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The African monsoon during the early Eocene from the DeepMIP simulations
  • +17
  • Charles Williams,
  • Daniel J. Lunt,
  • Ulrich Salzmann,
  • Tammo Reichgelt,
  • Gordon N. Inglis,
  • David R Greenwood,
  • Wing-Le Chan,
  • Ayako Abe-Ouchi,
  • Yannick Donnadieu,
  • David Hutchinson,
  • Agatha Margaretha De Boer,
  • Jean-Baptiste Ladant,
  • Polina A Morozova,
  • Igor Niezgodzki,
  • Gregor Knorr,
  • Sebastian Steinig,
  • Zhang Zhong-Shi,
  • Jiang Zhu,
  • Matthew Huber,
  • Bette L Otto-Bliesner
Charles Williams
University of Bristol

Corresponding Author:c.j.r.williams@bristol.ac.uk

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Daniel J. Lunt
University of Bristol
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Ulrich Salzmann
Northumbria University
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Tammo Reichgelt
University of Connecticut
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Gordon N. Inglis
University of Southampton
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David R Greenwood
Brandon University
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Wing-Le Chan
University of Tokyo
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Ayako Abe-Ouchi
University of Tokyo
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Yannick Donnadieu
CEREGE (Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement)
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David Hutchinson
University of New South Wales
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Agatha Margaretha De Boer
Stockholm University
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Jean-Baptiste Ladant
Laboratoire des Sciences du Climat et de l'Environnement
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Polina A Morozova
Institute of Geography, Russian Academy of Sciences
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Igor Niezgodzki
Institute of Geological Sciences PAN
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Gregor Knorr
AWI Bremerhaven
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Sebastian Steinig
University of Bristol
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Zhang Zhong-Shi
Bjerknes Centre for Climate Research
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Jiang Zhu
National Center for Atmospheric Research
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Matthew Huber
Purdue University
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Bette L Otto-Bliesner
National Center for Atmospheric Research (UCAR)
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The early Eocene (~56-48 million years ago) is characterised by high CO2 estimates (1200-2500 ppmv) and elevated global temperatures (~10 to 16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g. Africa). Here we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations and modern observations suggests that model biases are model- and geographically dependent, however these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO2 increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa, whereas it is likely that changes in vegetation in the models are responsible for the simulated region of drying over equatorial Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO2 rises. There are also important dynamical changes, with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at high CO2 levels. Lastly, a model-data comparison using newly-compiled quantitative climate estimates from palaeobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO2.