The tropical Indian Ocean (TIO) has been warming at a rate of 0.02 °C/year during the period 1982–2024. The highest sea surface temperature (SST) over the past 43 years were recorded in 2015, 2016, 2023, and 2024, coinciding with intense and prolonged marine heatwave (MHW) events. In both instances, extreme SSTs began during the boreal fall and peaked in the following spring. Unlike in 2016, SSTs in 2024 remained persistently high throughout the year, resulting in a near-permanent MHW state across the TIO during 2023/24. The CMIP6 models were unable to accurately capture the observed SST anomalies during these events, largely due to uncertainties in representing MHW occurrences and their spatial variability. Nevertheless, the models reproduced the increasing trends in annual MHW days, particularly after 2000. Biases in the simulated mean state contributed to errors in representing MHW intensities across five identified hotspot regions. Both the intensity and duration of MHWs, in observations and CMIP6 simulations, are strongly modulated by the phase of the Indian Ocean Basin Mode (IOBM). The misrepresentation of MHWs is largely attributed to model deficiencies in capturing the IOBM, which are, in turn, linked to inaccuracies in simulating El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events. This study highlights the critical importance of accurately representing Indo-Pacific climate modes in order to reliably simulate extreme SST anomalies over the TIO, which has emerged as a key warming hotspot in the global ocean basins.
Krishna et al. (Sun,) studied this question.