NOAA/WDS Paleoclimatology - Global Hydro-sensitive Coral d18O Records for Improved High-Resolution Temperature and Salinity Reconstructions

Stable oxygen isotopic ratios in corals (d18Ocoral) are commonly utilized to reconstruct climate variability beyond the limit of instrumental observations. These measurements provide constraints on past seawater temperature, due to the thermodynamics of isotopic fractionation, but also past salinity, as both salinity and seawater d18O (d18Osw) are similarly affected by precipitation/evaporation, advection, and other processes. We use historical observations, isotope-enabled model simulations, and the PAGES Iso2k database to assess the potential of d18Ocoral to provide information on past salinity. Using ‘pseudocorals’ to represent d18Ocoral as a function of observed or simulated temperature and salinity/d18Osw, we find that d18Osw contributes up to 89% of d18Ocoral variability in the Western Pacific Warm Pool. Although uncertainty in the d18Osw-salinity relationship influences the inferred salinity variability, corals from these sites could provide valuable d18Osw reconstructions. Coordinated in situ monitoring of salinity and d18Osw is vital for improving estimates of hydroclimatic change.