This study investigated mechanisms for the intraseasonal variability of sea-ice concentration in the Antarctic, using Complex Empirical Orthogonal Function (CEOF) analysis of daily sea-ice concentration data during the period 1992 through 2001 derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I). The first CEOF mode clearly showed that the large amplitudes of sea-ice concentration occur in the marginal sea-ice zone of the western Antarctic. The first mode also revealed the existence of eastward propagating phases with a period of 10--20 days in the western Antarctic. Regression analysis of meridional wind velocity onto the temporal coefficient of the first CEOF mode showed that the spatial phase of the meridional wind velocity precedes that of sea-ice concentration by about 90 degrees, indicating that the maximum change of sea-ice concentration occurs at the maximum wind velocity. From data analyses of ice-drifting velocity and simple sea-ice model results, it is suggested that thermodynamical effects such as sea-ice production are likely to contribute dominantly to the intraseasonal variability of sea-ice concentration in the marginal sea-ice zone of the western Antarctic.