Abstract
The tropical Pacific exhibits decadal El Niño-Southern Oscillation (ENSO)-like variability, characterized by meridionally broad sea surface temperature anomalies in the eastern Pacific. In this study, we focus on the variability in the equatorial Pacific band (5°S–5°N), termed equatorial Pacific decadal variability (EPDV). While it is known that ocean dynamics plays an essential role in EPDV, the simulations by air-sea thermodynamically coupled slab ocean models (SOM) obscure the nature of the role of ocean dynamics. To confront this issue, we use a mechanically decoupled simulation, which isolates the effects of thermodynamic coupling processes and mean ocean circulation on EPDV. Thus, by comparing the simulation to a SOM, we investigate the role of mean ocean circulation and show that it plays a role in damping EPDV, primarily through mean equatorial Pacific upwelling. By comparing the simulation to a fully coupled dynamic ocean model (DOM), we examine the role of anomalous wind-driven ocean circulation and demonstrate that it plays a role in amplifying EPDV. Further, this amplification strength overwhelms the upwelling damping effect, resulting in the anomalous wind-driven ocean circulation forcing EPDV. Finally, we examine the origin of EPDV in the DOM and show that it originates from a zonal dipole mode in the tropical Pacific, which is strongly associated with decadal modulation of ENSO amplitude. Taking EPDV as an example, our study advances the understanding of the two distinct dynamical systems (SOM and DOM), benefiting the physical interpretation of other climate variabilities.
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Data availability
The SOM data are available from: https://nomads.gfdl.noaa.gov/dods-data/gfdl_sm2_1/MLM2.1U_Control-1990_D1/pp/atmos/ts/monthly/. The Clim-\(\tau \) data are available from: https://data.mendeley.com/datasets/ctn5k77ttr/draft?a=c9db68b4-d4af-48a4-b14d-709edc7fa1b7. The DOM data are available from: https://data.mendeley.com/datasets/mrg8g4w9zk/draft?a=4d2e535f-7dc6-4f10-b2ad-c1bf565637ce
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Acknowledgements
We appreciate three anonymous reviewers for providing constructive comments and substantially improving the manuscript.
Funding
Y.Z. and X.L. were supported by the National Natural Science Foundation of China (92058203 and 41925025). Y.Z. was supported by the Fundamental Research Funds for the Central Universities (202213050) and the project funded by China Postdoctoral Science Foundation (2021M703034). Q.P. was supported by the National Natural Science Foundation of China (42005035) and the Science and Technology Planning Project of Guangzhou (202102020935). Y.K. was supported by the Japan Society for the Promotion of Science (JP18H01278 and JP19H05703) and the Japanese Ministry of Education, Culture, Sports, Science and Technology (JPMXD0717935457 and JPMXD1420318865). J.-C.Y. was supported by the National Natural Science Foundation of China (42105019 and 92058203) and the project funded by China Postdoctoral Science Foundation (2020M672138). S.M.L. was supported by the National Science Foundation (AGS-1951713). A.J.M. was supported by the National Science Foundation (OCE2022868 and CCE-LTER OCE1637632) and NOAA (MAPP NA17OAR4310106). L.F. was supported by the Natural Science Foundation of China (41975089).
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Zhang, Y., Yu, SY., Xie, SP. et al. Role of ocean dynamics in equatorial Pacific decadal variability. Clim Dyn 59, 2517–2529 (2022). https://doi.org/10.1007/s00382-022-06312-2
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DOI: https://doi.org/10.1007/s00382-022-06312-2