March 12th /2025 minutes
Present: @cbull @Wilton_Aguiar @claireyung @fabiobdias @adele157 @helen @aekiss @ezhilsabareesh8
Not present: @angus-g @AndyHoggANU
The discussion focused on three main topics (mostly updates):
Ice shelf thickness product to use:
· Background: It seems that the ice sheet modelling community widely agrees that AntGG2021 (Charrassin et al., 2025) provides the best representation of ice shelf cavities, with BedMachine v3 being the second-best. The general consensus is that we should avoid using BedMachine v2.
· Issue: GEBCO2024 is currently being used for the topography and incorporates BedMachine v2. Using either AntGG2021 or BedMachine v3 will require significant testing to ensure that the ice shelves are properly connected/stitched to the bathymetry. Waiting for the stitched product to be ready could slow down the workflow for producing model bathymetry, ice shelf thicknesses, and initial conditions.
· Next steps: Continue the model workflow using the current GEBCO2024, while the proper ice shelf thickness/bathymetry dataset is being developed. This decision will allow us to advance the workflows and model development, providing more time for thorough debugging.
· PS: We will likely revisit this discussion at the next meeting, where we aim to get input from other ice sheet modelers
Extrapolation of Initial conditions:
· Background: In MOM6-Panan, we used a backward filling method to propagate offshore temperature-salinity (TS) fields southward, where ice shelf cavities would be. This method undesirably leaked properties from the Amundsen Sea into the Weddell Sea cavities. Additionally, previous insights from ocean-ice sheet modeling with ROMS suggest that the sharp density gradients created by backward filling can be a challenge for the ocean model. We attempted to extrapolate the surface offshore TS using Inverse Radius Weighting (IRW) interpolation instead, which seems to fix the leakage problem, and reduce sharp gradients.
· Issue: While this method resolves the leakage issue, it does not fix the warmer surface conditions near the Amery Ice Shelf. Furthermore, the evaluation of the IRW propagation is not ideal, as ice shelf cavities are much deeper ( z~ 1000m).
· Next steps:
- Evaluate how the IRW extrapolation performs at the depth of ice shelf cavities (~1000 m?).
- Compare the TS on the shelf with previous ocean-ice shelf model outputs (e.g., are the warmer waters in Amery reasonable).
- Test other observational products containing data closer to the ice shelf (~1000 m), such as Pauthenet and Kaihe’s climatology.
Target horizontal grid:
· Issue: We do not yet have the target horizontal grid (with the southern boundary extended to 86.5°S) that will be used for the model testing phase or the final version of the model. Currently, the workflows are using grids from Panan 1/10°, ACCESS 1/10°, or ACCESS 1/4°.
· Next steps: We have decided to start with a 1/12° grid for testing, which is still computationally inexpensive for testing in a regional, Pan-Antarctic domain. @angus-g volunteered to create a global 1/12° grid that we can cut to the desired domain. Once testing is complete, we will transition to the final 1/20° (or 1/24°) grid.
There were no updates on the vertical coordinate choice.