A Bayesian, multivariate calibration for Globigerinoides ruber Mg/Ca. (6th September 2015)

• Record Type: Journal Article
• Authors: Khider, D.; Huerta, G.; Jackson, C.; Stott, L. D.; Emile‐Geay, J.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 16:Number 9(2015:Sep.)
• Page Start: 2916
• Page End: 2932
• Publication Date: 2015-09-06
• Subjects: Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2015GC005844
• Languages: English
• ISSNs: 1525-2027

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>The use of Mg/Ca in marine carbonates as a paleothermometer has been challenged by observations that implicate salinity as a contributing influence on Mg incorporation into biotic calcite and that dissolution at the sea‐floor alters the original Mg/Ca. Yet, these factors have not yet been incorporated into a single calibration model. We introduce a new Bayesian calibration for <italic>Globigerinoides ruber</italic> Mg/Ca based on 186 globally distributed core top samples, which explicitly takes into account the effect of temperature, salinity, and dissolution on this proxy. Our reported temperature, salinity, and dissolution (here expressed as deep‐water <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgkg3fbg8n" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:15252027:media:ggge20793:ggge20793-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>Δ</mml:mo><mml:msubsup><mml:mrow><mml:mtext>CO</mml:mtext></mml:mrow><mml:mn>3</mml:mn><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula>) sensitivities are (±2σ) 8.7±0.9%/°C, 3.9±1.2%/psu, and 3.3±1.3%/μmol.kg<sup>−1</sup> below a critical threshold of 21 μmol/kg in good agreement with previous culturing and core‐top studies. We then perform a sensitivity experiment on a published record from the western tropical Pacific to investigate the bias introduced by these secondary influences on the interpretation of past temperature variability. This experiment highlights the potential for misinterpretations of past oceanographic changes when the secondary influences of salinity and dissolution are not accounted for. Multiproxy approaches could potentially help deconvolve the contributing influences but this awaits better characterization of the spatio‐temporal relationship between salinity and δ<sup>18</sup>O<sub>sw</sub> over millennial and orbital timescales.</p> </abstract>