Calibration of the carbon isotope composition (δ¹³C) of benthic foraminifera

Summary, in English

The carbon isotope composition (δ¹³C) of seawater provides valuable insight on ocean circulation, air-sea exchange, the biological pump, and the global carbon cycle and is reflected by the δ¹³C of foraminifera tests. Here more than 1700 δ¹³C observations of the benthic foraminifera genus Cibicides from late Holocene sediments (δ¹³C_Cibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ¹³C of dissolved inorganic carbon (δ¹³C_DICnat) 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 δ¹³C_Cibnat and δ¹³C_DICnat, 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^-3‰ m^-1 (depth) effects, which we use to propose a new global calibration for predicting δ¹³C_DICnat from δ¹³C_Cibnat. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ¹³C_DICnat = δ¹³C_Cibnat). 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 δ¹³C record.

• Author: Andreas Schmittner; Helen C. Bostock; Olivier Cartapanis; William B. Curry; Helena L. Filipsson; Eric D. Galbraith; Julia Gottschalk; Juan Carlos Herguera; Babette Hoogakker; Samuel L. Jaccard; Lorraine E. Lisiecki; David C. Lund; Gema Martínez-Méndez; Jean Lynch-Stieglitz; Andreas Mackensen; Elisabeth Michel; Alan C. Mix; Delia W. Oppo; Carlye D. Peterson; Janne Repschläger; Elisabeth L. Sikes; Howard J. Spero; Claire Waelbroeck
• Department/s: Quaternary Sciences; BECC: Biodiversity and Ecosystem services in a Changing Climate
• Publishing year: 2017-06-03
• Language: English
• Pages: 512-530
• Publication/Series: Paleoceanography
• Volume: 32
• Issue: 6
• Links: http://dx.doi.org/10.1002/2016PA003072
• Document type: Journal article
• Publisher: John Wiley & Sons Inc.
• Topic: Geology; Climate Research
• Keywords: Benthic; Calibration; Carbon; Foraminifera; Isotopes
• Status: Published
• ISBN/ISSN/Other: ISSN: 0883-8305