Degree Granting Department
Quinn, Terrence M.
corals, paleoclimate, reproducibility, oxygen isotopes, sr/ca ratios, new caledonia
Coral-based climate studies commonly use elemental ratios and stable isotopes of coral skeletons to address seawater temperature and hydrologic balance issues in the tropical surface oceans. Replication, or cross-checking, a standard technique used to assess the fidelity of proxy records in paleoclimatology has not been widely applied in coral-based climate studies, primarily because of the time and cost associated with generating multiple records from a single reef site. Modern and paleoclimate reconstructions based on a single proxy-coral record from a site may contain errors if individual corals from the same reef record different geochemical signals. In this study we perform a replication test using elemental ratios and stable isotopes in three Porites corals from New Caledonia.
The reef complex offshore AmÃ©dÃ©e Island, New Caledonia is an ideal site to perform a coral replication test because instrumental sea surface temperatures (SST) and sea surface salinity measurements (SSS) have been made there for over 25 years. In this study, we compare sub-monthly resolved, geochemical variations (Sr/Ca, d18O and d13C) in three Porites lutea coral heads, located ~500 m apart, with the instrumental SST and SSS records over the interval 1992-1967. The monthly coral Sr/Ca and d18O time series are well correlated to each other (r=0.86, p<.0001) and to the monthly instrumental SST record (r= -0.86, p<.0001, coral Sr/Ca to SST; r= -0.77, p<.0001, coral d18O to SST). The three, sub-monthly resolved, 30-year coral Sr/Ca-SST time series have mean SST values that agree within 0.2oC with the instrumental mean SST value. A similar comparison for the coral d18O-SST records indicate a maximum difference between predicted and observed mean SST of 0.5Â°C.
Analysis of the monthly climatological means also indicates that Sr/Ca-SST records closely match the instrumental SST record Â±0.4Â°C; a similar comparison using the d18O-SST record yields an average offset of Â±0.6Â°C between observed and predicted monthly SST. Stacking the three records to form composite Sr/Ca-SST and d18O-SST records does not appreciably improve the goodness of fit between the proxy and instrumental SST records; hence a coral-based proxy climate record from a single coral accurately reflects the observed record of climate variability at this locality. These results support the concept that high fidelity climate records can be generated using a single coral core.
Scholar Commons Citation
Stephans, Christie L., "Assessing the reproducibility of coral-based climate records: A multi-proxy replication test using three Porites lutea coral heads from New Caledonia" (2003). Graduate Theses and Dissertations.