Abstract
As large-scale ocean circulation is a key regulator in the redistribution of oceanic energy, evaluating the multi-decadal trends in the western Pacific Ocean circulation under global warming is essential for not only understanding the basic physical processes but also predicting future climate change in the western Pacific. Employing the hydrological observations of World Ocean Atlas 2018 (WOA18) from 1955 to 2017, this study calculated the geostrophic currents, volume transport and multi-decadal trends for the North Equatorial Current (NEC), the North Equatorial Countercurrent (NECC), the Mindanao Current (MC), the Kuroshio Current (KC) in the origin and the New Guinea Coastal Undercurrent (NGCUC) within tropical western Pacific Ocean over multi-decades. Furthermore, this study examined the contributions of temperature and salinity variations. The results showed significant strengthening trends in NEC, MC and NGCUC over the past six decades, which is mainly contributed by temperature variations and consistent with the tendency in the dynamic height pattern. Zonal wind stress averaged over the western Pacific Ocean in the same latitude of each current represents the decadal variation and multi-decadal trends in corresponding ocean currents, indicating that the trade wind forcing plays an important role in the decadal trend in the tropical western Pacific circulation. Uncertainties in the observed hydrological data and trends in the currents over the tropical western Pacific are also discussed. Given that the WOA18 dataset covers most of the historical hydrological sampling data for the tropical western Pacific, this paper provides important observational information on the multi-decadal trend of the large-scale ocean circulation in the western Pacific.
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Acknowledgements
The WOA18 dataset provided by the National Centers for Environmental Information is available at https://www.nodc.noaa.gov/OC5/woa18/. The OFES data is provided by the Japan Agency for Marine-Earth Science and Technology, distributed by the Asia-Pacific Data-Research Center of the IPRC and is available at http://apdrc.soest.hawaii.edu/index.php. The ECMWF ORA S3 dataset is from the European Centre For Medium Range Weather Forecasts. We are grateful to two anonymous reviewers for their constructive and helpful comments and suggestions. This work was supported by the National Natural Science Foundation of China (Grant No. 41776018), the Strategic Priority Research Program of Chinese Academy of Sciences (CAS) (Grant No. XDB42010403), the National Natural Science Foundation of China (Grant No. 91858101), the Key Deployment Project of Centre for Ocean Mega-Research of Science of CAS (Grant Nos. COMS2019Q01 & COMS2019Q03) and the CAS-CSIRO Project Fund (Grant No. 133244KYSB20190031). SH is a member of the Youth Innovation Promotion Association of CAS (Grant No. 2018240).
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Hu, S., Lu, X., Li, S. et al. Multi-decadal trends in the tropical Pacific western boundary currents retrieved from historical hydrological observations. Sci. China Earth Sci. 64, 600–610 (2021). https://doi.org/10.1007/s11430-020-9703-4
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DOI: https://doi.org/10.1007/s11430-020-9703-4
Keywords
- Pacific
- Western boundary current
- Multi-decadal trend
- Global variation
- Hydrological observation