Disable land ice frazil unless ISMF is on

[cbegeman]

This PR turns land ice frazil off by default and re-enables it when ice-shelf melt fluxes are enabled in standalone or coupled mode. Land ice frazil is not enabled in data ISMF because frazil fluxes are already included in satellite-derived ISMF products.

[non-BFB] when ice-shelf cavities are present in the mesh and (ocn_ismf is off or ocn_ismf is data)
[BFB] when ice-shelf cavities are absent from the mesh or ice-shelf cavities are present in the mesh and (ocn_ismf is coupled or ocn_ismf is internal)

[cbegeman]

Further discussion located at E3SM-Ocean-Discussion#101

[xylar]

Approving based on code inspection and previous review in E3SM-Ocean-Discussion#101

[xylar]

This will affect current production runs so will need to wait for maint-3.0 to be created.

[darincomeau]

Approved based on review in Ocean Discussions PR.

[jonbob]

@cbegeman -- would you expect this PR to cause non-BFB behavior for a typical IcoswISC30E3r5 fully-coupled case?

[xylar]

@jonbob, that would be expected because there was frazil forming in the otherwise inactive cavities in WCYCL cases. That is the main reason we wanted to turn it off here -- we don't want that behavior when cavities are inactive.

[jonbob]

Thanks @xylar. Do we have a long-ish comparison run to document the changed behavior then? I didn't see anything on the discussions page

[darincomeau]

When this first came up several months ago, we quantified the impact of the unintentional land-ice frazil term in a WCYCL1850 case and confirmed it was very small. But we did not actually do a run with the desired behavior added here, where land-ice frazil is off when ice-shelf cavities are otherwise thermodynamically inactive (e.g. WCYCL cases).

I've started that run now on Anvil, will update.

[rljacob]

@darincomeau any update?

[darincomeau]

@darincomeau any update?

The run is in year 20 now, I think we were going to assess climate impact (relative to v3 piControl) at year 20 or 30.