[Mitgcm-support] Re: pkg/seaice and pkg/exf

[mitgcm-support at dev.mitgcm.org]

>> It now seems to work fine. I've integrated for several 10,000 steps
>> without any problems. I'll look in detail and let you know if I find any
>> other issues. What did you fix?

Tom, thanks for all your help in the testing and debugging the sea-ice code.
What I changed was the way in which option SEAICE_EXTERNAL_FLUXES is
implemented.  Jinlun and I rely on internal, pkg/seaice, bulk formulae to
compute fluxes over the complete integration domain, whether there is sea-ice
or not.  Option SEAICE_EXTERNAL_FLUXES allows one to mix and match pkg/exf
bulk formulae over open ocean and pkg/seaice fluxes where there is sea-ice.
The first thing that pkg/seaice does is to compute open ocean fluxes.  Then it
goes ahead and modifies these fluxes where there is sea-ice.  In previous
implementation of SEAICE_EXTERNAL_FLUXES, I replaced the results of pkg/seaice
open-ocean, bulk-formulae fluxes with those computed by pkg/exf.  This seems
to work fine for heat and salt fluxes (and also for wind stress in my small
test domain).  But in your configuration you found that the wind stress
computed by pkg/exf is incompatible with the sea-ice code, especially near the
edges where there are issues of interpolating from C to B and back to C grid.
I don't fully understand what caused your configuration to blow up.  But a
quick fix is to let pkg/seaice use its own internal estimates of wind stress
for its computations, and then to replace wind stress with that produced by
pkg/exf at all grid locations where there is no sea-ice.

Dimitris

-- 
Dimitris Menemenlis                      menemenlis at jpl.nasa.gov
Jet Propulsion Lab, MS 300-323           tel: 818-354-1656
4800 Oak Grove Dr, Pasadena CA 91109     fax: 818-393-6720