Influence of orbital cycles on chemical weathering and marine redox conditions under greenhouse climates

Cretaceous Oceanic Anoxic Event 2 (OAE2) coincided with the emplacement of several large igneous provinces. The rapid exhalation of volcanic CO₂ intensified the global climate and accelerated the hydrological cycle. Cyclic variations in marine redox conditions linked to weathering are documented in OAE2 successions, indicating an orbital control on global weathering rates, and thus, marine nutrient availability. However, the impact of the cyclicity varies in intensity, particularly at the end of OAE2, which is characterized by dampened weathering variability. In this conceptual approach, we assess the influence of orbital forcing on global chemical weathering rates under different atmospheric CO₂ concentrations and orbital configurations using HadCM3L. We find that with increasing pCO₂, chemical weathering rates significantly increase and the influence of changes in obliquity is amplified. This suggests a strong coupling between orbital cyclicity and global weathering fluxes under hot climates, with significant influence on the carbon cycle driven by weathering-derived nutrients.