Regional calibration of coral-based climate reconstructions from palau, west pacific warm pool (WPWP)

摘要

Stable isotopic and trace element records from corals collected within the West Pacific Warm Pool (WPWP) are well suited to examine interannual to decadal climate variability associated with the El Ni?o-Southern Oscillation (ENSO) phenomenon. The most commonly used climate recorder in corals is δ~(18)O (δ~(18)O_(CRL)), a parameter subject to multiple regional and local environmental influences. Location-specific calibration of δ~(18)O_(CRL) is a necessary first step for developing long-term paleoceanographic reconstructions. Here we present four new coral δ~(18)O stratigraphies from the Republic of Palau (7.5°N 134.5°E), and compare our records with instrumental measurements for the period 1950-2008. We also compare our results with a previously published coral record from Palau. We employ a new sea surface salinity (SSS) product and validate its utility for coral-based paleoclimate calibrations. We not only examine differences among the records but also identify strong and regionally coherent environmental signals. We find that SSS variability is the dominant influence on δ~(18)O_(CRL) in Palau, while sea surface temperature (SST) is of secondary importance. Our results show that time-averaging multiple δ~(18)O_(CRL) records into a single composite series produce greater correlations with instrumental data and indices than individual stratigraphies alone. Our results are consistent with observations of a strengthening of the hydrological cycle in the WPWP region over the past 50years, though the magnitudes of long term linear trends differ among the different Palau δ~(18)O_(CRL) records. Interannual and interdecadal variabilities between the Palau δ~(18)O_(CRL) records are more consistent than the long term linear trends. Monthly Palauan δ~(18)O_(CRL) anomalies capture strong El Ni?o events with high fidelity over the calibration period. This study provides constraints for future paleoenvironmental investigations in Palau using longer coral records.