Interannual and Decadal Variability of the Western Pacific Sea Surface Condition for the Years 1787-2000: Reconstruction Based on Stable Isotope Record from a Guam Coral

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coral, western Pacific warm pool, decadal variability

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We present a monthly resolved, 213-year stable isotope time series from a coral from Guam (13 degrees N, 145 degrees E), which is located on the northern edge of the western Pacific warm pool. Oxygen isotopic composition of the coral skeleton (delta(18)O(coral)) shows seasonal, interannual, and decadal variability, which documents significant oceanographic changes related to thermal and hydrologic variations in this region. The delta(18)O(coral) anomaly reflects sea surface temperature (SST) anomaly and sea surface salinity (SSS) anomaly with significant r values of - 0.69 and 0.49, respectively, which are strongly linked to oceanographic changes that occur during El Nino - Southern Oscillation (ENSO) warm and cool phases. We identified 46 ENSO warm ( El Nino) and 53 cool phases ( La Nina) in the coral record, which are consistent with those phases reconstructed by Nino 3.4 SST anomaly. Spectral analyses of the delta(18)O(coral) anomaly record for the years 1790 - 1999 identified significant peaks around similar to 3 to similar to 7 years. These results indicate that the Guam coral has recorded ENSO periodicity. The delta(18)O(coral) anomaly shows decadal variability of similar to 15- to similar to 45-year periodicity with significant shifts (< 0.2%) from warmer to cooler condition and vice versa. An accumulative decrease in delta(18)O(coral) time series may imply similar to 0.75 degrees C warming of SST and similar to 0.23 parts per thousand freshening of seawater delta(18)O, corresponding to a decrease of SSS by similar to 0.85, in the northwestern tropical Pacific over the last 2 centuries.

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Journal of Geophysical Research - Oceans, v. 110, no. C5, article C05018.