New Mesh: SOwISC12to30E3r4

[xylar]

Long name: SOwISC12to30kmL80E3SMv3r4

This version of the Southern Ocean Regionally Refined Mesh (SORRM) has resolution that is:

• 12 km resolution around Antarctica
• 30 km elsewhere

It is intended to be similar to the Icos30 mesh except in the Southern Ocean and around Antarctica.

This mesh differs from r3 in #807 in that:

• MALI topography as well as masks for land ice, floating ice and ocean get combined with BedMachine Antarctica/GEBCO.

Checklist

• User's Guide has been updated
• Developer's Guide has been updated
• API documentation in the Developer's Guide (api.rst) has any new or modified class, method and/or functions listed
• Documentation has been built locally and changes look as expected
• The E3SM-Project submodule has been updated with relevant E3SM changes
• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[xylar]

This is based off of #807 (which is based off of #813) so it will be a bit before this is ready to go in. It also needs documentation.

[xylar]

Comparison with SOwISC12to30E3r3

Here are the landIceMask fields for the SORRM mesh with MALI topography:

And the same but with BedMachine from #807:

[xylar]

Updated Comparison with SOwISC12to30E3r3

Here are the landIceMask fields for the SORRM mesh with MALI (AIS_2to10km) topography:

And the same but with BedMachine from #807:

[xylar]

I was able to run the workflow through the performance test. In a discussion with @cbegeman, @matthewhoffman and @trhille, we decided we'd like to work with a 4km initial condition that's more similar to the 2km one I used in the plots above, and that that initial condition would also be swapped into E3SM-Project/E3SM#6440, the PR bringing in the new MALI AIS meshes and initial conditions.

[xylar]

Another Updated Comparison with SOwISC12to30E3r3

Here are the landIceMask fields for the SORRM r4 mesh with MALI (AIS_4to20km) topography:

And the same but SORRM r3 with BedMachine topography from #807:

[xylar]

The same as above but zooming in on the Amundsen Sea.

SORRM r4:

SORRM r3:

[cbegeman]

@xylar have you been looking at all at landIceFloatingFraction?

[xylar]

Not yet. I should.

[xylar]

landIceFloatingFraction

SORRM r4

SORRM r3

@cbegeman, no surprises to me. What do you think?

[cbegeman]

@xylar Thanks for sharing those.

The new map is nice in that the "shadow" islands of floating ice are removed near the peninsula.

It looks like not all the cells near the coastline are capped at 0.5. Isn't that supposed to be the case? Or is that only true when there's grounded ice upstream as opposed to exposed rock?

What do you think of the pocket of partial ice cover at Brunt near an island? I'm thinking that since it's part of the ice mask there won't be sea ice formation. And there also won't be any interaction with the atmosphere, right (like fluxes scaled by the ice fraction)? We could potentially get a bit of frazil there since frazil doesn't change the surface pressure. But I don't know if this is really worth worrying about. Should we look at the land ice pressure field and make sure that that's reasonably smooth. I see one other low fraction "island" between Ross and Getz.

[xylar]

It looks like not all the cells near the coastline are capped at 0.5. Isn't that supposed to be the case? Or is that only true when there's grounded ice upstream as opposed to exposed rock?

No that's no longer the case. That was a change with r3. I think we want to allow melting in partial open ocean, partial ice-shelf cells for conservation. Otherwise, we need to reroute the missing melt somewhere else. When melt is happening in the coupler, this will presumably be happening anyway so this is to make melt computed in MPAS-Ocean more similar to what will happen in the coupler.

[cbegeman]

@xylar That's ringing some bells. Thanks for the reminder

[xylar]

What do you think of the pocket of partial ice cover at Brunt near an island? I'm thinking that since it's part of the ice mask there won't be sea ice formation. And there also won't be any interaction with the atmosphere, right (like fluxes scaled by the ice fraction)? We could potentially get a bit of frazil there since frazil doesn't change the surface pressure. But I don't know if this is really worth worrying about. Should we look at the land ice pressure field and make sure that that's reasonably smooth. I see one other low fraction "island" between Ross and Getz.

These are presumably places where isolated pockets of open ocean have been filled in because they're not resolved enough. Frazil could certainly form here but I would expect these mostly to be pretty passive areas. You could be right though that it's worth looking at ice draft or land-ice pressure here to make sure these areas don't look too weird. They could be isolated pockets of essentially zero-thickness ice shelf where water just gets trapped.

[xylar]

The files are in:

/lcrc/group/e3sm/ac.xylar/compass_1.5/chrysalis/e3smv3-meshes/sowisc12to30e3r4/ocean/global_ocean/SOwISC12to30/MALI_topo_AIS_4to20km/

and also staged for testing in:

/lcrc/group/e3sm/data/inputdata/ocn/mpas-o/SOwISC12to30E3r4

[xylar]

I will make a proper review page soon.

[xylar]

@matthewhoffman found issues with thickness in the dataset we are using from MALI. I'll need to rerun once that's fixed.