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Fix land-locked cells at calving fronts #752

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merged 2 commits into from
Feb 3, 2024

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xylar
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@xylar xylar commented Jan 3, 2024

If there are land-locked cells at calving fronts of ice shelves, they need to be added to the land-ice mask so sea-ice doesn't get trapped there.

This merge also gets the minimum latitude and number of sweeps used in finding land-locked cells from config options.

Checklist

  • Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

closes #746

If there are land-locked cells at calving fronts of ice shelves,
they need to be added to the land-ice mask so sea-ice doesn't
get trapped there.

This merge also gets the minimum latitude and number of sweeps
used in finding land-locked cells from config options.
@xylar
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xylar commented Jan 3, 2024

Testing

I created a version of the SORRM mesh using this branch. Below are screenshots from ParaView before and after adding land-locked cells to the land-ice mask:

Before:
before_land_locked_cells

After:
after_land_locked_cells

Two cells are filled in this example (and 40 more around Antarctica).

Comment on lines +444 to +447
dsMask = add_land_locked_cells_to_mask(
dsMask, dsCulledMesh, latitude_threshold=latitude_threshold,
nSweeps=sweep_count)

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These 3 lines are the real fix here. The rest is clean up to reduce the number of hard-coded parameters.

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xylar commented Jan 25, 2024

@mark-petersen, this would be nice to get merged. Would you be able to take a look at these 2 meshes:

/lcrc/group/e3sm/data/inputdata/ocn/mpas-o/RRSwISC6to18E3r4/mpaso.RRSwISC6to18E3r4.20240105.nc
/lcrc/group/e3sm/data/inputdata/ocn/mpas-o/SOwISC12to30E3r2/mpaso.SOwISC12to30E3r2.20240104.nc

and tell me if you think the land-locked cells at calving fronts are fixed (as in the plots I made above)?

Also, if you can follow the Compass code changes I made, it would be great to know if they look right to you.

@mark-petersen
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Thanks. I can see why this would be a problem for sea ice getting caught in the calving front. It's great that the solution is a simple additional call to add_land_locked_cells_to_mask with the ice_coverage mask. It's also good to change the hard-coded numbers to config options. I'm looking at those files now. Sorry for the delay.

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Very nice! I do not see any land-locked cells (landice-locked cells) in the sample I looked at, from your RRS mesh above:
image
image
image

Thanks, looks good!

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Does it matter if there is a cell with landIceMask = 1 but landIcePressure=0 ? I guess it is land ice cover to the coupling fields and sea ice, but the ocean doesn't get pushed down there, as if it were a very thin layer of land ice. I think that should be fine.

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xylar commented Feb 3, 2024

Thanks so much @mark-petersen! I lost track of this but I really appreciate your review.

Does it matter if there is a cell with landIceMask = 1 but landIcePressure=0 ?

No, that's perfectly fine, just a little odd. It won't have melt fluxes because I'm only updating landIceMask, not landIceFraction, which will remain zero and which is what is used to scale melt fluxes. In actual fact, landIcePressure can have non-zero values right now even where landIceMask = 0 because we sometimes smooth the calving front over a small distance. So there is currently no assumption about the correspondence between landIceMask = 1 and landIcePressure > 0

I guess it is land ice cover to the coupling fields and sea ice, but the ocean doesn't get pushed down there, as if it were a very thin layer of land ice. I think that should be fine.

Right, with the added factor that the land ice also won't melt there, the cell is just insulated from the atmosphere. This is clearly much better than having trapped but thermodynamically active sea ice.

@xylar xylar merged commit a1b433d into MPAS-Dev:main Feb 3, 2024
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@xylar xylar deleted the fix-land-locked-cells-at-calving-fronts branch February 3, 2024 17:33
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Sea ice trapped in isolated cells adjacent to ice shelves
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