Atmospheric and oceanic evidences of El Nino-Southern Oscillation events in the south central Pacific Ocean from coral stable isotopic records over the last 137 years

Abstract

We measured δ18O and δ13C in Porites lutea collected in the Moorea lagoon where the instrumental records show that an El Nino-Southern Oscillation (ENSO) event implies both a cloud cover decrease and a weak sea surface temperature (SST) increase. Two proxies allow an ENSO record to be reconstructed at Moorea: the annual δ13C anomaly, associated with the South Pacific Convergence Zone motion, and an annual δ18O anomaly showing increased SST. The frequency bands exhibited by the singular spectral analysis (SSA) and the multitaper method of the annual δ18O and δ13C records are centered on 2.5 and 5.2 years and 2.4 and 3.2 years, respectively, which are the main ENSO modes. We used SSA to reconstruct ENSO events at Moorea over the past 137 years. Results indicate that climate variability at this site is strongly affected by ENSO events.