Sea-Ice Model Intercomparison Project (SIMIP)

Greg Flato (

The Sea Ice Model Intercomparison Project (SIMIP) is an international effort to develop an improved representation of sea ice in climate models. SIMIP is carried out by co-ordinated numerical experiments with contributions from several institutes in the framework of the Arctic Climate System Study (ACSYS) within the World Climate Research Programme (WCRP).

One of the main objectives of the ACSYS is to provide a valid scientific basis for the representation of the Arctic region in coupled atmosphere-ice-ocean models. The ACSYS implementation plan consists of four observational programs concerned with atmospheric, oceanic, sea ice and hydrological activities, and a modelling program which integrates these observations for improving the numerical representation of atmosphere, ocean, sea ice and hydrology.

The importance of the role of sea ice in the climate system calls for an improved representation of sea ice in global climate models. However, the interaction of atmosphere and ocean through the moving sea ice cover is one of the weak parts in current climate models. Therefore, SIMIP has been initiated within the ACSYS modelling programme to develop an improved representation of sea ice in climate simulations.

SIMIP2 is a joint initiative of the WCRP ACSYS/CliC Numerical Experimentation Group and the GEWEX Cloud System Study, Working Group on Polar Clouds. The main goal of SIMIP2 is to isolate, evaluate and improve the representation of vertical sea-ice thermodynamic processes in climate models.

At the initial planning meeting in Boulder, and subsequently at the NEG meeting in Fairbanks, a general outline of the intercomparison effort was laid out. In the following, a more concrete description of the experiment is provided, along with links to the fording, initialization and evaluation data, and a proposed list of default model parameters. At this point, only a basic experiment is described which, it is hoped, will be done by all participating modeling groups. A more comprehensive set of experiments and evaluation procedures, will arise from discussions with SIMIP2 participants. As discussed at the planning meeting, the idea would be that individual modeling groups would take the lead in focusing/coordinating efforts targeted a particular model parameterizations or numerical details.

The basic set of experiments will be strictly one-dimensional - i.e. a representation of a uniform slab of ice. Comparisons will be made to observations (by Dr. D. Perovich and colleagues) of the thermodynamic evolution of a multi-year ice floe during the SHEBA field experiment - very nearly a 1-D situation. The effects of leads and ice deformation will therefore not be included.

The basic experiment is an initial value problem, with the initial ice thickness, snow depth, temperature and salinity profiles specified from observations and corresponding to 31/October/1997. The initial conditions and a tentative list of proposed parameter values is provided in the file simip2_initialization_data.txt which can be viewed by clicking on the file name. Forcing data are also based on observations from the SHEBA experiment. Atmospheric forcing data were provided by Prof. J. Curry and colleagues, while ocean heat flux data was obtained from D. Perovich.

In addition to the basic experiment described above, the hope is that individual investigators or modeling groups will conduct a variety of experiments aimed at studying the role of individual processes, introducing more sophisticated parameterizations, evaluating the models' sensitivity to parameter values, etc. The desire is that such experiments should be coordinated in some way so as to avoid overlap and maximize the utility of this project.

Kreyscher, M., M. Harder, and P. Lemke: First results of the Sea Ice Model Intercomparison Project (SIMIP), Ann. Glaciol. 25, 8-11, 1997.

Lemke, P., W.D. Hibler, G.M. Flato, M. Harder, and M. Kreyscher: On the improvement of sea ice models for climate simulations: the Sea Ice Model Intercomparison Project, Ann. Glaciol. 25, 183-87, 1997.

Kreyscher, M., M. Harder, P. Lemke, and G. M. Flato: Results of the Sea Ice Model Intercomparison Project: Evaluation of sea ice rheology schemes for use in climate simulations. J. Geophys. Res. 105(C5), 11299 - 11320, 2000.

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Updated 4/24/03