MOM6 configuration changes for compatibility with CICE6 B-grid

[DeniseWorthen]

In the 1-deg MOM6 configuration, there is no land at the southern boundary (j=1). Since CICE6 obtains its land mask from the MOM6 configuration, CICE6 currently has no land at j=1 either.

MOM6 utilizes a C-grid while CICE6 utilizes the B-grid. During testing by the hygrid-godas team running the 1-deg configuration with the DATM, locations of very thick ice were seen developing in isolated single point locations.

Information provided by @apcraig addresses both these issues:

1. The open boundary at j=1 is going to be problematic in the long term as the CICE6 ns_boundary_type='tripole' which means it's using "open" on the southern boundary.

2. The thick ice seen in hybrid-godas configuration appear to be related to isolated ocean points. In other words, they are connected to only 1 other active gridcell. In pop, this was always a no-no because there could be no velocity in a gridcell that was isolated like that. I don't know what the restrictions are on MOM, but my guess is that the thick ice is related to this choice of masking. Because of the pop constraint, I don't have any experience running CICE with isolated cells like this. But the problem is that in a B-grid, you probably will not get any velocity at that cell.

[DeniseWorthen]

I'm going to close the issue here and reopen it on ufs-weather #445 since it should not involve any changes to MOM6 directly.