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Fidelity of Stable Isotope Records in Coral Skeletons: An Assessment of Multiple Records From a Single Site Terrence M. Quinn 1 (727-553-1658; quinn@seas.marine.usf.edu) Thomas J. Crowley 2 (409-845-0795; tom@ocean.tamu.edu) Frederick W. Taylor 3 (512-471-6156; fred@utig.ig.utexas.edu) Thierry Correge 4 (687 26 08 06; correge@noumea.ird.nc) 1Dept. of Marine Science, University of South Florida, St. Petersburg, FL 33701, United States 2Dept. of Oceanography, Texas A\&M University , College Station, TX 77843, United States 3Institute for Geophysics, University of Texas , Austin, TX 78759, United States 4Inst. de Recherche pour le Developp., BPA5 , Noumea, New Caledonia Time series of geochemical variations in coralline aragonite are now widely used as proxy records of tropical climate change. A great deal of effort has gone in to producing long, subannually resolved records of geochemical variations in corals (e.g., \delta^{18}$O and Sr/Ca) because such records are needed to address questions of decadal-to-century scale climate variations in the tropical ocean-atmosphere system. Most of the published long coral records are produced from a single coral head and questions have been raised about the reliability of such records. We have investigated this issue by generating stable isotopic time series from 3 {\it Porites lutea} coral heads (PAA, PAC and PAD) collected in 1992 offshore of the Am\'{e}d\'{e}e Lighthouse, New Caledonia ($22\deg$S, $167\deg$E). Each time series extends back through 1978, has at least monthly resolution and exhibits regular seasonality in both \delta$^{18}$O and \delta$^{13}$C. The average \delta$^{18}$O value for each coral time series agrees within 1 standard deviation. The three coral \delta$^{18}$O time series are consistent with each other (shared variance ranges between 67\% and 74\%). The average \delta$^{13}$C value of the PAA and PAD time series agree within 1 standard deviation, whereas the average \delta$^{13}$C value for the coral PAC time series is greater than the others. The three coral \delta$^{13}$C time series all display a trend of decreasing \delta$^{13}$C values towards the present, however these records are not entirely consistent with one another. Calibration of the \delta$^{18}$O time series with SST time series yields a strong relation (minimum shared variance of 72\%) between the proxy and instrumental SST records. A comparison of a composite stack of the three coral \delta$^{18}$O time series with instrumental SST data indicates that there is 89\% shared variance between them. The \delta$^{18}$O/SST slope values differ by $<$4\% between corals PAA and PAD, whereas the \delta$^{18}$O/SST slope value of coral PAC differs by 11\% and 15\%, respectively, from that of corals PAA and PAD. Results of this study support the notion that coral \delta$^{18}$O records are robust proxy records of climate change, whereas environmental interpretation of coral \delta$^{13}$C records remain equivocal. |
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