26 August 2014

Sea Ice Volume and Age: Sensitivity to physical parameterizations and thickness resolution in the CICE sea ice model


As the complexity of sea ice models escalates with the inclusion of ever more detailed processes, the need for more and better sea ice measurements from the field and laboratory compounds. The addition of a new data type, sea ice age, combined with a detailed comparison of fundamental processes sheds light on physical and model sensitivities to more complex processes and their controlling parameters. Thermodynamic processes can have opposing effects on ice age and volume; for instance, growth of new ice increases the volume while decreasing the age of the pack. Therefore, age data provides additional information useful for differentiating among process parameterization effects and sensitivities to other model parameters. This study investigates the effect of a new anisotropic rheology and variable drag parameterization on Arctic sea ice volume and age simulations, along with the effects of several pre-existing model options and resolution of the ice thickness distribution.  By increasing shear stress between floes, the anisotropic rheology slows the ice motion, producing a thicker, older ice pack. The inclusion of variable drag coefficients, which depend on modeled roughness elements such as deformed ice and melt pond edges, leads to thinner ice and a more realistic simulation of sea ice age.  Several feedback processes act to enhance differences among the runs.  Resolution of thicker ice types is crucial for proper modeling of sea ice volume, because the volume of ice in the thicker ice categories determines the total ice volume.


This work was performed within the Climate, Ocean and Sea Ice Modeling (COSIM) program at Los Alamos National Laboratory, as a contribution to the Sea Ice Prediction Network with funding from the Regional and Global Climate Modeling Program of the U. S. Department of Energy, Office of Science, Biological and Environmental Research Division. Los Alamos National Laboratory is operated by the National Nuclear Security Administration of the U.S. Department of Energy under Contract No. DE-AC52-06NA25396.