Ocean Science www.ocean-sci.net 1812-0784 1812-0792 3 2 2007 10.5194/os-3-321-2007 http://www.ocean-sci.net/3/321/2007/ http://www.ocean-sci.net/3/321/2007/os-3-321-2007.html http://www.ocean-sci.net/3/321/2007/os-3-321-2007.pdf 321 335 2007-06-08 On the assimilation of ice velocity and concentration data into large-scale sea ice models V. Dulière duliere@astr.ucl.ac.be T. Fichefet Université Catholique de Louvain, Institut d'Astronomie et de Géophysique Georges Lemaître, Louvain-la-Neuve, Belgium Data assimilation into sea ice models designed for climate studies has started about 15 years ago. In most of the studies conducted so far, it is assumed that the improvement brought by the assimilation is straightforward. However, some studies suggest this might not be true. In order to elucidate this question and to find an appropriate way to further assimilate sea ice concentration and velocity observations into a global sea ice-ocean model, we analyze here results from a number of twin experiments (i.e. experiments in which the assimilated data are model outputs) carried out with a simplified model of the Arctic sea ice pack. Our objective is to determine to what degree the assimilation of ice velocity and/or concentration data improves the global performance of the model and, more specifically, reduces the error in the computed ice thickness. A simple optimal interpolation scheme is used, and outputs from a control run and from perturbed experiments without and with data assimilation are thoroughly compared. Our results indicate that, under certain conditions depending on the assimilation weights and the type of model error, the assimilation of ice velocity data enhances the model performance. 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