COSIMA TWG Meeting Minutes 2026

COSIMA TWG
, , , ,
1

Minutes for 2026, please set new posts to Wiki for easier editing.

2

Date: 14 Jan 2026

Attendees: @sofarrell, @AndyHoggANU, @aekiss, @kieranricardo, @MartinDix, @helen, @NoahDay, @anton, @ashjbarnes, @dougiesquire
Chair: @cbull
Minutes: @minghangli

1. Regional Ocean Model Automation Planning - Regional MOM6 Stencil · Issue #1044 · ACCESS-NRI/access-om3-configs · GitHub

@ashjbarnes’s role and scope

Current goal is to make rOM3 ocean model setup faster and to support regional coupling (rOM3 + rAM3). @ashjbarnes has just started, is currently based in Canberra working on automating the setup of regional ocean model domains, and plans to move to Tasmania later to focus on coupling rOM3 and rAM3.

Stencils concepts and long-term plan

A long term plan is forming around stencils (template configurations) that users can download and then have the tooling rewrite paths/files to match a specific regional domain setup. The intent is that multiple stencils will exist over time, starting with a rMOM6 stencil and later expanding to additional templates, including a WOMBAT stencil aligned with prior work.

Regional MOM6 vs ACCESS-NRI configs

Current regional MOM6 copies default configuration files, such as MOM_input, config.yaml etc, and hard coded for a default FMS run. The proprosal is to shift rOM3 relevant defaults to ACCESS-NRI configuration repos, so regional MOM6 inherits from those maintained configs.

An alternative way is to keep rMOM6 doing the heavy lifting, such as regridding etc, while a thin ACCESS-NRI wrapper repo handles only configuration manipulation. But this would split the workflow across repos which is less desirable for users.

Constraints

A practical constraint discussed: putting content in ACCESS-NRI org repos enables internal testing (and potentially running tests on Gadi). Collaborators can still contribute via PRs but direct pushing to main is restricted.

Another discussion was on whether stencils are just one-off templates or they must be kept up-to-date alongside evolving supported configs. A likely outcome is a hybrid:

  • Some components must stay aligned with global/supported setups.
  • Other parts will diverge for regional needs, such as parameter choices and other specific tuning work.

Others

Some disagreement on MOM_input vs MOM_override:

  • keep regional changed in a maintainable way via MOM_override, easier to track changes
  • keep a regional MOM_input and potentially multiple selectable variants, similar to how diag_table are handled, because regional configs are inherently perturbations relative to global defaults.

Workflow discussion - generate from scratch or subset from global config

  • Generate regional grids/topog from scratch from defining corner points/region definition.
  • Subset from an existing global parent grid, keeping exact alignment with a global config (Claire’s needs).

2. OM2 25km config issues and testing updates

Restart reproducibility in released 25km configs

All released 25km ACCESS-OM2 configs are currently not restart reproducible. The issue is now resolved and can be found in 0.25deg configurations are not restart reproducible · Issue #245 · ACCESS-NRI/access-om2-configs · GitHub

25km IAF configuration instability after exe updates

The most recent 25km IAF release crashes after ~9months, debugging work will start since the restart repro issue is fixed now.

Restart repo testing was not routinely run for these configs (scheduled tests). PR testing has been updated and scheduled testing will be updated once the underlying issue is fixed.

3. WOMBAT status and release framing

25km WOMBAT-lite run results

A 25km WOMBAT-lite RYF run kicked off before Christmas and output looks good. Pierce has been reviewing. Hence this is likely sufficient to demonstrate progress and tick prior milestones, especially since the milestone was framed as 2025-era.

RYF vs IAF for WOMBAT-lite

No strong preference; switching between RYF/IAF is mostly forcing file selection and could be done quickly. For stakeholders, “it runs and looks reasonable” is likely enough.

CM3 priorities

WOMBAT is not a high CM3 priority right now. The WOMBAT update is primarily about demonstrating progress rather than immediate integration demand.

4. OM3 upstream updates

A conflict with an existing patch in CDEPS is seen as a chance to move away from patching toward using maintained forks. Current plan includes having contributors to commit their work so history/authorship is preserved.

5. Iceberg spreading discussion

details:

Adapt CM3 river spreading for OM3 iceberg spreading

An idea is raised to reuse the existing mass-conserving exponential smoothing used for river spreading in CM3 and apply it to iceberg spreading in OM3. This would keep most flux near the coast while spreading it outward smoothly - potentially reducing extreme local build up.

Thickness spikes and total volume bias

Currently OM3 has some extreme points exceeding 10km thickness! CM3 avoids extreme spikes by distributing more evenly, but still has a total ice volume bias.

Latent heat extraction

There’s another discussion about latent heat extraction when runoff/iceberg flux enters the ocean. A possible way is to split snowfall/runoff 50/50 frozen vs liquid so latent heat is not extracted for the entire volume.

Likely causes

We need to fix the core issues first - polar landmask / non-advective cells before relying on engineering fixes, while still keeping spreading improvements as an option.

A note was mentioned that NASA ran similar processing and didn’t see the same issues, so the land mask differences might be a key factor?