Extreme IOD induced tropical Indian Ocean warming in 2020

The tropical Indian Ocean (TIO) basin-wide warming occurred in 2020, following an extreme positive Indian Ocean Dipole (IOD) event instead of an El Nino event, which is the first record since the 1960s. The extreme 2019 IOD induced the oceanic downwelling Rossby waves and thermocline warming in the southwest TIO, leading to sea surface warming via thermocline-SST feedback during late 2019 to early 2020. The southwest TIO warming triggered equatorially antisymmetric SST, precipitation, and surface wind patterns from spring to early summer. Subsequently, the cross-equatorial C-shaped wind anomaly, with northeasterly-northwesterly wind anomaly north-south of the equator, led to basin-wide warming through wind-evaporation-SST feedback in summer. This study reveals the important role of air-sea coupling processes associated with the independent and extreme IOD in the TIO basin-warming mode, which allows us to rethink the dynamic connections between the Indo-Pacific climate modes.

Automated summary

The tropical Indian Ocean basin experienced warming in 2020 due to an extreme positive Indian Ocean Dipole event, rather than an El Nino event. The study highlights the role of the extreme IOD event in triggering the warming pattern in the TIO basin, which was influenced by factors such as thermocline-SST feedback and wind anomalies. Additionally, equatorially antisymmetric SST, precipitation, and surface wind patterns also played a role in the warming process.