Stable Hydrogen Isotopic Composition of Sedimentary Plant Waxes as Quantitative Proxy for Rainfall in the West African Sahel

Abstract:

Multiple studies have demonstrated that the stable hydrogen isotopic composition (δD) of terrestrial leaf waxes (δD_wax) tracks that of precipitation (δD_precip) both spatially across climate gradients and on a range of different timescales. Yet, reconstructed estimates of δD_precip and corresponding rainfall typically remain largely relative, due mainly to uncertainties in plant ecosystem net fractionation, relative humidity, and the stability of the amount effect through time.

We present δD_wax together with corresponding stable carbon isotopic compositions (δ¹³C_wax) from a marine sediment core offshore from the North West (NW) African Sahel covering the past 100 years and overlapping with the instrumental record of rainfall. We developed a framework within which we produced a quantitative reconstruction of rainfall based on a δD_wax time series, and compared it to records of rainfall in the terrestrial catchment area. The combined datasets demonstrate the feasibility to derive an accurate quantitative estimate of precipitation based on δD_wax in specific depositional settings.