What's new in CICE4?

CICE4 is an upgraded version of the Community Sea Ice Model, CSIM5, which was based on CICE3, and was released in June 2004. The model physics are similar to that of CSIM5, but it was decided to move to CICE, the LANL sea ice model for practical reasons. The major changes are:

• The incremental remapping transport scheme is now the default and is available in the modules called ice_transport_driver.F90 and ice_transport_remap.F90. The MPDATA transport scheme, is no longer supported in CICE4. The upwind advection scheme is the only additional option and is contained in ice_transport_driver.F90.

• The standalone ice model is now only available through Los Alamos National Laboratory.

• Several physics options have been shifted around into other or new modules. For example, most of ice_albedo.F90 is now in ice_shortwave.F90. The new module contains all of the shortwave radiative transfer plus the basic albedo calculations.

• The mechanical redistribution scheme has been changed significantly and is available in ice_mechred.F90.

• A new drivers area has been created for modules that are specific to the CCSM as opposed to the standalone CICE model. The new CCSM drivers are contained in the cpl_mct and cpl_share subdirectories. The ESMF driver (cpl_esmf) is still under development. The source subdirectory now contains driver independent source code for the most part.

• A new bld subdirectory has been introduced which contains CCSM specific build and configure scripts. These scripts handle the namelist generation, defaults, and configuration details.

The CICE source code is based on the Los Alamos sea ice model CICE model version 4. The main source code is very similar in both versions, but the drivers are significantly different. If there are some topics that are not covered in the CICE documentation, users are encouraged to look at the CICE documentation (Hunke and Lipscomb(2008)). It is available at Los Alamos National Laboratory at:

http://oceans11.lanl.gov/trac/CICE. http://oceans11.lanl.gov/trac/CICE.