EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-5064 The accuracy of barotropic and baroclinic tides in global non-assimilative ocean general circulation models Ansong Joseph K. https://orcid.org/0000-0002-2214-377X 1 2 Arbic Brian K. https://orcid.org/0000-0002-7969-2294 2 Bourdalle-Badié Romain 3 Bricaud Clément https://orcid.org/0000-0003-3677-414X 3 Chanut Jérôme 3 Menemenlis Dimitris https://orcid.org/0000-0001-9940-8409 4 Ray Richard D. https://orcid.org/0000-0003-2644-9271 5 Schindelegger Michael https://orcid.org/0000-0001-6250-7921 6 Wallcraft Alan J. 7 Wang He 2 8 9 Adcroft Alistair J. 10 Briol Frédéric 11 Buijsman Maarten C. https://orcid.org/0000-0001-8478-5957 12 Carrère Loren 11 Chassignet Eric P. https://orcid.org/0000-0003-4710-7502 7 Dibarboure Gerald 13 Hallberg Robert W. 8 Hill Christopher N. 14 Koch-Larrouy Ariane 15 Lyard Florent 15 Mazloff Matthew R. https://orcid.org/0000-0002-1650-5850 16 Nguyen An T. 17 Picot Nicolas 13 Ponte Rui M. https://orcid.org/0000-0001-7206-6461 18 Shriver Jay F. 19 Department of Mathematics, University of Ghana, Legon, Accra, Ghana Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, Michigan, USA Mercator Ocean International, Toulouse, France Moss Landing Marine Laboratories, San José State University, San José, California, USA NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Institute of Geodesy and Geoinformation, University of Bonn, Bonn, Germany Center for Oceanic-Atmospheric Prediction Studies, Florida State University, Tallahassee, Florida, USA Geophysical Fluid Dynamics Laboratory/NOAA, Princeton, NJ, USA University Corporation for Atmospheric Research, Boulder, CO, USA Atmospheric and Oceanic Sciences, Princeton University, Princeton, NJ, USA Space Oceanography Division, Collecte Localisation Satellites, Toulouse, France School of Ocean Science and Engineering, University of Southern Mississippi, Hattiesburg, Mississippi, USA Centre National d’Etudes Spatiales, Toulouse, France Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA CECI CNRS/Cerfacs/IRD, Université de Toulouse, Toulouse, France Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas, USA Atmospheric and Environmental Research, Lexington, Massachusetts, USA Oceanography Division, Naval Research Laboratory, Stennis Space Center, Mississippi, USA 08 09 2026 2026 1 28 Copyright: © 2026 Joseph K. Ansong et al. 2026 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/2026/egusphere-2026-5064/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5064/egusphere-2026-5064.pdf

<p style="-qt-block-indent: 0; text-indent: 0px; margin: 0px;">We investigate the accuracy of barotropic tides and phase-locked baroclinic (internal) tides in forward (non-data-assimilative) simulations of four different high-resolution global ocean models: the HYbrid Coordinate Ocean Model (HYCOM), the Modular Ocean Model Version 6 (MOM6), the Nucleus for European Modelling of the Ocean (NEMO), and the Massachusetts Institute of Technology general circulation model (MITgcm). Consistent with a previous study that employed only HYCOM, we find that the phase-locked internal tides in our HYCOM, MOM6 and MITgcm simulations are large relative to altimeter observations unless an explicit parameterized topographic internal wave drag, which damps barotropic and baroclinic tides, is included. We also find that harmonic analysis of long records of model output results in estimates of phase-locked internal tides that compare more favorably with observed baroclinic surface elevations from along-track satellite-altimetry. Increasing the resolution within the same dynamical core reduces amplitudes of phase-locked internal tides, possibly due to a more efficient energy cascade to higher-frequency internal wave continuum motions. We also document details of the astronomical tidal forcing in the MITgcm runs, which have been widely used by the wideswath altimetry community, that adversely affect the accuracy of modeled barotropic and baroclinic tides. We verify the impacts of the erroneous tidal forcing with results of less expensive shallow-water simulations that also employ the erroneous forcing.