P5 Paleoclimatology - Stable oxygen (18O/16O) and hydrogen (2H/1H) isotopic composition of plants, soils and rainfall along altitudinal transects, and in paleoclimate archives of the Bale Mountains

埃塞俄比亚的大部分降水来自东非夏季风系统在北半球夏季月份提供的南风。然而，东非夏季风的强度在第四纪晚期有所不同，西风带提供的降水量在过去也可能相当高。在过去十年中，某些生物标志物和稳定同位素技术成为(半)定量古气候/水文研究的极具创新性和前景的工具。通过评估和应用这种生物标志物和稳定同位素工具，该项目旨在促进(半)定量重建埃塞俄比亚贝尔山脉的古气候/水文历史。更具体地说，应重建温度、相对空气湿度和降雨源和降水量。一个工作包将侧重于现代降水的空间和时间/季节同位素特征(2H/1H和18O/16O)。所获得的数据将有助于增进对影响贝尔山脉的现代大气环流模式的了解，包括其特定的同位素特征。第二个工作包将评估降水的同位素特征以及相对空气湿度和温度对植物和土壤的生物标记物和稳定同位素组成的影响程度。这将通过研究贝尔山脉的气候和海拔横断面来实现。方法学重点将放在叶蜡衍生的正构烷烃和脂肪酸生物标志物的化合物特异性2H分析、半纤维素衍生糖生物标志物的化合物特异性18O分析和土壤细菌衍生的甘油二烷基甘油四醚(GDGT)脂肪生物标志物上。第三个工作包有助于恢复沉积物岩心和建立年代地层学。这些岩心将与P2-人为土和P4-古生态分项目联合调查，作为重建人类占领史以及Bale山脉晚第四纪古环境/气候/水文史的档案。因此，上述指定的生物标记物和稳定同位素技术将在这一分项目中应用。

Ethiopia receives most of its precipitation from southerly winds provided by the East African Summer Monsoon system during Northern Hemispheric summer months. However, the strength of the East African Summer Monsoon varied during the Late Quaternary and the amount of precipitation provided by the westerlies may have been considerably higher in the past as well. During the last decade, certain biomarker and stable isotope techniques emerged as highly innovative and promising tools for (semi-)quantitative paleoclimate/hydrological research. By evaluating and applying such biomarker and stable isotope tools, this project aims at contributing to a (semi-)quantitative reconstruction of the paleoclimate/-hydrological history of the Bale Mountains, Ethiopia. More specifically, temperature, relative air humidity and precipitation source and amount shall be reconstructed.One work package will focus on the spatial and temporal/seasonal isotopic characterisation (2H/1H and 18O/16O) of modern day precipitation. The obtained data shall help to improve the understanding of the modern day atmospheric circulation patterns including their specific isotopic signatures affecting the Bale Mountains. A second work package will evaluate how accurately the isotopic signature of precipitation as well as relative air humidity and temperature are imprinted on the biomarker and stable isotopic composition of plants and soils. This will be achieved by studying climate and altitudinal transects on the Bale Mountains. The methodological focus will lay on compound-specific 2H-analyses of leaf wax-derived n-alkane and fatty acid biomarkers, on compound-specific 18O-analyses of hemicellulose-derived sugar biomarkers and on soil bacteria-derived glycerol dialkyl glycerol tetraether (GDGT) lipid biomarkers. The third work package contributes to the retrieval of sediment cores and the establishment of chronostratigraphies. These cores will be jointly investigated with the subprojects P2-Anthrosols and P4-Paleoecology as archives for the reconstruction of the human occupation history as well as the Late Quaternary paleoenvironmental/climate/hydrological history of the Bale Mountains. The above specified biomarker and stable isotope techniques will therefore be applied within this subproject.