Modelling the response and impacts of terrestrial feedbacks to orbital forcing

Milankovitch cycles in paleoclimate records demonstrate that astronomical forcing has impacted Earth’s climate-carbon dynamics throughout Earth’s history. Its influence is especially pronounced during warmer intervals like the Early Eocene Climatic Optimum during which periodic carbon release events, or ‘hyperthermals’, occurred at a pacing consistent with eccentricity. Yet, the reservoirs and mechanisms responsible for orbitally driven carbon release-sequestration are poorly understood. With the cGENIE Earth system model, we pick apart how different components of the Earth system respond to insolation forcing. Detailed evaluation of marine carbon cycle feedbacks has demonstrated that organic carbon and nutrient cycling can greatly amplify orbital climate and CO₂ variability but results also hint at important missing feedback processes, possibly of terrestrial origin. Here, I present ongoing model development to include a terrestrial scheme in our model. I show preliminary results of how vegetation growth and soil carbon storage change with orbital forcing and their feedback on climate and atmospheric CO₂. Importantly, I will also address land-ocean interaction and evaluate how orbitally driven changes to the surface dynamics and terrestrial carbon storage impact ocean circulation and biogeochemistry. Ultimately, our research will reveal what reservoirs and processes are most sensitive to orbital forcing and can be used to guide hypotheses for orbitally driven triggers of larger-scale events.