CICE5.1.2 is the latest version of the Los Alamos Sea Ice Model, sometimes referred to as the Community Ice CodE [6]. It is the result of a community effort to develop a portable, efficient sea ice model that can be run coupled in a global climate model or uncoupled as a standalone ice model. CICE5 has been released as the sea ice component of the Community Earth System Model (CESM), a fully-coupled global climate model that provides simulations of Earth’s past, present, and future climate states. CICE5 in the CESM is supported on high- and low-resolution Greenland Pole and tripole grids, which are identical to those used by the Parallel Ocean Program (POP) ocean model. The high resolution version is best suited for simulating present-day and future climate scenarios while the low resolution option is used for paleoclimate simulations and debugging.

An uncoupled version of CICE5.1.2 is available separately:

https://github.com/CICE-Consortium/CICE-svn-trunk

This standalone CICE configuration provides a means of running the sea ice model independent of the other CESM components. It can read in atmospheric and ocean forcing, which eliminates the need for the flux coupler, and the atmosphere, land and ocean data models. It can be run on a reduced number of processors, or without MPI (Message Passing Interface) for researchers without access to these computer resources.

CICE is a dynamic-thermodynamic model that includes a subgrid-scale ice thickness distribution [6]. It uses the energy conserving thermodynamics of [10] or [2], has multiple layers in each thickness category, and accounts for the influences of brine pockets within the ice cover. The ice dynamics utilizes the elastic-viscous-plastic (EVP) rheology of [4]. Sea ice ridging has the options of [8] and [9] or the newer ridging scheme of [7]. A slab ocean mixed layer model is included. A Scientific Reference Guide [6] is available that contains more detailed information on the model physics. The physics available in the uncoupled ice model are identical to those in the ice model used in the fully coupled system.

This document uses the following text conventions: Variable names used in the code are typewritten. Subroutine are given in italic. File and directory names are in boldface.

What’s new in CICE5?

CICE5 is very similar in code structure to the previous version CICE4 and was released in March of 2015. CICE4 was an upgraded version of the Community Sea Ice Model, CSIM5, which was based on CICE3. The major changes are:

• The new mushy-layer thermodynamics (ktherm = 2) is the default [10].
• The new level melt pond scheme (tr_pond_lvl = .true.) is the default [5].
• The default number of ice layers is now 8 (previously 4).
• The default number of snow layers is now 3 (previously 1).
• The freezing point at the sea ice-ocean interface is now salinity dependent following [1].

The CICE source code used in the CESM is based on the Los Alamos Sea Ice Model CICE model version 5. The main source code is very similar in both versions, but the drivers are significantly different. If there are topics that are not covered in this CICE documentation, users are encouraged to look at the CICE documentation available at:

https://github.com/CICE-Consortium/CICE-svn-trunk