Calibration of the carbon isotope composition (δ13C) of benthic foraminifera. (3rd June 2017)

• Record Type: Journal Article
• Authors: Schmittner, Andreas; Bostock, Helen C.; Cartapanis, Olivier; Curry, William B.; Filipsson, Helena L.; Galbraith, Eric D.; Gottschalk, Julia; Herguera, Juan Carlos; Hoogakker, Babette; Jaccard, Samuel L.; Lisiecki, Lorraine E.; Lund, David C.; Martínez‐Méndez, Gema; Lynch‐Stieglitz, Jean; Mackensen, Andreas; Michel, Elisabeth; Mix, Alan C.; Oppo, Delia W.; Peterson, Carlye D.; Repschläger, Janne; Sikes, Elisabeth L.; Spero, Howard J.; Waelbroeck, Claire
• Is Part Of: Paleoceanography. Volume 32:Number 6(2017)
• Page Start: 512
• Page End: 530
• Publication Date: 2017-06-03
• Subjects: carbon -- isotopes -- benthic -- foraminifera -- calibration; Paleoceanography -- Periodicals; 551.46
• DOI: 10.1002/2016PA003072
• Languages: English
• ISSNs: 0883-8305

Abstract

Abstract: The carbon isotope composition (δ 13 C) of seawater provides valuable insight on ocean circulation, air‐sea exchange, the biological pump, and the global carbon cycle and is reflected by the δ 13 C of foraminifera tests. Here more than 1700 δ 13 C observations of the benthic foraminifera genus Cibicides from late Holocene sediments (δ 13 CCibnat ) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ 13 C of dissolved inorganic carbon (δ 13 CDICnat ) as part of the international Ocean Circulation and Carbon Cycling (OC3) project. Using selection criteria based on the spatial distance between samples, we find high correlation between δ 13 CCibnat and δ 13 CDICnat, confirming earlier work. Regression analyses indicate significant carbonate ion (−2.6 ± 0.4) × 10 −3 ‰/(μmol kg −1 ) [CO3 2− ] and pressure (−4.9 ± 1.7) × 10 −5 ‰ m −1 (depth) effects, which we use to propose a new global calibration for predicting δ 13 CDICnat from δ 13 CCibnat . This calibration is shown to remove some systematic regional biases and decrease errors compared with the one‐to‐one relationship (δ 13 CDICnat = δ 13 CCibnat ). However, these effects and the error reductions are relatively small, which suggests that most conclusions from previous studies using a one‐to‐one relationship remain robust. The remaining standard error of the regression is generally σ ≅ 0.25‰, with larger values found in the southeast Atlantic and Antarctic ( σ ≅ 0.4‰) and for species other than Cibicides wuellerstorfi . Discussion of species effects and possible sources of the remaining errors may aid future attempts to improve the use of the benthic δ 13 C record. Key Points: Global comparison of bottom‐water and benthic foraminifera ( Cibicides ) carbon isotope (δ 13 C) data Cibicides δ 13 CCib reflect sea water dissolved inorganic carbon δ 13 CDIC Carbonate ion and pressure effects impact δ 13 CCib