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Eocene global warming events driven by ventilation of oceanic dissolved organic carbon

Eocene global warming events driven by ventilation of oceanic dissolved organic carbon
Eocene global warming events driven by ventilation of oceanic dissolved organic carbon
‘Hyperthermals’ are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (65–34 million years (Myr) ago)1–13. The most extreme hyperther-
( mal was the 170 thousand year (kyr) interval2 of 5–7 ºC global warming3 during the Palaeocene–Eocene Thermal Maximum (PETM, 56Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs1,3,6,11,14–17, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon3,6,11,16,17. Here we show, using new 2.4-Myr-long Eocene deep ocean records, that the comparatively modest hyperthermals are much more numerous than previously documented, paced by the eccentricity
of Earth’s orbit and have shorter durations ( recovery phases than the PETM. These findings point to the operation of fundamentally different forcing and feedback mechanisms than for the PETM, involving redistribution of carbon among Earth’s readily exchangeable surface reservoirs rather than carbon exhumation from, and subsequent burial back into, the sedimentary reservoir. Specifically, we interpret our records to indicate repeated, large-scale releases of dissolved organic carbon (at least 1,600 gigatonnes) from the ocean by ventilation (strengthened oxidation) of the ocean interior. The rapid recovery of the carbon cycle following each Eocene hyperthermal strongly suggests that carbon was resequestered by the ocean, rather than the much slower process of silicate rock weathering proposed for the PETM1,3. Our findings suggest that these pronounced climate warming events were driven not by repeated releases of carbon from buried sedimentary sources3,6,11,16,17, but, rather, by patterns of surficial carbon redistribution familiar from younger intervals of Earth history.
0028-0836
349-353
Sexton, P.F.
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Norris, R.D.
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Wilson, P.A.
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Pälike, H.
b9bf7798-ad8c-479b-8487-dd9a30a61fa5
Westerhold, T.
89fa20ad-d5fc-4f89-9e86-076156510286
Röhl, U.
e3029111-f8cc-4bf9-9433-829590c8645d
Bolton, Clara T.
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Gibbs, S.J.
82dfbcbc-3a8a-40da-8a80-fe7ad83f3110
Sexton, P.F.
afcf936a-8a57-49ae-98d8-73c69b181090
Norris, R.D.
81ac4a17-2a84-4c7c-9c02-c9f14bb2695e
Wilson, P.A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Pälike, H.
b9bf7798-ad8c-479b-8487-dd9a30a61fa5
Westerhold, T.
89fa20ad-d5fc-4f89-9e86-076156510286
Röhl, U.
e3029111-f8cc-4bf9-9433-829590c8645d
Bolton, Clara T.
d3f550f0-1fe9-4d18-8a9c-a61034ab0280
Gibbs, S.J.
82dfbcbc-3a8a-40da-8a80-fe7ad83f3110

Sexton, P.F., Norris, R.D., Wilson, P.A., Pälike, H., Westerhold, T., Röhl, U., Bolton, Clara T. and Gibbs, S.J. (2011) Eocene global warming events driven by ventilation of oceanic dissolved organic carbon. Nature, 471 (7338), 349-353. (doi:10.1038/nature09826).

Record type: Article

Abstract

‘Hyperthermals’ are intervals of rapid, pronounced global warming known from six episodes within the Palaeocene and Eocene epochs (65–34 million years (Myr) ago)1–13. The most extreme hyperther-
( mal was the 170 thousand year (kyr) interval2 of 5–7 ºC global warming3 during the Palaeocene–Eocene Thermal Maximum (PETM, 56Myr ago). The PETM is widely attributed to massive release of greenhouse gases from buried sedimentary carbon reservoirs1,3,6,11,14–17, and other, comparatively modest, hyperthermals have also been linked to the release of sedimentary carbon3,6,11,16,17. Here we show, using new 2.4-Myr-long Eocene deep ocean records, that the comparatively modest hyperthermals are much more numerous than previously documented, paced by the eccentricity
of Earth’s orbit and have shorter durations ( recovery phases than the PETM. These findings point to the operation of fundamentally different forcing and feedback mechanisms than for the PETM, involving redistribution of carbon among Earth’s readily exchangeable surface reservoirs rather than carbon exhumation from, and subsequent burial back into, the sedimentary reservoir. Specifically, we interpret our records to indicate repeated, large-scale releases of dissolved organic carbon (at least 1,600 gigatonnes) from the ocean by ventilation (strengthened oxidation) of the ocean interior. The rapid recovery of the carbon cycle following each Eocene hyperthermal strongly suggests that carbon was resequestered by the ocean, rather than the much slower process of silicate rock weathering proposed for the PETM1,3. Our findings suggest that these pronounced climate warming events were driven not by repeated releases of carbon from buried sedimentary sources3,6,11,16,17, but, rather, by patterns of surficial carbon redistribution familiar from younger intervals of Earth history.

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Published date: 17 March 2011
Organisations: Ocean and Earth Science

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Local EPrints ID: 177595
URI: http://eprints.soton.ac.uk/id/eprint/177595
ISSN: 0028-0836
PURE UUID: 615b09d9-a5c8-43a4-8fdb-a6561c60bb1e

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Date deposited: 18 Mar 2011 11:00
Last modified: 20 Nov 2021 02:28

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Contributors

Author: P.F. Sexton
Author: R.D. Norris
Author: P.A. Wilson
Author: H. Pälike
Author: T. Westerhold
Author: U. Röhl
Author: Clara T. Bolton
Author: S.J. Gibbs

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