Reconstructing 20th Century SST Variability in the Southwest Pacific: A Replication Study Using Multiple Coral Sr/Ca Records From New Caledonia
Abstract
Coral-based climate reconstructions typically have not used multiple cores from a region to capture and replicate a climate signal largely because of concerns focused on coral conservation, analytical expense, and time constraints. Coral Sr/Ca reproducibility through the 20th century was investigated using three intra-colony and three inter-colony coral records, from the reefs offshore of the Amédée Island, New Caledonia. The coral Sr/Ca signal is highly reproducible; the average absolute offset between coeval monthly Sr/Ca determinations between any two coral Sr/Ca time series is 0.036 mmol/mol (~0.65 °C), which is <2x the analytical precision of the coral Sr/Ca measurements. The stack average of the monthly coral Sr/Ca variations and monthly anomalies are significantly correlated with monthly in situ SST (r = -0.95, -0.56, respectively, p < 0.05, n = 304) for the period 1967 to 1992 and monthly 1° gridded SST data product (r = -0.95, -0.53, respectively, p < 0.05, n = 1198) for the period 1900 to 1999. The coral Sr/Ca-SST reconstruction exhibits decadal-scale fluctuations that exceed those observed in the gridded SST time series, which may reflect true differences between the SST at a shallow reef site and those averaged over a 1°-grid box or they may reflect inadequacies in the methodology used to create the gridded SST product when few observations are available. A warming trend of ~0.65 °C is observed in the coral Sr/Ca-SST record, which is consistent with estimates of warming of the tropical surface oceans over the 20th century. Monthly coral Sr/Ca records and a seasonally resolved coral δ18O record from this site share variance in the later half of the 20th century, but not in the early 20th century, suggestive of a change in seawater δ18O. The 20th century trend in the coral δ18O record is consistent with a 20th century freshening of surface seawater at Amédée.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS11A1472D
- Keywords:
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- 0473 Paleoclimatology and paleoceanography (3344;
- 4900);
- 1065 Major and trace element geochemistry;
- 4916 Corals (4220);
- 4954 Sea surface temperature;
- 9355 Pacific Ocean