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CSIM5 is an upgraded version of CSIM4 which was released in October 2002.
The model physics are similar to that of CSIM4, but a majority of the code
has been rewritten for vectorization and to make the CSIM code similar
to that of CICE, the LANL sea ice model. The major changes are:
- A module for a new incremental remapping transport scheme was added
called ice_transport_remap.F. The MPDATA transport scheme,
formerly in ice_transport.F, was moved to ice_transport_mpdata.F.
Open water advection was added to the incremental remapping.
- A bug in ice_albedo.F was fixed to avoid negative albedos for thin,
bare, melting ice.
- A bug in ice_ocean.F was fixed to include fswthru in the calculation
of sea surface temperature.
- A salt flux calculation was added so the ice reference salinity could
be changed to a non-zero value.
- The sea ice momentum equation modified for the free drift regime. The
dynamics scheme treats areas with lower ice concentrations more accurately.
See (Hunke and Dukowicz(2003)).
- ice_coupling.F has been rewritten to be compatible with the latest
version of the CCSM coupler.
- An additional field Qref is calculated in atmo_boundary_layer
and passed to the coupler.
- Each ice thickness category has 4 thickness layers. Previously, the two thinnest
categories had two layers.
- A sub-cycling timestep ndyn_dt was added to the dynamics to get around
a model instability that would manifest itself in MPDATA.
- The snow and ice albedos, used for coupled model tuning, were moved to the
namelist to make modification easier.
- It is now possible to run CSIM as an uncoupled model. The module
ice_flux_in.F has been added to read in forcing data.
- Most modules have been modified to run efficiently on vector platforms.
Grid indices i, j are no longer passed into subroutines. Shorter
loops over ice categories and vertical layers have been moved outside
the longer loops over i and j. Directives have been placed
before certain loops to enforce vectorization.
- The thermodynamics modules from CSIM4, ice_tstm.F, ice_vthermo.F,
ice_therm_driver.F, and ice_dh.F, have been replaced by two new
modules ice_therm_vertical.F and ice_therm_itd.F. The caclulations
in ice_therm_vertical.F are done before the to_coupler call,
and those in ice_therm_itd.F are done after this call.
- New modules ice_exit.F and ice_work.F have been added that
contain code for aborting the model and globally accessible work arrays.
- The gx3v4 grid had been replaced by a new gx3v5 grid. The coupled model
produced a poor meridional overturning circulation (MOC) with the gx3v4 grid.
The new grid has points in different locations and has higher resolution
in the North Atlantic than gx3v4. The simulation with gx3v5 gives a better ice
thickness distribution and produces a better MOC.
- The prescribed ice model is not supported in this release.
- Most CSIM and CICE modules are very similar, except for the mechanical
redistribution modules.
The CSIM source code is based on the LOS Alamos sea ice model CICE model.
After a code merger with CICE was carried out to take advantage of the vector-
friendly code, the models are very similar. If there are some topics that
are not covered in the CSIM documentation, users are encouraged to look
at the CICE documentation (Hunke and Lipscomb(2004)). It is available at
http://climate.lanl.gov/Models/CICE/index.htm.
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