PRELIMINARY DATA ON THE TIMING OF POST GLACIAL CLIMATE CHANGE IN WEST AFRICA FROM LAKE BOSUMTWI SEDIMENT RECORDS

Paleoclimate records of the last glacial termination with good age control are difficult to find in tropical locations. Records with annual or near annual resolution are even more difficult to find. Typical records with annual resolution (e.g. ice cores, tree rings, varved sediments) are rare or nonexistent in the tropics. For this reason, the timing of climate change in equatorial Africa is poorly known. Thus, it is difficult to test whether climate change in tropical Africa is synchronous with that of other tropical regions and with the high latitudes. Lake Bosumtwi, a varved lake in Ghana, West Africa, offers the potential to provide new information on the timing and character of hydrological change in West Africa during the last deglaciation. Here we present a revised lake level curve for Lake Bosumtwi, based on new radiocarbon dates of lake level high stands and on preliminary studies of the varved sediments preserved in Bosumtwi lake sediment cores. While the trend of lake level change following the last deglaciation and through the Holocene appears to reflect the influence low latitude summer insolation on the West African monsoon, changes following deglaciations were also characterized by several abrupt changes that appear to be synchronous with those recorded in northern hemisphere paleoclimate records. If true, this result would indicate a teleconnection between the climate in the eastern tropical Atlantic and that of the high latitude Northern Hemisphere.