ACCESS-OM3 development highlights/updates

COSIMA Working Group
1

These are presented fortnightly at COSIMA meetings.

First, some context

[This is a wiki post - free free to edit.]

2

2026-02-12

Working towards next IAF 25km test configuration and 66-year run

Also working on (maybe not ready for the next run)

Call out for missing diagnostics:

3

2026-03-05

Continuing work towards next ACCESS-OM3 IAF 25km test configuration and 66-year run:

Request diagnostics for new run:

Other ACCESS-OM3 development

ACCESS-OM2

  • new release soon: WOMBAT-lite and GCC compiler support
5

2026-04-02

ACCESS-OM3 evaluation update

6

2026-04-16

3rd ACCESS-OM3 25km IAF 1958-2023 test run

  • currently underway; details here
  • currently simulating 2008; should be finished (to end of 2023) by early next week
  • data: /g/data/ol01/outputs/access-om3-25km/MC_25km_jra_iaf+wombatlite-test3v2-00532b88

many of the problems highlighted in the last update are now resolved or much improved in the new run :tada:

  • reverted to previous MOM6 and CICE6 code to sidestep still-unresolved mediator NaN bug
  • SSS restoring limited by MAX_DELTA_SRESTORE = 1.0 psu (rather than 0.5 psu, to avoid error)
  • no crashes so far :crossed_fingers:
  • B-grid compatible land mask in polar regions has prevented unbounded ice and snow thickness growth. Thickest ice is <50m thick rather than 10km. Still thicker than OM2, but this would probably be reduced further by spreading solid runoff and associated latent cooling of the ocean.
  • Improved GM parameters have significantly reduced abyssal temperature drift
  • Indonesian throughflow has been improved by topography edits
  • Constricting Bosporus has greatly reduced Black Sea and eastern Mediterranean SSS bias
  • WOMBAT-lite BGC is looking good - @pearseb tells me
    • Chlorophyll looks amazing
    • CO2 flux and iron limitation look great
    • Surface nitrate looks great, but surface iron is too high in coastal areas. Not sure why it’s not being removed rapidly at those concentrations.
    • Vert integrated NPP much too high in a weird place in the Amazon outflow. Otherwise it looks great. However, the weird high values are causing globally integrated rates of NPP that are 3x higher than the median estimate from observations. And much higher than what is considered reasonable.
    • Zooplankton is too low.
7

2026-04-30

3rd ACCESS-OM3 25km IAF 1958-2023 test run

  • 66-year IAF cycle completed
  • includes WOMBAT-lite BGC
  • details here
  • data here: /g/data/ol01/outputs/access-om3-25km/MC_25km_jra_iaf+wombatlite-test3v2-00532b88
  • we welcome analysis/scrutiny of this data - especially the BGC output

Some current ACCESS-OM3 development issues

8

2026-05-14

Good news :tada:

9

2026-05-28

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2026-06-11

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2026-06-24