Geochimica et Cosmochimica Acta, May 1, 2013, Vol.108, p.125(16)
To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.gca.2012.12.049 Byline: Anna-Lena Grauel (a), Thomas W. Schmid (a), Bin Hu (a)(b), Caterina Bergami (c), Lucilla Capotondi (c), Liping Zhou (b)(d), Stefano M. Bernasconi (a) Abstract: The reconstruction of past ocean temperatures is fundamental to the study of past climate changes, therefore considerable effort has been invested in developing proxies for seawater temperatures. One of the most recent and promising new proxy is carbonate 'clumped isotope' thermometry, in particular because it is based on thermodynamic equilibrium and not on biogeochemical proxies. Here, we present a new calibration of the 'clumped isotope' thermometer to foraminifera based on seven species of planktic and benthic foraminifera spanning a growth temperature range of [approximately equal to]2-28[degrees]C. We used a newly developed technique for the measurements of small samples to improve the applicability of this method to paleoceanography. Our data have a comparable precision ([approximately equal to]0.005-0.013a[degrees]) and confirm previous calibration studies based on biogenic and inorganic calcite. We discuss possible sources of uncertainty such as over-/underestimation of the calcification temperatures, species-specific vital effects, pH variations between the seawater and the vacuole water of the species and possible kinetic effects on the 'clumped isotope' calibration. To validate our calibration study and test the applicability of our measuring technique to paleoclimate and paleoceanographic studies we measured the isotope composition of Globigerinoides ruber (white) at high-resolution in a sediment core covering the last 700years in the Gulf of Taranto (Mediterranean Sea). The results show that it is necessary to average a relatively large number of analyses to achieve a consistent temperature signal for the detection of small sea surface temperature changes. Although with the current analytical system, 'clumped isotope' thermometry is only applicable to the analysis of relatively large SST changes in marine sediments, further technical improvements may make this a very powerful technique for paleoceanographic studies. Author Affiliation: (a) Geological Institute, ETH Zurich, 8092 Zurich, Switzerland (b) Department of Geography, Peking University, 100871 Beijing, China (c) CNR - National Research Council of Italy, ISMAR - Institute of Marine Sciences, Bologna, Italy (d) Centre for Ocean Research, Peking University, 100871 Beijing, China Article History: Received 12 May 2012; Accepted 29 December 2012 Article Note: (miscellaneous) Associate editor: Edwin Schauble
Measuring Instruments ; Climate
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