1.1. About CICE

CICE is a computationally efficient model for simulating the growth, melting, and movement of polar sea ice. Designed as one component of coupled atmosphere-ocean-land-ice global climate models, today’s CICE model is the outcome of more than two decades of effort led by scientists at Los Alamos National Laboratory. The current version of the model has been enhanced greatly through collaborations with members of the community.

CICE has several interacting components: a model of ice dynamics, which predicts the velocity field of the ice pack based on a model of the material strength of the ice; a transport model that describes advection of the areal concentration, ice volumes and other state variables; and a vertical physics package, called “Icepack”, which includes mechanical, thermodynamic, and biogeochemical models to compute thickness changes and the internal evolution of the hydrological ice-brine ecosystem. When coupled with other earth system model components, routines external to the CICE model prepare and execute data exchanges with an external “flux coupler”.

Icepack is implemented in CICE as a git submodule, and it is documented at https://cice-consortium-icepack.readthedocs.io/en/master/index.html. Development and testing of CICE and Icepack may be done together, but the repositories are independent. This document describes the remainder of the CICE model. The CICE code is available from https://github.com/CICE-Consortium/CICE.

The standard standalone CICE test configuration uses a 3 degree grid with atmospheric data from 1997, available at https://github.com/CICE-Consortium/CICE/wiki/CICE-Input-Data. A 1-degree configuration and data are also available, along with some idealized configurations. The data files are designed only for testing the code, not for use in production runs or as observational data. Please do not publish results based on these data sets.

The CICE model can run serially or in parallel, and the CICE software package includes tests for various configurations. MPI is used for message passing between processors, and OpenMP threading is available.

Major changes with each CICE release (https://github.com/CICE-Consortium/CICE/releases) will be detailed with the included release notes. Enhancements and bug fixes made to CICE since the last numbered release can be found on the CICE wiki (https://github.com/CICE-Consortium/CICE/wiki/CICE-Recent-changes). Please cite any use of the CICE code. More information can be found at Citing the CICE code.

This document uses the following text conventions: Variable names used in the code are typewritten. Subroutine names are given in italic. File and directory names are in boldface. A comprehensive Index of primary variables and parameters, including glossary of symbols with many of their values, appears at the end of this guide.