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

Schmittner, Andreas; Bostock, Helen C.; Cartapanis, Olivier; Curry, William B.; Filipsson, Helena L. LU ; Galbraith, Eric D.; Gottschalk, Julia; Herguera, Juan Carlos; Hoogakker, Babette and Jaccard, Samuel L., et al. (2017) In Paleoceanography
Abstract

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 (δ13CCibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ13C of dissolved inorganic carbon (δ13CDICnat) 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... (More)

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 (δ13CCibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ13C of dissolved inorganic carbon (δ13CDICnat) 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 δ13CCibnat and δ13CDICnat, 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 δ13CDICnat from δ13CCibnat. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ13CDICnat = δ13CCibnat). 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.

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@article{93994d53-ee3f-4912-be36-2434985fd621,
  abstract     = {<p>The carbon isotope composition (δ<sup>13</sup>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<sup>13</sup>C of foraminifera tests. Here more than 1700 δ<sup>13</sup>C observations of the benthic foraminifera genus Cibicides from late Holocene sediments (δ<sup>13</sup>C<sub>Cibnat</sub>) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ<sup>13</sup>C of dissolved inorganic carbon (δ<sup>13</sup>C<sub>DICnat</sub>) 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<sup>13</sup>C<sub>Cibnat</sub> and δ<sup>13</sup>C<sub>DICnat</sub>, confirming earlier work. Regression analyses indicate significant carbonate ion (-2.6 ± 0.4) × 10<sup>-3</sup>‰/(μmol kg<sup>-1</sup>) [CO<sub>3</sub> <sup>2-</sup>] and pressure (-4.9 ± 1.7) × 10<sup>-3</sup>‰ m<sup>-1</sup> (depth) effects, which we use to propose a new global calibration for predicting δ<sup>13</sup>C<sub>DICnat</sub> from δ<sup>13</sup>C<sub>Cibnat</sub>. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ<sup>13</sup>C<sub>DICnat</sub> = δ<sup>13</sup>C<sub>Cibnat</sub>). 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<sup>13</sup>C record.</p>},
  author       = {Schmittner, Andreas and Bostock, Helen C. and Cartapanis, Olivier and Curry, William B. and Filipsson, Helena L. and Galbraith, Eric D. and Gottschalk, Julia and Herguera, Juan Carlos and Hoogakker, Babette and Jaccard, Samuel L. and Lisiecki, Lorraine E. and Lund, David C. and Martínez-Méndez, Gema and Lynch-Stieglitz, Jean and Mackensen, Andreas and Michel, Elisabeth and Mix, Alan C. and Oppo, Delia W. and Peterson, Carlye D. and Repschläger, Janne and Sikes, Elisabeth L. and Spero, Howard J. and Waelbroeck, Claire},
  issn         = {0883-8305},
  keyword      = {Benthic,Calibration,Carbon,Foraminifera,Isotopes},
  language     = {eng},
  month        = {06},
  publisher    = {American Geophysical Union},
  series       = {Paleoceanography},
  title        = {Calibration of the carbon isotope composition (δ<sup>13</sup>C) of benthic foraminifera},
  url          = {http://dx.doi.org/10.1002/2016PA003072},
  year         = {2017},
}