The CCSM4 Sea Ice Component and the Challenges and Rewards of Community Modeling

The Community Climate System Model version 4 (CCSM4) is due to be released in late 2009. The new sea ice component of CCSM4 is the Los Alamos Sea Ice Model (CICE) version 4. This sea ice component contains many new numerical and computational enhancements in addition to several new physics options. The computational changes allow for better scalability characteristics on massively parallel architectures. The new physics options include an explicit melt pond parameterization, a new shortwave radiative transfer scheme, aerosol deposition from the atmosphere and cycling within the sea ice, and the ability to efficiently carry multiple tracers. A basic description of the new model will be provided as well as the impacts of some of the new physics and computational options. This work was carried out with the input of community members in the Polar Climate Working Group (PCWG). Aspects of community modeling in general will also be discussed.