Abstract
The Pacific subtropical cells (STCs) are shallow meridional overturning circulations connecting the tropics and subtropics, and are assumed to be an important driver of the tropical Pacific decadal variability. The variability of STCs under global warming is investigated using multimodal outputs from the latest phase of the Coupled Model Inter-comparison Project (CMIP6) and ocean reanalysis products. Firstly, the volume transport diagnostic analysis is employed to evaluate how coupled models and ocean reanalysis products reproduce interior STC transport. The variation of heat transport by the interior STC under the high-emissions warming scenarios is also analyzed. The results show that the multimodal-mean linear trends of the interior STC transport along 9°S and 9°N are −0.02 Sv/a and 0.04 Sv/a under global warming, respectively, which is mainly due to the combined effect of the strengthened upper oceanic stratification and the weakening of wind field. There is a compensation relationship between the interior STC and the western boundary transport in the future climate, and the compensation relationship of 9°S is more significant than that of 9°N. In addition, compared with ocean reanalysis products, the coupled models tend to underestimate the variability of the interior STC transport convergence, and thus may lose some sea surface temperature (SST) driving force, which may be the reason for the low STC-SST correlation simulated by the model. The future scenario simulation shows that the heat transport of interior STC is weakened under global warming, with a general agreement across models.
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Data Availability Statement
We thank the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the Climate Modeling Group for producing and providing its model output. CMIP6 data are available at the ESGF website (https://esgf-node.llnl.gov/projects/cmip6). The GODAS dataset is available at the Physical Science Laboratory (https://psl.noaa.gov/data/gridded/data.godas.html). The SODA3.4.2 reanalysis datasets are available through www.soda.umd.edu. ORAS5 datasets are available free of charge at the University of Hamburg (https://www.cen.unihamburg.e/en/icdc/data/ocean/easy-init-ocean/ecmwforas5.html). Argo data are available through https://sio-argo.ucsd.edu/RG_Climatology.html.
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Acknowledgment
The authors would like to thank Dr. Qingye WANG of the Institute of Oceanology, Chinese Academy of Sciences for their useful discussion during this study. We also thank the editor and anonymous reviewers, whose constructive suggestions and comments lead to a great improvement of the manuscript.
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Supported by the National Natural Science Foundation of China (NSFC) (No. 41976027)
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Han, X., Feng, J., Lu, Y. et al. Variability of the Pacific subtropical cells under global warming in CMIP6 models. J. Ocean. Limnol. 42, 24–40 (2024). https://doi.org/10.1007/s00343-023-2315-2
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DOI: https://doi.org/10.1007/s00343-023-2315-2