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Terrestrial methane cycle perturbations during the onset of the Paleocene-Eocene Thermal Maximum

Terrestrial methane cycle perturbations during the onset of the Paleocene-Eocene Thermal Maximum
Terrestrial methane cycle perturbations during the onset of the Paleocene-Eocene Thermal Maximum

Terrestrial methane (CH 4) emissions may have increased during the Paleocene-Eocene Thermal Maximum (PETM; ca. 56 Ma) and promoted additional warming, especially in the high latitudes. Although there is evidence for increased CH 4 cycling in a single Northern Hemisphere site, whether enhanced methane cycling was globally widespread is unknown because there have been no subsequent investigations. The mechanism of CH4 release is also unknown because a direct comparison between temperature and CH 4 cycling has so far not been possible. Here we use biomarkers to reconstruct temperature change and CH 4 cycling in a new PETM-aged succession in New Zealand. Our results indicate that the stable carbon isotopic composition (δ 13C) of bacterial hopanoids decreased to very low values (−60‰) during the onset of the PETM, indicating enhanced consumption of CH 4. These values are much lower than found in modern wetlands and suggest a major perturbation of the CH 4 cycle during the onset of the PETM. Low hopanoid δ 13C values do not persist into the early Eocene, despite evidence for elevated temperatures. This indicates that the terrestrial CH 4 cycle operates differently during transient compared to gradual warming events. Enhanced CH 4 cycling during the PETM may help to resolve the temperature data-model mismatch in the high latitudes and could yield higher estimates of Earth system sensitivity than expected from CO 2alone.

0091-7613
520-524
Inglis, Gordon
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Rohrssen, Megan
f60bc8a6-3ec9-49cf-812c-d4a3dd286368
Kennedy, Elizabeth M.
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Crouch, Erica M.
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Raine, J. Ian
69d571fe-172c-4b34-acf3-2a66e6c634a3
Strogen, Dominic
7bd477c2-0434-4f78-8735-804b25fe1835
Naafs, David
0d093b34-0ed0-45a2-8bbd-269762966af2
Collinson, Margaret E.
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Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Inglis, Gordon
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Rohrssen, Megan
f60bc8a6-3ec9-49cf-812c-d4a3dd286368
Kennedy, Elizabeth M.
77346796-f312-4310-afd1-8192dc45a089
Crouch, Erica M.
8d93a076-3dd9-4435-896d-c5c4ebc01b01
Raine, J. Ian
69d571fe-172c-4b34-acf3-2a66e6c634a3
Strogen, Dominic
7bd477c2-0434-4f78-8735-804b25fe1835
Naafs, David
0d093b34-0ed0-45a2-8bbd-269762966af2
Collinson, Margaret E.
4558b0e7-a6c1-4b1c-a6e8-36e3e9f3c320
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1

Inglis, Gordon, Rohrssen, Megan, Kennedy, Elizabeth M., Crouch, Erica M., Raine, J. Ian, Strogen, Dominic, Naafs, David, Collinson, Margaret E. and Pancost, Richard D. (2021) Terrestrial methane cycle perturbations during the onset of the Paleocene-Eocene Thermal Maximum. Geology, 49 (5), 520-524. (doi:10.1130/G48110.1).

Record type: Article

Abstract

Terrestrial methane (CH 4) emissions may have increased during the Paleocene-Eocene Thermal Maximum (PETM; ca. 56 Ma) and promoted additional warming, especially in the high latitudes. Although there is evidence for increased CH 4 cycling in a single Northern Hemisphere site, whether enhanced methane cycling was globally widespread is unknown because there have been no subsequent investigations. The mechanism of CH4 release is also unknown because a direct comparison between temperature and CH 4 cycling has so far not been possible. Here we use biomarkers to reconstruct temperature change and CH 4 cycling in a new PETM-aged succession in New Zealand. Our results indicate that the stable carbon isotopic composition (δ 13C) of bacterial hopanoids decreased to very low values (−60‰) during the onset of the PETM, indicating enhanced consumption of CH 4. These values are much lower than found in modern wetlands and suggest a major perturbation of the CH 4 cycle during the onset of the PETM. Low hopanoid δ 13C values do not persist into the early Eocene, despite evidence for elevated temperatures. This indicates that the terrestrial CH 4 cycle operates differently during transient compared to gradual warming events. Enhanced CH 4 cycling during the PETM may help to resolve the temperature data-model mismatch in the high latitudes and could yield higher estimates of Earth system sensitivity than expected from CO 2alone.

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Accepted/In Press date: 27 October 2020
Published date: 1 May 2021
Additional Information: Funding Information: We thank three anonymous reviewers for constructive and helpful feedback. This research is funded via the European Research Council (grant 340923) and the UK Natural Environment Research Council (grant NE\J008591\1). Pancost acknowledges a Royal Society Wolfson Research Merit Award. Inglis acknowledges a Royal Society Dorothy Hodgkin Fellowship (grant DHF\R1\191178). Naafs acknowledges a Royal Society Tata University Research Fellowship. Inglis thanks H. Whelton and the National Environment Isotope Facility at the University of Bristol (NEIF-B) for analytical support, and E. Dearing Crampton-Flood for generating BayMBT model values. Kennedy, Raine, Crouch, and Strogen were supported by the “Global Change Through Time” program at GNS Science (New Zealand). Funding Information: We thank three anonymous reviewers for constructive and helpful feedback. This research is funded via the European Research Council (grant 340923) and the UK Natural Environment Research Council (grant NE\J008591\1). Pancost acknowledges a Royal Society Wolfson Research Merit Award. Inglis acknowledges a Royal Society Dorothy Hodgkin Fellowship (grant DHF\R1\191178). Naafs acknowledges a Royal Society Tata University Research Fellowship. Inglis thanks H. Whelton and the National Environment Isotope Facility at the University of Bristol (NEIF-B) for analytical support, and E. Dearing Crampton-Flood for generating BayMBT model values. Kennedy, Raine, Crouch, and Strogen were supported by the ?Global Change Through Time? program at GNS Science (New Zealand). Publisher Copyright: © 2020 Geological Society of America. For permission to copy, contact editing@geosociety.org.
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Identifiers

Local EPrints ID: 444897
URI: http://eprints.soton.ac.uk/id/eprint/444897
DOI: doi:10.1130/G48110.1
ISSN: 0091-7613
PURE UUID: c7ad3348-aba0-4b70-a3d1-c628172648ab
ORCID for Gordon Inglis: ORCID iD orcid.org/0000-0002-0032-4668

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Date deposited: 10 Nov 2020 17:31
Last modified: 17 Mar 2024 06:02

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Author: Gordon Inglis ORCID iD
Author: Megan Rohrssen
Author: Elizabeth M. Kennedy
Author: Erica M. Crouch
Author: J. Ian Raine
Author: Dominic Strogen
Author: David Naafs
Author: Margaret E. Collinson
Author: Richard D. Pancost

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