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ACCESS OM3 Configurations
Release: release-MC_25km_jra_ryf-1.0-beta
This is an initial beta prerelease of a model configuration of ACCESS-OM3. This uses a release of the ACCESS-OM3 software (version 2025.05.001), a global grid with 25km nominal resolution, bathymetry generated from GEBCO 2024 and initial conditions generated from WOA2023. A 1990-91 Repeat Year Forcing (RYF) extracted from the JRA55-do v1.6 reanalysis is used as input data.
ACCESS-OM3 is the third generation of the ACCESS global ocean - sea ice model. It uses up-to-date releases of the MOM6 ocean model and CICE6 sea ice model. It is the first ACCESS model that couples model components using CMEPS (Community Mediator for Earth Prediction Systems), built on top of NUOPC (National Unified Operational Prediction Capability) infrastructure.
This configuration release is for two key purposes:
- to assess scientific validity of the configuration;
- 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
There is a data from short control experiment using this model configuration at
/g/data/ol01/access-om3-output/access-om3-025/MC_25km_jra_ryf-1.0-beta
and two examples loading data are provided:
For researchers interested in point 1 above, we suggest starting with this dataset.
Model Configurations
This is the first public release for ACCESS-OM3; further coarse and high resolution configurations are planned. More supported model configurations will be added as time and resources permit. Future release of ACCESS-OM3 configurations will be announced using this topic.
How to use the model
The configuration is run using the payu experiment manager. For instructions, see the access-hive Run ACCESS-OM3 documentation.
What we expect youâll be able to do with this release:
- Clone the config repo;
- Run the 25km global configuration with JRA55-do RYF forcing;
- Look at output from the model;
- Test sensitivity to model parameter choices
- Discover how the model is configured through ACCESS-OM3 configuration documentation
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 modelâs results. Users should take care to note results and analysis using this configuration relate to the release-MC_25km_jra_ryf-1.0 tag and later releases will produce different results.
Features
25km global configuration with ocean and sea ice models using data atmosphere and runoff forcings;
global tripolar grid with nearly double the ACCESS-OM2-025 meridional resolution around Antarctica (3.6 km vs. 5.9 km)
vertical z* grid with 75 levels of thicknesses 1.1 m (top) - 198 m (bottom, 5808 m), up from 50 levels from 2.3 m (top) - 220 m (bottom, 5363 m) in ACCESS-OM2-025
CICE6 sea-ice model configured with Bitz & Lipscomb (1999) thermodynamics and Elastic-Viscous Plastic dynamics (Hunke and Dukowicz 1997);
MOM6 ocean model configured with:
- TEOS-10 equation of state: more accurate thermodynamics, especially important for energy budgets and density-driven processes.
- Improved vertical mixing using ePBL: handles mixing based on a local TKE budget rather than fixed vertical shapes, e.g. KPP. ePBL also allows more natural inclusion of effects like Langmuir turbulence.
- Interior shear-driven mixing: Jackson et al. (2008) parameterisation activates mixing when stratification is weak and shear is strong. This is usually used along with ePBL vertical mixing.
- Mixed layer restratification: Bodner et al. (2023) sub-mesoscale parameterisation improves on the original Fox-Kemper formulation. This prevents the restratifying overturning streamfunction from growing unphysically large when surface turbulence is weak.
- Interior diapycnal mixing: tidal-driven diapycnal mixing captures the effects of internal tide-driven turbulence, particularly important over rough topography and in the deep ocean. Uses new bottom roughness data calculated from SYNBATH, and tidal speeds from TPXO10.
- Isopycnal mixing: both the Mesoscale Eddy Kinetic Energy (MEKE), and GentâMcWilliams (GM) schemes based on the streamfunction formulation by Ferrari et al. (2010) are applied. With MEKE enabled, the model is resolution-aware, allowing the thickness diffusion coefficient to adapt to the model resolution.
1990-1991 Repeat Year Forcing using JRA55-do v1.6
bathymetry generated from GEBCO 2024
initial conditions and reference salinity for restoring are generated from WOA2023 (see Limitations below)
known provenance and reproducibility of all input data
deterministic and reproducible outputs and software builds
run-time configuration of model outputs/diagnostics and parameterisations
MOM6 diagnostics on density coordinates are included by default. Note however that these add ~30 min per model year to the runtime and can be removed if not needed. (See instructions)
Limitations
As a beta release, there is no guaranteed support and there is no published model validation.
- Not scientifically validated
- Ocean model configuration allows nonphysical extreme values of sea surface temperature and salinity
- CICE6 uses âB-gridâ points for vector quantities (see issue 409)
- Unrealistic ocean salinities at runoff locations (see issue 396)
- Cold-start initial conditions and salt restoring are practical salinity but should be absolute salinity (see issue 235)
- When starting from scratch, the first model year runs more slowly, taking about 5 hours of walltime and ~17.5kSU. From the second year onward, performance improves to around 4 hours 30 minutes of walltime and ~15.5kSU per model year.
- UPDATE: MOM6 scalar diagnostics
thetaogaandtosgaare actually conservative temperature, despite their metadata indicating that they are potential temperature. Similarly,sogaandsosgaare absolute salinity, not practical salinity. See this issue for further details.
For a complete list of known issues, see GitHub issues page.
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
Scoping and approach @aekiss @micael @kieranricardo @MartinDix @AndyHoggANU
Model build infrastructure @harshula @micael @anton @dougiesquire @minghangli
Deployment infrastructure @TommyGatti
Documentation: @atteggiani @aekiss @cbull @ezhilsabareesh8 @anton @dougiesquire @minghangli
Graphics: @OwKal
Grids, initial conditions and bathymetry: @ezhilsabareesh8 @aekiss @dougiesquire @anton @kial
Configuration advice @AndyHoggANU @sofarrell @adele-morrison @MartinDix @aekiss @Luwei @angus-g
Payu development @dougiesquire @jo-basevi @Aidan @anton @minghangli
Test infrastructure & tests @jo-basevi @TommyGatti @dougiesquire @anton @minghangli @Aidan
Model validation and parameter choices: @minghangli @cbull @aekiss @dougiesquire @AndyHoggANU
Performance and software optimisation: @minghangli @micael @manodeep
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.
Resources
ACCESS OM3 Configurations
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 1959â2024 together with several targeted scientific, performance, and diagnostic upgrades.
This configuration release is for two key purposes:
-
to assess scientific validity of the configuration;
-
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 MC_25km_jra_iaf-1.0-beta-5165c0f8 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 youâll 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 modelâs 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 â 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 (â 28.5 % faster than release-MC_25km_jra_ryf-1.0-beta-1âs 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 oceanâice 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
-
Configuration Release Announcement
-
Software Build Release
-
General Feedback Thread
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
Scoping and approach: @aekiss @micael @kieranricardo @MartinDix @AndyHoggANU
Model build infrastructure: @harshula @micael @anton @dougiesquire @minghangli
Deployment infrastructure: @TommyGatti
Documentation: @atteggiani @aekiss @cbull @ezhilsabareesh8 @anton @dougiesquire @minghangli @helen
Grids, initial conditions and bathymetry: @ezhilsabareesh8 @aekiss @dougiesquire @anton
Configuration advice: @AndyHoggANU @sofarrell @adele-morrison @MartinDix @aekiss @Luwei @angus-g
Payu development: @dougiesquire @jo-basevi @Aidan @anton @minghangli
Test infrastructure & tests: @jo-basevi @TommyGatti @dougiesquire @anton @minghangli @Aidan
Model validation and parameter choices: @minghangli @cbull @aekiss @dougiesquire @AndyHoggANU
Performance and software optimisation: @minghangli @micael @manodeep
Model evaluation: @aekiss @AndyHoggANU @cbull @minghangli @ezhilsabareesh8 @dougiesquire @anton @claireyung @wghuneke @hrsdawson @jemmajeffree @Helen-J-S @CharlesTurner
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.
ACCESS OM3 Configurations
ACCESS-NRI has released four beta versions of ACCESS-OM3 global configurations. Of these four releases, two are updates to previously-released physics-only configurations and two are new configurations that include the WOMBATlite ocean BGC model.
All released configurations use ACCESS-OM3 2026.05.002, a global grid with a nominal resolution of 25km, GEBCO 2024-based bathymetry, and initial conditions generated from WOA2023.
The configuration releases are intended to serve two purposes:
- to assess scientific validity of the configuration;
- to seek feedback from Australian ocean, sea ice and climate researchers on model suitability, usability and documentation.
Feedback on these two points can be provided in the general feedback thread.
Updated physics-only configurations
Releases
release-MC_25km_jra_ryf-2.0-beta
release-MC_25km_jra_iaf-2.0-beta
These are the second beta releases of repeat-year forced (RYF) and inter-annually forced (IAF) configurations of ACCESS-OM3.
Key updates relative to the previous 1.0-beta version are:
Updated to recent version of all component models, including a number of bug fixes.
Updated liquid runoff remapping so that runoff is only added to cells that are directly adjacent to land. See here for details.
Added spatial spreading of frozen runoff according to the Mankoff et al. 2025 iceberg melt climatology. See here for details.
Implemented global freshwater balance in the mediator by scaling precipitation such that the sum of the global precipitation, runoff and evaporation is zero, and there are no constraints on net water flux into MOM6. See here for details.
Updated land mask to help address unrealistically thick sea-ice in fjords. The new mask eliminates B-grid non-advective channels in regions where sea-ice forms. See here for details.
Fixed bug in ocean mesh areas at 65°N. See here for details.
Artificially narrowed the width of the Dardanelles and Bosporus to reduce transport through these regions. See here for details.
Updated ocean Mesoscale Eddy Kinetic Energy GentâMcWilliams parameters. See here for details.
Now adjust net global ocean salt restoring to zero by scaling it, rather than applying a global offset. See here for details.
Additional ocean mixing is now applied wherever there is runoff, mixing it down to 40m depth where the ocean is deep enough.
Spatial regridding from the JRA55-do grid to the ice/ocean grid now uses conservative interpolation for fluxes and the patch method for all other fields, replacing the previous bilinear interpolation. See here for details.
Corrected the ocean bottom roughness used by the internal tidal dissipation parameterisation. See here for details.
Corrected the chlorophyll climatology used to calculate short-wave penetration into the ocean. See here for details.
Improved model efficiency and performance.
For a complete list of changes relative to the previously released versions, see:
Control experiments
No control experiments are included with these releases. However, the released WOMBATlite configurations do include control experiments with a physical ocean that is bitwise identical to the physics-only releases (see below).
Expected performance
| Walltime / model year | SU / model year |
|---|---|
| ~3 hr 6 min | ~16.5 kSU |
New WOMBATlite configurations
Releases
release-MC_25km_jra_ryf+wombatlite-1.0-beta
release-MC_25km_jra_iaf+wombatlite-1.0-beta
There is a new WOMBATlite-enabled configuration for each of the physics-only configurations described above (i.e. global 25km with both repeat-year and inter-annual JRA55-do forcing). These configurations follow the same naming scheme as the physics-only configurations, but with +wombatlite appended. E.g. the RYF configuration release branch is called release-MC_25km_jra_ryf+wombatlite.
Key features are:
New WOMBATlite model, version 2026.05.000. See the WOMBATlite 2026.05.000 documentation for features and details.
Based on the 2.0-beta physics-only configurations.
Control experiments
Control experiments using these configurations are included in the experiment list here. The experiment names are:
MC-25km_jra_ryf+wombatlite-test3-f4d79e82: 31 years of RYF dataMC_25km_jra_iaf+wombatlite-test4-d28e0359: one complete IAF cycle (1958-2023).
Note the IAF experiment was originally started with a tight limit on the strength of ocean surface salinity restoring (MAX_DELTA_SRESTORE = 0.5 [PSU]). However, this led to crashes and was subsequently relaxed, initially to MAX_DELTA_SRESTORE = 1.0 and finally to the value in the corresponding released configuration (MAX_DELTA_SRESTORE = 2.0).
A Jupyter notebook showing how to find/load the data using intake can be found here.
Expected performance
| Walltime / model year | SU / model year |
|---|---|
| ~3 hrs 50 min | ~20.5 kSU |
Known limitations
These configurations are still undergoing scientific evaluation.
Known limitations include:
There are unresolved surface salinity biases, particularly in the Arctic and North Atlantic Ocean and at large river mouths.
Liquid runoff is not spread horizontally. See here for more details.
Land mask requires some improvements to avoid ice buildup. See here for more details.
Latent heat due to basal melting is not accounted for. See here for more details.
There are two known problems with the new frozen runoff spreading scheme:
- Frozen runoff has a spurious column of zeros at â180° longitude. See here for more details.
- Frozen runoff has an unphysical seasonal cycle around Antarctica. See here for more details.
CICE6 still uses a B-grid. See here for more details.
Sea surface salinity restoring is incorrect along top and bottom rows of the grid. See here for more details.
Shortwave radiation forcing shows sawtoothing in its global sum due to issues with the âcoszenâ time interpolation in CDEPS. See here for more details.
Ice fields show unphysical patterns at and near the tripolar fold. See here for more details.
Outputting MOM6 diagnostics on density coordinates add ~30 min per model year to the runtime. These diagnostics can be removed if not needed (see here).
WOMBATlite diagnostic output can only be output on the native MOM6 vertical coordinate. See here for more details.
How to use
The released configurations can be run using the payu experiment manager. For instructions, see the access-hive Run ACCESS-OM3 documentation.
What we expect youâll be able to do with these releases:
- Clone the config repo and run the configuration;
- 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, while 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 modelâs results. Users should note that results and analysis using these configurations relate to the released versions only. Future releases will produce different results.
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.
See the CITATION.cff file included with each configuration for a full list of contributors. Contributors to the configuration versions in this release announcement include:
Configuration development, testing and advice: @anton, @aekiss, @dougiesquire, @minghangli, @pearseb, @ezhilsabareesh8, @AndyHoggANU, @cbull, @adele-morrison, @Callum_Shakespeare, @Luwei, @sofarrell
Model development: @anton, @dougiesquire, @pearseb, @ezhilsabareesh8
Build infrastructure: @TommyGatti, @harshula, @anton, @dougiesquire
Documentation: @anton, @dougiesquire, @minghangli, @JuliaN, @cbull, @ezhilsabareesh8
Performance and optimization: @minghangli, @manodeep
Evaluation: @aekiss, @cbull, @AndyHoggANU, @ezhilsabareesh8, @pearseb, @minghangli, @dougiesquire, @anton, @claireyung, @wghuneke, @hrsdawson, @jemmajeffree, @Helen_Shea, @CharlesTurner, @NoahDay
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.