Abstract
The Miocene Climatic Optimum was characterized by global mean temperatures 8-10 °C above the preindustrial level, yet such extreme warmth remains difficult to reproduce in climate models. Using two climate models (IPSL-CM5A2 and NorESM1-F) with updated boundary conditions, we show that the simulated climate of this interval strongly depends on ocean-ice dynamics. The NorESM1-F model produces surface temperatures more consistent with proxy reconstructions, driven by a stronger overturning circulation, enhanced poleward heat and salt transport, and near-permanent sea-ice loss. In contrast, IPSL-CM5A2 simulates a weaker overturning circulation and limited polar amplification, which is generally consistent with previous modeling results. Our results suggest that the Miocene Climatic Optimum may represent a distinct high-latitude climate regime, emphasizing the critical role of ocean–ice feedbacks in driving the strong polar amplification and the necessity of multi-model comparisons together with proxy constraints to understand the climate of this interval.
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Data availability
Modeling data for 17 Ma used in the results’ analysis have been deposited in the public depository Figshare (https://doi.org/10.6084/m9.figshare.28760048). The related pre-industrial experiment data of both models can be found in previous publications30,31. Figures were plotted with the NCAR Command Language (version NCL 6.4.0, https://www.ncl.ucar.edu/.) and Python 2.7 (https://www.python.org/download/releases/2.7/).
Code availability
The information for the applied model IPSL-CM5A2 can be found in the IPSL Climate Modeling Centre Wiki page (https://forge.ipsl.jussieu.fr/igcmg_doc/wiki/Doc/Config/IPSLCM5A2, last access: 28 Jan., 2026) and the code of this model can be downloaded through svn as introduced on this webpage, but requires additional authentication. The code of NorESM1-F can be obtained upon request. Instructions on how to obtain a copy are in: https://wiki.met.no/noresm/gitbestpractice (last access: 28 Jan., 2026).
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Acknowledgements
The authors thank Jean-Baptiste Ladant, Haibin Wu, Chunxia Zhang, and Qingzhen Hao for their helpful discussions. This work is supported by the grant of the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0710000), the National Key Research and Development Program (Grant no. 2022YFF0801504), and NSFC program (42488201). Zhilin He acknowledges support from the Second Tibetan Plateau Scientific Expedition and Research Program (Grant No. 2024QZKK0301). Frédéric Fluteau and Gilles Ramstein were granted access to the HPC resources of TGCC under the allocation 2020-A0090107601 and 2021-A0110107601 made by GENCI. Gilles Ramstein acknowledges support from CNRS/INSU/LEFE project. Ning Tan acknowledges support from the IGGCAS key program (No. IGGCAS-202201).
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N.T., F.F., G.R., and Z.Z. contributed to the conceptual development of this work. N.T. conducted the analysis, and produced the figures and results. F.F. and N.T. conducted the Miocene simulations, C.G. and P.S. conducted the PI simulations. N.T., F.F., G.R., and Z.Z. drafted the original manuscript, C.G., Z.G., Z.H., P.S., and Z.J.Z. helped to review the manuscript.
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Tan, N., Fluteau, F., Zhang, Z. et al. A critical role of ocean–sea ice interactions in the pronounced warmth during the Miocene Climatic Optimum. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03324-2
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DOI: https://doi.org/10.1038/s43247-026-03324-2
