Lake Bosumtwi lies in a million-year-old meteorite impact crater located in the tropical forest lowlands of Ghana, in West Africa. The lake is hydrologically closed and known to be very sensitive to the precipitation/evaporation balance and the strength of the West African Monsoon. Lake Bosumtwi contains one of a very few, long annually laminated sediment records in the tropics, and has by far the longest, highest-resolution paleoclimate record in equatorial West Africa. Intellectual Merit: This grant studies interannual to millennial-scale West African monsoon dynamics over the last ~430 kyr (i.e., back through Marine Isotopic Stage [MIS] 11). This work provides insight into the role of the tropics in triggering, intensifying and propagating climate changes, as well as in responding to global and highlatitude changes. This work will produce the first continuous well-dated terrestrial record of West African climate & aerosol variability over multiple glacial cycles, and provide hydrologic constraints on a key methane source region, and use the annually-laminated sediments to examine globally significant questions regarding the exact timing and patterns of change over multiple glacial terminations (e.g., What is the low-latitude response to deglaciation events, and can we assess how fast large ice sheets melt and lead to interglacial conditions? What is the nature of climatic reversals on previous terminations? How long was MIS11, how was it manifested in the tropics, and how does it really relate to orbital forcing, particularly at the end? What is the full range of drought variability during warm climates?)
