How 17O excess in clumped isotope reference-frame materials and ETH standards affects reconstructed temperature

Eastern Mediterranean climate change deduced from the Soreq Cave fluid inclusion stable isotopes and carbonate clumped isotopes record of the last 160 ka

“…Assuming that this is the typical value for freshwater carbonates, so that our samples have a similar 17 Oexcess, results in an offset of 0.005±0.001‰ in 47. This offset is consistent with recent estimates of the effect on 47 of variable 17 Oexcess in CO2 standards (Saenger et al, 2021). As this offset is almost constant for all our samples it does not affect the temperatures derived from 47 and we therefore neglect it.…”

Temperature Estimates of Lower Miocene (Burdigalian) Coastal Water of Southern India Using a Revised Otolith “Clumped” Isotope Paleothermometer

“…In addition to the substantial errors in reconstructed temperature introduced by analytical uncertainties and other uncertainties related to the slopes and intercepts of Δ 47 ‐ T calibrations, recent studies suggest that the direct measurement of triple oxygen isotope compositions (Δ 17 O) of reference materials may improve the accuracy and precision of Δ 47 determinations (Saenger et al., 2021). Traditionally, laboratories assume the Δ 17 O value of the carbonates (or CO 2 analyte) to be zero (i.e., Δ 17 O = 0).…”

“…Traditionally, laboratories assume the Δ 17 O value of the carbonates (or CO 2 analyte) to be zero (i.e., Δ 17 O = 0). Such an assumption has the potential to yield small inaccuracies in Δ 47 reconstructed values, depending on the composition of the mass spectrometer working gas and data normalization procedures, that can potentially be up to 0.6°C–5.8°C (Saenger et al., 2021). While the choice of 17 O correction parameters yields negligible differences in the slopes and intercepts of the otolith Δ 47 ‐ T calibrations (anchored to ETH standards), the use of the accurate Δ 17 O values of these and other commercial standards (Fosu et al., 2020; Saenger et al., 2021; Wostbrock et al., 2020) may improve the agreement between inter‐laboratory calibrations and the overall accuracy of Δ 47 measurements.…”

“…These observations showed that the Δ 47 values of otoliths varied with growth temperature, making it a potential archive for paleo‐climate reconstruction. Since these early studies, the clumped isotope proxy has been applied to various geological archives and there have been significant advances in calibrations, analytical developments, standardization, and data reduction efforts (Bernasconi et al., 2021; Daëron, 2021; Daëron et al., 2016; Dennis et al., 2011; Fernandez et al., 2017; Kelson et al., 2017; Meckler et al., 2014; Petersen et al., 2019; Saenger et al., 2021). These advances were necessary because of discrepancies in Δ 47 ‐temperature ( T ) calibrations and Δ 47 data acquisition regimes.…”

Temperature dependence of isotopic fractionation in the CO2‐O2 isotope exchange reaction

“…The CO 2 ‐O 2 exchange technique has been used in different laboratories to study the carbon cycle 1 , 2 , 3 , 4 , 6 , 22 , 23 and precise measurement of Δ′ 17 O is used to correct for biases in clumped isotope measurements of CO 2. 24 , 25 , 26 , 27 However, the fractionation factor in CO 2 ‐O 2 isotope exchange is not well established, and different values have been reported by different laboratories.…”