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<p>A correct understanding of the human perturbation on the carbon cycle is a fundamental prerequisite of future climate modelling on large timescales.</p>
<p>However, &#171;&#160;classical&#160;&#187; carbon cycle theories barely take into account the &#171;&#160;organic&#160;&#187; part of the carbon cycle and are not able to reproduce past &#948;<sup>13</sup>C data.</p>
<p>Analysis of sediment data reveals the presence of cycles in the &#948;<sup>13</sup>C record. A 400 kyr cycle has been observed at several time periods, from the Eocene to present [1-4]. Moreover, longer cycles have been observed : 2.4, 4.6 and 9 Myr [5-8]. The 9 Myr cycle is present since the start of the Mesozoic. These periodicities seem linked to eccentricity periods.</p>
<p>By forcing astronomically the (net) organic matter burial in a carbon cycle conceptual model, Paillard [9] reproduced 400 kyr and 2.4 Myr cycles in &#948;<sup>13</sup>C.</p>
<p>The net organic matter burial has a key role on &#948;<sup>13</sup>C, as terrestrial and marine biology preferentially use <sup>12</sup>C during photosynthesis. Therefore if the burial of (<sup>12</sup>C rich) organic matter is relatively more important, the &#948;<sup>13</sup>C of the superficial system will decrease, and inversely.</p>
<p>However, this conceptual model was not able to explain longer term cycles at 4.6 and 9 Myr.</p>
<p>Here, we develop a new conceptual model based on Paillard [9], which includes the role of oxygen. Indeed, oxygen also influences the organic matter burial.</p>
<p>With this new conceptual model coupling carbon and oxygen cycle, it is possible to obtain 400 kyr, 2.4 Myr, but also longer cycles.</p>
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<p>References&#160;:</p>
<p>[1] Sexton et al, 2011, Eocene global warming events driven by ventilation of oceanic dissolved organic carbon</p>
<p>[2] P&#228;like et al, 2006 The Heartbeat of the Oligocene Climate System</p>
<p>[3] Billups et al, 2004 Astronomic calibration of the late Oligocene through early Miocene geomagnetic polarity time scale</p>
<p>[4]Wang et al, 2010, Obscuring of long eccentricity cyclicity in Pleistocene oceanic carbon isotope records</p>
<p>[5] Boulila et al, 2012, A ~9 myr cycle in Cenozoic &#948;13C record and long-term orbital eccentricity modulation: Is there a link?</p>
<p>[6] Ikeda et al, 2014, 70 million year astronomical time scale for the deep-sea bedded chert sequence (Inuyama, Japan): Implications for Triassic&#8211;Jurassic geochronology.</p>
<p>[7] Martinez et al, 2015, Orbital pacing of carbon fluxes by a &#8764;9-My eccentricity cycle during the Mesozoic</p>
<p>[8] Sprovieri M, et al. (2013) Late Cretaceous orbitally-paced carbon isotope stratigraphy from the Bottaccione Gorge (Italy).</p>
<p>[9] Paillard, 2017, The Plio-Pleistocene climatic evolution as a consequence of orbital forcing on the carbon cycle.</p>
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Precipitation and streamflow data from the Fort Carson Military Reservation and precipitation, streamflow, and suspended-sediment data from the Piñon Canyon Maneuver Site, Southeastern Colorado, 2008-2012
