HPSF Conference 2025

High-resolution simulations of the Earth system require resources available only on the world's largest supercomputers, which are increasingly based on GPUs. However, CPU-based systems are still frequently used to conduct simulations at coarse resolutions. To be able to take advantage of all compute platforms, we are developing Omega: the Ocean Model for E3SM Global Applications, a new ocean model written in C++ using Kokkos for performance portability. Omega will replace MPAS-Ocean to become the new ocean component of the DOE’s Energy Exascale Earth System Model (E3SM). Omega is an unstructured mesh ocean model based on the same finite-volume scheme as the current ocean component. Work on Omega began in 2023. Currently, Omega is a layered shallow water model with passive tracers. While still simple, this initial version can run on realistic size meshes and contains computational kernels representative of the full model horizontal numerics. After briefly describing Omega, this talk will go into our experiences with Kokkos and present initial performance results from a variety of compute platforms.)