Paleoevaporation and Paleoprecipitation in the Tanganyika Basin at 18,000 Years B.P. Inferred from Hydrologic and Vegetation Proxies

Abstract

Paleo-hydrologic and -vegetation proxy data from the Tanganyika basin are integrated in energy and water balance equations to infer past evaporation and precipitation during the last glacial maximum (LGM). Our approach is first validated on the modern system. Large variations are assigned to input variables to simulate the interannual precipitation variability. Equations are then applied to the LGM. We first change those input parameters inferred from proxies (basin and lake surfaces, temperature, and land albedo). Our LGM simulation suggests (in percent of modern mean values) decreases in evaporation from the lake [E_l: −5% (between −13% and +3%)] and land [E_c: −8% (−19/+5)] bodies, in precipitation [P: −11% (−21/0)] and (P − E_c): −42% (−44/−40). Decreases in P and E are amplified [E_l: −8% (−16/0); E_c: −14% (−24/−2); P: −17% (−26/−6)] when including empirical changes in atmospheric transmission coefficient and Bowen ratio. Sensitivity runs suggest that even large changes in cloud cover and air humidity should not modify these trends. The results suggest that the Earth's glacial/interglacial boundary conditions play a significant role on climate of subequatorial southern Africa.