstract

In the last decades climate change research became more and more important due to the increasing impact of human activities on the Earth s climate system. The consideration of perspectives and results from paleoclimate observations has proven useful for climate change research, the verification of model outputs and thus future projections. The late Quaternary is characterised by large and abrupt climatic shifts on millennial and centennial time scales, the so-called Dansgaard-Oeschger (D-O) cycles and Heinrich Stadials (HS). Both, the D-O cycle and HS are thought to originate in the North Atlantic and are transmitted through the atmosphere and ocean circulation which results in a near-global footprint. It has been suggested that the abrupt climatic shifts associated with HS are the effect of a reduction in the strength of the Atlantic Meridional Overturning Circulation (AMOC). According to the hypothesis of the bipolar seesaw, a reduction in the AMOC leads to a build-up of heat in the South Atlantic. Although the tropics have the potential to alter the global atmosphere-ocean dynamics through changes in the heat and freshwater balance, little is known of their role in relation to abrupt climate perturbations. This thesis contains a compilation of high-resolution pollen records from South America and Africa covering the last glacial that documents the impact, timing and amplitude of abrupt climate change on the tropical vegetation. This thesis also focuses on the reconstruction of the vegetation, climate and oceanography of southern hemisphere Africa during the last glacial using marine sediments of Ocean Program Drilling Site 1078 (off Angola).