Rivers are essential components of the landscape, providing waterways, nutrients and water to human populations and ecosystems. Fluvial systems also play an important role to shape the landscape and connect the continent to the ocean. From a paleoclimatic point-of-view, studying past rivers using sedimentary archives allows us to determine the response of fluvial regimes to changes in rainfall patterns and climate dynamics. By targeting past time intervals encompassing rapid climatic changes or warmer conditions, we can derive useful information on potential future changes.
In this presentation, I will show two examples of past river systems that cover different time intervals and have different temporal resolutions. The first example will deal with extinct rivers, which flew in now hyper-arid parts of Libya. Tracked using their specific geochemical signature, sediments transported by these rivers enabled us to reconstruct past precipitation dynamics and reactivation phases during the last glacial cycle. In the second example, I will show new results on past Nile floods during the last African humid period from an annually-laminated archive. This unique record allows us to examine how the Nile River responded to warmer and more humid conditions, which are similar end-of-the-century forecasts. Both examples of past river flow are tightly related to the dynamics of past human populations.
I will also shortly present new projects on lake records and how these can extend our knowledge of past hydroclimate variability.