Integrating satellite observations, coral Sr/Ca proxies, and model simulations to analyze sea surface temperature variability (1915-2003) in Indonesia

• CCSM4 demonstrates superior performance compared to other CMIP5 models. • The phases of ENSO and IOD exhibit a weak relationship with SST distribution. • The ENSO and IOD phenomena exert minimal influence on SST variability over Indonesia. Coral reefs are vital indicators of past oceanic conditions due to their ability to record environmental changes in their calcium carbonate structures. Specifically, the strontium-to-calcium ratio (Sr/Ca) in coral skeletons serves as a reliable proxy for reconstructing SST over time. The purpose of this study is to evaluate the similarity between sea surface temperature (SST) variability simulated by climate models and actual observations. The study utilized a comprehensive dataset that integrates satellite-derived SST observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations with coral Sr/Ca records from three locations in Indonesia: Gili Selang, Kupang, and Nusa Penida. Based on the result, CCSM4 is the model with high robustness for simulation the sea surface temperature variability in Indonesia. CCSM4 has a higher correlation than other models when comparing data SST with OISST satellite and Sr/Ca record, whose correlation values are 0.7 and 0.32. The phases of ENSO and IOD exhibit a weak relationship with sea surface temperature (SST) distribution in the Indonesian region, as indicated by the low correlation values in the spatial correlation maps with CCSM4. These low correlation values suggest that the ENSO and IOD phenomena have a minimal impact on SST variability over Indonesia, as simulated by the CCSM4 model. The correlation coefficients between CCSM4 SST and the Niño index and Dipole Mode Index (DMI) during the two periods range from -0.213 to 0.055. Moreover, CCSM4 often simulates SST responses that are opposite to the expected effects of ENSO and IOD phases. These results indicate that, despite its relative strength among CMIP5 models, CCSM4 still lacks sufficient accuracy in reproducing the regional impacts of ENSO and IOD on SST variability in the Indonesian seas