Sr thermometer for Porites corals. Little need to measure Ca?

Abstract

Cubic sub-samples of 1 mm 3 (about 0.5 mg) were obtained from a Porites coral slice collected from Xisha Island, South China Sea, and analysed for Sr and Ca concentrations by ID-TIMS after precise weigh ing. Ca contents in the coral are quite uniform (mean = 38.16 wt%, 2a = 0.11 wt%). The variation corre sponds to ±0.4°C, about the level of uncertainty of the Sr/Ca-SST calibration. Sr concentrations and Sr/Ca ratios covary linearly, and the line can be defined by the equation Sr/Ca x 103 = 0.111 Sr 0.5061 (corre lation coefficient r = 0.9955), where Sr is in umol/gm. Consequently, our results demonstrate that the previously established coral Sr/Ca thermometer,

Variation of initial 230Th/232Th and limits of high precision U–Th dating of shallow-water corals

“…Porites coral skeletal Ca content is 38.2-38.5% by mass in the South China Sea and western Pacific (Sun et al, 1999). The calculated molar coral U/Ca ratio, [U/Ca] coral , is 1.0-1.2 Â 10…”

Strontium contents of a Porites coral from Xisha Island, South China Sea: A proxy for sea‐surface temperature of the 20th century

“…The above linearity indicates that coral Sr concentrations closely covary with the ambient water temperature so there is no need to involve Ca in the SST study using the Xisha coral. In fact, the coral Sr thermometry is just a simplification of the conventional Sr/Ca thermometry, because of the uniform Ca content in this coral sample [ Sun et al , 1999]. Uniform skeletal Ca content has also been reported for Porites corals from Nature Reserve Reef (29.5°N, 34.9°E), northern Red Sea [ Enmar et al , 2000], Tarawa Atoll (1°N, 172°E), western Pacific [ Allison et al , 2001] and Johnston Atoll (16°N, 169°W), north‐central Pacific [ Cohen et al , 2001].…”

“…In contrast, the ratios of some trace elements to Ca, such as Sr/Ca, Mg/Ca and U/Ca in coral skeletons, seem to faithfully record ambient seawater temperature [ Smith et al , 1979; Swart and Hubbard , 1982; Min et al , 1995; McCulloch et al , 1994; Mitsuguchi et al , 1996; Wei et al , 2000]. Among these ratios, the Sr/Ca ratio has mostly been used in previous studies because coral skeletons possess very high Sr contents (∼7500 μg/g; Sun et al [1999]). Accordingly, coral Sr/Ca thermometry has been established for SST studies based on the observed linear relationship between skeletal Sr/Ca ratios and SST records [ Beck et al , 1992; Shen et al , 1996; Alibert and McCulloch , 1997].…”

“…This study uses a Porites coral drilled from Xisha Island of the South China Sea, which is about one meter long and covers almost the entire 20th century. Based on the previous finding that the coral sample has a uniform Ca content [ Sun et al , 1999], this study aims at establishing a Sr thermometer for the Xisha coral and reconstructing SST records for the last century. Because the South China Sea extends from the west Pacific warm pool to the south coast of the Asian continent, the Pacific decadal oscillation, ENSO and the Asian monsoon all affect the climate of the region.…”

Na/Ca variability in coral skeletons

“…In Fig. 4, element/Ca ratios for the data of Bar-Matthews et al (1993) and Busenberg and Plummer (1985) have been calculated on the basis of the observation that coral skeletons and secondary aragonites have approximately the same Ca concentration: 385,000 ± 5,000 ppm (e.g., Sun et al, 1999;Enmar et al, 2000;Sun et al, 2005;T. Mitsuguchi, unpublished data).…”