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 similar to 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 similar to 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 Nino-Southern Oscillation events in the Eastern Equatorial Pacific.