Drought and dust deposition in the West African Sahel: a 5500-year record from Kajemarum Oasis, northeastern Nigeria

A high-resolution, multiproxy palaeolimnological record from the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholds were crossed. Desert-dust deposition began to increase 4700 cal. BP. Rainfall during the summer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, giving rise to multidecadal to centennial-scale droughts and enhanced dust deposition, occurred 1500 cal. BP. Hence, the post-1968 Sahel drought is not unique. The prolonged arid episode that occurred around 1200–1000 cal. BP in Ethiopia, the Sahel and tropical Mexico may have been linked to an abrupt cooling event in the North Atlantic and to a cluster of intense El Niño-Southern Oscillation events in the Eastern Equatorial Pacific.