Preprints
https://doi.org/10.5194/cp-2022-57
https://doi.org/10.5194/cp-2022-57
 
18 Aug 2022
18 Aug 2022
Status: a revised version of this preprint was accepted for the journal CP and is expected to appear here in due course.

Using data and model to infer climate and environmental changes during the Little Ice Age in tropical West Africa

Anne-Marie Lézine1, Maé Catrain1, Julián Villamayor1,2, and Myriam Khodri1 Anne-Marie Lézine et al.
  • 1Laboratoire d’Océanographie et du Climat. Expérimentation et Approche numérique/IPSL. Sorbonne Université-CNRS-IRD-MNHN. 4 Place Jussieu. 75005. Paris. France
  • 2Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain

Abstract. Here we present hydrological and vegetation paleo-data extracted from 28 sites in West Africa from 5° S to 19° N and the past1000/PMIP4 IPSL-CM6A-LR climate model simulations covering the 850–1850 CE period to document the environmental and climatic changes that occurred during the Little Ice Age (LIA). The comparison between paleo-data and model simulations shows a clear contrast between the area spanning the Sahel and the Savannah in the North, characterized by widespread drought, and the equatorial sites in the South, where humid conditions prevailed. Particular attention was paid to the Sahel, whose climatic evolution was characterized by a progressive drying trend between 1250 and 1850 CE. Three major features are highlighted: (1) the detection of two early warning signals around 1170 and 1240 CE preceding the onset of the LIA drying trend; (2) an irreversible tipping point at 1800–1850 CE characterized by a dramatic rainfall drop and a widespread environmental degradation in the Sahel; and (3) a succession of drying events punctuating the LIA, the major of which was dated around 1600 CE. The climatic long-term evolution of the Sahel is associated with a gradual southward displacement of the Inter-Tropical Convergence Zone induced by the radiative cooling impacts of major volcanic eruptions that have punctuated the last millennium.

Anne-Marie Lézine et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-57', Anonymous Referee #1, 23 Sep 2022
    • CC1: 'Reply on RC1', Anne-Marie Lezine, 06 Oct 2022
    • AC2: 'Reply on RC1', Anne-Marie Lezine, 18 Oct 2022
  • RC2: 'Comment on cp-2022-57', Anonymous Referee #2, 06 Oct 2022
    • AC1: 'Reply on RC2', Anne-Marie Lezine, 13 Oct 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-57', Anonymous Referee #1, 23 Sep 2022
    • CC1: 'Reply on RC1', Anne-Marie Lezine, 06 Oct 2022
    • AC2: 'Reply on RC1', Anne-Marie Lezine, 18 Oct 2022
  • RC2: 'Comment on cp-2022-57', Anonymous Referee #2, 06 Oct 2022
    • AC1: 'Reply on RC2', Anne-Marie Lezine, 13 Oct 2022

Anne-Marie Lézine et al.

Anne-Marie Lézine et al.

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Short summary
Data and climate simulations were used to discuss the West African Little Ice Age. We show a clear opposition between a dry Sahel-Savannah zone and a humid equatorial sector. In the Sahel region, the LIA was characterized by a gradual drying trend starting in 1250 CE after two early warning signals since 1170 CE. A tipping point was reached at 1800 CE. Drying events punctuated the LIA, the largest of which dated ca 1600 CE was also recorded in the Savannah zone.