[MITgcm-support] seaice_saltFrac and SEAICE_VARIABLE_SALINITY

[Martin Losch]

Hi Dan,

I’m afraid, that the sea ice thermodynamics are really not very well documented.

I usually spend time reading the code of seaice_growth.F if I need to find out how a particular parameter works. I think you are right about SEAICE_saltFrac only being used when SEAICE_VARIABLE_SALINITY is defined. The parameter determines how much salt is retained in sea ice, when ice forms. This salt (variable HSALT) is advected conservatively and released when sea ice melts.

In contrast seaice_salt0 is only used when SEAICE_VARIABLE_SALINITY is undefined.

Then there are the sea ice tracers where salinity can also be used as a tracer. I think that this code is more consistent than the SEAICE_VARIABLE_SALINITY code but there’s even less documentation.

Martin


> On 3. Aug 2022, at 15:19, Daniel Goldberg <dan.goldberg at ed.ac.uk> wrote:
> 
> Hello All
> 
> I am interested in varying salt retention with pkg/seaice, and am curious about the parameter SEAICE_saltFrac. Firstly, it seems from looking at seaice_growth.F that setting the parameter has no impact unless #define SEAICE_VARIABLE_SALINITY is set -- is this the case? (it is not something i can determine from readthedocs.)
> 
> Secondly, I just want to make sure that the parameter does what I think it does. Readthedocs states it is the "salinity newly formed ice (as fraction of ocean surface salinity)" but does not give further detail. Is this salinity advected conservatively, and accounted for in the surface salinity tendency (or freshwater flux, depending on configuration) when sea ice forms, and also when sea ice melts?
> 
> Also -- the parameter seaice_salt0 exists -- but is not mentioned in Readthedocs. Is it now deprecated?
> 
> Many thanks for your time!
> Dan
> 
> -- 
> Daniel Goldberg, PhD (he/him)
> Reader in Glaciology
> School of Geosciences, University of Edinburgh
> Geography Building, Drummond Street, Edinburgh EH8 9XP
> 
> 
> em: dan.goldberg at ed.ac.uk <mailto:dan.goldberg at ed.ac.uk>
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