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Reconciling the apparent discrepancy between Cenozoic deep-sea temperatures from proxies and from benthic oxygen isotope deconvolution

Reconciling the apparent discrepancy between Cenozoic deep-sea temperatures from proxies and from benthic oxygen isotope deconvolution
Reconciling the apparent discrepancy between Cenozoic deep-sea temperatures from proxies and from benthic oxygen isotope deconvolution
Understanding past deep-sea temperature and sea-water oxygen isotope ratios is fundamental to environmental Earth science. For example, it provides crucial insight into past ice-volume variations, an important climate system feedback. Moreover, deep-sea temperature is important to deep-sea ecology and biogeochemical cycling. Here we compare deep-sea temperature and sea-water oxygen isotope ratios from model-based deconvolution of benthic foraminiferal carbonate δ18O with clumped isotope-based deep-sea temperature data in 1000-year timesteps over the Cenozoic. To assess wider implications of the observed differences, we quantitatively evaluate a range of potential explanatory hypotheses—such as diagenetic overprints, carbonate ion effects, ice-sheet morphology changes, and warm saline deep-water admixture—but find that, individually, none can explain the observed differences satisfactorily. We then evaluate the implications of possible combined effects and recent advances in clumped isotope temperature calibration. We find that combined consideration of a recently proposed cool clumped isotope calibration and possible carbonate ion or pH influences can provide results that approximate deep-sea temperature reconstructions based on conventional δ18Oc deconvolution. The match can be further improved if modest warm saline deep-water contributions are considered during past warm periods. This contrasts with ice-volume and ice-sheet morphology changes, which appear unrealistic or insignificant, respectively. Our quantitative comparison offers a means toward formulation of a comprehensive and internally consistent understanding of Cenozoic variability in sea level (ice volume), GIA-corrected ice-sheet heights and mean ice δ18O, sea-water δ18O, sea-water δ18Ow, deep-sea temperature, and deep-sea [CO32−] variations.
2572-4525
Rohling, E.J.
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Gernon, T.M.
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Heslop, D.
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Reichart, G.J.
e394690f-772e-4a38-80ef-902712af36e8
Roberts, A.P.
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Yu, J.
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Rohling, E.J.
a2a27ef2-fcce-4c71-907b-e692b5ecc685
Gernon, T.M.
658041a0-fdd1-4516-85f4-98895a39235e
Heslop, D.
f32aae36-7f51-40e1-bf7d-54a561369a8d
Reichart, G.J.
e394690f-772e-4a38-80ef-902712af36e8
Roberts, A.P.
4f062491-5408-4edb-8dd1-140c6a42e93f
Yu, J.
9558e475-ac9f-44d3-8c1a-b0540e3b7c3d

Rohling, E.J., Gernon, T.M., Heslop, D., Reichart, G.J., Roberts, A.P. and Yu, J. (2025) Reconciling the apparent discrepancy between Cenozoic deep-sea temperatures from proxies and from benthic oxygen isotope deconvolution. Paleoceanography and Paleoclimatology, 39, [e2024PA004872]. (doi:10.1029/2024PA004872).

Record type: Article

Abstract

Understanding past deep-sea temperature and sea-water oxygen isotope ratios is fundamental to environmental Earth science. For example, it provides crucial insight into past ice-volume variations, an important climate system feedback. Moreover, deep-sea temperature is important to deep-sea ecology and biogeochemical cycling. Here we compare deep-sea temperature and sea-water oxygen isotope ratios from model-based deconvolution of benthic foraminiferal carbonate δ18O with clumped isotope-based deep-sea temperature data in 1000-year timesteps over the Cenozoic. To assess wider implications of the observed differences, we quantitatively evaluate a range of potential explanatory hypotheses—such as diagenetic overprints, carbonate ion effects, ice-sheet morphology changes, and warm saline deep-water admixture—but find that, individually, none can explain the observed differences satisfactorily. We then evaluate the implications of possible combined effects and recent advances in clumped isotope temperature calibration. We find that combined consideration of a recently proposed cool clumped isotope calibration and possible carbonate ion or pH influences can provide results that approximate deep-sea temperature reconstructions based on conventional δ18Oc deconvolution. The match can be further improved if modest warm saline deep-water contributions are considered during past warm periods. This contrasts with ice-volume and ice-sheet morphology changes, which appear unrealistic or insignificant, respectively. Our quantitative comparison offers a means toward formulation of a comprehensive and internally consistent understanding of Cenozoic variability in sea level (ice volume), GIA-corrected ice-sheet heights and mean ice δ18O, sea-water δ18O, sea-water δ18Ow, deep-sea temperature, and deep-sea [CO32−] variations.

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Paleoceanog and Paleoclimatol - 2024 - Rohling - Reconciling the Apparent Discrepancy Between Cenozoic Deep‐Sea - Version of Record
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Accepted/In Press date: 16 October 2024
Published date: 1 November 2025

Identifiers

Local EPrints ID: 504316
URI: http://eprints.soton.ac.uk/id/eprint/504316
ISSN: 2572-4525
PURE UUID: 937a4cf9-dddc-441d-9657-18d6f963c428
ORCID for E.J. Rohling: ORCID iD orcid.org/0000-0001-5349-2158
ORCID for T.M. Gernon: ORCID iD orcid.org/0000-0002-7717-2092

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Date deposited: 04 Sep 2025 16:38
Last modified: 06 Sep 2025 01:44

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Contributors

Author: E.J. Rohling ORCID iD
Author: T.M. Gernon ORCID iD
Author: D. Heslop
Author: G.J. Reichart
Author: A.P. Roberts
Author: J. Yu

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