DATE2022-07-04 11:06:54
TITLERelating the Mediterranean climate to the green Sahara
AUTHORSRachid Cheddadi (1) ,Matthieu Carré (2) ,Louis François (3) ,Enno Schefuss (4)
  1. 1) Institut Des Sciences De L’Évolution De Montpellier, Montpellier (Frace) ,2) Institut Pierre-simon Laplace-laboratoire D’océanographie Et Du Climat: Expérimentations Et Approches Numériques, Paris (France) ,3) Ur-spheres, University Of Liège,, Liège (Belgium) ,4) Marum - Center For Marine Environmental Sciences, Bremen (Germany)
ABSTRACTThe greening of the Sahara during the Holocene is still challenging the paleoclimate community. A strengthening of the African monsoon caused by increased summer insolation is usually invoked to explain why the Sahara was vegetated from 14,000 to 5,000 years ago (called the African Humid period or AHP). Recent paleoclimate studies and syntheses suggested that the monsoon front may have reached some Mediterranean latitudes (up to 31°N - 32°N) during the Holocene optimum. Here, we provide a unique climate record of quantified winter, spring, and summer precipitation from Lake Tislit (32°N) in Morocco over the past 18,500 years. This record shows that the NW Mediterranean region was wetter than today during the AHP because of increased winter precipitation and was not influenced by the monsoon. We explain that the increased seasonal contrast of insolation during the Holocene led to an intensification and southward shift of the Mediterranean winter precipitation system in addition to the intensified summer monsoon and we suggest that a winter rainfall zone must have met and possibly overlapped the monsoonal zone in the Sahara during the AHP Using a mechanistic vegetation model in Early Holocene conditions, we show that moisture contributions from the Mediterranean area and the North Atlantic Ocean in winter, were as important as an expanded summer monsoon up to the Mediterranean alone, for the greening of the Sahara during the African humid. In this talk we will provide both a past climate reconstruction and different vegetation model simulations for a better interpretation of the seasonal rainfall distribution over the Sahara. This conceptual framework should be taken into consideration in Earth system paleoclimate simulations used to explore the mechanisms of African climatic and environmental sensitivity. This study will help to better understand and simulate climate variability over northern Africa, including the African Mediterranean.