Improved simulation of feedbacks between atmosphere and sea ice over the Arctic Ocean in a coupled regional climate model

Modeling sea ice in a realistic manner is still a great challenge, in particular with respect to the minimum ice extent at the end of the summer. Modified descriptions of ice growth, snow and ice albedo, and snow cover on ice have been incorporated into the coupled regional atmosphere–ocean–ice model HIRHAM–NAOSIM, and a series of sensitivity experiments has been performed in order to assess the need for more sophisticated parameterizations of these processes in coupled regional and global models. It is found that the simulation of Arctic summer sea ice responds very sensitively to the parameterization of snow and ice albedo but also to the treatment of ice growth. The parameterization of the snow cover fraction on ice plays an important role in the onset of summertime ice melt. This has crucial impact on summer ice decay when more sophisticated schemes for ice growth and ice albedo are used. It is shown that in case of using a harmonized combination of more sophisticated parameterizations the simulation of the summer minimum in ice extent can be considerably improved due to a more realistic representation of the interactions between atmosphere and sea ice.