Impacts of tectonic and orbital forcing on East African climate: a comparison based on global climate model simulations
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A global atmosphere–ocean model has been forced with topographic and orbital scenarios in order to evaluate the relative role of both factors for the past climate of East Africa. Forcing the model with a significantly reduced topography in Eastern and Southern Africa leads to a distinct increase in moisture transport from the Indian Ocean into the eastern part of the continent and increased precipitation in Eastern Africa. Simulations with step-wise reduced height show that this climate change occurs continuously with the change in topography, i.e., an abrupt change of local climatic features with a critical height is not found. Simulations of the last interglacial (at 125,000 years before present, i.e., the Eemian interglacial) and the last glacial inception (at 115,000 years before present) are used as examples for the role of orbital-induced changes in insolation. Here, changes in meridional temperature gradients lead to modifications in moisture transport of similar order of magnitude, but with different spatial and seasonal structure. For the Eemian interglacial, a distinct increase in summer moisture transport from the Atlantic deep into the continent at around 20°N is simulated.
KeywordsClimate simulation Paleoclimate Africa East African Rift System Tectonics Orbital forcing Interglacial Glacial Quaternary Cenozoic Human evolution
We are grateful to Pierre Sepulchre for fruitful discussions and providing his topographic scenarios. The study was performed within the research group RiftLink, which is financially supported by the Deutsche Forschungsgemeinschaft (DFG research unit 703). The ECHO-G model was provided by the Model and Data Group at the Max-Planck-Institute for Meteorology (Hamburg, Germany). The simulations were run on the facilities of the German Climate Computing Centre (DKRZ, Hamburg). We thank Stefanie Legutke, Ingo Kirchner and Stephan J. Lorenz for supporting the preparation of the simulations. We would like to thank the anonymous reviewers for their constructive suggestions and comments.
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