Sea ice motion is a key component of the Antarctic sea ice–ocean system, influencing the redistribution, deformation, and export of sea ice. Strong circumpolar winds and ocean currents make Antarctic sea ice highly mobile, suggesting that the free-drift approximation may provide a useful first-order representation of its motion. In this study, we investigate the applicability of a free-drift sea ice motion model in the Southern Ocean without accounting for sea ice thickness dependence or internal ice stresses. The model represents sea ice velocity as the sum of a wind-driven component and an ocean-current term, governed by a wind–ice–ocean transfer coefficient and a wind turning angle. Daily buoy drift vectors are derived from irregularly sampled buoy positions using time-weighted averages of consecutive position-based velocity estimates. The wind–ice–ocean transfer coefficient, turning angle, and spatially varying ocean-current term are estimated iteratively using a least-squares minimization procedure. The calculated free drift is evaluated against buoy-derived daily drift vectors and further compared with NSIDC observational sea ice motion field. The comparison indicates that the free-drift model captures the broad-scale pattern of Antarctic sea ice drift across much of the Southern Ocean but exhibits substantial biases in coastal regions.

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