The spatiotemporal extent of the Green Sahara during the last glacial period

Yassine Ait Brahim; Lijuan Sha; Jasper A Wassenburg; Khalil Azennoud; Hai Cheng; Francisco W Cruz; Lhoussaine Bouchaou

doi:10.1016/j.isci.2023.107018

The spatiotemporal extent of the Green Sahara during the last glacial period

iScience. 2023 Jun 7;26(7):107018. doi: 10.1016/j.isci.2023.107018. eCollection 2023 Jul 21.

Authors

Yassine Ait Brahim¹, Lijuan Sha², Jasper A Wassenburg^{3

4}, Khalil Azennoud¹, Hai Cheng², Francisco W Cruz⁵, Lhoussaine Bouchaou^{1

6}

Affiliations

¹ International Water Research Institute, Mohammed VI Polytechnic University, Benguerir, Morocco.
² Institute of Global Environmental Change, Xi'an Jiaotong Uniersity, Xi'an, China.
³ Center for Climate Physics, Institute for Basic Science, Busan, 46241, Republic of Korea.
⁴ Pusan National University, Busan, 46241, Republic of Korea.
⁵ Instituto de Geociências, University of Sao Paulo, Sao Paulo, Brazil.
⁶ Laboratory of Applied Geology and Geo-Environmental, Ibn Zohr University, Agadir, Morocco.

Abstract

The Sahara Desert, one of today's most inhospitable environments, has known periods of enhanced precipitation that supported pre-historic humans. However, the Green Sahara timing and moisture sources are not well known due to limited paleoclimate information. Here, we present a multi-proxy (δ¹⁸O, δ¹³C, Δ¹⁷O, and trace elements) speleothem-based climate record from Northwest (NW) Africa. Our data document two Green Sahara periods during Marine Isotope Stage (MIS) 5a and the Early to Mid-Holocene. Consistency with paleoclimate records across North Africa highlights the east-west geographical extent of the Green Sahara, whereas millennial-scale North Atlantic cooling (Heinrich) events consistently resulted in drier conditions. We demonstrate that an increase in westerly-originating winter precipitation during MIS5a resulted in favorable environmental conditions. The comparison of paleoclimate data with local archaeological sequences highlights the abrupt climate deterioration and the decline in human density in NW Africa during the MIS5-4 transition, which suggests climate-forced dispersals of populations, with possible implications for pathways into Eurasia.

Keywords: Earth history; Global change; Paleontology; Physical geography.