Comparison of Satellite Observed and Model Simulated Sea Ice: Evaluation for the 4th IPCC Assessment

Three decades of satellite microwave monitoring of polar sea ice provides valuable information for the evaluation of the performance of climate models. The newest climate model simulations for the 4th IPCC Climate Change Assessment provide gridded monthly averaged sea ice concentration and sea ice thickness as output variables. Using the same criterion that has been used for the interpretation of satellite microwave observations we estimate sea ice extents defined as areas with sea ice concentrations greater than 15% and ice thicknesses greater than 6 cm. We also applied a new, statistical definition for the multi-year mean position of sea ice as an area where sea ice occurrence exceeds 50%. Using this definition we then retrieved sea ice extents from the modeled data and compared them with the satellite observations. We found that the modern generation of climate models simulates rather realistically the satellite observed geographical patterns, seasonal cycles, trends and interannual variability of polar sea ice in both hemispheres of the Earth.