# ACCESS CM3 technical meeting minutes

**URL:** <https://forum.access-hive.org.au/t/access-cm3-technical-meeting-minutes/5429>\
**Category:** Coupled Model\
**Tags:** access-cm3\
**Created:** [23 October 2025 23:38 UTC](https://forum.access-hive.org.au/t/access-cm3-technical-meeting-minutes/5429 "2025-10-23T23:38:14Z")\
**Posts on this page:** 1\
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**Author:** ![MartinDix](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/martindix/32/32_2.png) [@MartinDix](https://forum.access-hive.org.au/u/MartinDix)\
**Post date:** [8 December 2025 22:39 UTC](https://forum.access-hive.org.au/t/access-cm3-technical-meeting-minutes/5429/4 "2025-12-08T22:39:34Z")

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**Date: Dec 3**

AM3 is now upgraded to vn13.8. This allows direct comparison with Met Office GC5 central configurations.

 ![amip_toa](https://us1.discourse-cdn.com/flex020/uploads/access1/original/2X/e/e5ed192511bcc4caf535052392bc44226cb7bcbd.png)

Upcoming release of an updated OM3 25km configuration includes bathymetry changes and chlorophyll based opacity.

**Sea-ice**

Both CM3 and OM3 have too large NH ice volume, [Arctic sea-ice depth ~2x higher than previous configs · Issue #65 · ACCESS-NRI/dev\_coupling · GitHub](https://github.com/ACCESS-NRI/dev_coupling/issues/65). OM3 has some very thick ice stuck in coastal features but CM3 problem seems different. @sofarrell says CM3 has very little bottom melting.

**Datastore related issues**

Test creating single variable UM output with a new run and check if datastore based on this fixes the slowdown. Ensure CM3 uses OM3 diag table

Problems with virtualisation of Wilma’s CM2 run, [CM2 25km present day control run for comparison · Issue #43 · ACCESS-Community-Hub/access-cm3-paper-1 · GitHub](https://github.com/ACCESS-Community-Hub/access-cm3-paper-1/issues/43#issuecomment-3520160001). Consider splitting the most importatnt atmospheric variables to a separate collection?

Consider adding CM2 piControl to the notebook template?

@kieranricardo reports loading CM3 ice data is slower than OM3. @anton suggests this may be because files have coordinate variables (which were removed from OM3). However files like `/g/data/zv30/non-cmip/ACCESS-CM3/cm3-run-11-08-2025-25km-beta-om3-new-um-params/archive/2000/ice/access-cm3.cice.1mon.mean.2000-01.nc` don’t have grid variables, though do have `angle` and `anglet` which are probably unnecessary.

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