Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe
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 nota...
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00060305 2023-05-15T16:39:05+02:00 Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe Godbillot, Camille Minoletti, Fabrice Bassinot, Franck Hermoso, Michaël 2022-03 electronic https://doi.org/10.5194/cp-18-449-2022 https://noa.gwlb.de/receive/cop_mods_00060305 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00059949/cp-18-449-2022.pdf https://cp.copernicus.org/articles/18/449/2022/cp-18-449-2022.pdf eng eng Copernicus Publications Climate of the Past -- http://www.copernicus.org/EGU/cp/cp/published_papers.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2217985 -- 1814-9332 https://doi.org/10.5194/cp-18-449-2022 https://noa.gwlb.de/receive/cop_mods_00060305 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00059949/cp-18-449-2022.pdf https://cp.copernicus.org/articles/18/449/2022/cp-18-449-2022.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2022 ftnonlinearchiv https://doi.org/10.5194/cp-18-449-2022 2022-03-14T00:09:05Z 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 microseparation 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 outline a first-order trend between the coccolith differential vital effects and aqueous CO2 in the range of Quaternary CO2 concentrations. Although this study would benefit from further constraints on the other controls at play on coccolith geochemistry (growth rate, air–sea gas exchange, etc.), this test of the drivers of coccolith Δδ13C and Δδ18O in natural conditions is a new step in the development of a coccolith paleo-CO2 probe. Article in Journal/Newspaper ice core North Atlantic Niedersächsisches Online-Archiv NOA Climate of the Past 18 3 449 464 |
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article Verlagsveröffentlichung Godbillot, Camille Minoletti, Fabrice Bassinot, Franck Hermoso, Michaël Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
topic_facet |
article Verlagsveröffentlichung |
description |
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 microseparation 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 outline a first-order trend between the coccolith differential vital effects and aqueous CO2 in the range of Quaternary CO2 concentrations. Although this study would benefit from further constraints on the other controls at play on coccolith geochemistry (growth rate, air–sea gas exchange, etc.), this test of the drivers of coccolith Δδ13C and Δδ18O in natural conditions is a new step in the development of a coccolith paleo-CO2 probe. |
format |
Article in Journal/Newspaper |
author |
Godbillot, Camille Minoletti, Fabrice Bassinot, Franck Hermoso, Michaël |
author_facet |
Godbillot, Camille Minoletti, Fabrice Bassinot, Franck Hermoso, Michaël |
author_sort |
Godbillot, Camille |
title |
Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
title_short |
Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
title_full |
Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
title_fullStr |
Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
title_full_unstemmed |
Parallel between the isotopic composition of coccolith calcite and carbon levels across Termination II: developing a new paleo-CO2 probe |
title_sort |
parallel between the isotopic composition of coccolith calcite and carbon levels across termination ii: developing a new paleo-co2 probe |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/cp-18-449-2022 https://noa.gwlb.de/receive/cop_mods_00060305 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00059949/cp-18-449-2022.pdf https://cp.copernicus.org/articles/18/449/2022/cp-18-449-2022.pdf |
genre |
ice core North Atlantic |
genre_facet |
ice core North Atlantic |
op_relation |
Climate of the Past -- http://www.copernicus.org/EGU/cp/cp/published_papers.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2217985 -- 1814-9332 https://doi.org/10.5194/cp-18-449-2022 https://noa.gwlb.de/receive/cop_mods_00060305 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00059949/cp-18-449-2022.pdf https://cp.copernicus.org/articles/18/449/2022/cp-18-449-2022.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/cp-18-449-2022 |
container_title |
Climate of the Past |
container_volume |
18 |
container_issue |
3 |
container_start_page |
449 |
op_container_end_page |
464 |
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1766029420543344640 |