Thermodynamic air-sea equilibration controls carbon isotopic composition of the South Atlantic thermocline during the last glacial period

Pinho, Tainã M.L.; Chiessi, Cristiano M.; Campos, Marília C.; Portilho-Ramos, Rodrigo C.; Martínez-Méndez, Gema; Venancio, Igor M.; Nascimento, Rodrigo A.; Crivellari, Stefano; Albuquerque, Ana L.S.; Arz, Helge W.; Tiedemann, Ralf; Bahr, André; Mulitza, Stefan

doi:10.1016/j.gloplacha.2023.104223

Cited by 2 publications

(2 citation statements)

References 105 publications

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“…This is not entirely new and has already been discussed before (e.g. Lynch-Stieglitz et al, 2019;Shao et al, 2021;Pinho et al, 2023). However, the 13 C cycle is more complex than stated previously (Lynch-Stieglitz et al, 2019;Hu et al, 2020;Pinho et al, 2023) which suggest that one might calculate a mean surface ocean 13 C DIC as function of atmospheric 13 CO 2 and a temperature-dependent fractionation during gas exchange.…”

Section: Discussionsupporting

confidence: 51%

“…Lynch-Stieglitz et al, 2019;Shao et al, 2021;Pinho et al, 2023). However, the 13 C cycle is more complex than stated previously (Lynch-Stieglitz et al, 2019;Hu et al, 2020;Pinho et al, 2023) which suggest that one might calculate a mean surface ocean 13 C DIC as function of atmospheric 13 CO 2 and a temperature-dependent fractionation during gas exchange. We here assumed, based on modern data from Verwega et al (2021), that species composition and therefore isotopic fractionation during marine photosynthesis might also be temperature-dependent having an important impact…”

Section: Discussionmentioning

confidence: 88%

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No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

Köhler,

Mulitza

2023

Preprint

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Abstract. Laboratory experiments showed that the isotopic fractionation of δ13C and of δ18O during calcite formation of planktic foraminifera are species-specific functions of oceanic CO32--concentration. This effect became known as the carbonate ion effect (CIE), whose role during the interpretation of marine sediment data will be investigated here in an in-depth analysis of the 13C cycle. For that effort we compiled new 160 kyr-long mono-specific stacks of changes in both δ13C and of δ18O from either the planktic foraminifera G. ruber (rub) or T. sacculifer (sac) from 112 and 40 non-polar marine records, respectively. Both mono-specific time series Δ(δ13Crub) and Δ(δ13Csac) are very similar to each other and a linear regression through a scatter plot of both data sets has a slope of ∼0.99 — although the laboratory-based CIE for both species differ by nearly a factor of two, implying that they should record distinctly different changes in δ13C, if we accept that the carbonate ion concentration changes on glacial/interglacial timescales. For a deeper understanding we use the global carbon cycle model BICYCLE-SE to calculate how surface ocean CO32- should have varied over time in order to be able to calculate the potential corrections which would follow the laboratory-based CIE. Our simulations are forced with atmospheric reconstructions of CO2 and δ13CO2 derived from ice cores to obtain a carbon cycle which should at least at the surface ocean be as close as possible to expected conditions and which agrees in the deep ocean in the carbon isotope of dissolved inorganic carbon (DIC), δ13CDIC, with reconstruction from benthic foraminifera. We find that both Δ(δ13Crub) and Δ(δ13Csac) agree better with changes in simulated δ13CDIC when ignoring the CIE than those time series which where corrected for the CIE. The combination of data- and model-based evidence for the lack of a role for the CIE in Δ(δ13Crub) and Δ(δ13Csac) suggests to us that the CIE as measured in laboratory experiments is not directly transferable to the interpretation of marine sediments records. We hypothesise that both foraminifera species can optimise their light environments via vertical motion and therefore calcify under nearly stable CO32--concentration. The much smaller CIE-to-glacial/interglacial-signal-ratio in δ18O, when compared to δ13C prevents us to draw robust conclusions on the role of the CIE on δ18O as recorded in the hard shells of both species. However, theory proposes that the CIE in δ13C and δ18O depends both on the pH in the surrounding water, suggesting that the CIE should be detectable in neither or both of the isotopes. Whether this lack of role of the CIE in the interpretation of planktic paleo data is a general feature, or restricted to the two species investigated here, needs to be checked with further data from other planktic foraminiferal species.

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Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 88%

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

Köhler,

Mulitza

2023

Preprint

View full text Add to dashboard Cite

show abstract

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

Köhler,

Mulitza

2024

Clim. Past

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Abstract. Laboratory experiments showed that the isotopic fractionation of δ13C and of δ18O during calcite formation of planktic foraminifera are species-specific functions of ambient CO32- concentration. This effect became known as the carbonate ion effect (CIE), whose role for the interpretation of marine sediment data will be investigated here in an in-depth analysis of the 13C cycle. For this investigation, we constructed new 160 kyr long mono-specific stacks of changes in both δ13C and δ18O from either the planktic foraminifera Globigerinoides ruber (rub) or Trilobatus sacculifer (sac) from 112 and 40 marine records, respectively, from the wider tropics (latitudes below 38°). Both mono-specific time series Δ(δ13Crub) and Δ(δ13Csac) are very similar to each other, and a linear regression through a scatter plot of both data sets has a slope of ∼ 0.99 – although the laboratory-based CIE for both species differs by a factor of nearly 2, implying that they should record distinctly different changes in δ13C, if we accept that the carbonate ion concentration changes on glacial–interglacial timescales. For a deeper understanding of the 13C cycle, we use the Solid Earth version of the Box model of the Isotopic Carbon cYCLE (BICYLE-SE) to calculate how surface-ocean CO32- should have varied over time in order to be able to calculate the potential offsets which would by caused by the CIE quantified in culture experiments. Our simulations are forced with atmospheric reconstructions of CO2 and δ13CO2 derived from ice cores to obtain a carbon cycle which should at least at the surface ocean be as close as possible to expected conditions and which in the deep ocean largely agrees with the carbon isotope ratio of dissolved inorganic carbon (DIC), δ13CDIC, as reconstructed from benthic foraminifera. We find that both Δ(δ13Crub) and Δ(δ13Csac) agree better with changes in simulated δ13CDIC when ignoring the CIE than those time series which were corrected for the CIE. The combination of data- and model-based evidence for the lack of a role for the CIE in Δ(δ13Crub) and Δ(δ13Csac) suggests that the CIE as measured in laboratory experiments is not directly transferable to the interpretation of marine sediment records. The much smaller CIE-to-glacial–interglacial-signal ratio in foraminifera δ18O, when compared to δ13C, prevents us from drawing robust conclusions on the role of the CIE in δ18O as recorded in the hard shells of both species. However, theories propose that the CIE in both δ13C and δ18O depends on the pH in the surrounding water, suggesting that the CIE should be detectable in neither or both of the isotopes. Whether this lack of role of the CIE in the interpretation of planktic paleo-data is a general feature or is restricted to the two species investigated here needs to be checked with further data from other planktic foraminiferal species.

show abstract

Thermodynamic air-sea equilibration controls carbon isotopic composition of the South Atlantic thermocline during the last glacial period

Cited by 2 publications

References 105 publications

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

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Thermodynamic air-sea equilibration controls carbon isotopic composition of the South Atlantic thermocline during the last glacial period

Cited by 2 publications

References 105 publications

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ13C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ13C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ13C) of shallow dwelling planktic foraminifera over the past 160 kyr

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No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160 kyr