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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  04 Aug 2020

04 Aug 2020

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This preprint is currently under review for the journal CP.

The transient impact of the African monsoon on Plio-Pleistocene Mediterranean sediments

Bas de Boer1, Marit Peters2,a, and Lucas J. Lourens2 Bas de Boer et al.
  • 1Earth and Climate Cluster, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
  • 2Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
  • anow at: United Experts cvba, Beringen, Belgium

Abstract. Over the Plio-Pleistocene interval a strong linkage exists between Northern African climate changes with the supply of dust over the surrounding oceans and continental runoff towards the Mediterranean Sea. Both these signatures in the sedimentary record are determined by orbital cycles influencing on the one hand glacial variability and on the other hand Northern African monsoon intensity. In this paper, we use the intermediate complexity model CLIMBER-2 to simulate African climate during the Plio-Pleistocene between 3.2 and 2.3 million years ago (Myr ago) and compare our simulations with existing and new climate reconstructions. The CLIMBER-2 model is externally forced with atmospheric CO2 concentrations, ice-sheet topography and orbital variations, all of which strongly influence climate during the Pliocene and Pleistocene. Our simulations indicate that the records of Northern Africa climate oscillate in phase with climatic precession. For the Earth's obliquity cycle, the time lag between the 41,000-year component in insolation forcing and the climatic response increased after inception of Northern Hemisphere (NH) glaciation around 2.8 Myr ago. To test the outcome of our simulations, we have put emphasis on the comparison between the simulated runoff of grid boxes encompassing the Sahara desert and the Sahel region and the sedimentary records of marine sediment cores ODP Site 659 (Atlantic Ocean) and ODP Site 967 (Mediterranean). In this study we will show for the first time an extended Ti/Al record of Site 967 down to 3.2 Myr ago. This record strongly correlates with runoff in the Sahara and Sahel regions, whereas correlation with the dust record of Site 659 is moderate and slightly improves after NH ice-sheet inception. We investigated the transient variability of the individual and combined contributions of the Sahel and Sahara regions and found significant transient behaviour, overlapping with the Plio-Pleistocene transition and inception of NH ice sheets. Prior to 2.8 Myr ago, a larger contribution from the Sahara region is required to explain variability of Mediterranean dust input. After this transition, we found that a more equal contribution of the two regions is required, representing an increased influence of Sahel runoff and wet periods.

Bas de Boer et al.

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Bas de Boer et al.

Bas de Boer et al.


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