Ice cover data simulated by a coupled sea ice-ocean model of the North Atlantic and the Arctic Ocean are compared with satellite observations for the period 1978--2001. The capability of the model in reproducing the long-term mean state and the interseasonal variability is demonstrated. The main modes of variability of the satellite data and the simulation in the summer and winter half years are highly similar. Using NCEP/NCAR reanalysis data and the results from the sea ice-ocean model, we describe the relationship with atmospheric and oceanic variables for the first two modes of sea ice concentration variability in winter and in summer. The first winter mode shows a time-delayed response to the Arctic Oscillation due to advection of heat anomalies in the ocean. The second winter mode is dominated by an event in the late 1990s that is characterized by anomalously high pressure over the eastern Arctic. The first summer mode is strongly influenced by the Arctic Oscillation of the previous winter. The second summer mode is caused by anomalous air temperature in the Arctic. This mode shows a distinctive trend and is related to an ice extent reduction of about 4 ¿ 105 km2 over the 23 years of analysis.