Seasonal changes in sea surface temperature and salinity during the Little Ice Age in the Caribbean Sea deduced from Mg/Ca and 18O/16O ratios in corals
✍ Scribed by Tsuyoshi Watanabe; Amos Winter; Tadamichi Oba
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 487 KB
- Volume
- 173
- Category
- Article
- ISSN
- 0025-3227
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✦ Synopsis
The oxygen isotopic composition (d 18 O) of coral skeletons re¯ects a combination of sea surface temperature (SST) and the d 18 O of seawater, which is related to sea surface salinity (SSS). In contrast, the magnesium/calcium (Mg/Ca) ratio of a coral skeleton re¯ects SST independent of salinity. By using the relationships among coral Mg/Ca ratios, coral d 18 O, seawater d 18 O and SST, it is possible to determine past SST and SSS uniquely. Such determinations were made and calibrated using the Mg/Ca ratio and the d 18 O of the modern part of a 3 m long coral core (Montastrea faveolata), collected from the southwest coast of Puerto Rico in the Caribbean Sea where both SST and SSS changes seasonally and the seawater d 18 O measured at the coral site. Our results yielded three relationships (coral Mg/Ca±SST, d 18 O coral ±d 18 O water -SST, and d 18 O water ±SSS). With these calibration equations seasonal changes in SST and SSS during the little ice age (LIA) in the Caribbean Sea were reconstructed. The d 18 O and Mg/Ca ratio of the coral skeleton between 1699 and 1703 suggests that the SST during the LIA was approximately 28C cooler than present with the SSS showing greater seasonal changes as well. These results are in good agreement with climatebased reconstruction from corals based on oxygen isotopes, although the possibility of some uncertainty remain in our estimation including long-term decadal scale trends in climate.