Peter Lemke

On the improvement of sea ice models for climate simulations: the Sea Ice Model Intercomparison Project

Experiments with dynamic-thermodynamic sea-ice models indicate a strong dependence of the net freezing rate, sea-ice transport and variability on dynamic model parameters. Although current dynamic-thermodynamic sea-ice models show relatively good agreement with observations, an optimization seems to be necessary, especially for the parameterizations of dynamic processes. Presently, only a few coupled climate models use dynamic-thermodynamic sea-ice models. In order to promote, by means of coordinated numerical experiments, the development of an optimal sea-ice model for climate research, the Sea Ice Ocean Modelling Panel of the Arctic Climate System Study (ACSYS, a project of the World Climate Research Programme) has initiated the Sea Ice Model Intercomparison Project (SIMIP). The first results from this model hierarchy approach are presented

Modelling Sea Ice Roughness in the Arctic

The variability of sea ice in the polar regions is an important factor in the climate system particularly because of its strong influence on heat and freshwater transports as well as momentum exchange between ocean and atmosphere. To describe these effects accurately ice conditions need to be known over long time periods and wide regions. Models are able to produce such data but need to be verified by observations (Lemke et al., 1998). One classical model variable which can be validated quite well with remote sensing methods (SMMR, SSM/I) is the ice coverage. Modelled ice drift can be verified by comparing observed and simulated drift trajectories (Kreyscher et al., 1998). Ice thickness observations, however, are only rarely available from drillings, sonar measurements and laser altimeter recordings.