ACCESS-OM2: Release Information

ACCESS-NRI Releases
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6

ACCESS-OM2 release update, 24/06/2026

ACCESS-NRI has released 12 ACCESS-OM2 global configurations. Of these 12 releases, 6 are updates to the existing physics-only configurations and 6 are new configurations that use the new WOMBATlite ocean BGC model.

Updated physics-only configurations

All previously-released physics-only configurations have been updated (global 1°, 0.25° and 0.1°, with both repeat-year (RYF) and interannual (IAF) JRA55-do forcing).

Key updates

  • Consistent latent heat of vaporisation used in MOM and CICE.
  • Multiple time steps per history file in CICE native output.
  • Updated ocean diagnostic filename convention for consistency with other ACCESS models.
  • Configuration performance info now available in README.
  • Moved make_diag_table.py to a shared location in /g/data/vk83/apps.
  • IAF only: Updated forcing from JRA55-do 1.4.0 to 1.6.0 and extend cycle end from 2019 to 2024.
  • 0.25° only: Fixed issue with configurations not being restart reproducible (meaning two short consecutive runs, separated by a restart, gave different results than a single long run).

What version are these released configurations?

The released configurations are version 4.0 indicating that they are not bitwise reproducible with their previous versions (version 3.0). Specifically, the changes to the latent heat of vaporisation do not preserve answers.

New WOMBATlite configurations

There is a new WOMBATlite-enabled configuration for each of the physics-only configurations described above (i.e. global 1°, 0.25° and 0.1°, with both repeat-year and interannual JRA55-do forcing). These configurations follow the same naming scheme as the physics-only configurations, but with +wombatlite appended. E.g. the 1° RYF configuration release branch is called release-1deg_jra55_ryf+wombatlite.

These configurations replace the ACCESS-OM2 release-*_bgc configurations which use a legacy version of WOMBAT and will no longer be maintained.

Key features

  • New WOMBATlite model, version 2026.05.000. Key improvements over the legacy version of WOMBAT are:
    • More realistic phytoplankton physiology: phytoplankton photo-acclimate (vary Chl), perform luxury uptake of Fe, have size-dependent nutrient affinities, and respond mechanistically to Fe, light and nutrient limitation.
    • Improved iron cycle: Fe includes ligand binding, scavenging, colloidal coagulation, and zooplankton-driven Fe-rich egestion into particles.
    • Expanded carbon, nitrogen and particle cycles: WOMBATlite includes dynamic CaCO₃ production and dissolution, optional N-fixation and denitrification, variable particle sinking velocities, river inputs, updated atmospheric Fe sources and sediment burial.
    • Model calibration: WOMBATlite has been constrained/optimized against eight global observational datasets.
    • Overall, WOMBATlite is a more complete, yet still computationally efficient, ocean biogeochemical model. See the WOMBATlite 2026.05.000 documentation for more details.
  • Unlike the configurations that use the legacy version of WOMBAT, the new configurations:
    • are restart reproducible;
    • do not include the CICE5 skeletal layer BGC scheme.
  • Based on the latest (version 4.0) physics-only configurations.

What version are these released configurations?

The released configurations are the first set of released configurations that use WOMBATlite. They are version 1.0.

Control experiments

ACCESS-NRI plan to generate and share control experiments for at least a subset of these new configurations. We will reach out soon to gather input from the community, particularly on what diagnostics may be of interest.

How do I use these releases?

See the ACCESS-Hive instructions for using the ACCESS-OM2 model.

Details of the releases, including a full list of changes, are here:

Credits

These releases build on the collective efforts of many people over many years. Contributors to the configuration versions in this release announcement include:

Where do I ask questions?

Replies to this topic are disabled.

If you have specific questions about the releases in this topic please follow the guidelines for requesting help from ACCESS-NRI.