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Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum

Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum
Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum
Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene–Eocene Thermal Maximum (PETM) at  ∼ 56Ma and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transfer of carbon from surface reservoirs to the atmosphere. Theory suggests that tipping points in complex dynamical systems should be preceded by critical slowing down of their dynamics, including increasing temporal autocorrelation and variability. However, reliably detecting these indicators in palaeorecords is challenging, with issues of data quality, false positives, and parameter selection potentially affecting reliability. Here we show that in a sufficiently long, high-resolution palaeorecord there is consistent evidence of destabilisation of the carbon cycle in the  ∼ 1.5Myr prior to the PETM, elevated carbon cycle and climate instability following both the PETM and Eocene Thermal Maximum 2 (ETM2), and different drivers of carbon cycle dynamics preceding the PETM and ETM2 events. Our results indicate a loss of resilience (weakened stabilising negative feedbacks and greater sensitivity to small shocks) in the carbon cycle before the PETM and in the carbon–climate system following it. This pre-PETM carbon cycle destabilisation may reflect gradual forcing by the contemporaneous North Atlantic Volcanic Province eruptions, with volcanism-driven warming potentially weakening the organic carbon burial feedback. Our results are consistent with but cannot prove the existence of a tipping point for abrupt carbon release, e.g. from methane hydrate or terrestrial organic carbon reservoirs, whereas we find no support for a tipping point in deep ocean temperature.
1814-9332
1515-1527
Armstrong Mckay, David I.
9e7fc75d-311e-4980-9911-288d965a9e56
Lenton, Timothy M.
245a93ab-92e4-4719-a8b7-7ef66d65d048
Armstrong Mckay, David I.
9e7fc75d-311e-4980-9911-288d965a9e56
Lenton, Timothy M.
245a93ab-92e4-4719-a8b7-7ef66d65d048

Armstrong Mckay, David I. and Lenton, Timothy M. (2018) Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum. Climate of the Past, 14 (10), 1515-1527. (doi:10.5194/cp-14-1515-2018).

Record type: Article

Abstract

Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene–Eocene Thermal Maximum (PETM) at  ∼ 56Ma and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transfer of carbon from surface reservoirs to the atmosphere. Theory suggests that tipping points in complex dynamical systems should be preceded by critical slowing down of their dynamics, including increasing temporal autocorrelation and variability. However, reliably detecting these indicators in palaeorecords is challenging, with issues of data quality, false positives, and parameter selection potentially affecting reliability. Here we show that in a sufficiently long, high-resolution palaeorecord there is consistent evidence of destabilisation of the carbon cycle in the  ∼ 1.5Myr prior to the PETM, elevated carbon cycle and climate instability following both the PETM and Eocene Thermal Maximum 2 (ETM2), and different drivers of carbon cycle dynamics preceding the PETM and ETM2 events. Our results indicate a loss of resilience (weakened stabilising negative feedbacks and greater sensitivity to small shocks) in the carbon cycle before the PETM and in the carbon–climate system following it. This pre-PETM carbon cycle destabilisation may reflect gradual forcing by the contemporaneous North Atlantic Volcanic Province eruptions, with volcanism-driven warming potentially weakening the organic carbon burial feedback. Our results are consistent with but cannot prove the existence of a tipping point for abrupt carbon release, e.g. from methane hydrate or terrestrial organic carbon reservoirs, whereas we find no support for a tipping point in deep ocean temperature.

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Accepted/In Press date: 2 October 2018
e-pub ahead of print date: 22 October 2018
Published date: 22 October 2018

Identifiers

Local EPrints ID: 426029
URI: https://eprints.soton.ac.uk/id/eprint/426029
ISSN: 1814-9332
PURE UUID: 77a61e39-b3a8-446c-87ec-5b7b3ec11a6c
ORCID for David I. Armstrong Mckay: ORCID iD orcid.org/0000-0002-0020-7461

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Date deposited: 09 Nov 2018 17:30
Last modified: 13 Mar 2019 17:52

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Author: David I. Armstrong Mckay ORCID iD
Author: Timothy M. Lenton

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