[MITgcm-support] seaice, LSR_ERROR, EVP

[Stanislav Martyanov]

Hello!

Recently I've found a conversation at github about possible problems with
the seaice package related to too large LSR_ERROR value set by default to
1.0e-4.
https://github.com/MITgcm/MITgcm/issues/171

In that topic it was suggested to use a smaller value of LSR_ERROR: 1.0e-5
or 1.0e-6, for convergence reasons. It was in 2019.

I wonder if a consensus has been achieved in the MITgcm community for now
about this tuning?

This question has arisen because I periodically get NaNs (I suspect it is
because of sea ice) in a high-res model with resolution O(1 km). It occurs
during the melting period in summer. Reducing the deltaT from 120 sec to 90
solved the problem, but it occurred again already with 90 sec in the next
month . Surprisingly, returning back to 120 sec allowed me to get through
it. I use the default LSR solver and suspect that the problem may be a bed
convergence of the sea ice model.

What can be a better remedy in this case:
1) continue to use LST solver but set LSR_ERROR  = 1.0e-5, everything else
is default. Should I also change SEAICEnonLinIterMax in this case from
default 2 to 10?
2) LSR is not good for high-res. Entirely switch to EVP solver
(SEAICEuseEVPrev or SEAICEuseEVPstar?), everything is default.

Thanks,
Stanislav Martyanov
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