[MITgcm-support] Diagnosing internal ice stress with the seaice pkg

[Martin Losch]

Hi there,

(for the standard VP model) the internal stress is not a state variable that is carried from one timestep to the next. When seaice_diagnostics_state is called at the beginning of the time step, the internal stress is not properly defined but only computed later in seaice_dynsolver.F. That why most stress related diagnostics are “filled” at the end of seaice_dynsolver.F
For example, the principle components (diagonalized internal stress tensor) SIsig1 and SIsig2 are store there. The diagnostic ‘SIenpi  ‘ is also computed and saved for which the stress divergence is required. That’s probably the best place to add your new diagnostics.

Martin

> On 10. Oct 2024, at 06:11, Leng Hengling <hengling_leng at hotmail.com> wrote:
> 
> Dear MITgcm community,
> 
> I am studying sea ice-ocean interactions with the seaice pkg. Note that the internal ice stress (divergence) is calculated in seaice_calc_stressdiv.F but not defined as a diagnostic. I have tried adding it to the list of diagnostics, via calling DIAGNOSTICS_ADDTOLIST in seaice_diagnostics_init.F as:
> ...
>       CALL DIAGNOSTICS_ADDTOLIST( diagNum,
>      I     diagName, diagCode, diagUnits, diagTitle, diagMate, myThid )
>       diagName  = 'SIfx    '
>       diagTitle = 'SEAICE zonal internal stress'
>       diagUnits = 'N/m^2           '
>       diagCode  = 'UU      M1      '
>       diagMate  = diagNum + 2
>       CALL DIAGNOSTICS_ADDTOLIST( diagNum,
>      I     diagName, diagCode, diagUnits, diagTitle, diagMate, myThid )
>       diagName  = 'SIfy    '
>       diagTitle = 'SEAICE meridional internal stress'
>       diagUnits = 'N/m^2           '
>       diagCode  = 'VV      M1      '
>       diagMate  = diagNum
> ...
> and filling the fields in seaice_diagnostics_state.F:
> ...
>        CALL DIAGNOSTICS_FILL(
>      I stressDivergenceX, 'SIfx    ',0,1, 0,1,1,myThid)
>        CALL DIAGNOSTICS_FILL(
>      I stressDivergenceY, 'SIfy    ',0,1, 0,1,1,myThid)
> ...
> The model ran smoothly for 100 days without any errors. However, the ouput internal ice stress (both zonal and meridional components) is zero everywhere during the model period. Other output variables (sea ice concentration, thickness, velocity, etc) look fine. I would appreciate any insights or suggestions on what might be causing the internal ice stress to output as zero.
> 
> Best regards,
> 
> Hengling Leng
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