GEOCLIM7, an Earth system model for multi-million-year evolution of the geochemical cycles and climate

Abstract. The numerical model GEOCLIM, a coupled Earth system model for the long-term biogeochemical cycle and climate, has been revised. This new version (v 7.0) allows a flexible discretization of the oceanic module for any paleogeographic configuration, coupling to any general circulation model (GCM), and the determination of all boundary conditions from the GCM coupled to GEOCLIM, notably the oceanic water exchanges and the routing of land-to-ocean fluxes. These improvements make GEOCLIM7 a unique, powerful tool, devised as an extension of GCMs, to investigate the Earth system evolution at timescales (several million years) and with processes that could not be simulated otherwise. We present a complete description of the model, whose current state gathers features that have been developed and published in several articles since its creation and some that are original contributions of this article, like the seafloor sediment routing scheme and the inclusion of orbital parameters. We also present a detailed description of the method to generate the boundary conditions of GEOCLIM, which is the main innovation of the present study. In a second step, we discuss the results of an experiment where GEOCLIM7 is applied to the Turonian paleogeography, with 10 Myr orbital cycle forcings. This experiment focuses on the effects of orbital parameters on oceanic O2 concentration, particularly in the proto-Atlantic and Arctic oceans, where the experiment revealed the largest O2 variations.