North-West African Hydrologic Changes in the Holocene: A Combined Isotopic Data and Model Approach
To achieve a better understanding of the hydrologic evolution of the North-West (NW) African monsoon system during the Holocene, in particular during inferred abrupt climate changes at the end of the African Humid Period (AHP), we investigated terrigenous plant lipids deposited in marine sediments offshore NW Africa. Changes in rainfall amount were estimated by compound-specific hydrogen isotope (δD) analyses. The spatial gradient of rainfall isotopic compositions is reflected in marine surface sediments. δD changes in plant waxes covering the last 100 years confirm the observed decrease in rainfall during the late twentieth century Sahel drought, and thus can be used for a quantitative calibration of δD and precipitation. δD changes in sedimentary plant waxes show no abrupt change at the end of the AHP suggesting a gradual precipitation decline. These results are supported by Holocene climate simulations using a coupled atmosphere-land surface model, which includes an explicit modeling of isotopic fractionation within the hydrological cycle.
KeywordsNorth-West africa Hydrology Compound-specific deuterium analysis Climate simulations Isotope modeling
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