EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Thermocline warming induced extreme Indian Ocean Dipole in 2019

Yan Du1,2,3, Yuhong Zhang1,3, Lian-Yi Zhang1,3, Tomoki Tozuka4, and Wenju Cai5,6
Yan Du et al.
  • 1South China Sea Institute of Oceanology, State Key Laboratory of Tropical Oceanography, 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
  • 4Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
  • 5Centre for Southern Hemisphere Oceans Research (CSHOR), CSIRO Oceans and Atmosphere, Hobart, Tasmania, Australia
  • 6Key Laboratory of Physical Oceanography, Institute for Advanced Ocean Studies, Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.

The 2019 positive Indian Ocean Dipole (IOD) was the strongest event since the 1960s which developed independently without coinciding El Niño. The dynamics is not fully understood. Here we show that in March-May, westward propagating oceanic Rossby waves, a remnant consequence of the weak 2018 Pacific warm condition, led to anomalous sea surface temperature warming in the southwest tropical Indian Ocean (TIO), inducing deep convection and anomalous easterly winds along the equator, which triggered the initial cooling in the east. In June-August, the easterly wind anomalies continued to evolve through ocean-atmosphere coupling involving Bjerknes feedback and equatorial nonlinear ocean advection, until its maturity in September-November. This study clarifies the contribution of oceanic Rossby waves in the south TIO in different dynamic settings and reveals a new triggering mechanism for extreme IOD events that will help to understand IOD diversity.

How to cite: Du, Y., Zhang, Y., Zhang, L.-Y., Tozuka, T., and Cai, W.: Thermocline warming induced extreme Indian Ocean Dipole in 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3639,, 2021.


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