Novel implementation of nitrogen isotopes in the Bern3D model to constrain its past utilization

Anthropogenic climate change threatens to push many Earth system components towards uncharted territory, including the ocean circulation and marine ecosystems, which may substantially impact the oceans capacity to take up additional CO2 in the future. Paleoceanographic reconstructions offer critical insights into how these systems respond to past abrupt and long-term climate changes. Yet, their interpretation often remains challenging and uncertain due to the inherent local signal of marine sediment cores as well as confounding factors from other environmental variables. Proxy-enabled Earth system models have emerged as essential tools to address these challenges. Here we present initial results from a new nitrogen isotope implementation in the Bern3D Earth system model of intermediate complexity. Nitrogen isotopes are sensitive indicators of the oceanic fixed nitrogen inventory, which regulates the strength of the biological pump, and are increasingly reconstructed from marine sediments. In the Bern3D model, they are complemented by a wide array of already implemented proxies for ocean circulation and marine biogeochemistry, which further strengthens the robustness of this approach. New reconstructions and data compilations of a range of proxies, including N-isotopes, are generated within the Past-To-Future Horizon Europe project and will be crucial to constrain the model’s biogeochemical response to past climate change, here investigated for snapshot and transient simulations.