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Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

Hathorne, Ed C. and Gagnon, Alex and Adkins, Jess F. and Case, David (2013) Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements. Geochemistry Geophysics Geosystems, 14 (9). pp. 3730-3750. ISSN 1525‐2027.

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The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

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Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2013 American Geophysical Union. Received 27 March 2013; Revised 3 July 2013; Accepted 19 July 2013; Published 23 September 2013. Thanks, Danke and Merci to all participants and laboratories. E.C.H. (MARUM Fellowship) and T.F. were supported by the DFG-Research Center/Excellence Cluster "The Ocean in the Earth System," University of Bremen. The Geological Survey of Japan prepared the reference materials and kindly supplied them for this study. Christina Gnade (MARUM) helped distribute reference powders and collected the data. HVM was supported by an AINSE Research Fellowship.
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DFG-Research Center/Excellence ClusterUNSPECIFIED
AINSE Research FellowshipUNSPECIFIED
Issue or Number:9
Record Number:CaltechAUTHORS:20131125-141418131
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Official Citation:Hathorne, E. C., et al. (2013), Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements, Geochem. Geophys. Geosyst., 14, 3730–3750, doi:10.1002/ggge.20230.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42694
Deposited By: Jason Perez
Deposited On:27 Nov 2013 17:52
Last Modified:24 Feb 2020 10:30

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