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ACCESS-OM3 25 km IAF - 1.0 (Beta)

🚀 Release: release-MC_25km_jra_iaf-1.0-beta

This is the first beta prerelease of an Inter-annual Forcing (IAF) configuration of ACCESS-OM3. It is closely based on the 25 km Repeat-Year Forcing (RYF) setup, retaining the same software version (ACCESS-OM3 v2025.08.001), global 25 km grid, GEBCO 2024-based bathymetry, and initial conditions generated from WOA2023. Building on this baseline, the IAF configuration adds the JRA55-do v1.6 forcing for 1959–2024 together with several targeted scientific, performance, and diagnostic upgrades.

This configuration release is for two key purposes:

  1. to assess scientific validity of the configuration;

  2. to seek feedback from Australian climate researchers on model suitability, usability and documentation.

Feedback on these two points can be provided in the general feedback thread.

Control experiment

A short control experiment using this configuration is included in the experiment list here, and two examples loading data are provided:

For researchers interested in point 1 above, we suggest starting with this dataset.

How to use

The configuration is run using the payu experiment manager. For instructions, see the access-hive Run ACCESS-OM3 documentation.

What we expect you’ll be able to do with this release:

  • Clone the config repo;

  • Run the 25km global configuration with JRA55-do IAF forcing;

  • Look at output from the model;

  • Test sensitivity to model parameter choices

  • Discover how the model is configured through ACCESS-OM3 configuration documentation

  • Contribute to the ongoing ACCESS-OM3 development and evaluation effort by sharing or improving notebooks in the ACCESS-Community-Hub repository.

Importantly, whilst this configuration is considered stable in the software sense, the parameter choices, input files and software code will continue to evolve and improve for some time into the future. There will be newer versions of this configuration which change and improve the model’s results. Users should take care to note results and analysis using this configuration relate to the release-MC_25km_jra_iaf-1.0-beta tag and later releases will produce different results.

Highlights & Key Updates since the previous ACCESS OM3 25km RYF -1.0 release

✅ IAF forcing stream using full inter-annual forcing from JRA55-do v1.6.

✅ Salt-restoring file corrected from practical to absolute salinity

✅ Updated bathymetry and grids:

  • Grid refined from 1142 → 1152 latitudes (y-grid) to ensure consistent output chunk sizes by making the total row count divisible by common tile dimensions.
  • New regional bathymetric corrections in Baltic Sea, Sulu Sea, and Indonesian Straits

✅ Sub-mesoscale parameterisation (Bodner et al., 2023) fully enabled

✅ Tidal mixing now parameterised using SYNBATH bottom roughness and TPXO10 tidal speeds

✅ Chlorophyll-based shortwave opacity for improved vertical light penetration

✅ Performance improvement: updated load balance gives

➡ ~3 h 11 min wall-time / yr (≈ 28.5 % faster than release-MC_25km_jra_ryf-1.0-beta-1’s 4 h 27 min)

✅ Expanded diagnostics: new variables for heat/salt budgets, sub-mesoscale fluxes, and mixed-layer energetics

✅ Fixed bug with scalar temperature and salinity diagnostics. These diagnostics are now what their metadata says they are.

✅ Enabling full MOM6 density diagnostics adds ~30 min / year

Model Configuration Summary

Component Version / Key Features
MOM6 TEOS-10 EOS, ePBL vertical mixing, interior shear mixing (Jackson et al. 2008), MEKE + GM eddy schemes, mixed-layer restratification
CICE6 Bitz & Lipscomb (1999) thermodynamics; EVP dynamics (Hunke & Dukowicz 1997)
CMEPS + NUOPC Coupler framework for ocean–ice exchanges
Grid Global tripolar, 25 km nominal, 75 vertical z* levels. More details at ACCESS-OM3-Grids
Forcing Inter-annual JRA55-do v1.6 atmosphere & runoff
Bathymetry GEBCO 2024 + manual regional edits
Initial Conditions and salinity restoring WOA 2023

Expected Performance

Wall-time / model year SU / model year
~3 h 11 min ~17.2 k SU

Limitations (Beta)

⚠️ This configuration is still undergoing scientific evaluation.

Known issues include:

  • Non-physical extremes in SST/SSS/SSH occasionally re-appear under strong forcing years

  • CICE6 still uses B-grid vectors (#409)

For a full list of open issues, see the GitHub issues page.

Resources

Credits

The ACCESS-OM3 software is built upon shared components of climate models, developed and supported across many organisations globally. This includes but is not limited to contributors and member organisations of the MOM consortium, the CICE consortium and the Earth System Modelling Framework organization. This configuration is developed from international and local expertise.

  • Based on configuration choices from Geophysical Fluid Dynamics Laboratory (GFDL) OM5, Community Earth System Model (CESM) 3.0-alpha and ACCESS-OM2

Support

Replies to this topic are disabled. For feedback, use the General Feedback Thread

For bugs/support requests, Create a topic on the ACCESS-Hive Forum in #cosima and tag it with #help. Support is provided by ACCESS-NRI for products it releases.

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