Atmosphere-ocean dynamics in the Western Indian Ocean recorded in corals.

We present a set of Porites coral oxygen isotope records from the tropical and subtropical Western Indian Ocean covering the past 120-336 years. All records were thoroughly validated for proxy response to regional climate factors and their relation to large-scale climate modes. The records show markedly different imprints of regional climate factors. At the same time, all coral records show clear teleconnections between the Western Indian Ocean and the El Nino-Southern Oscillation (ENSO). The multi-proxy site analysis enables the detection of the covariance structure between individual records and climate modes such as ENSO. This method unravels shifts in ENSO teleconnectivity of the Western and Central Indian Ocean on multi-decadal time-scales (after 1976). The Seychelles record shows a stationary correlation with ENSO, Chagos corals show evidence for non-stationary delta18O/ENSO relationships and the Southwestern Indian Ocean corals show a strong relationship with ENSO when the forcing is strong (1880-1920, 1970 to present). Our results indicate that the coral delta18O, in combination with other proxies, can be used to monitor temporal and spatial variations in the sea-surface temperature and the fresh water balance within the Indian Ocean on interannual to interdecadal time-scales.