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Thermocline Warming Induced Extreme Indian Ocean Dipole in 2019
Author(s) -
Du Yan,
Zhang Yuhong,
Zhang LianYi,
Tozuka Tomoki,
Ng Benjamin,
Cai Wenju
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl090079
Subject(s) - thermocline , rossby wave , indian ocean dipole , climatology , equator , ocean heat content , geology , advection , equatorial waves , ocean dynamics , oceanography , subtropical indian ocean dipole , sea surface temperature , convection , forcing (mathematics) , ocean current , atmospheric sciences , latitude , meteorology , geography , physics , geodesy , thermodynamics
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.