Exploring branching corals as high-resolution paleo-SST archives

Branching coral reconstructions have the potential to significantly enrich paleoclimate records derived from fossil reef cores. This study explores the utility of Acropora and Pocillopora corals as high-resolution archives for paleo-sea surface temperatures (paleo-SSTs) in the western tropical Pacific. Analyses of biweekly-to weeklyresolution Sr/Ca ratios in modern corals revealed distinct seasonal variations consistent with local SSTs, particularly during the 2016 El Nino event. Given the evident interspecies variabilities in Sr/Ca, separate calibration equations from combined Sr/Ca-SST records were established for each genus. These equations were applied to derive paleo-SSTs from subfossil core records, which were subsequently integrated into a similar to 1000-year paleo-SST reconstruction. Our paleo-SST records showed comparability with reconstructed SSTs from other archives in adjacent regions. These findings highlight the potential of branching corals as novel and abundant sources of paleo-SST data. Additionally, this study emphasizes the need to address uncertainties arising from sample size limitations and inter-colony offsets. Incorporating data from both branching genera and massive corals, such as Porites, could further expand and enhance subfossil archives for robust paleoclimate reconstructions.