Articles | Volume 7, issue 6
Research article
01 Dec 2016
Research article |  | 01 Dec 2016

Stepwise drying of Lake Turkana at the end of the African Humid Period: a forced regression modulated by solar activity variations?

Alexis Nutz and Mathieu Schuster

Abstract. Although the timing of the termination of the African Humid Period (AHP) is now relatively well established, the modes and controlling factors of this drying are still debated. Here, through a geomorphological approach, we characterize the regression of Lake Turkana at the end of the AHP. We show that lake level fall during this period was not continuous but rather stepwise and consisted of five episodes of rapid lake level fall separated by episodes marked by slower rates of lake level fall. Whereas the overall regressive trend reflects a decrease in regional precipitations linked to the gradual reduction in Northern Hemisphere summer insolation, itself controlled by orbital precession, we focus discussion on the origin of the five periods of accelerated lake level fall. We propose that these periods are due to temporary reductions in rainfall across the Lake Turkana area associated with repeated westward displacement of the Congo Air Boundary (CAB) during solar activity minima.

Short summary
From the geomorphology of a palaeodelta complex of Lake Turkana (Kenya), we explore the end of the Holocene African Humid Period (AHP) that corresponded to a major change in climate of Africa and that had important environmental impacts. Here, we propose that the transition from a wet to a dry period at the end of the AHP is stepwise, discussing a potential control by short-term variations in solar activity. Understanding this climate event is crucial to facing future climate changes.