Article (Scientific journals)
Early Holocene greening of the Sahara requires Mediterranean winter rainfall
Cheddadi, R.; Carré, M.; Nourelbait, M. et al.
2021In Proceedings of the National Academy of Sciences of the United States of America, 118 (23)
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Keywords :
African humid period green Sahara; Holocene; Paleoclimate reconstructions; Vegetation model simulations
Abstract :
[en] The greening of the Sahara, associated with the African Humid Period (AHP) between ca. 14,500 and 5,000 y ago, is arguably the largest climate-induced environmental change in the Holocene; it is usually explained by the strengthening and northward expansion of the African monsoon in response to orbital forcing. However, the strengthened monsoon in Early to Middle Holocene climate model simulations cannot sustain vegetation in the Sahara or account for the increased humidity in the Mediterranean region. Here, we present an 18,500-y pollen and leaf-wax δD record from Lake Tislit (32° N) in Morocco, which provides quantitative reconstruction of winter and summer precipitation in northern Africa. The record from Lake Tislit shows that the northern Sahara and the Mediterranean region were wetter in the AHP because of increased winter precipitation and were not influenced by the monsoon. The increased seasonal contrast of insolation led to an intensification and southward shift of the Mediterranean winter precipitation system in addition to the intensified summer monsoon. Therefore, a winter rainfall zone must have met and possibly overlapped the monsoonal zone in the Sahara. Using a mechanistic vegetation model in Early Holocene conditions, we show that this seasonal distribution of rainfall is more efficient than the increased monsoon alone in generating a green Sahara vegetation cover, in agreement with observed vegetation. This conceptual framework should be taken into consideration in Earth system paleoclimate simulations used to explore the mechanisms of African climatic and environmental sensitivity. © 2021 National Academy of Sciences. All rights reserved.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Cheddadi, R.;  Institut des Sciences de l'Évolution de Montpellier, CNRS, Institut de Recherche pour le Développement, University of Montpellier, Montpellier, 34000, France
Carré, M.;  Institut Pierre-Simon Laplace-Laboratoire d'Océanographie et du Climat, Expérimentations et approches numériques, CNRS, Institut de Recherche pour le Développement, Muséum National d'Histoire naturelle, Sorbonne Université, Pierre and Marie Curie University, Paris, 75006, France, Centro de Investigaciòn Para el Desarrollo Integral y Sostenible, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, 15102, Peru
Nourelbait, M.;  LGMSS, URAC45, University Chouaib Doukkali, El Jadida, 24000, Morocco
François, Louis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Modélisation du climat et des cycles biogéochimiques
Rhoujjati, A.;  Laboratoire Géoressources, URAC42, Université Cadi Ayyad, Marrakech, 40000, Morocco
Manay, R.;  Centro de Investigaciòn Para el Desarrollo Integral y Sostenible, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, 15102, Peru
Ochoa, D.;  Centro de Investigaciòn Para el Desarrollo Integral y Sostenible, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, 15102, Peru
Schefuß, E.;  MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, 28359, Germany
Language :
English
Title :
Early Holocene greening of the Sahara requires Mediterranean winter rainfall
Publication date :
2021
Journal title :
Proceedings of the National Academy of Sciences of the United States of America
ISSN :
0027-8424
eISSN :
1091-6490
Publisher :
National Academy of Sciences
Volume :
118
Issue :
23
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
ANR-15-JCLI-0003-01Fonds De La Recherche Scientifique - FNRS, FNRS: PDR-WISD-05
Available on ORBi :
since 23 June 2021

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