Observational assessment of Arctic Ocean sea ice motion, export, and thickness in CMIP3 climate simulations

We compare the CMIP3 model fields with observations of sea ice motion, export, extent, and thickness and analyze fields of sea level pressure and geostrophic wind of the Arctic Ocean. These variables play important roles in the distribution and annual balance of sea ice volume within the basin. While it is not expected that uninitialized simulations agree completely with observations, these assessments serve to summarize ensemble behavior, as baselines for measuring improvements, and to evaluate reliability of CMIP3 simulations (and potentially CMIP5) for projection of decline rates of Arctic sea ice coverage. We find the model-data differences and intermodel scatter in summarizing statistics are large. In a majority of model fields the mean high-pressure pattern in the southern Beaufort is significantly displaced toward the central Arctic Basin, leading to difficulties in reproducing the mean spatial patterns of sea ice circulation, thickness, and ice export. Thus, even though the CMIP3 multimodel data set agrees that increased greenhouse gas concentrations will result in reductions of Arctic sea ice area and volume, these comparisons suggest considerable uncertainties in the projected rates of sea ice decline.