Global carbon cycle perturbation across the Eocene-Oligocene climate transition
Global carbon cycle perturbation across the Eocene-Oligocene climate transition
The Eocene-Oligocene transition (EOT), ~34?Ma, marks a tipping point in the long-term Cenozoic greenhouse to icehouse climate transition. Paleorecords reveal stepwise rapid cooling and ice growth across the EOT tightly coupled to a transient benthic ?13C excursion and a major and permanent deepening of the carbonate compensation depth (CCD). Based on biogeochemical box modeling, Merico et al. (2008) suggested that a combination of (1) glacioeustatic sea level fall-induced shelf-basin carbonate burial fractionation and (2) shelf carbonate weathering can account for the carbon cycle perturbation, but this finding has been questioned. Alternative proposed mechanisms include increased ocean ventilation, decreased carbonate burial, increased organic carbon burial, increased silicate weathering, and increased ocean calcium concentration. Here we use an improved version of the biogeochemical box model of Merico et al. (2008) to reevaluate these competing hypotheses and an additional mechanism, the expansion of “carbon capacitors” such as permafrost and peatlands. We find that changes in calcium concentration, silicate weathering, and carbonate or organic carbon burial each yield a response that is fundamentally at odds with the form and/or sign of the paleorecords. Shelf-basin carbonate burial fractionation (CCD change), plus shelf carbonate weathering, sequestration of 12C-enriched carbon into carbon capacitors, and possibly increased ocean ventilation (?13C excursion), offers the best fit to the paleorecords. Further work is needed to understand why the EOT carbon cycle perturbation is so unique when the forcing mechanisms hypothesized to be responsible (cooling and ice growth) are not peculiar to this event.
Eocene-Oligocene transition, Cenozoic cooling, Antarctic glaciation, permafrost, carbonate shelf-basin fractionation, carbon cycle
311-329
Armstrong Mckay, David
9e7fc75d-311e-4980-9911-288d965a9e56
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
20 February 2016
Armstrong Mckay, David
9e7fc75d-311e-4980-9911-288d965a9e56
Tyrrell, Toby
6808411d-c9cf-47a3-88b6-c7c294f2d114
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Armstrong Mckay, David, Tyrrell, Toby and Wilson, Paul A.
(2016)
Global carbon cycle perturbation across the Eocene-Oligocene climate transition.
Paleoceanography, 31 (2), .
(doi:10.1002/2015PA002818).
Abstract
The Eocene-Oligocene transition (EOT), ~34?Ma, marks a tipping point in the long-term Cenozoic greenhouse to icehouse climate transition. Paleorecords reveal stepwise rapid cooling and ice growth across the EOT tightly coupled to a transient benthic ?13C excursion and a major and permanent deepening of the carbonate compensation depth (CCD). Based on biogeochemical box modeling, Merico et al. (2008) suggested that a combination of (1) glacioeustatic sea level fall-induced shelf-basin carbonate burial fractionation and (2) shelf carbonate weathering can account for the carbon cycle perturbation, but this finding has been questioned. Alternative proposed mechanisms include increased ocean ventilation, decreased carbonate burial, increased organic carbon burial, increased silicate weathering, and increased ocean calcium concentration. Here we use an improved version of the biogeochemical box model of Merico et al. (2008) to reevaluate these competing hypotheses and an additional mechanism, the expansion of “carbon capacitors” such as permafrost and peatlands. We find that changes in calcium concentration, silicate weathering, and carbonate or organic carbon burial each yield a response that is fundamentally at odds with the form and/or sign of the paleorecords. Shelf-basin carbonate burial fractionation (CCD change), plus shelf carbonate weathering, sequestration of 12C-enriched carbon into carbon capacitors, and possibly increased ocean ventilation (?13C excursion), offers the best fit to the paleorecords. Further work is needed to understand why the EOT carbon cycle perturbation is so unique when the forcing mechanisms hypothesized to be responsible (cooling and ice growth) are not peculiar to this event.
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Published date: 20 February 2016
Keywords:
Eocene-Oligocene transition, Cenozoic cooling, Antarctic glaciation, permafrost, carbonate shelf-basin fractionation, carbon cycle
Organisations:
Ocean and Earth Science, Paleooceanography & Palaeoclimate
Identifiers
Local EPrints ID: 388252
URI: http://eprints.soton.ac.uk/id/eprint/388252
ISSN: 0883-8305
PURE UUID: 825f9395-99dd-40cd-9677-99dc4f905028
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Date deposited: 22 Feb 2016 14:55
Last modified: 15 Mar 2024 03:05
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Author:
David Armstrong Mckay
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