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 Amédée 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, δ18O and δ13C) 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 δ18O 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 δ18O to SST). The three, sub-monthly resolved, 30-year coral Sr/Ca-SST time series have mean SST values that agree within 0.2o C with the instrumental mean SST value. A similar comparison for the coral δ18O-SST records indicate a maximum difference between predicted and observed mean SST of 0.5˚C. Analysis of the monthly climatological means also indicates that Sr/Ca-SST records closely match the instrumental SST record ±0.4˚C; a similar comparison using the δ18O-SST record yields an average offset of ±0.6˚C between observed and predicted monthly SST. Stacking the three records to form composite Sr/Ca-SST and δ18O-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.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-2485 |
| Date | 05 November 2003 |
| Creators | Stephans, Christie L |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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