[MITgcm-support] problem in pkg/seaice

[Martin Losch]

Hi Tom,

the fact that it happens at the bottom of the column makes me think  
that it has to do with numerical stability in the ocean (not the  
seaice code, although the seaice model may trigger this). May it's  
just a matter of time step? After all you are hitting the system hard  
with 40m/s winds.

What's your mixing scheme?

the seaice package has evolved a lot since checkpoint57y_post; in  
particular, I have moved it to a C-grid discretization which makes  
the wind stress coupling easier. In your version the windstress that  
the ocean feels is not affected by the ice at all. Maybe it's worth  
trying this with a more recent version of the code.

Martin
On 22 May 2007, at 16:21, Thomas Haine wrote:

> Hi,
>
> I've been having a problem in pkg/seaice that causes a sudden  
> divergence
> of T & S adjacent to the ice edge under strong winds:
>
> The resolution is 2km horizontal with 2m thick upper level. I've run
> fine with NCEP 6-hrly forcing (atmospheric state) and have now  
> switched
> to a 1/4 deg-resolution 6-hrly satellite-derived 10m wind product  
> (only
> change). This has caused the trouble. At the time of the crash the  
> wind
> speed is ~40m/s with strong gradients (an intense polar low - the
> numbers are realistic!).
>
> Code is: checkpoint57y_post.
>
> Symptom: Both S & T go wild (+/- 10^6) in 2 cells at the sea floor  
> in a
> single step. The ~80m deep column is adjacent to ice with thickness of
> ~40cm.
>
> Switching off pkg/seaice allows the code to carry on fine for at least
> several more steps.
>
> Switching off seaice dynamics makes only small changes (survives 1  
> more
> step, symptoms the same).
>
> So, it looks to me like this is a seaice thermodynamics issue.
>
> Any suggestions?
>
> Thanks, Tom.
> -- 
> --------------------------------------------
>  Thomas W. N. Haine
>
>  Professor of Physical Oceanography,
>  Department of Earth & Planetary Sciences,
>  329 Olin Hall, The Johns Hopkins University,
>  Baltimore, MD 21218, USA.
>  Tel : 410 516 7048,   Fax : 410 516 7933
>  Thomas.Haine at jhu.edu
>  http://www.jhu.edu/~eps/faculty/haine
> --------------------------------------------
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