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

Gordon N Inglis*, Megan Rohrssen, Elizabeth M. Kennedy, Erica M. Crouch, J. Ian Raine, Dominic P. Strogen, B D A Naafs, Margaret E. Collinson, Rich D Pancost

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Terrestrial methane (CH4) emissions could have increased during the Paleocene–Eocene Thermal Maximum (~ 56 million years ago; Ma) and promoted additional warming, especially in the high latitudes. Although there is evidence for increased CH4 cycling in a single Northern Hemisphere site, whether enhanced methane cycling was globally widespread is unknown as there have been no subsequent investigations. The mechanism of CH4 release is also unknown because a direct comparison between temperature and CH4 cycling has so far not been possible. Here we use biomarkers to reconstruct temperature change and CH4 cycling in a new PETM-aged succession in New Zealand. Our results indicate that the stable carbon isotopic composition (δ13C) of bacterial hopanoids decreased to very low values (-60 ‰) during the onset of the PETM, indicating enhanced consumption of CH4. These values are much lower than found in modern wetlands and suggest a major perturbation of the CH4 cycle during the onset of the PETM. Low hopanoid δ13C values do not persist into the early Eocene, despite evidence for elevated temperatures. This indicates that the terrestrial CH4 cycle operates differently during transient compared to gradual warming events. Enhanced CH4 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 CO2 alone.
Original languageEnglish
Pages (from-to)520-524
Number of pages5
JournalGeology
Volume49
Issue number5
Early online date30 Dec 2020
DOIs
Publication statusPublished - 1 May 2021

Bibliographical note

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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