El Niño-Southern Oscillation-related salinity variations recorded in the skeletal geochemistry of a Porites coral from Espiritu Santo, Vanuatu

Abstract

Coral skeletal geochemistry offers the potential to reconstruct the sea surface salinity (SSS) history of the tropical oceans on seasonal to interannual and perhaps centennial timescales because of the strong link between variation in SSS and seawater δ18O in tropical regions. We explore this potential using a monthly resolved, 65-year record of skeletal δ18O and Sr/Ca variations in a Porites coral from Espiritu Santo, Vanuatu. We demonstrate that El Niño-Southern Oscillation-related climate variability strongly influences coral δ18O at Santo through local salinity changes associated with the position of the South Pacific Convergence Zone and the movement of its associated salinity front. Such a demonstration provides the "ground truth" data that can be used to place paleoclimate variability estimated using existing fossil coral records from this region into a modern conceptual framework. We also evaluate different methods of combining coral δ18O and Sr/Ca to reconstruct SSS and conclude that the coral δ 18O anomaly time series provides the best fit to recent in situ SSS data at Santo. Copyright 2004 by the American Geophysical Union.