Todorovic S. auteur aut IRD Linsley B. K. auteur aut IRD Kuhnert H. auteur aut IRD Dissard Delphine auteur aut IRD Menkès Christophe auteur aut IRD Wu H. C. auteur aut IRD text journalArticle eng text/pdf reformatted digital access In the South Pacific Convergence Zone (SPCZ), interannual to interdecadal oceanic and atmospheric variability is especially pronounced. The El Niño Southern Oscillation and the Interdecadal Pacific Oscillation significantly influence the SPCZ diagonal axis and salinity front. Regional coral-based paleo-environmental reconstructions extend the relatively short and discontinuous instrumental sea surface temperature (SST) and sea surface salinity (SSS) record to elucidate past variability. We present monthly resolved, composite indices of coral skeletal delta 18O, Sr/Ca, and calculated delta 18Osw utilizing coral geochemical time-series from Rotuma, Fiji, Tonga, and Rarotonga, dubbed the SPCZcoral (SPCZc) indices. The new indices build upon previous efforts to describe variability and trends in the SPCZ region with expanded coverage due to a new northwestern coral addition from the SPCZ fresh pool. The increased spatial and temporal resolution of the new indices allows for higher-fidelity sub-annual reconstructions of SST and SSS in the region dating back to 1848. The results confirm the secular warming trend of 1 degrees C in the SPCZ region and show a 0.4 Sp freshening starting in the 1880s. The SPCZc delta 18Osw is the first regional reconstruction of delta 18Osw and provides valuable insights into past SSS variability, including elucidating responses to El Niño and La Niña events, as well as identifying past SPCZ zonal events. The SPCZc delta 18Osw reconstruction extends the instrumental records by similar to 100 years. The SPCZc indices prove the utility of the compositing approach in describing regional oceanographic variability with the increased signal-to-noise ratio of the obtained coral climatic data. specialized climate indices reconstruction SPCZ composite coral 032 021 40 5 e2025PA005108 [17 ] 2025 2572-4517 https://www.documentation.ird.fr/hor/fdi:010093592 10.1029/2025pa005108 2572-4517 [F B010093592] https://www.documentation.ird.fr/hor/fdi:010093592 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-07/010093592.pdf IRD - Base Horizon / Pleins textes 2025-07-15 2025-11-04 fdi:010093592 fre