WARNING: For now, the test case ICE_ADV2D only works if the logical "ll_neg" is set to FALSE in the routine icedyn_adv_umx.F90
                  (it is still unclear why)
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Purpose
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This demonstration case can serve different purposes:

1) The main one: study of the advection of a patch of ice in a bi-periodic channel with a slab ocean (i.e. 1 ocean layer)
              ==> set ln_icethd=false in namelist_ice_cfg

2) Secondary: study of ice thermodynamics in the same basin
              ==> set ln_icedyn=false in namelist_ice_cfg
              ==> eventually change usrdef_sbc.F90 in MY_SRC to fit your needs

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Experiments
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Two experiments can be configured:

a) A simple channel at 3km horizontal resolution (slightly variable => +- 10%)
              ==> in MY_SRC/usrdef_hgr.F90, uncomment the part "variable scale factors" and comment part "constant scale factors"

b) A simple channel at 3km horizontal resolution (constant scale factors)
              ==> in MY_SRC/usrdef_hgr.F90, comment the part "variable scale factors" and uncomment part "constant scale factors"

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How to run
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a) Compile and run the model once to get a mesh_mask.nc file with the following command:
../../../makenemo -r ICE_ADV2D -n ICE_ADV2D -m X64_ADA -j 4
mpirun ./nemo -np 1

b) Create the initial condition file for sea-ice (initice.nc) by running this python script: 
python ./make_INITICE.py

c) Run the model a second time
mpirun ./nemo -np 4

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What to look at
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In case of purpose 1, One can test
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a) the advection scheme: Ultimate-Macho (ln_adv_UMx=T) versus Prather (ln_adv_Pra=T)
   for a square (ice concentration) or a gaussian (ice volume)
      with either a constant velocity (ln_dynADV2D=T)
               or a constant ice-atm. stress, thus velocity is calculated by rheology (ln_dynRHGADV=T)
      with 1 or 5 ice categories (jpl=1 or 5).
         (note that ln_dynADV2D=T only works with jpl=1)

In case of purpose 2, one can test conservation of properties:
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b) ice should not change at all if surface fluxes = 0 and SST = freezing temperature

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Interpretation of the results (remarks)
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- Prather conserves the max values but also creates side lobes
- UM does not conserve the max but does not create side lobes
- The "unmoving" ice (if any) is due to ice rheology which states that ice mass below a certain thresold (1kg/m2) is considered to move at the ocean velocity (thus 0 m/s)