West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad
North Africa was wetter 15,000-5,000 years ago than today, with wetlands and lakes formed in the Sahara due to an enhanced monsoon. We reconstruct the lake-level history of Lake Mega-Chad, when it was the largest African lake, and demonstrate that this humid period ended abruptly 5,000 years ago, indicating that the African monsoon exhibits a nonlinear response to insolation forcing. The northern basin of Lake Mega-Chad, currently the world's greatest dust source, became dry around 1,000 years ago. Prior to that time dust output from the northern basin would have been limited, and suggestions that this dust plays an important role in fertilizing Atlantic and Amazonian ecosystems are either overstated or only true for the last thousand years.
Proceedings of the National Academy of Science
- Pub Date:
- July 2015