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

Andreas Schmittner (1) , Helen Bostock (2) , Olivier Cartapanis (3) , William Curry (4) , Helena Filipsson (5) , Eric D Galbraith (6) , Julia Gottschalk (3) , Juan Carlos Herguera (7) , Babette Hoogakker (8) , Samuel L. Jaccard (9) , Lorraine Lisiecki (10) , David Lund (11) , Gema Martínez-Méndez (12) , Jean Lynch-Stieglitz (13) , Andreas Mackensen (14) , Elisabeth Michel (15, 16) , Alan C. Mix (17) , Delia W. Oppo (4) , Carlye Peterson (18) , Janne Repschläger (19) , Elisabeth Sikes (20) , Howard J. Spero (18) , Claire Waelbroeck (16)

1 OSU - Oregon State University
2 NIWA - National Institute of Water and Atmospheric Research [Wellington]
3 Institute of Geological Sciences [Bern]
4 WHOI - Woods Hole Oceanographic Institution
5 Skane University Hospital [Lund]
6 EPS - Department of Earth and Planetary Sciences [Montréal]
7 Centro de Investigacion Científica y de Educacion Superior de Ensenada
8 HWU - Heriot-Watt University [Edinburgh]
9 OCCR - Oeschger Centre for Climate Change Research
10 UC Santa Barbara - University of California [Santa Barbara]
11 UCONN - University of Connecticut
12 MARUM - Center for Marine Environmental Sciences [Bremen]
13 Georgia Institute of Technology [Atlanta]
14 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
15 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
16 PALEOCEAN - Paléocéanographie
17 CEOAS - College of Earth, Ocean and Atmospheric Sciences [Corvallis]
18 UC Davis - University of California [Davis]
19 MPIC - Max Planck Institute for Chemistry
20 WINLAB Rutgers University

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 C Cibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ 13 C of dissolved inorganic carbon (δ 13 C 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 δ 13 C Cibnat and δ 13 C DICnat , confirming earlier work. Regression analyses indicate significant carbonate ion (À2.6 ± 0.4) × 10 À3 ‰/(μmol kg À1) [CO 3 2À ] and pressure (À4.9 ± 1.7) × 10 À5 ‰ m À1 (depth) effects, which we use to propose a new global calibration for predicting δ 13 C DICnat from δ 13 C Cibnat. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ 13 C DICnat = δ 13 C 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 δ 13 C record.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Andreas Schmittner, Helen Bostock, Olivier Cartapanis, William Curry, Helena Filipsson, et al.. Calibration of the carbon isotope composition (δ¹³C) of benthic foraminifera. Paleoceanography, 2017, 32 (6), pp.512-530. ⟨10.1002/2016PA003072⟩. ⟨hal-02916860⟩