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ACCESS-ESM1.6 configurations and experiments

ACCESS-NRI supports and maintains several released configurations for ACCESS-ESM1.6, which have primarily been used to run CMIP7 experiments. These configurations will be actively updated with bug fixes and improvements. Documentation on how these configurations have been set up is available under the Configurations drop-down.

Many other CMIP7 experiments have been run using ACCESS-ESM1.6 which do not have ACCESS-NRI released or supported configurations. These experiments will not automatically include improvements and updates, and manual updates may be required to rerun them. Documentation on how these experiments were set up is available under the Experiments drop-down.

Common settings

There are some aspects which are consistent across all configurations and experiments.

  • Changing the MPI layout: When changing the MPI layout, modifications are required in both the config.yaml and the respective component's configuration. See the Changing number of processes section under Build a Model in the Hive docs for information on setting this for each model component.

CICE5

In ACCESS-ESM1.6, the sea ice component is CICE5 (Hunke et al., 2015)1 updated from CICE4 used in ACCESS-ESM1.5.

Scientifically the sea ice model is configured the same as ESM1.5 (Ziehn et al., 2020)2. The scientific configuration is summarised as follows:

  • Zero-layer thermodynamics (Semtner, 1976)3
    • One layer of snow and one layer of ice
    • UM calculates ice surface temperature, and conductive heat flux into the sea-ice
  • Ice transport (Lipscomb, 2001)4 and ridging (Rothrock, 1975)5
  • Internal Ice Stress follow EVP (Hunke & Dukowicz, 2002)6

There are significant improvements to diagnostics to support CMIP style diagnostics (Notz et al., 2016)7(Fox-Kemper et al., 2025)8 natively and error handling.

Meltwater Runoff

Like ESM1.5, the OASIS3-MCT coupler is used and the sea ice model acts as the interface between the atmosphere and ocean models. The only significant change to this interface since ESM1.5 is changes to meltwater from Antarctica and Greenland. In all models in ACCESS 1-2 generations, there is no ice sheet model and the snow accumulates over each ice sheet. When the snow thickness is greater than 1100m, the snow volume is added to the river scheme and flows to the coast over a relatively short timescale (~7 days). The volume of meltwater discharge from Antarctica and Greenland is therefore equal to the recent snowfall over each continent. In ESM1.6, this meltwater is partially discharged at the coastline of each continent (to represent ice shelf basal melt) and partially spread in open ocean (to represent melt from icebergs). In ESM1.5 all meltwater is at the coastlines. In addition, the latent heat to melt this water is now taken from the ocean. Meltwater runoff is configured in the input_ice.nml namelist with a prescribed pattern from the lice_discharge_iceberg.nc input file.

References

  1. Hunke, E., Lipscomb, W., Turner, A., Jeffery, N., & Elliott, S. (2015). CICE: The los alamos sea ice model documentation and software user's manual, version 5.1. doc. LA-CC-06-012. ↩

  2. Ziehn, T., Chamberlain, M. A., Law, R. M., Lenton, A., Bodman, R. W., Dix, M., Stevens, L., Wang, Y.-P., & Srbinovsky, J. (2020). The Australian Earth System Model: ACCESS-ESM1.5. Journal of Southern Hemisphere Earth Systems Science, 70(1), 193--214. https://doi.org/10.1071/ES19035 ↩

  3. Semtner, A. J. (1976). A model for the thermodynamic growth of sea ice in numerical investigations of climate. Journal of Physical Oceanography, 6(3), 379--389. https://doi.org/10.1175/1520-0485(1976)006\<0379:AMFTTG>2.0.CO;2 ↩

  4. Lipscomb, W. H. (2001). Remapping the thickness distribution in sea ice models. Journal of Geophysical Research: Oceans, 106(C7), 13989--14000. https://doi.org/https://doi.org/10.1029/2000JC000518 ↩

  5. Rothrock, D. A. (1975). The steady drift of an incompressible arctic ice cover. Journal of Geophysical Research (1896-1977), 80(3), 387--397. https://doi.org/https://doi.org/10.1029/JC080i003p00387 ↩

  6. Hunke, E., & Dukowicz, J. K. (2002). The elastic--viscous--plastic sea ice dynamics model in general orthogonal curvilinear coordinates on a sphere---incorporation of metric terms. Monthly Weather Review, 130(7), 1848--1865. https://doi.org/10.1175/1520-0493(2002)130\<1848:TEVPSI>2.0.CO;2 ↩

  7. Notz, D., Jahn, A., Holland, M., Hunke, E., Massonnet, F., Stroeve, J., Tremblay, B., & Vancoppenolle, M. (2016). The CMIP6 Sea-Ice Model Intercomparison Project (SIMIP): Understanding sea ice through climate-model simulations. Geoscientific Model Development, 9(9), 3427--3446. https://doi.org/10.5194/gmd-9-3427-2016 ↩

  8. Fox-Kemper, B., DeRepentigny, P., Treguier, A. M., Stepanek, C., O'Rourke, E., Mackallah, C., Meucci, A., Aksenov, Y., Durack, P. J., Feldl, N., Hernaman, V., Heuzé, C., Iovino, D., Madan, G., Marquez, A. L., Massonnet, F., Mecking, J., Samanta, D., Taylor, P. C., ... Vancoppenolle, M. (2025). CMIP7 data request: Ocean and sea ice priorities and opportunities. EGUsphere, 2025, 1--58. https://doi.org/10.5194/egusphere-2025-3083 ↩