Calibration and application of the 'clumped isotope' thermometer to foraminifera for high-resolution climate reconstructions

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...

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Bibliographic Details
Published in:Geochimica et Cosmochimica Acta
Main Authors: Grauel, Anna-Lena, Schmid, Thomas W., Hu, Bin, Bergami, Caterina, Capotondi, Lucilla, Zhou, Liping, Bernasconi, Stefano M.
Other Authors: Grauel, AL (reprint author), Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, England., ETH, Inst Geol, CH-8092 Zurich, Switzerland., Peking Univ, Dept Geog, Beijing 100871, Peoples R China., ISMAR Inst Marine Sci, Natl Res Council Italy, CNR, Bologna, Italy., Peking Univ, Ctr Ocean Res, Beijing 100871, Peoples R China., Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, England.
Format: Journal/Newspaper
Language:English
Published: geochimica et cosmochimica acta 2013
Subjects:
LAST GLACIAL MAXIMUM
MULTIPLY-SUBSTITUTED ISOTOPOLOGUES
PLANKTONIC-FORAMINIFERA
PLEISTOCENE TEMPERATURES
CARBONATE MINERALS
MEDITERRANEAN SEA
C-13-O-18 BONDS
SURFACE WATERS
ADRIATIC SEA
OXYGEN
Planktonic foraminifera
Online Access:https://hdl.handle.net/20.500.11897/224321
https://doi.org/10.1016/j.gca.2012.12.049
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Summary: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 similar 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 (similar to 0.005-0.013 parts per thousand) 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 700 years 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. (C) 2013 Elsevier Ltd. All rights reserved. Geochemistry & Geophysics SCI(E) 16 ARTICLE 125-140 108

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