EGU21-6871, updated on 04 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Structure and Seasonal Variation of the Indian Ocean Tropical Gyre Based on Surface Drifters

Wei Wu1,2,3, Yan Du1,2,3, Yu-Kun Qian1,3, Xuhua Cheng4, Tianyu Wang1,3, Lianyi Zhang1,2,3, and Shiqiu Peng1,2,3
Wei Wu et al.
  • 1State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China (
  • 2College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
  • 3Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China
  • 4College of Oceanography, Hohai University, Nanjing, China

Using the Gauss–Markov decomposition method, this study investigates the mean structure and seasonal variation of the tropical gyre in the Indian Ocean based on the observations of surface drifters. In the climatological mean, the clockwise tropical gyre consists of the equatorial Wyrtki Jets (WJs), the South Equatorial Current (SEC), and the eastern and western boundary currents. This gyre system redistributes the water mass over the entire tropical Indian Ocean basin. Its variations are associated with the monsoon transitions, featuring a typical clockwise pattern in the boreal spring and fall seasons. The relative importance of the geostrophic and Ekman components of the surface currents as well as the role of eddy activity were further examined. It was found that the geostrophic component dominates the overall features of the tropical gyre, including the SEC meandering, the broad eastern boundary current, and the axes of the WJs in boreal spring and fall, whereas the Ekman component strengthens the intensity of the WJs and SEC. Eddies are active over the southeastern tropical Indian Ocean and transport a warm and fresh water mass westward, with direct impact on the southern branch of the tropical gyre. In particular, the trajectories of drifters reveal that during strong Indian Ocean Dipole or El Niño-Southern Oscillation events, long-lived eddies were able to reach the southwestern Indian Ocean with a moving speed close to that of the first baroclinic Rossby waves.

How to cite: Wu, W., Du, Y., Qian, Y.-K., Cheng, X., Wang, T., Zhang, L., and Peng, S.: Structure and Seasonal Variation of the Indian Ocean Tropical Gyre Based on Surface Drifters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6871,, 2021.


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