ESM working group: Meeting notes 2024

Earth System Working Group
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39

Date: 10/4/2025
Chair: @tiloz
Participants: 13

  1. Next Working Group Meeting:
  • The working group meeting scheduled for 24/04 has been cancelled, as many working group members will be away between the public holidays. Working group meetings will return on 08/05.
  • There are no speakers confirmed for future meetings. Please consider presenting, or inviting a colleague to present. Members are encouraged to reach out to @spencerwong or any co-chair if they are interested in presenting.
  1. Brief CMIP7 update:
  • New spinup simulations of ESM1.6 are currently in progress. These simulations combine ocean and land model developments from the last few months. The ESM WG meeting on 08/05 may be used to provide an update on the new spinup.
  1. Shared Resources and Experiments:
  • ESM project lg87 used 411 KSU allocation for quarter 1. /g/data storage remains at 54.3TB.
  • @georgyfalster’s tropical SST variability experiments have been allocated 500 KSU, and there are currently no other proposals for this quarter.
  • Proposals are now open for this quarter. Do you have any proposals for shared experiments? See guidelines for how to do this. There are often used resources we can access if there are projects to use them.
  1. Working group day at the 2025 ACCESS-NRI Community Workshop:
  • The format of the ESM WG meeting and 2025 ACCESS-NRI Workshop was discussed. Planning is not currently advanced enough to provide concrete details. The idea of holding a joint session with another working group was raised, due to the ESM working group’s overlap in interests with the other working groups.
  1. Science Presentation:
  • Wilma Huneke presented on The ACCESS-CM2 climate model with a higher resolution ocean-sea ice component.
  • Background:
    • A new configuration of ACCESS-CM2 was set up, where the ocean and sea ice resolution was increased from 1-degree to quarter-degree. The atmosphere component was left unchanged from the existing CM2 configurations.
    • The ocean resolution matches the quarter degree OM2 configuration, allowing for investigation both the effects of the higher resolution, and the effects of the coupling.
    • Changes in bathymetry were required to prevent model crashes, and the regridding method for wind stresses was also changed from bilinear to patch to prevent an imprint of the atmospheric grid appearing in the regridded data.
  • Results:
    • A 500 year present day simulation was run with higher resolution model. Analysis focused on the final 100 years of the simulation. Comparisons were made with 1 degree CM2 present day experiment, and 0.25 and 1 degree OM2 simulations using repeat year forcings.
    • Sea surface temperature drifted over the whole simulation. Ocean interior temperatures drifted towards different values for each model/configuration, however the higher resolution simulations appeared to equilibrate faster.
    • Many biases seen in the 1 degree coupled model also appear in the 0.25 degree coupled model, including a large Southern Ocean warm bias which is larger in the higher resolution model. SST biases in eastern upwelling regions show similar patterns between the two models.
    • Ocean energetics as measured by sea level standard deviation were best represented in the coupled 0.25 degree model, while all analysed models generally underestimated this quantity.
    • All models show issues in surface mixed layer depths, with extra deep convection areas in the Wedell Sea and Ross Sea. Quarter degree OM2 significantly overestimates deep convection in the North Atlantic. The quarter degree coupled model appears to do the best job, however still shows biases.
    • The quarter degree coupled model shows similar biases in the ENSO pattern as the one degree model, however has an improved ENSO lifecycle, with less of a biennial cycle.
    • The quarter degree coupled model also displace a spurious North Atlantic multi-decadal variability, with simultaneous oscillations in the North Atlantic SST anomaly and overturning, related to the interplay between fresh water anomalies and AMOC strength. This was not present in the one degree model, however has appeared in other coupled models.
  • Future work:
  • Future work could include further increasing the ocean resolution or increasing the ocean vertical resolution.

Additional information