SUMMARY

• Main Authors: A. Mclaren, H. Banks, C. Durman, J. Gregory, T. Johns, A. Keen, J. Ridley, M. Roberts
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: ice pack; North Atlantic; North Atlantic oscillation; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.502.3942; http://icoads.noaa.gov/marcdat2/P_Alison_McLaren.pdf

HadGEM1 is a new coupled atmosphere-ocean climate model developed at the Met Office’s Hadley Centre, which contains a more sophisticated sea ice sub-model than that used in our previous climate model (HadCM3). A rapid increase in the variety, quality and quantity of observations in polar regions has led to a significant improvement in the understanding of sea-ice dynamic and thermodynamic processes and their representation in global climate models. We assess the simulation of sea ice in HadGEM1 against the latest available observations and against HadCM3. The evaluation is focused on the mean state of the key model variables of ice concentration, thickness and velocity. The model shows good agreement with the observations, except for ice speed, which is too fast. This could be either because the wind stress is too strong, or because the momentum coupling of the ice to the ocean is too weak. The variability of the ice forced by the North Atlantic Oscillation is also found to agree with observations. 1. MODEL AND EXPERIMENTAL DESIGN The sea-ice model in HadGEM1 resolves the sub-gridscale ice thickness distribution by dividing the ice pack into five thickness categories and one open water category (leads). The ice velocities are calculated using the Elastic-