There are various ice rheology implemented in Elmer/Ice.

This is a SIF entry for Glen's flow law (after: Cuffey and Paterson, 2010. The Physics of Glaciers. Pergamon Press, Oxford etc., 4th edt.) using the built-in Elmer viscosity law (recommended, as it is evaluated at Gauss-points):

! Define some constant at the top of the SIF file (using LUA)
! Define the parameter in MPa - a - m
#yearinsec = 365.25*24*60*60
#rhoi = 900.0/(1.0e6*yearinsec^2)
#rhow = 1000.0/(1.0e6*yearinsec^2)
#gravity = -9.81*yearinsec^2

! Prefactor from Cuffey and Paterson (2010) in MPa^{-3} a^{-1}
#A1 = 2.89165e-13*yearinsec*1.0e18
#A2 = 2.42736e-02*yearinsec*1.0e18
#Q1 = 60.0e3
#Q2 = 115.0e3


Material 1
  Density = Real #rhoi
  
  ! Glen's flow law (using Glen)
  !----------------
  ! viscosity stuff
  !----------------

  Viscosity Model = String "glen"
  Viscosity = 1.0 ! Dummy but avoid warning output
  Glen Exponent = Real 3.0

  Limit Temperature = Real -10.0
  Rate Factor 1 = Real #A1
  Rate Factor 2 = Real #A2
  Activation Energy 1 = Real #Q1
  Activation Energy 2 = Real #Q2
  Glen Enhancement Factor = Real 1.0
  Critical Shear Rate = Real 1.0e-10

  Constant Temperature = Real -1.0 
End

With the values of the activation energies above, the gas constant has to be given in SI units, i.e., 8.314 J/(mol K). If you do not provide the following section

Constants
  Gas Constant = Real 8.314 !Joule/mol x  K 
End

the suggested SI default value is used automatically.

This Material section gives the law with a fixed rate factor:

Material 1
! Glen's flow law (using Glen)
!-----------------
! viscosity stuff
!----------------
  Viscosity Model = String "Glen"
  Viscosity = Real 1.0 ! To avoid warning output 
  Glen Exponent = Real 3.0
  Critical Shear Rate = Real 1.0e-10
  ! gives a fixed value in MPa^-3a^-1
  Set Arrhenius Factor = Logical True
  Arrhenius Factor = Real $1.0E-16 * 1.0E18
  Glen Enhancement Factor = Real 1.0
End

This is a SIF entry for Glen's flow law (after: Paterson, W. S. B. 1994. The Physics of Glaciers. Pergamon Press, Oxford etc., 3rd edt.) using the old power law (MATC function) (Not recommended, use build-in implementation of Glen's flow law - first solution on this page):

!! Glen's flow law (using power law)
!-----------------
$ function glen(Th) {\
   EF = 1.0;\
   AF = getArrheniusFactor(Th);\
   _glen = (2.0*EF*AF)^(-1.0/3.0);\
}

!! Arrhenius factor needed by glen
!! (in SI units)
!---------------------------------
$ function getArrheniusFactor(Th){ \
    if (Th<-10) {_getArrheniusFactor=3.985E-13 * exp( -60.0E03/(8.314 * (273.15 + Th)));}\
    else {\
       if (Th>0) _getArrheniusFactor=1.916E03 * exp( -139.0E03/(8.314 *  (273.15)));\
            else _getArrheniusFactor=1.916E03 * exp( -139.0E03/(8.314 *  (273.15 + Th)));}\
}

Its call within the Material section looks as follows:

!! call in SI units
Viscosity = Variable Temperature
  Real MATC "glen(tx)"
Critical Shear Rate = 1.0E-09

!! call in scaled units (m-MPa-years)
Viscosity = Variable Temperature
       Real MATC "glen(tx)*31556926.0^(-1.0/3.0)*1.0E-06"
Critical Shear Rate = $1.0E-09 * 31556926.0

!! this holds for both unit systems
Viscosity Model = String "power law"
Viscosity Exponent = $1.0/3.0

Strictly speaking the homologous temperature should be used as input to the Glen function above, but if homologous temperature is not readily available then using temperature (in Celsius) is a good approximation (which deteriorates for thicker glaciers/ice sheets).

Be very careful in choosing the correct value of the critical shear rate. A too high value leads to a way too soft ice at low shear rates, a too low value can have consequences on the numerical stability (singularity of shear thinning fluid at zero shear).

An example using Glen's flow law can be found in [ELMER_TRUNK]/elmerice/examples/Test_Glen_2D..

The flow of anisotropic ice can be modelled using the General Orthotropic Flow Law (GOLF) from Gillet-Chaulet et al. (2005) implemented in the AIFlow Solver or the Continuum-mechanical Anisotropic Flow model based on an anisotropic Flow Enhancement factor (CAFFE, Seddik et al., 2008) implemented in the User Function CAFFE. The evolution of the fabric as a function of stress and velocity gradient for both anisotropic models can be computed using the Fabric Solver.

The rheology of porous ice, namely firn and snow, is represented using the porous law proposed by Gagliardini and Meyssonnier (1997). This law is implemented in Elmer/Ice in the Porous Solver. Density evolution can be computed from the mass conservation equation.

Damage is accounted for through the enhancement factor. Damage evolution is modelled following the approach in Krug et al. (2014). More information can be found here.