EERIE is developing a new generation of Earth System Models (ESMs) that can explicitly represent the ocean mesoscale, a crucial but still largely unexplored part of the Earth system. By leveraging recent scientific and technological advances, EERIE aims to improve the ability of ESMs to simulate the long-term dynamics of the global climate, including its variability, extreme events, and potential tipping points influenced by mesoscale ocean processes. ICOsahedral Nonhydrostatic (ICON)-Sapphire-ER is one of these novel ESMs.
ICON‑Sapphire, developed at the Max Planck Institute for Meteorology, is designed to simulate the coupled components of the Earth system (atmosphere, land, ocean, and sea ice) at kilometer to sub-kilometer scales on both global and regional domains. It explicitly resolves deep atmospheric convection (storm-resolving at ~10 km or finer) and captures mesoscale and sub-mesoscale ocean eddies. The global ocean grid can be locally refined to create a “computational telescope,” focusing higher resolution on regions of interest.
The atmospheric component uses a nonhydrostatic icosahedral C‑grid with a hybrid sigma-z vertical coordinate. Only physical processes that cannot be resolved at kilometer scales are parameterized, including radiation, microphysics, and turbulence. The ocean component (ICON‑O) runs on a matching icosahedral triangular grid, solving the hydrostatic Boussinesq equations for ocean dynamics. At high resolution, only a subset of ICON‑O parameterizations is used, specifically for vertical turbulent mixing and velocity dissipation. Sea ice is simulated as part of ICON‑O, with thermodynamics represented via a single-category, zero-layer formulation and ice dynamics based on the Finite-Element Sea Ice Model (FESIM). The ocean biogeochemistry is handled by HAMOCC6, simulating over 20 biogeochemical tracers, including nutrients, plankton, detritus, and dissolved organic matter. The land component employs JSBACH 4 to simulate surface fluxes, soil hydrology, and energy balance, using prescribed vegetation and simplified hydrological processes.
Coupling of the model components is managed through the YAC coupler (version 2.4.2), facilitating the exchange of fluxes, state variables, and other interactions between the atmosphere, ocean, land, and sea ice components.