Oceanic forcing of interannual and multidecadal climate variability in the southwestern Indian Ocean: Evidence from a 160 year coral isotopic record (La Réunion, 55°E, 21°S)

We have developed a new 163-year bimonthly coral δ¹⁸O record from La Réunion (55°E, 21°S). Interannual variations in coral δ¹⁸O 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 δ¹⁸O (δ¹⁸O_sw) 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 δ¹⁸O are coherent with regional SST, but the sign is of opposite sense as expected ftom the coral δ ¹⁸O-temperature relationship. This requires multidecadal changes in salinity large enough to overprint the SST contribution in the coral δ¹⁸O 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.