Multi-million-year cycles in modelled <i>δ</i><sup>13</sup>C as a response to astronomical forcing of organic matter fluxes
<p>Along with 400 kyr periodicities, multi-million-year cycles have been found in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C records over different time periods. An <span class="inline-formula">∼</span> 8–9 Myr...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-03-01
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| Series: | Earth System Dynamics |
| Online Access: | https://esd.copernicus.org/articles/14/291/2023/esd-14-291-2023.pdf |
| Summary: | <p>Along with 400 kyr periodicities, multi-million-year cycles have been found in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C records over different time periods. An <span class="inline-formula">∼</span> 8–9 Myr periodicity is found throughout the Cenozoic and part of the Mesozoic. The robust presence of this periodicity in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C 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 <span class="inline-formula"><i>δ</i><sup>13</sup></span>C variations for moderate carbon variations. Therefore, astronomical forcing of organic matter fluxes is a plausible candidate to explain the oscillations observed in the <span class="inline-formula"><i>δ</i><sup>13</sup></span>C records. So far, modelling studies forcing astronomically the organic matter burial have been able to produce 400 kyr and 2.4 Myr cycles in <span class="inline-formula"><i>δ</i><sup>13</sup></span>C but were not able to produce longer cycles, such as 8–9 Myr cycles. Here, we propose a mathematical mechanism compatible with the biogeochemistry that could explain the presence of multi-million-year cycles in the <span class="inline-formula"><i>δ</i><sup>13</sup></span>C records and their stability over time: a preferential phase locking to multiples of the 2.4 Myr eccentricity period. 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 – more specifically, multi-million-year periods.</p> |
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| ISSN: | 2190-4979 2190-4987 |