Preprints
https://doi.org/10.5194/esd-2022-46
https://doi.org/10.5194/esd-2022-46
 
10 Oct 2022
10 Oct 2022
Status: this preprint is currently under review for the journal ESD.

Multi-million year cycles in modelled δ13C as a response to astronomical forcing of organic matter fluxes

Gaëlle Leloup1,2 and Didier Paillard2 Gaëlle Leloup and Didier Paillard
  • 1Agence Nationale pour la gestion des déchets radioactifs (ANDRA), 1 Rue Jean Monnet, 92290 Châtenay-Malabry, France
  • 2Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ-Université Paris-Saclay, 91198 Gif-sur-Yvette, France

Abstract. Along with 400 kyr periodicities, multi-million year cycles have been found in δ¹³C records over different time periods. A ~8–9 Myr periodicity is found throughout the Cenozoic, and part of the Mesozoic. The robust presence of this periodicity in δ¹³C records suggests an astronomical origin. However, this periodicity is barely visible in the astronomical forcing. Due to the large fractionation factor of organic matter, its burial or oxidation produces large δ¹³C variations for moderate carbon variations. Therefore, astronomical forcing of organic matter fluxes is a plausible candidate to explain the oscillations observed in the δ¹³C records. So far, modelling studies forcing astronomically the organic matter burial have been able to produce 400 kyr and 2.4 Myr cycles in δ¹³C, but were not able to produce longer cycles, such as 8–9 Myr cycles. Here, we propose a mechanism that could explain the presence of multi-million year cycles in the δ¹³C records, and their stability over time, as a result of preferential periodicity locking to multiples of astronomical forcing periods. With a simple non linear conceptual model for the carbon cycle that has multiple equilibria, we are able to extract longer periods than with a simple linear model, and more specifically, multi-million year periods.

Gaëlle Leloup and Didier Paillard

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2022-46', Anonymous Referee #1, 25 Oct 2022
  • RC2: 'Comment on esd-2022-46', Anonymous Referee #2, 07 Nov 2022

Gaëlle Leloup and Didier Paillard

Data sets

Code and data for results and figures of the manuscript "Multi-million year cycles in modelled δ13C as a response to astronomical forcing of organic matter fluxes." submitted to Earth System Dynamics Gaelle LELOUP https://doi.org/10.5281/zenodo.7129166

Gaëlle Leloup and Didier Paillard

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Short summary
Records of past carbon isotopes exhibit oscillations. It is clear over very different time periods, that oscillations of 400 kyr take place. Also, strong oscillations of approximately 8–9 Myr are seen over different time periods. While earlier modelling studies have been able to produce 400 kyr oscillations, none of them produced 8–9 Myr cycles. Here, we propose a simple model for the carbon cycle that is able to produce 8–9 Myr oscillations in the modelled carbon isotopes.
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