FN Archimer Export Format
PT J
TI Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: Developing a new paleo-CO2 probe
BT 
AF Godbillot, Camille
   Minoletti, Fabrice
   Bassinot, Franck
   Hermoso, Michaël
AS 1:1;2:1;3:2;4:3;
FF 1:;2:;3:;4:;
C1 Institut des Sciences de la Terre de Paris (UMR 7193 ISTeP), CNRS, Sorbonne Université, 75005 Paris, France
   Laboratoire des Sciences de l’Environnement et du Climat (UMR 8212 LSCE), CEA, CNRS, Université Versailles Saint Quentin, 91191, Gif sur Yvette, France
   Laboratoire d’Océanologie et de Géosciences (UMR 8187 LOG), Université du Littoral Côte d’Opale, CNRS, Université de Lille, 62930 Wimereux, France
C2 UNIV SORBONNE, FRANCE
   CEA, FRANCE
   UNIV LITT, FRANCE
IN DOAJ
IF 4.3
TC 1
UR https://archimer.ifremer.fr/doc/00703/81525/85959.pdf
   https://archimer.ifremer.fr/doc/00703/81525/85960.pdf
   https://archimer.ifremer.fr/doc/00703/81525/93437.pdf
   https://archimer.ifremer.fr/doc/00703/81525/93438.zip
LA English
DT Article
CR IMAGES 1-MD101
BO Marion Dufresne
AB Beyond the pCO2 records provided by ice core measurements, the quantification of atmospheric CO2 concentrations and changes thereof relies on proxy data, the development of which represents a foremost challenge in paleoceanography. In the paleoceanographic toolbox, the coccolithophores occupy a notable place, as the magnitude of the carbon isotopic fractionation between ambient CO2 and a type of organic compounds that these photosynthetic microalgae synthesize (the alkenones) represents a relatively robust proxy to reconstruct past atmospheric CO2 concentrations during the Cenozoic. The isotopic composition of coeval calcite biominerals found in the sediments and also produced by the coccolithophores (the coccoliths) have been found to record an ambient CO2 signal through culture and sediment analyses. These studies have, however, not yet formalized a transfer function that quantitatively ties the isotopic composition of coccolith calcite to the concentrations of aqueous CO2, and, ultimately, to atmospheric CO2 levels. Here, we make use of a micro-separation protocol to compare the isotopic response of two size-restricted coccolith assemblages from the North Atlantic to changes in surface ocean CO2 during Termination II (ca. 130–140 ka). Performing paired measurements of the isotopic composition (δ13C and δ18O) of relatively large and small coccoliths provides an isotopic offset that can be designated as a “differential vital effect”. We find that the evolution of this offset follows that of aqueous CO2 concentrations computed from the ice core CO2 curve and an independent temperature signal. We interpret this biogeochemical feature to be the result of converging carbon fixation strategies between large and small cells as the degree of carbon limitation for cellular growth decreases across the deglaciation. We are therefore able to determine a transfer function between the coccolith differential vital effects and aqueous CO2 in the range of Quaternary CO2 concentrations. We here consolidate a new coccolith ∆δ13C proxy that overtakes the strong assumptions that have to be made pertaining to the chemistry of the carbonate system in seawater, as required in CO2 proxy methods such as the boron isotope and alkenone proxies. 
PY 2022
PD MAR
SO Climate Of The Past
SN 1814-9324
PU Copernicus GmbH
VL 18
IS 3
UT 000766886000001
BP 449
EP 464
DI 10.5194/cp-18-449-2022
ID 81525
ER

EF