NOAA/WDS Paleoclimatology - St. Gilles Reef - Oxygen Isotope Data

We have developed a new 163-year bimonthly coral d18O record from La Réunion (55°E, 21°S). Interannual variations in coral d18O are coherent with the Southern Oscillation Index but not with regional sea surface temperature (SST). Correlations with the global SST field suggest more negative seawater d18O (d18Osw) during La Niña years. We propose that the signal results from changes in the strength of the South Equatorial Current and the Indonesian throughflow, which carry low salinity water. Multidecadal variations in coral d18O are coherent with regional SST, but the sign is of opposite sense as expected from the coral d18O-temperature relationship. This requires multidecadal changes in salinity large enough to overprint the SST contribution in the coral d18O record. Our results suggest that multidecadal salinity variations result from modulations in the transport of the South Equatorial Current, which varies in response to the surface wind field and/or the Indonesian throughflow.