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Coupling MOM6 to an ice sheet model


Willem Huiskamp
New Member
(Cross-posted from the MOM forums)

Dear MOM community,

Recently we've completed an offline coupling of MOM5 to the ice sheet model PISM in an ocean-sea ice - ice sheet only setup (GMDD - Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO) however there was a caveat with this approach - we inserted the mass and energy fluxes from the sub-shelf melt into the ocean via the river runoff module. As we are now upgrading to MOM6, the aim is to do this properly and provide a 3D field of mass and energy fluxes to MOM at the correct depths.

My question then (particularly to the developers), is what would your recommendation be in going about this (or has anyone thought about this problem in the CESM community?)? I know that the coupler has a 3D data override structure, but no fields for ice shelf melt. Furthermore, the mass fluxes need to be inserted in such a way that allow dynamic sea level change (currently any runoff/ synthetic mass flux is necessarily cancelled out at the coupler level to avoid spurious mass drift due to it being an ocean-sea ice only configuration).



Alistair Adcroft
New Member
The top interface of MOM6, and all layers below, are depressed to follow the depth of the ice shelf so the depth of injection of a 2d melt field will be at depth. Internally, the mass flux is in `fluxes%iceshelf_melt` declared at NOAA-GFDL/MOM6. In our iceshelf module (under dev and not quite working yet) this flux is set in NOAA-GFDL/MOM6 . In your case, I imagine you have your own coupled interface and you should set the iceshelf fluxes there (usually in the file starting mom_surface_forcing_* unique to each coupler). There are several variants of the coupled interface (which now live under config_src/drivers) but I don't think any of them set these fluxes yet, but could.


Willem Huiskamp
New Member
Thanks for the reply, Alistair. Having a look at the code, I don't think this solution will be appropriate because, as you note, the ice shelf module utilises a 2D field for the injection of mass into the ocean. As we are using an offline coupling approach, the ocean is not aware of the shelf's existence and any mass/energy fluxes would be inserted at the ocean surface instead of at the correct depths. It sounds like we may require a more creative solution to implement this properly in our configuration.


Gustavo Marques
Staff member
We have coupled MOM6 to CISM, using the CESM framework, and run the MISOMIP set of experiments. This was done a few years ago. We followed an asynchronous approach, where CISM advances for one coupling interval, passing the ice thickness to MOM6 at the end of this interval via the coupler. MOM6 receives the updated ice thicknesses and adjusts to the new thicknesses incrementally over one coupling interval. At the end of this interval, MOM6 sends the melt rates (computed by the ice shelf module) to CISM via the coupler, and the steps are repeated. Additional details can be found in the following presentations: