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Global- and regional-scale hydrological response to early Eocene warmth
  • +19
  • Margot Cramwinckel,
  • Natalie J Burls,
  • Abdullah A Fahad,
  • Scott Knapp,
  • Christopher K West,
  • Tammo Reichgelt,
  • David R Greenwood,
  • Wing-Le Chan,
  • Yannick Donnadieu,
  • David Hutchinson,
  • Agatha Margaretha De Boer,
  • Jean-Baptiste Ladant,
  • Polina Morozova,
  • Igor Niezgodzki,
  • Gregor Knorr,
  • Sebastian Steinig,
  • Zhongshi Zhang,
  • Jiang Zhu,
  • Ran Feng,
  • Daniel J. Lunt,
  • Ayako Abe-Ouchi,
  • Gordon N. Inglis
Margot Cramwinckel
Utrecht University
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Natalie J Burls
George Mason University
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Abdullah A Fahad
George Mason University
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Scott Knapp
George Mason University
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Christopher K West
University of Alberta
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Tammo Reichgelt
University of Connecticut
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David R Greenwood
Brandon University
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Wing-Le Chan
University of Tokyo
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Yannick Donnadieu
Centre national de la recherche scientifique
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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 Morozova
Skolkovo Institute of Science and Technology
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Igor Niezgodzki
ING PAN - Institute of Geological Sciences Polish Academy of Sciences
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Gregor Knorr
AWI Bremerhaven
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Sebastian Steinig
University of Bristol
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Zhongshi Zhang
Bjerknes Centre for Climate Research
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Jiang Zhu
National Center for Atmospheric Research
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Ran Feng
University of Connecticut
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Daniel J. Lunt
University of Bristol
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Ayako Abe-Ouchi
University of Tokyo
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Gordon N. Inglis
University of Southampton

Corresponding Author:[email protected]

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Abstract

Earth’s hydrological cycle is expected to intensify in response to global warming, with a ‘wet-gets-wetter, dry-gets-drier’ response anticipated. The subtropics (~15-30°N/S) are predicted to become drier, yet proxy evidence from past warm climates suggests these regions may be characterised by wetter conditions. Here we use an integrated data-modelling approach to reconstruct global- and regional-scale rainfall patterns during the early Eocene (~48-56 million years ago), with an emphasis on the subtropics. Model-derived precipitation–evaporation (PE) estimates in the tropics (0-15° N/S) and high latitudes (>60° N/S) are positive and increase in response to higher temperatures, whereas model-derived PE estimates in the subtropics (15-30° N/S) are negative and decrease in response to higher temperatures. This is consistent with a ‘wet-gets-wetter, dry-gets-drier’ response. However, some DeepMIP model simulations predict increasing – rather than decreasing – subtropical precipitation at higher temperatures (e.g., CESM, GFDL). Using moisture budget diagnostics we find that the models with higher subtropical precipitation are characterised by a reduction in the strength of subtropical moisture circulation due to weaker meridional temperature gradients. These model simulations (e.g., CESM, GFDL) agree more closely with various proxy-derived climate metrics and imply a reduction in the strength of subtropical moisture circulation during the early Eocene. Although this was insufficient to induce subtropical wetting, if the meridional temperature was weaker than suggested by the DeepMIP models, this may have led to wetter subtropics. This highlights the important role of the meridional temperature gradient when predicting past (and future) rainfall patterns.