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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 1 | Copyright
Clim. Past, 14, 73-84, 2018
https://doi.org/10.5194/cp-14-73-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 16 Jan 2018

Research article | 16 Jan 2018

Hybrid insolation forcing of Pliocene monsoon dynamics in West Africa

Rony R. Kuechler, Lydie M. Dupont, and Enno Schefuß Rony R. Kuechler et al.
  • MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str. 8, 28359 Bremen, Germany

Abstract. The Pliocene is regarded as a potential analogue for future climate with conditions generally warmer-than-today and higher-than-preindustrial atmospheric CO2 levels. Here we present the first orbitally resolved records of continental hydrology and vegetation changes from West Africa for two Pliocene time intervals (5.0–4.6Ma, 3.6–3.0Ma), which we compare with records from the last glacial cycle (Kuechler et al., 2013). Our results indicate that changes in local insolation alone are insufficient to explain the full degree of hydrologic variations. Generally two modes of interacting insolation forcings are observed: during eccentricity maxima, when precession was strong, the West African monsoon was driven by summer insolation; during eccentricity minima, when precession-driven variations in local insolation were minimal, obliquity-driven changes in the summer latitudinal insolation gradient became dominant. This hybrid monsoonal forcing concept explains orbitally controlled tropical climate changes, incorporating the forcing mechanism of latitudinal gradients for the Pliocene, which probably increased in importance during subsequent Northern Hemisphere glaciations.

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Measuring deuterium and stable carbon isotopes of higher plant wax extracted from marine sediments offshore of Mauritania, we recovered a record of hydrology and vegetation change in West Africa for two Pliocene intervals: 5.0–4.6 and 3.6–3.0 Ma. We find that changes in local summer insolation cannot fully explain the variations in the West African monsoon and that latitudinal insolation and temperature gradients are important drivers of tropical monsoon systems.
Measuring deuterium and stable carbon isotopes of higher plant wax extracted from marine...
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