The impact of the lower-boundary forcing over ocean grid points, namely of sea surface temperature (SST), sea ice fraction, and sea ice thickness, on the mean atmospheric simulation is investigated with an Arctic atmospheric regional climate model. The assessment shows that the sea ice/SST forcing has an impact on the atmospheric simulations. The near-surface air temperature response shows a strong, seasonally dependent sensitivity to sea ice changes. The response is small in summer but significant in winter, and changes in the marginal ice zone have the largest impact on the atmosphere. During winter, the realistic representation of the marginal sea ice zone is important as it contributes to the simulation of regional atmospheric circulation patterns and temperature profiles. Changes in sea ice thickness of the western Arctic lower boundary indicate an Arctic-wide response in the large-scale circulation and seem to have an impact on the troposphere-stratosphere coupling. During summer the direct thermodynamic effect of sea ice changes is small, while the dynamic response is still of importance but smaller than in winter. Copyright 2006 by the American Geophysical Union.