Data and models reveal humid environmental conditions during MIS 3 in two of the world’s largest deserts

MIS 3 environmental conditions in Africa north of the Equator and the Arabian Peninsula have long been controversial due to data scarcity and methodological caveats. In this paper we compare 245 continental hydrological records and 11 long and continuous continental and marine cores with results from the IPSL general circulation model to discuss hydrological changes between 59 and 29 ka in North Tropical Africa, North (Mediterranean) Africa and the Arabian Peninsula. Despite a generally glacial context, wet conditions widely expanded giving place to numerous lakes, rivers and wetlands. The major result of our study is to show that humid conditions appeared much earlier and were more prevalent in the Arabian Peninsula than in Africa, due to the conjunction of monsoon rains in summer and Mediterranean rains in winter. The mechanisms driving MIS 3 humidity in our study area involve global cooling factors such as greenhouse concentrations and ice volume, which have impacted available moisture, orbital forcing, which impacts monsoon circulation and amplitude and sensitivity to the state of the Atlantic Meridional Overturning Circulation (AMOC).