Global and Zonal-Mean Hydrological Response to Early Eocene Warmth

Margot J. Cramwinckel, Natalie J. Burls, Abdullah A. Fahad, Scott Knapp, Christopher K. West, Tammo Reichgelt, David R. Greenwood, Wing Le Chan, Yannick Donnadieu, David K. Hutchinson, Agatha M. de Boer, Jean Baptiste Ladant, Polina A. Morozova, Igor Niezgodzki, Gregor Knorr, Sebastian Steinig, Zhongshi Zhang, Jiang Zhu, Ran Feng, Daniel J. LuntAyako Abe-Ouchi, Gordon N. Inglis*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

12 Citations (Scopus)

Abstract

Earth's hydrological cycle is expected to intensify in response to global warming, with a “wet-gets-wetter, dry-gets-drier” response anticipated over the ocean. Subtropical regions (∼15°–30°N/S) are predicted to become drier, yet proxy evidence from past warm climates suggests these regions may be characterized by wetter conditions. Here we use an integrated data-modeling approach to reconstruct global and zonal-mean rainfall patterns during the early Eocene (∼56–48 million years ago). The Deep-Time Model Intercomparison Project (DeepMIP) model ensemble indicates that the mid- (30°–60°N/S) and high-latitudes (>60°N/S) are characterized by a thermodynamically dominated hydrological response to warming and overall wetter conditions. The tropical band (0°–15°N/S) is also characterized by wetter conditions, with several DeepMIP models simulating narrowing of the Inter-Tropical Convergence Zone. However, the latter is not evident from the proxy data. The subtropics are characterized by negative precipitation-evaporation anomalies (i.e., drier conditions) in the DeepMIP models, but there is surprisingly large inter-model variability in mean annual precipitation (MAP). Intriguingly, we find that models with weaker meridional temperature gradients (e.g., CESM, GFDL) are characterized by a reduction in subtropical moisture divergence, leading to an increase in MAP. These model simulations agree more closely with our new proxy-derived precipitation reconstructions and other key climate metrics and imply that the early Eocene was characterized by reduced subtropical moisture divergence. If the meridional temperature gradient was even weaker than suggested by those DeepMIP models, circulation-induced changes may have outcompeted thermodynamic changes, leading to wetter subtropics. This highlights the importance of accurately reconstructing zonal temperature gradients when reconstructing past rainfall patterns.

Original languageEnglish
Article numbere2022PA004542
JournalPaleoceanography and Paleoclimatology
Volume38
Issue number6
Early online date5 Jun 2023
DOIs
Publication statusPublished - Jun 2023

Bibliographical note

Funding Information:
G.N.I was supported by a Royal Society Dorothy Hodgkin Fellowship (DHF\R1\191178). G.N.I. was also supported by additional funds from the Royal Society (DHF\ERE\210068). N.J.B. was supported by the National Science Foundation, via award AGS‐1844380. D. G was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through Discovery Grants (DG 311934 and 2016‐04337). C.K.W acknowledges funding from a private donor to the Northern Climates Postdoctoral Fellowship at the University of Alberta. D.K.H acknowledges support from Australian Research Council grant DE22010079 and the Australian Centre for Excellence in Antarctic Science, project number SR200100008. R.F is supported by NSF‐2114204. A.dB was supported by Swedish Research Council project 2020‐04791. The GFDL simulations were performed by resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC), partially funded by the Swedish Research Council through Grant agreement 2018‐05973. W.L.C and A.A.O acknowledge funding from JSPS KAKENHI (Grant 17H06104) and MEXT KAKENHI (Grant 17H06323). The CESM project is supported primarily by the National Science Foundation (NSF); this material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement 1852977.

Funding Information:
G.N.I was supported by a Royal Society Dorothy Hodgkin Fellowship (DHF\R1\191178). G.N.I. was also supported by additional funds from the Royal Society (DHF\ERE\210068). N.J.B. was supported by the National Science Foundation, via award AGS-1844380. D. G was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through Discovery Grants (DG 311934 and 2016-04337). C.K.W acknowledges funding from a private donor to the Northern Climates Postdoctoral Fellowship at the University of Alberta. D.K.H acknowledges support from Australian Research Council grant DE22010079 and the Australian Centre for Excellence in Antarctic Science, project number SR200100008. R.F is supported by NSF-2114204. A.dB was supported by Swedish Research Council project 2020-04791. The GFDL simulations were performed by resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC), partially funded by the Swedish Research Council through Grant agreement 2018-05973. W.L.C and A.A.O acknowledge funding from JSPS KAKENHI (Grant 17H06104) and MEXT KAKENHI (Grant 17H06323). The CESM project is supported primarily by the National Science Foundation (NSF); this material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement 1852977.

Publisher Copyright:
© 2023. The Authors.

Keywords

  • DeepMIP
  • Eocene
  • evaporation
  • hydrology
  • Paleocene
  • precipitation

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  • SWEET NERC Large Grant

    Lunt, D. (Principal Investigator)

    1/10/1730/09/23

    Project: Research

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