Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene
Atmospheric carbon dioxide concentrations (pCO 2 ) beyond ice core records have been reconstructed from δ 11 B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio‐Pleistocene to evaluate the assumptions leading to these numbers. D...
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ftsubggeo:oai:e-docs.geo-leo.de:11858/11074 2023-10-09T21:52:22+02:00 Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene Köhler, Peter 2023-02-21 https://doi.org/10.1029/2022PA004439 http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11074 eng eng doi:10.1029/2022PA004439 http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11074 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. ddc:551 carbon cycle modeling CO2 boron isotopes pH Plio‐Pleistocene doc-type:article 2023 ftsubggeo https://doi.org/10.1029/2022PA004439 2023-09-17T22:12:30Z Atmospheric carbon dioxide concentrations (pCO 2 ) beyond ice core records have been reconstructed from δ 11 B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio‐Pleistocene to evaluate the assumptions leading to these numbers. During glacials times, simulated atmospheric pCO 2 was unequilibrated with pCO 2 in the equatorial surface ocean by up to 35 ppm while the δ 11 B‐based approaches assume unchanged (quasi)equilibrium between both. In the Pliocene, δ 11 B‐based estimates of surface ocean pH are lower in the Pacific than in the Atlantic resulting in higher calculated pCO 2 . This offset in pH between ocean basins is not supported by models. To calculate pCO 2 in surface waters out of the δ 11 B‐based pH some assumptions on either total alkalinity or dissolved inorganic carbon are necessary. However, the assumed values of these under‐constrained variables were according to my results partly inconsistent with chemically possible combinations within the marine carbonate system. The model results show glacial/interglacial variability in total alkalinity of the order of 100 μmol/kg, which is rarely applied to proxy reconstructions. Simulated atmospheric pCO 2 is tightly (r 2 > 0.9) related to equatorial surface‐ocean pH, which can be used for consistency checks. Long‐term trends in volcanic CO 2 outgassing and the strength of the continental weathering fluxes are still unconstrained, allowing for a wide range of possible atmospheric pCO 2 across the Plio‐Pleistocene. Nevertheless, this carbon cycle analysis suggests that reported atmospheric pCO 2 above 500 ppm in the Pliocene might, for various reasons, need to be revised to smaller numbers. Key Points: Simulated equatorial surface ocean ????CO 2 is near‐equilibrium with atmosphere during interglacials but enriched (≤35 ppm) during glacials. Models suggest similar equatorial surface ????H in Pacific and in Atlantic in high CO 2 worlds while Pliocene reconstructions show offsets. Carbon cycle ... Article in Journal/Newspaper ice core GEO-LEOe-docs (FID GEO) Pacific Paleoceanography and Paleoclimatology 38 2 |
institution |
Open Polar |
collection |
GEO-LEOe-docs (FID GEO) |
op_collection_id |
ftsubggeo |
language |
English |
topic |
ddc:551 carbon cycle modeling CO2 boron isotopes pH Plio‐Pleistocene |
spellingShingle |
ddc:551 carbon cycle modeling CO2 boron isotopes pH Plio‐Pleistocene Köhler, Peter Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
topic_facet |
ddc:551 carbon cycle modeling CO2 boron isotopes pH Plio‐Pleistocene |
description |
Atmospheric carbon dioxide concentrations (pCO 2 ) beyond ice core records have been reconstructed from δ 11 B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio‐Pleistocene to evaluate the assumptions leading to these numbers. During glacials times, simulated atmospheric pCO 2 was unequilibrated with pCO 2 in the equatorial surface ocean by up to 35 ppm while the δ 11 B‐based approaches assume unchanged (quasi)equilibrium between both. In the Pliocene, δ 11 B‐based estimates of surface ocean pH are lower in the Pacific than in the Atlantic resulting in higher calculated pCO 2 . This offset in pH between ocean basins is not supported by models. To calculate pCO 2 in surface waters out of the δ 11 B‐based pH some assumptions on either total alkalinity or dissolved inorganic carbon are necessary. However, the assumed values of these under‐constrained variables were according to my results partly inconsistent with chemically possible combinations within the marine carbonate system. The model results show glacial/interglacial variability in total alkalinity of the order of 100 μmol/kg, which is rarely applied to proxy reconstructions. Simulated atmospheric pCO 2 is tightly (r 2 > 0.9) related to equatorial surface‐ocean pH, which can be used for consistency checks. Long‐term trends in volcanic CO 2 outgassing and the strength of the continental weathering fluxes are still unconstrained, allowing for a wide range of possible atmospheric pCO 2 across the Plio‐Pleistocene. Nevertheless, this carbon cycle analysis suggests that reported atmospheric pCO 2 above 500 ppm in the Pliocene might, for various reasons, need to be revised to smaller numbers. Key Points: Simulated equatorial surface ocean ????CO 2 is near‐equilibrium with atmosphere during interglacials but enriched (≤35 ppm) during glacials. Models suggest similar equatorial surface ????H in Pacific and in Atlantic in high CO 2 worlds while Pliocene reconstructions show offsets. Carbon cycle ... |
format |
Article in Journal/Newspaper |
author |
Köhler, Peter |
author_facet |
Köhler, Peter |
author_sort |
Köhler, Peter |
title |
Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
title_short |
Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
title_full |
Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
title_fullStr |
Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
title_full_unstemmed |
Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene |
title_sort |
atmospheric co2 concentration based on boron isotopes versus simulations of the global carbon cycle during the plio‐pleistocene |
publishDate |
2023 |
url |
https://doi.org/10.1029/2022PA004439 http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11074 |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
ice core |
genre_facet |
ice core |
op_relation |
doi:10.1029/2022PA004439 http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11074 |
op_rights |
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
op_doi |
https://doi.org/10.1029/2022PA004439 |
container_title |
Paleoceanography and Paleoclimatology |
container_volume |
38 |
container_issue |
2 |
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1779315515816148992 |