[MITgcm-devel] seaice code beyond checkoint61j blows for ECCO-GODAE

[Martin Losch]

Hi all,
can I summarize, what has happened so far in terms of new sea ice  
code? I am a little confused as to what works and what not. Correct me  
if I am wrong:

A. Martin's experiments of a lat/lon grid:
1. 0.25deg rotated regional grid of Arctic ocean with CORE forcing  
(1958-2004) work with new code for
SEAICE_clipVelocities = .false.,
SEAICE_zetaMin = 0.,
SEAICE_advSnow=.true.
both SEAICE_no_slip=.true. and .false.
different types of open boundary conditions for sea ice and varying  
oceanic conditions
2. 2deg global ("isotropic") grid works
3. 1deg and 0.5deg regional ("isotropic") grid of the Weddell Sea  
works for at least 10years (Olaf Klatt's experiment)

B. Patrick's ECCO-GODAE 1deg global runs (are they all iteration 75?)
1. blows up after transition from old to new seaice code in iteration 75
2. runs (iteration 75?) with SEAICE_OLD_AND_BAD_DISCRETIZATION defined  
and old defaults (e.g. SEAICEadvSnow = .FALSE., SEAICE_clipVelocities  
= .TRUE.,, the rest shouldn't matter)
3. blows up with  with SEAICE_OLD_AND_BAD_DISCRETIZATION defined and
      SEAICEadvSnow = .TRUE.,
      SEAICEadvSalt = .TRUE.,
      SEAICEadvAge  = .TRUE.,
      SEAICE_clipVelocities = .TRUE.,

C. Hong's CS510 experiments
1.a pure forward run works with SEAICE_OLD_AND_BAD_DISCRETIZATION  
undefined and use
     SEAICEadvSnow      = .TRUE.,
     SEAICEadvSalt      = .TRUE.,
     SEAICEuseFlooding  = .TRUE.,
2. adjoint run breaks with new code, but works with old code (pre- 
checkpoint61j)
3. any news?

So in summary, forward simulations seem to work, except for Patrick's  
ECCO-GODAE (which is probably the most important one). What's  
different for that configurations? The only thing I can think of is,  
that Patrick probably does not scale dy with cos(lat), so that there  
are elongated grid boxes near the poles. Could that be a problem  
numerically for the new code? I find it hard to believe, but it is  
true that my lat/lon-runs are all with nearly "quadratic" grid cells,  
and so are the CS-grid cells.

How can we continue with this? How can I help?

Martin