/[MITgcm]/manual/s_phys_pkgs/text/seaice.tex
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revision 1.14 by mlosch, Mon Feb 28 16:05:07 2011 UTC revision 1.15 by mlosch, Mon Feb 28 16:27:56 2011 UTC
# Line 689  thermodynamic model --- \citet{semtner84 Line 689  thermodynamic model --- \citet{semtner84
689  phase (one month lead) and amplitude ($\approx$50\%\,overestimate) in  phase (one month lead) and amplitude ($\approx$50\%\,overestimate) in
690  such models --- so that today many sea ice models employ more complex  such models --- so that today many sea ice models employ more complex
691  thermodynamics. The MITgcm sea ice model provides the option to use  thermodynamics. The MITgcm sea ice model provides the option to use
692  the thermodynamics model of \citet{win00}, which in turn is based  the thermodynamics model of \citet{win00}, which in turn is based on
693  on the 3-layer model of \citet{sem76} and which treats brine  the 3-layer model of \citet{sem76} and which treats brine content by
694  content by means of enthalpy conservation. This scheme requires  means of enthalpy conservation; the corresponding package
695  additional state variables, namely the enthalpy of the two ice layers  \code{thsice} is described in section~\ref{sec:pkg:thsice}. This
696  (instead of effective ice salinity), to be advected by ice velocities.  scheme requires additional state variables, namely the enthalpy of the
697    two ice layers (instead of effective ice salinity), to be advected by
698    ice velocities.
699  %  %
700  The internal sea ice temperature is inferred from ice enthalpy.  To  The internal sea ice temperature is inferred from ice enthalpy.  To
701  avoid unphysical (negative) values for ice thickness and  avoid unphysical (negative) values for ice thickness and
702  concentration, a positive 2nd-order advection scheme with a SuperBee  concentration, a positive 2nd-order advection scheme with a SuperBee
703  flux limiter \citep{roe:85} is used in this study to advect all  flux limiter \citep{roe:85} is used in this study to advect all
704  sea-ice-related quantities of the \citet{win00} thermodynamic  sea-ice-related quantities of the \citet{win00} thermodynamic model.
705  model.  Because of the non-linearity of the advection scheme, care  Because of the non-linearity of the advection scheme, care must be
706  must be taken in advecting these quantities: when simply using ice  taken in advecting these quantities: when simply using ice velocity to
707  velocity to advect enthalpy, the total energy (i.e., the volume  advect enthalpy, the total energy (i.e., the volume integral of
708  integral of enthalpy) is not conserved. Alternatively, one can advect  enthalpy) is not conserved. Alternatively, one can advect the energy
709  the energy content (i.e., product of ice-volume and enthalpy) but then  content (i.e., product of ice-volume and enthalpy) but then false
710  false enthalpy extrema can occur, which then leads to unrealistic ice  enthalpy extrema can occur, which then leads to unrealistic ice
711  temperature.  In the currently implemented solution, the sea-ice mass  temperature.  In the currently implemented solution, the sea-ice mass
712  flux is used to advect the enthalpy in order to ensure conservation of  flux is used to advect the enthalpy in order to ensure conservation of
713  enthalpy and to prevent false enthalpy extrema.  enthalpy and to prevent false enthalpy extrema. %
714    In order to use the \code{seaice}-package with the more sophisticated
715    thermodynamics of \code{thsice}, compile both packages and turn both
716    package on in \code{data.pkg}; see an example in
717    \code{global\_ocean.cs32x15/input.icedyn}.
718    
719  %----------------------------------------------------------------------  %----------------------------------------------------------------------
720    

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