1. Introduction¶
1.1. What is CICE6?¶
This CICE User’s Guide accompanies the CESM3.0 User’s Guide, and is intended for those who would like to run CICE coupled, on a supported platform, and “out of the box”. It includes a quick start guide for downloading the CESM3 source code and input datasets, and information on how to configure, build and run the model. The supported configurations and scripts for building the fully coupled model are also described in the CESM3 User’s Guide:
http://www.cesm.ucar.edu/models/cesm3.0
The CICE User’s Guide is intended for users interested in making modifications to the ice model scripts or namelists within the CESM. Users interested in modifying the source code or using the standalone version should see the CICE Code Reference/Developer’s Guide [].
CICE6.6.3 is the latest version of the CICE Consortium sea ice model. 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. CICE6 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. CICE6 in the CESM is supported on different resolution Greenland Pole and tripole grids, which are identical to those used by the Parallel Ocean Program version 2 (POP2) and Modular Ocean Model version 6 (MOM6) ocean models. The standard resolution version is best suited for simulating present-day and future climate scenarios while the lower resolution option is used for paleoclimate simulations and debugging.
An uncoupled version of CICE6.6.3 is available separately:
https://github.com/CICE-Consortium/CICE
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 []. It uses the energy conserving thermodynamics of [] or [], 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 []. Sea ice ridging has the options of [] and [] or the newer ridging scheme of []. A slab ocean mixed layer model is included. A Scientific Reference Guide [] 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.
1.2. What’s new in CICE6?¶
CICE6 is structurally different from previous versions of CICE and has a separate vertical column package known as Icepack. Icepack can be run using its standalone driver and can be found here:
https://github.com/CICE-Consortium/Icepack
The major changes are:
The new sea level melt pond scheme (
tr_pond_lvl = .true.) is the default (Clemens-Sewall et al. in preparation).The one-step congelation growth of Plante et al. is the default.
A new floe-size distribution which allows for wave-sea ice interaction is on by default (Tremblay and Roach in review).
The CICE source code used in the CESM is based on the CICE Consortium Sea Ice Model version 6. 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 science, user, and developer guide documentation available at: