Abstract
This study uses two reanalysis datasets and ocean model experiments to examine the dynamics of the interannual variability of the equatorial currents in the Indian Ocean, and to quantify the effects of the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) climate modes on the currents. Strong interannual variability of the equatorial currents mainly occurs in the upper-central basin (UCB) where the Wyrtki jets are located, and in the subsurface-eastern basin (SEB) where the equatorial undercurrent is located. Equatorial waves directly forced by equatorial winds dominate the interannual current anomalies in both the UCB and the SEB, and the reflected waves have a secondary role. The reflected waves tend to weaken the current anomalies in the UCB but intensify the currents in the SEB. In general, ENSO and the IOD have a comparable effect on the interannual current anomalies in the SEB, but the IOD has a larger role than ENSO in the UCB. In some years, either ENSO or the IOD may play a dominant role. Composite analysis suggests that the interannual current anomalies occur about two months prior to the peaks the climate modes. As ENSO and the IOD have apparent seasonality, the current anomalies mainly occur during August to October for pure IOD years, and during October to December for pure ENSO years. The co-occurrence of ENSO and the IOD enhances their respective impact, resulting in the surface current anomalies lasting from July to December and the subsurface current anomalies from July to March of the following year.
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Data Availability
All data used in this study are publicly accessible. BRAN2020 were downloaded at https://research.csiro.au/bluelink/outputs/data-access/. ORAS4 were downloaded at http://apdrc.soest.hawaii.edu/erddap/griddap/hawaii_soest_3512_a2e8_e3ce.html.
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Acknowledgements
The numerical simulation is supported by the High-Performance Computing Division in the South China Sea Institute of Oceanology.
Funding
This work is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA 20060502, XDB42000000), National Natural Science Foundation of China (41976016, 42076021 and 41822602), Guangdong Basic and Applied Basic Research Foundation (2021A1515011534), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (GML2019ZD0306), Youth Innovation Promotion Association CAS (Y2021093), and State Key Laboratory of Tropical Oceanography (LTOZZ2002).
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G. C., X. C., and W. H. designed the research and wrote the main manuscript text. W. H. and L. Z. performed model experiments.
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Chu, X., Han, W., Zhang, L. et al. Effects of climate modes on interannual variability of the equatorial currents in the Indian ocean. Clim Dyn 60, 3681–3694 (2023). https://doi.org/10.1007/s00382-022-06515-7
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DOI: https://doi.org/10.1007/s00382-022-06515-7