IMPORTANT: Condolidation and refactoring due to the sea-ice model

[arango]

We need to consolidate the changes to ROMS due to the refactoring and development of the sea-ice model. Originally written by Paul Budgell (2005), maintained by Kate Hedstrom, and updated by Scott Durski (Durski and Kurapov, 2019, 2020). It is primarily based on Mellor and Kantha (1989) and Parkinson and Washington (1979).

The sea-ice model has been cleaned, documented, and redesigned to facilitate adjoint-based applications in the future. It has only two state variables, Fi and Si, that can be expanded. The original code has at least 39 arrays.

! Define derived-type structure ice model state and internal arrays.
 
     TYPE T_ICE
        real(r8), pointer :: Fi(:,:,:)               ! [i,j,1:nIceF]
        real(r8), pointer :: Si(:,:,:,:)             ! [i,j,1:2,1:nIceS]
      END TYPE T_ICENgrids
      TYPE (T_ICE), allocatable :: ICE(:)            ! [Ngrids]

! Ice model state prognostic variables indices.

      integer, parameter :: nIceS = 15  ! number of ice state variables
      integer :: iSice(nIceS)           ! state I/O indices
      integer, parameter :: isAice =  1 ! ice concentration
      integer, parameter :: isHice =  2 ! ice thickness
      integer, parameter :: isHmel =  3 ! melt water thickness on ice
      integer, parameter :: isHsno =  4 ! snow thickness
      integer, parameter :: isIage =  5 ! ice age
      integer, parameter :: isISxx =  6 ! internal ice xx-stress
      integer, parameter :: isISxy =  7 ! internal ice xy-stress
      integer, parameter :: isISyy =  8 ! internal ice yy-stress
      integer, parameter :: isTice =  9 ! ice interior temperature
      integer, parameter :: isUice = 10 ! ice U-velocity
      integer, parameter :: isVice = 11 ! ice V-velocity
      integer, parameter :: isEnth = 12 ! ice/brine enthalpy
      integer, parameter :: isHage = 13 ! thickness linked with ice age
      integer, parameter :: isUevp = 14 ! EVP ice U-velocity
      integer, parameter :: isVevp = 15 ! EVP ice V-velocity

! Ice model internal variables indices.

      integer, parameter :: nIceF = 24  ! number of ice field variables
      integer :: iFice(nIceF)           ! internal fields I/O indices
      integer, parameter :: icAIus =  1 ! surface Air-Ice U-stress
      integer, parameter :: icAIvs =  2 ! surface Air-Ice V-stress
      integer, parameter :: icBvis =  3 ! ice bulk viscosity
      integer, parameter :: icHsse =  4 ! sea surface elevation
      integer, parameter :: icIOfv =  5 ! Ice-Ocean friction velocity
      integer, parameter :: icIOmf =  6 ! Ice-Ocean mass flux
      integer, parameter :: icIOmt =  7 ! Ice-Ocean momentum transfer
      integer, parameter :: icIOvs =  8 ! Ice-Ocean velocity shear
      integer, parameter :: icIsst =  9 ! ice/snow surface temperature
      integer, parameter :: icPgrd = 10 ! gridded ice strength
      integer, parameter :: icPice = 11 ! ice pressure or strength
      integer, parameter :: icQcon = 12 ! ice/snow heat conductivity
      integer, parameter :: icQrhs = 13 ! RHS heat flux over ice/snow
      integer, parameter :: icSvis = 14 ! ice shear viscosity
      integer, parameter :: icS0mk = 15 ! molecular sublayer salinity
      integer, parameter :: icT0mk = 16 ! molecular sublayer temperature
      integer, parameter :: icUavg = 17 ! average mixed-layer U-velocity
      integer, parameter :: icVavg = 18 ! average mixed-layer V-velocity
      integer, parameter :: icWdiv = 19 ! ice divergence rate
      integer, parameter :: icW_ai = 20 ! melt/freeze rate at Air/Ice
      integer, parameter :: icW_ao = 21 ! melt/freeze rate at Air/Ocean
      integer, parameter :: icW_fr = 22 ! ice accretion rate by frazil
      integer, parameter :: icW_io = 23 ! melt/freeze rate at Ice/Ocean
      integer, parameter :: icW_ro = 24 ! melt/freeze rate runoff

The sea-ice model kernel is located in the ROMS/Nonlinear/SeaIce subdirectory and will be found soon in the GitHub repository feature/seaice branch. It needs testing. We hope the beta testers with some expertise in sea-ice modeling help us with testing and further development.

The data input data management is still missing but can easily be added in get_data.F and set_data.F. It was postponed until we worked on the required atmospheric fields for coupling using the ESMF/NUOPC infrastructure.

Notice that the sub-directory SeaIce containing the sea-ice model is not released yet. I am only releasing the modifications needed in the ROMS infrastructure. Our strategy is to isolate model kernels for flexibility, as we have done with Biology, Sediment, and WEC in the Nonlinear kernel sub-directory.