Spatial complexity of 'Little Ice Age' climate in East Africa: sedimentary records from two crater lake basins in western Uganda

摘要

Lithostratigraphic analyses of the sedimentary record from two contrasting crater lake basins in western Uganda, Africa, provide evidence for three major century-scale arid intervals during the last 2000 years. Variations in sedimentation and salt mineralogy of hypersaline Lake Kitagata, and a succession of fine-grained lake sediments and peat in the freshwater Lake Kibengo, suggest century-scale droughts centred on ad 0, ～ 1100, ～ 1550 and 1750. These results broadly support data from nearby Lake Edward on the timing of drought in western Uganda, but contrast with lake sediment records from eastern equatorial Africa. In particular, our results suggest regional variability of East African climate during the main phase of the 'Little Ice Age' (ad ～ 1500 to 1800), with westernmost East Africa experiencing drought while areas farther east were wet. This spatial pattern highlights the strongly regional nature of century-scale climate changes over the African continent, and holds implications for the mechanisms governing African rainfall during the 'Little Ice Age'.