The thermal oceanographic signal of El Ni ~ noreconstructed from a Kiritimati Island coralMichael

Central equatorial Paciic sea surface temperature (SST) anomaly is a critical predictor of basin-wide oceanographic and atmospheric eeects of the El Ni~ no-Southern Oscillation (ENSO) phenomenon. We employ two geochemical thermometers measured on coralline aragonite to reconstruct an independent proxy-based measure of central equatorial Paciic sea surface temperature anomaly. In addition, we assess the observational error associated with extraction of large-scale SST anomalies from 18 O and Sr/Ca measurements. On the basis of paired data for the 1981{1987 period, RMS error for the estimation of SST from Kiritimati coral 18 O is about 0.4 o C, assuming no seawater 18 O innuence; for Sr/Ca, the observational error is about 0.5 o C. Singular spectrum analysis of the 18 O time series suggests that 1/3 of the variance is explained by SST anomaly and that this variance may be separated from other signals in the frequency domain. The interannual component of the 18 O record shares 70% variance with the interannual component of local SST anomaly estimates (=-0.84) and correlates as highly with NINO3 region (150 o W-90 o W, 5 o N-5 o S) SST anomaly estimates; comparison of annual averages of the 18 O data with analyzed SST for 55 years suggests that the error in deriving annually averaged SST anomalies at Kiri-timati is about 0.4 o C. A global SST correlation analysis suggests signiicant correlation with the rest of the Paciic Basin and the tropical Indian and Atlantic sectors. The ocean-wide level of correlation achieved using the coral data is indistinguishable from that achieved using the NINO3 SST anomaly index and suggests that a few well-located coral reconstructions with low observational error may be suucient to reconstruct the global SST anomaly eld associated with ENSO activity.