A 1.2 MA HISTORY OF TEMPERATURE AND HYDROCLIMATE IN THE LAKE MALAWI BASIN

In the East African Rift Valley, climate change is manifested as variability in both temperature and hydroclimate. While temperature changes are measureable, e.g. on glacial/interglacial timescales, they are quite muted compared to high latitudes. In contrast, significant variability in the hydrological cycle is observed, often resulting in major shifts of arid zones associated with global climate change. Such changes in temperature and hydrology can have a significant impact on both terrestrial and aquatic biota, including our hominin ancestors. We present a history of temperature in the Lake Malawi basin that spans the past 1.2 million years, based on analyses for TEX₈₆ on cores recovered by the Lake Malawi Drilling Project, and we compare this with the history of hydroclimate in the region, based on calcareous sediment accumulation when the lake was in closed-basin state and the carbon isotope composition of plant leaf waxes. Both Ca and d¹³C indicate a long term trend of increasing wetness in Malawi over the past 1.2 Ma, in contrast to the overall drying trend in East Africa over the past 3 Ma. The mean temperature in the basin has been about 24º C, somewhat cooler than today, but exhibiting no long-term trend over the 1.2 Ma history. The amplitude of glacial-interglacial temperature change has been on the order of 3º C over this time period.