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Widespread warming before and elevated barium burial during the Paleocene-Eocene thermal maximum: Evidence for methane hydrate release?

Widespread warming before and elevated barium burial during the Paleocene-Eocene thermal maximum: Evidence for methane hydrate release?
Widespread warming before and elevated barium burial during the Paleocene-Eocene thermal maximum: Evidence for methane hydrate release?

Current climate change may induce positive carbon cycle feedbacks that amplify anthropogenic warming on time scales of centuries to millennia. Similar feedbacks might have been active during a phase of carbon cycle perturbation and global warming, termed the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago). The PETM may help constrain these feedbacks and their sensitivity to warming. We present new high-resolution carbon isotope and sea surface temperature data from Ocean Drilling Program Site 959 in the Equatorial Atlantic. With these and existing data from the New Jersey Shelf and Maud Rise, Southern Ocean, we quantify the lead-lag relation between PETM warming and the carbon input that caused the carbon isotope excursion (CIE). We show ~2 °C of global warming preceded the CIE by millennia, strongly implicating CO 2 -driven warming triggered a positive carbon cycle feedback. We further compile new and published barium (Ba) records encompassing continental shelf, slope, and deep ocean settings. Based on this compilation, we calculate that average Ba burial rates approximately tripled during the PETM, which may require an additional source of Ba to the ocean. Although the precipitation pathway is not well constrained, dissolved Ba stored in sulfate-depleted pore waters below methane hydrates could represent an additional source. We speculate the most complete explanation for early warming and rise in Ba supply is that hydrate dissociation acted as a positive feedback and caused the CIE. These results imply hydrates are more temperature sensitive than previously considered, and may warrant reconsideration of the political assignment of 2 °C warming as a safe future scenario.

barium, carbon cycle feedbackglobal warming, methane hydrate, PETM
2572-4517
Frieling, J.
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Peterse, F.
471cf1d7-57d4-4954-ae8d-14fa03f0278b
Lunt, D. J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Bohaty, S. M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Sinninghe Damsté, J. S.
f87a01bb-9552-46a6-ba6e-757fee89528a
Reichart, G. J.
49920c7e-9771-4d90-95fe-98fba92cd840
Sluijs, A.
4f68782c-15c3-4d42-ae22-8ffb13887dc6
Frieling, J.
76c2d878-65e9-4945-bc6b-1ab1daf7cb4d
Peterse, F.
471cf1d7-57d4-4954-ae8d-14fa03f0278b
Lunt, D. J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Bohaty, S. M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Sinninghe Damsté, J. S.
f87a01bb-9552-46a6-ba6e-757fee89528a
Reichart, G. J.
49920c7e-9771-4d90-95fe-98fba92cd840
Sluijs, A.
4f68782c-15c3-4d42-ae22-8ffb13887dc6

Frieling, J., Peterse, F., Lunt, D. J., Bohaty, S. M., Sinninghe Damsté, J. S., Reichart, G. J. and Sluijs, A. (2019) Widespread warming before and elevated barium burial during the Paleocene-Eocene thermal maximum: Evidence for methane hydrate release? Paleoceanography and Paleoclimatology. (doi:10.1029/2018PA003425).

Record type: Article

Abstract

Current climate change may induce positive carbon cycle feedbacks that amplify anthropogenic warming on time scales of centuries to millennia. Similar feedbacks might have been active during a phase of carbon cycle perturbation and global warming, termed the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago). The PETM may help constrain these feedbacks and their sensitivity to warming. We present new high-resolution carbon isotope and sea surface temperature data from Ocean Drilling Program Site 959 in the Equatorial Atlantic. With these and existing data from the New Jersey Shelf and Maud Rise, Southern Ocean, we quantify the lead-lag relation between PETM warming and the carbon input that caused the carbon isotope excursion (CIE). We show ~2 °C of global warming preceded the CIE by millennia, strongly implicating CO 2 -driven warming triggered a positive carbon cycle feedback. We further compile new and published barium (Ba) records encompassing continental shelf, slope, and deep ocean settings. Based on this compilation, we calculate that average Ba burial rates approximately tripled during the PETM, which may require an additional source of Ba to the ocean. Although the precipitation pathway is not well constrained, dissolved Ba stored in sulfate-depleted pore waters below methane hydrates could represent an additional source. We speculate the most complete explanation for early warming and rise in Ba supply is that hydrate dissociation acted as a positive feedback and caused the CIE. These results imply hydrates are more temperature sensitive than previously considered, and may warrant reconsideration of the political assignment of 2 °C warming as a safe future scenario.

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Frieling_et_al-2019-Paleoceanography_and_Paleoclimatology - Version of Record
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More information

Accepted/In Press date: 8 March 2019
e-pub ahead of print date: 18 March 2019
Keywords: barium, carbon cycle feedbackglobal warming, methane hydrate, PETM

Identifiers

Local EPrints ID: 430788
URI: https://eprints.soton.ac.uk/id/eprint/430788
ISSN: 2572-4517
PURE UUID: 19f745cb-e2b0-4240-8149-15f9319c08c3
ORCID for S. M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

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Date deposited: 13 May 2019 16:30
Last modified: 10 Dec 2019 01:43

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