[MITgcm-devel] seaice dynamics questions

[Jean-Michel Campin]

Hi,

I have a couple of questions and remarks regarding pkg/seaice:

1) I found annoying not to be able to know where some CPP options
should be defined/undef, since they don't appears in any
*OPTIONS.h files, neither set at the top of the *.F file
in which they are used (might want to use this to keep some 
inactive pieces of code):
 DISABLE_SEAICE_OBCS <- I guess in SEAICE_OPTIONS.h ?
and many more in other seaice S/R.

2) LSR solver: we always do uIce first and then vIce, right ?
and I guess the vIce solution depend on the new uIce.
Now when the seaice extends over 2 faces of the CS-grid,
might have an issue with U/V not being continuous at the
face boundary. As I understand, it's not so much an issue on
regular CS grid (e.g., CS-510) for present day conditions 
but this is likely to happen on lat-lon cap grid. 
I guess the solution would be to have a 3 pass algorithm, 
like in multi-dim advection with CS topology.

3) I did not find many OBCS specific code in seaice_lsr.F
Would it make sense to prevent the LSR solver from updating
the ice velocity at the OB (like we do in CG2D) ?
Would it be useful ? Might not be too difficult with some masking.

4) I am going to add an EXCH call at the end of obcs_apply_uvice.F,
since it seems we need one. I am also tempted to remove
all the "if ( OB?u/vicefile .NE. ' ' ) then" : I think it's
not right and not safe to by-pass the setting of ice-velocity at
an open-boundary, and it's better to apply a default zero velocity
when no file is provided.

Cheers,
Jean-Michel