EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-3500 The Ocean Model for E3SM Global Applications: Omega Version 0.1.0. A New High-Performance Computing Code for Exascale Architectures Petersen Mark R. https://orcid.org/0000-0001-7170-7511 1 Asay-Davis Xylar S. https://orcid.org/0000-0002-1990-892X 1 Barthel Alice M. https://orcid.org/0000-0002-2481-8646 1 Begeman Carolyn Branecky https://orcid.org/0000-0001-9828-1741 1 Bishnu Siddhartha https://orcid.org/0000-0002-4227-9738 2 Brus Steven R. https://orcid.org/0000-0002-0314-9201 3 Jones Philip W. 1 Kang Hyun-Gyu 4 Kim Youngsung 4 Mametjanov Azamat 3 O’Neill Brian 1 Ringel Kieran K. 1 5 Smith Katherine M. https://orcid.org/0000-0002-1603-7727 1 Sreepathi Sarat https://orcid.org/0000-0002-4978-9423 4 Van Roekel Luke P. https://orcid.org/0000-0003-1418-5686 1 Waruszewski Maciej 6 Los Alamos National Laboratory, Los Alamos, NM 87545, USA Department of Earth Sciences, University of Cambridge Argonne National Laboratory, Lemont, IL 60439, USA Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA Center for Nonlinear Studies, Los Alamos National Laboratory, NM, 87545, USA Sandia National Laboratories, Albuquerque, NM 87123, USA 24 10 2025 2025 1 37 Copyright: © 2025 Mark R. Petersen et al. 2025 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3500/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3500/egusphere-2025-3500.pdf

Here we introduce Omega, the Ocean Model for E3SM Global Applications. Omega is a new ocean model designed to run efficiently on high performance computing (HPC) platforms, including exascale heterogeneous architectures with accelerators, such as Graphics Processing Units (GPUs). Omega is written in C++ and uses the Kokkos performance portability library. These were chosen because they are well-supported, and will help future-proof Omega for upcoming HPC architectures. Omega will eventually replace the Model for Prediction Across Scales-Ocean (MPAS-Ocean) in the US Department of Energy's Energy Exascale Earth System Model (E3SM). Omega runs on unstructured horizontal meshes with variable-resolution capability and implements the same horizontal discretization as MPAS-Ocean. In this paper, we document the design and performance of Omega Version 0.1.0 (Omega-V0), which solves the shallow water equations with passive tracers and is the first step towards the full primitive equation ocean model. On Central Processing Units (CPUs), Omega-V0 is 1.4 times faster than MPAS-Ocean with the same configuration. Omega-V0 is more efficient on GPUs than CPUs on a per-watt basis–by a factor of 5.3 on Frontier and 3.6 on Aurora, two of the world's fastest exascale computers.

 Biological and Environmental Research E3SM