Response of the East African climate to orbital forcing during the last interglacial (130-117 ka) and the early last glacial (117-60 ka)

Variations in the temporal and spatial distribution of solar radiation caus ed by changes in Earth's orbit provide a partial explanation for observed l ong-term fluctuations in African lake levels, The understanding of causal l inks between insolation changes and lake-level fluctuations is essential fo r the design of models predicting future changes in the hydrological budget s and water supply in Africa. Here we present a record of climate change in East Africa between 175 and 60 ka. This time span includes the last interg lacial (the Eemian, 130-117 ka), which may provide tile closest analogue to the present interglacial, Assessments of the nature and timing of East Afr ican climate changes are based on lake-level fluctuations of Lake Naivasha (Kenya) inferred from sediment characteristics, diatom assemblages, and Ar- 40/Ar-39 dating, Our results show dramatic alternation between deep, freshw ater and shallow, highly alkaline lake conditions. The Lake Naivasha record demonstrates that periods of increased humidity in East Africa mainly foll ow precessional insolation forcing in spring, causing more intense April-Ma y rains every 23 k.y.