Sylvestre et al. (2026) Decadal-scale droughts disrupted the African Humid Period in the Sahara

Identification

• Journal: Nature
• Year: 2026
• Date: 2026-03-25
• Authors: Florence Sylvestre, Martin Melles, Volker Wennrich, Michèle Dinies, Françoise Chalié, Didier Swingedouw, Anne Dallmeyer, Xiaoxu Shi, Martin Claussen, Andrea Jaeschke, Christine Cocquyt, Jens Karls, Jan Kuper, Baba Mallaye, Jean-Charles Mazur, Christine Paillès, Remadji Rirongarti, Janet Rethemeyer, Benedikt Ritter-Prinz, Enno Schefuß, Finn Viehberg, Bernd Wagner, Martin Werner, Abdallah N. Yacoub, Stefan Kröpelin
• DOI: 10.1038/s41586-026-10336-7

Research Groups

• Centre de Recherches et d’Enseignement en Géosciences de l’Environnement (CEREGE), Aix-Marseille Université, CNRS, IRD, INRAE, Aix-en-Provence, France
• Institute of Geology and Mineralogy, University of Cologne, Cologne, Germany
• Institute of Geographical Sciences, Freie Universität Berlin, Berlin, Germany
• Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Université de Bordeaux, Bordeaux, France
• Max Planck Institute for Meteorology, Hamburg, Germany
• Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
• Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
• Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Hamburg, Germany
• Institute for Crop Science and Resource Conservation (INRES), University of Bonn, Bonn, Germany
• Meise Botanic Garden, Meise, Belgium
• Limnology Unit, Ghent University, Ghent, Belgium
• Institute for Prehistoric Archaeology, University of Cologne, Cologne, Germany
• Centre National De Recherche Pour le Développement (CNRD), N’Djaména, Chad
• Laboratoire Hydro-Géosciences et Réservoir, Université de N’Djamena, N’Djaména, Chad
• MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
• University of Greifswald, Institute of Geography and Geology, Greifswald, Germany

Short Summary

This study reconstructs the hydrological history of Lake Yoa, Chad, over the past 10.25 thousand years, revealing that the African Humid Period was interrupted by decadal-scale droughts, particularly a prominent 8.2 kyr bp event linked to Atlantic Meridional Overturning Circulation weakening.

Objective

• To precisely date and characterize decadal-scale drought events that punctuated the African Humid Period in the central Sahara and investigate their potential links to North Atlantic climate forcings.

Study Configuration

• Spatial Scale: Central Sahara (Lake Yoa, Chad), Tibesti Mountains, North Africa, Sahel, North Atlantic.
• Temporal Scale: Past 10.25 thousand years (kyr bp), covering the early and mid-Holocene African Humid Period, with decadal-scale resolution for drought events.

Methodology and Data

• Models used: TraCE (CCSM3 model), LOVECLIM model, AWI-ESM2-wiso (AWI-ESM2.1 model).
• Data sources: Annually layered (varved) sedimentary archive from Lake Yoa, Chad (composite core Co1240 and OUNIK03/04); multiproxy time series including pollen, diatoms (planktonic/benthic ratio, inferred conductivity), leaf-wax n-alkane δD values, Sr/Ca ratio, CaCO3 content, Ca content, and grain-size distribution; chronology based on varve counting, 137Cs peak, and 14C dating; external data for model forcing (orbital configurations, greenhouse-gas concentrations, ice-sheet extents, volcanic eruptions); AMOC reconstruction from North Atlantic sea surface temperature records; Greenland temperature reconstruction from ice cores; Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM).

Main Results

• The African Humid Period (AHP) in the central Sahara was punctuated by two prominent decadal-scale droughts at approximately 9.3 kyr bp and 8.2 kyr bp, and a more tentatively identified drought at 6.3 kyr bp.
• The 8.2 kyr bp drought, lasting 77 years (from 8,229 to 8,152 years bp), was characterized by a reduction in local precipitation, decreased fluvial supply to Lake Yoa, a lake-level drop, and expansion of reed belts.
• Climate simulations, particularly those incorporating AMOC changes, suggest that the 8.2 kyr bp drought was a rapid response to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) due to sudden freshwater input into the North Atlantic.
• Simulations with freshwater input into the Labrador Sea showed a decrease in mean annual rainfall by approximately 50–100 mm per year across the Sahara and Sahel regions, linked to a weakening of the West African monsoon.
• The Lake Yoa record provides the first continuous, annually resolved hydrological and vegetation changes in the central Sahara over the past 10.25 kyr.
• Long-term hydrological changes in Lake Yoa occurred in four phases, with a maximum water depth of 81 meters (55 meters more than today) reached during the AHP peak, activating overflow towards Megalake Chad.

Contributions

• Provides the first continuous, annually resolved multiproxy record of hydrological and vegetation changes in the central Sahara spanning the past 10.25 kyr.
• Precisely dates and characterizes decadal-scale drought events (9.3, 8.2, and 6.3 kyr bp) that interrupted the African Humid Period, improving upon previous poorly constrained age and duration estimates.
• Offers strong evidence, supported by climate simulations, linking the 8.2 kyr bp drought in the central Sahara directly and rapidly to a weakening of the Atlantic Meridional Overturning Circulation (AMOC).
• Highlights the far-reaching and rapid impacts of AMOC-triggered droughts on regional ecosystems in the Sahara, emphasizing the need for improved decadal predictions for future drought risk assessment.

Funding

• German Research Foundation (DFG, grant number 57444011) as part of the Collaborative Research Center CRC 806 – ‘Our Way to Europe’.
• DFG Priority Programme SPP 2143 ‘Entangled Africa’ (project number 404354295).
• PalMod (grant no. 01LP1920A), financed by the German Federal Ministry of Education and Research (BMBF), Research for Sustainability initiative (FONA).
• Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (grant no. SML2023SP204).
• Guangdong Basic and Applied Basic Research Foundation (grant no. 2025A1515012165).
• Ocean Negative Carbon Emissions (ONCE) programme.
• French National Research Institute for Sustainable Development (IRD).
• French Embassy in Chad within the framework of the ‘Grands Ecosystèmes Lacustres Tchadiens (GELT)’ FSP 2013-18 project.

Citation

@article{Sylvestre2026Decadalscale,
  author = {Sylvestre, Florence and Melles, Martin and Wennrich, Volker and Dinies, Michèle and Chalié, Françoise and Swingedouw, Didier and Dallmeyer, Anne and Shi, Xiaoxu and Claussen, Martin and Jaeschke, Andrea and Cocquyt, Christine and Karls, Jens and Kuper, Jan and Mallaye, Baba and Mazur, Jean-Charles and Paillès, Christine and Rirongarti, Remadji and Rethemeyer, Janet and Ritter-Prinz, Benedikt and Schefuß, Enno and Viehberg, Finn and Wagner, Bernd and Werner, Martin and Yacoub, Abdallah N. and Kröpelin, Stefan},
  title = {Decadal-scale droughts disrupted the African Humid Period in the Sahara},
  journal = {Nature},
  year = {2026},
  doi = {10.1038/s41586-026-10336-7},
  url = {https://doi.org/10.1038/s41586-026-10336-7}
}