EVALUATING THE GEOCHEMISTRY FROM CORAL SPECIES HYDNOPHORA MICROCONOS AS A RELIABLE PROXY FOR TROPICAL PACIFIC CLIMATE

The tropical Pacific is a critical region for studying the impacts of climate change because of its central role in modulating global climate variability. This is most evident during extreme El Niño Southern Oscillation events, which cause large swings in global precipitation patterns. However, the lack of recorded instrumental data prior to the mid-20th century presents a challenge to quantify the extent of anthropogenic influence on tropical climate, preventing robust simulations of future climate impacts. Geochemical records from modern and fossil coral Porites are a reliable method to extend the instrumental sea surface temperature records through the preindustrial period. However, relying on one coral genus prohibits a robust reconstruction due to limited temporal sample availability spanning centuries to millennia. Here, we test a new species of coral, Hydnophora microconos, as a reliable archive to reconstruct sea surface temperature in the central tropical Pacific. As corals secrete their aragonite skeletal material (CaCO₃), they preserve the environmental conditions through incorporation of both oxygen isotopes (𝛿¹⁸O) and changes in their strontium (Sr) and calcium (Ca) ratios. Coral Sr/Ca ratios record sea surface temperature (SST), while coral 𝛿¹⁸O are influenced by both SST and sea surface salinity. Initial results from a modern paired record of 𝛿¹⁸O and Sr/Ca from a Hydnophora microconos coral from Kiritimati Island show that these corals reproduce the instrumental SST and track warming from recent El Niño events, suggesting these corals may be reliable proxies for paleoclimate reconstruction. Future work includes comparing young fossil Hydnophora microconos geochemical records with the well-established Porites geochemical records from Kiritimati Island to ensure the fossils reproduce the established Porites-based SST record for this island. If successful, Hydnophora microconos will be paired with Porites to create a record of the climate in the tropical Pacific for the past 200 years to quantify the timing and magnitude of warming and freshening in the tropical Pacific.