[MITgcm-support] sea ice volume conservation

[Martin Losch]

HI Gregory,

HEFF is already the seaice volume per grid cell area (in m), i.e. (mean ice thickness of ice covered area) * AREA. 
Compared to many other models that I know HEFF is a misleading name for the variable (effective thickness is often used for HEFF/AREA, i.e. the mean thickness of the ice covered area, so the total opposite of what it means in the MITgcm), but this has historical reasons, I guess. I think the all models based on Bill Hibler’s original code use this variable name.

So volume in m^3 is HEFF*RAC (RAC is the grid cell area). See if that solves your problem.

M.

> On 25 Aug 2016, at 23:04, Georgy Manucharayan <gmanuch at caltech.edu> wrote:
> 
> Hi all,
> 
> I am running MITGCM with the sea ice package in a configuration that has thermodynamics turned off (i.e. using #define DISABLE_SEAICE_GROWTH in CPP_OPTIONS.h). The domain is closed. While the sea  ice is being advected by the ocean currents only, its total volume (diagnosed as HEFF*AREA) is not conserved. In fact, the volume is quickly decreasing (by ~20% within the first few days). This is problematic for my analysis.
> 
> I have confirmed through diagnostics that the thickness changes due to ice-ocean and atm-ice fluxes are indeed absent (i.e. 'SIatmQnt','SIatmFW','SIfwSubl','SIdHbOCN','SIdHbATC' are all zeros). Surface temperature of the ocean also does not change, implying that the ice is not melting. Are there any other possible fluxes that might lead to ice loss when thermodynamics is off?
> 
> Can the ice volume loss be related to the numerical advection schemes that do not conserve volume when independently advecting area and thickness? I have tested SEAICEadvScheme = 77 and 7 which give nearly identical results, while scheme 2 is unstable (too much ice growth). Below are some of the relevant parameters from my data.seaice file.
> 
> &SEAICE_PARM01
>  SEAICE_no_slip     = .TRUE.,
>  SEAICE_drag        = 0.001,
>  SEAICE_tempFrz0    = -1.96,
>  SEAICE_dTempFrz_dS =0,
>  SEAICE_multDim     = 1,
>  SEAICE_mcPheeTaper = 0.92,
> #- seaice I/O params:
>  SEAICEwriteState   = .TRUE.,
> 
> &SEAICE_PARM03
>  SItrNumInUse       = 2,
>  SItrName(1)        = 'age',
>  SItrMate(1)        = 'AREA',
>  SItrUnit(1)        = 's',
>  SItrName(2)        = 'one',
> 
> 
> Any suggestions are highly appreciated,
> Georgy
> 
> -- 
> Georgy Manucharyan,
> Stanback Postdoctoral Scholar,
> Environmental Science and Engineering,
> California Institute of Technology,
> MS 131-24, 1200 California Blvd,
> Pasadena, CA, 91125
> 
> Office: L+R, Room 226; Tel: (626) 395-8715
> Web: http://www.its.caltech.edu/~gmanuch
> 
> 
> 
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