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In this paper, we investigate the characteristics and the mechanism underlying the formation of marine heatwaves (MHWs) in the Savu Sea, known as the richest marine biodiversity area in the world. The focus is on identifying the frequency, intensity, and duration of occurrence MHWs generated by local forcing in the form of net surface heat flux. The study utilizes the remote sensing data from NOAA Optimum Interpolation (OI) Sea Surface Temperature (SST) for SST and The European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA-5) for net surface heat flux components (shortwave radiation, longwave radiation, sensible heat flux, and latent heat flux). All data covers the period for the last 14 years (2008–2021) during the cold phase of the Pacific Decadal Oscillation (PDO) and then processed by statistical analysis methods. The results showed that the mean frequency, intensity, and duration of occurrence MHWs in the Savu Sea were around two times a year, 1.4–1.6 °C, and 10–12 days, respectively. The highest frequency and intensity MHWs occurred at around 122–124 °E and 8.30–9.30 °S (northern Savu Sea) generated by the most significant net surface heat flux in these areas. This study reveals the most dominant contribution of net surface heat flux in the northern Savu Sea comes from high shortwave radiation (heat gain) and low latent heat flux through the evaporation process (heat loss), thus keeping the ocean warm.

Marine heatwaves (MHWs) have caused devastating impacts on marine communities, especially on coastal ecosystems. A coral reef is a coastal community that is vulnerable to changes in the marine environment, especially sea surface temperature. This study focused on investigating the characteristics of MHWs in the Spermonde Islands (SI), which is home to coral reef communities. The dynamics of MHWs were examined during the cold phase of the Pacific Decadal Oscillation (PDO) in recent years (2008–2021) using satellite-observed sea surface temperature data provided by National Oceanic and Atmospheric Administration (NOAA). Statistical methods calculated the characteristics of MHWs such as frequency, intensity, and duration. The analysis results showed that frequency of occurrence, mean maximum intensity, and mean duration of MHWs in the SI were around three times a year, 0.9–1.5 °C, and 8–12 days, respectively. The linear trend of frequency of occurrence of MHWs in the SI showed a decrease of 1 event per decade. In contrast, the linear trend of maximum intensity and duration of MHWs showed an increasing trend in the SI. In addition, this study also showed that the MHWs characteristics in the SI were controlled remotely by El Niño Southern Oscillation (ENSO) climate phenomena. Towards the end of the strong El Niño periods, notably in 2016, the MHWs occurred longer and more intensely.