Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 7, 1351-1362, 2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
09 Dec 2011
Late Holocene plant and climate evolution at Lake Yoa, northern Chad: pollen data and climate simulations
A.-M. Lézine1, W. Zheng2, P. Braconnot1, and G. Krinner3 1Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CNRS-CEA-UVSQ, Orme des Merisiers, Bâtiment 701, 91191 Gif-sur-Yvette cedex, France
2LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, P.O. Box 9804, 100029 Beijing, China
3Laboratoire de Glaciologie et Géophysique de l'Environnement, UMR5183, CNRS-UJF Grenoble, Domaine Universitaire, 54 Rue Molière, BP 96, 38402 St Martin d'Hères cedex, France
Abstract. The discovery of groundwater-fed Lake Yoa (19.03° N, 20.31° E) in the hyperarid desert of northern Chad by the German research team ACACIA headed by S. Kröpelin provides a unique, continuous sedimentary sequence of late Holocene age available in the entire Saharan desert. Here we present pollen data and climate simulations using the LMDZ atmospheric model with a module representing the climatologically-relevant thermal and hydrological processes occurring above and beneath inland water surfaces to document past environmental and climate changes during the last 6000 cal yr BP. Special attention is paid to wind strength and direction, length and amplitude of the rainy season, and dry spell occurrence, all of which are of primary importance for plant distribution and pollen transport. In addition to climate changes and their impact on the natural environment, anthropogenic changes are also discussed. Two main features can be highlighted: (1) the shift from an earlier predominantly monsoonal climate regime to one dominated by northern Mediterranean fluxes that occurred after 4000 cal yr BP. The direct consequence of this was the establishment of the modern desert environment at Yoa at 2700 cal yr BP. (2) Changes in climate parameters (simulated rainfall amount and dry spell length) between 6 and 4000 cal yr BP were comparatively minor. However, changes in the seasonal distribution of precipitation during this time interval dramatically affected the vegetation composition and were at the origin of the retreat of tropical plant communities from Lake Yoa.

Citation: Lézine, A.-M., Zheng, W., Braconnot, P., and Krinner, G.: Late Holocene plant and climate evolution at Lake Yoa, northern Chad: pollen data and climate simulations, Clim. Past, 7, 1351-1362,, 2011.
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