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

Ed C. Hathorne, Alex Gagnon, Thomas Felis, Jess Adkins, Ryuji Asami, Wim Boer, Nicolas Caillon, David Case, Kim M. Cobb, Eric Douville, Peter Demenocal, Anton Eisenhauer, Dieter Garbe-Schönberg, Walter Geibert, Steven Goldstein, Konrad Hughen, Mayuri Inoue, Hodaka Kawahata, Martin Kölling, Florence L. CornecBraddock K. Linsley, Helen V. McGregor, Paolo Montagna, Intan S. Nurhati, Terrence M. Quinn, Jacek Raddatz, Hélène Rebaubier, Laura Robinson, Aleksey Sadekov, Rob Sherrell, Dan Sinclair, Alexander W. Tudhope, Gangjian Wei, Henri Wong, Henry C. Wu, Chen Feng You

Research output: Contribution to journalArticlepeer-review

159 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)3730-3750
Number of pages21
JournalGeochemistry, Geophysics, Geosystems
Issue number9
Publication statusPublished - Sept 1 2013
Externally publishedYes


  • coral Sr/Ca ratios

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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