[MITgcm-devel] inconsistencies with density conversion

[Ian Fenty]

Devel,

I will proceed as J-M proposes, first removing ICE2WATR from all the verification data.seaice files and then rewriting the saltFlux equation and, if possible, removing ICE2WATR altogether.  

I agree with the suggestion to take this as an opportunity to "use other meaningful defaults" and the use more transparent variable names.  

Specifically, the compile-time parameter SEAICE_SALINITY is misleading because it doesn't need to be defined for a nonzero ice salinity (e.g., SIsal0 specifies a constant ice salinity outside of SEAICE_SALINITY).  Also, Gael is quite right about the name of the run-time parameter SEAICE_salinity being misleading because it is not the seaice bulk salinity one might think, but actually a ratio.  Therefore, I propose changing SEAICE_SALINITY to SEAICE_VARIABLE_SALINITY (making a fixed seaice bulk salinity of SIsal0 the default) and using Gael's suggestion of changing SEAICE_salinity to SIsalFRAC.

Another example of using 'other meaningful defaults' is rhoConstFresh.  One of the reasons the sea ice salinity bug didn't pop up in budget-closing calculations is that the freshwater reference density is equal to seawater reference density by default.  From set_defaults.F:

C-- jmc : the default is to set rhoConstFresh to rhoConst (=rhoNil by default)
C         (so that the default produces same results as before)
c     rhoConstFresh       = 999.8 _d 0

And from ini_params.F:
      IF ( rhoConstFresh .EQ. UNSET_RL ) rhoConstFresh=rhoConst

Perhaps it is also time to allow the default reference freshwater density to be 999.8 kg/m^3 (the actual freshwater density at about 20 deg C).  If old results need to be reproduced, a different rhoConstFresh value can just be set in 'data'.    rhoConstFresh is used in the bulk formula equations so one would expect that using a more accurate number would reduce errors in EmPmR and buoyancy forcing. 

what do we think about that? 

-Ian

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