CICE

Overview

The Community Ice CodE (CICE) is a sea ice model that was first developed by Elizabeth Hunke as the Los Alamos Sea Ice Model. Its code base and capabilities have grown as a result of continued development by the broader geosciences community, an effort organized by the CICE Consortium.

Dr. Cecilia Bitz implemented support for the CICE model (as part of CESM) in DART. The DART model interface was developed to work with CICE’s dynamical core on an Arakawa B-grid. [1] When CICE is coupled to POP in CESM, the ocean and sea ice grids are identical.

According to the CICE manual:

The spatial discretization is specialized for a generalized orthogonal B-grid as in Murray (1996) [2] or Smith et al. (1995). [3] The ice and snow area, volume and energy are given at the center of the cell, velocity is defined at the corners, and the internal ice stress tensor takes four different values within a grid cell; bilinear approximations are used for the stress tensor and the ice velocity across the cell, as described in Hunke and Dukowicz (2002). [4] This tends to avoid the grid decoupling problems associated with the B-grid.

Hence, in the DART interface:

• U, V are at grid cell corners

• T, h, hs, and the various scalar quantities are at grid cell centers

CICE is under development to work with other grids, such as the unstructured grid in MPAS and the C-grid in MOM.

Namelist

&model_nml
   assimilation_period_days     = 1
   assimilation_period_seconds  = 0
   model_perturbation_amplitude = 0.00002
   update_dry_cell_walls        = .false.
   binary_grid_file_format      = 'big_endian'
   debug                        = 1
   model_state_variables        = 'aicen', 'QTY_SEAICE_CONCENTR',   'UPDATE',
                                  'vicen', 'QTY_SEAICE_VOLUME',     'UPDATE',
                                  ...
                                  'vsnon', 'QTY_SEAICE_SNOWVOLUME', 'UPDATE',
/

Description of each namelist entry

Item	Type	Description
time_step_days	integer	Number of days for dimensional timestep, mapped to deltat.
time_step_seconds	integer	Number of seconds for dimensional timestep, mapped to deltat.
model_perturbation_amplitude	real(r8)	Perturbation amplitude
update_dry_cell_walls	logical	Currently does nothing. Additional code is needed to detect the cells which are wet but within 1 cell of the bottom/sides/etc.
binary_grid_file_format	character(64)	Byte sequence for the binary grid. Valid values are native, big_endian & little_endian.
debug	integer	When set to 0, debug statements are not printed. Higher numbers mean more debug reporting.
model_state_variables	character(*)	List of model state variables

References

[1]

Arakawa, Akio and Vivian R. Lamb, 1977: Computational Design of the Basic Dynamical Processes of the UCLA General Circulation Model. Methods in Computational Physics: Advances in Research and Applications, 17, 173–265, doi:10.1016/B978-0-12-460817-7.50009-4

[2]

Murray, Ross J., 1996: Explicit Generation of Orthogonal Grids for Ocean Models. Journal of Computational Physics, 126, 251–273, doi:10.1006/jcph.1996.0136

[3]

Smith, Richard D., Samuel Kortas and Bertrand Meltz, 1995: Curvilinear Coordinates for Global Ocean Models. Technical Report LA-UR95-1146, Los Alamos National Laboratory.

[4]

Hunke, Elizabeth C., and John K. Dukowicz, 2002: The Elastic–Viscous–Plastic Sea Ice Dynamics Model in General Orthogonal Curvilinear Coordinates on a Sphere—Incorporation of Metric Terms. Monthly Weather Review, 130, 1848–1865, doi:10.1175/1520-0493(2002)130%3C1848:TEVPSI%3E2.0.CO;2