edu.ucar.opensky::articles:43681 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T17:50:47.693229 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.net/ark:/85065/d7fb57cb https://doi.org/10.5281/zenodo.14934790 https Related Dataset #1 Data and code for manuscript: "Stronger and prolonged El Niño-Southern Oscillation in the early Eocene warmth" Stronger and prolonged El Niño-Southern Oscillation in the Early Eocene warmth 2025-04-30T00:00:00Z publication https://n2t.net/ark:/85065/d7fb57cb https://doi.org/10.1038/s41467-025-59263-7 Abhik, S. author Dommenget, D. author McGregor, S. author Hutchinson, D. K. author Steinig, S. author Zhu, Jiang author Capitanio, F. A. author Lunt, D. J. author Niezgodzki, I. author Knorr, G. author Chan, W. author Abe-Ouchi, A. author UCAR/NCAR - Library publisher 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. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication <span style="font-family:Arial;font-size:10pt;font-style:normal;" data-sheets-root="1">Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.</span> None eng geoscientificInformation