Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth

Abstract The El Niño Southern Oscillation (ENSO) during the Early Eocene Climatic Optimum (EECO, 56–48 million years ago) is investigated using a multi-model ensemble of deep-time climate simulations. We reveal that ENSO sea surface temperature variability during the EECO had significantly longer pe...

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Main Authors: S. Abhik, Dietmar Dommenget, Shayne McGregor, David K. Hutchinson, Sebastian Steinig, Jiang Zhu, Fabio A. Capitanio, Daniel J. Lunt, Igor Niezgodzki, Gregor Knorr, Wing-Le Chan, Ayako Abe-Ouchi
Format: Article
Language:English
Published: Nature Portfolio 2025-04-01
Series:Nature Communications
Online Access:https://doi.org/10.1038/s41467-025-59263-7
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author S. Abhik
Dietmar Dommenget
Shayne McGregor
David K. Hutchinson
Sebastian Steinig
Jiang Zhu
Fabio A. Capitanio
Daniel J. Lunt
Igor Niezgodzki
Gregor Knorr
Wing-Le Chan
Ayako Abe-Ouchi
author_facet S. Abhik
Dietmar Dommenget
Shayne McGregor
David K. Hutchinson
Sebastian Steinig
Jiang Zhu
Fabio A. Capitanio
Daniel J. Lunt
Igor Niezgodzki
Gregor Knorr
Wing-Le Chan
Ayako Abe-Ouchi
author_sort S. Abhik
collection DOAJ
description Abstract The El Niño Southern Oscillation (ENSO) during the Early Eocene Climatic Optimum (EECO, 56–48 million years ago) is investigated using a multi-model ensemble of deep-time climate simulations. We reveal that ENSO sea surface temperature variability during the EECO had significantly longer periodicity and stronger amplitude than present-day conditions. These changes are attributed to intensified ocean-atmosphere feedback processes and enhanced in-phase tropical inter-basin interactions within a broader ocean basin compared to the present-day. Sensitivity experiments in coupled ocean-atmosphere models suggest that tectonic changes, particularly the expansion of the tropical ocean basin, play a dominant role in amplifying ENSO variability and extending its periodicity, while stronger inter-basin connections further enhance ENSO amplitude. Elevated atmospheric CO2 levels, though driving substantial mean-state changes, partially offset the tectonic influence on ENSO variability by modifying feedback processes. These findings underscore the role of tropical ocean basin geometry and atmospheric CO2 levels in shaping ENSO variability, offering insights into past climate dynamics and implications for future projections under sustained global warming.
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spelling doaj-art-0844fbea630e40d1b3a4f95038607e1f2025-08-20T01:47:32ZengNature PortfolioNature Communications2041-17232025-04-0116111310.1038/s41467-025-59263-7Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmthS. Abhik0Dietmar Dommenget1Shayne McGregor2David K. Hutchinson3Sebastian Steinig4Jiang Zhu5Fabio A. Capitanio6Daniel J. Lunt7Igor Niezgodzki8Gregor Knorr9Wing-Le Chan10Ayako Abe-Ouchi11School of Earth, Atmosphere, and Environment, Monash UniversitySchool of Earth, Atmosphere, and Environment, Monash UniversitySchool of Earth, Atmosphere, and Environment, Monash UniversityClimate Change Research Centre, University of New South WalesSchool of Geographical Sciences, University of BristolClimate and Global Dynamics Laboratory, NSF National Center for Atmospheric ResearchSchool of Earth, Atmosphere, and Environment, Monash UniversitySchool of Geographical Sciences, University of BristolInstitute of Geological Sciences, Polish Academy of SciencesAlfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchAtmosphere and Ocean Research Institute, University of TokyoAtmosphere and Ocean Research Institute, University of TokyoAbstract The El Niño Southern Oscillation (ENSO) during the Early Eocene Climatic Optimum (EECO, 56–48 million years ago) is investigated using a multi-model ensemble of deep-time climate simulations. We reveal that ENSO sea surface temperature variability during the EECO had significantly longer periodicity and stronger amplitude than present-day conditions. These changes are attributed to intensified ocean-atmosphere feedback processes and enhanced in-phase tropical inter-basin interactions within a broader ocean basin compared to the present-day. Sensitivity experiments in coupled ocean-atmosphere models suggest that tectonic changes, particularly the expansion of the tropical ocean basin, play a dominant role in amplifying ENSO variability and extending its periodicity, while stronger inter-basin connections further enhance ENSO amplitude. Elevated atmospheric CO2 levels, though driving substantial mean-state changes, partially offset the tectonic influence on ENSO variability by modifying feedback processes. These findings underscore the role of tropical ocean basin geometry and atmospheric CO2 levels in shaping ENSO variability, offering insights into past climate dynamics and implications for future projections under sustained global warming.https://doi.org/10.1038/s41467-025-59263-7
spellingShingle S. Abhik
Dietmar Dommenget
Shayne McGregor
David K. Hutchinson
Sebastian Steinig
Jiang Zhu
Fabio A. Capitanio
Daniel J. Lunt
Igor Niezgodzki
Gregor Knorr
Wing-Le Chan
Ayako Abe-Ouchi
Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
Nature Communications
title Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
title_full Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
title_fullStr Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
title_full_unstemmed Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
title_short Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth
title_sort stronger and prolonged el nino southern oscillation in the early eocene warmth
url https://doi.org/10.1038/s41467-025-59263-7
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