In the context of global warming, studies have shown that the Antarctic Ice Sheet (AIS) has been experiencing continuous mass loss, constituting a significant contribution to global sea level rise. Utilizing an optimized input-output method (IOM), this study evaluates the 2013–2022 mass balance of eight widely studied Antarctic drainage basins. By integrating RACMO2.4 surface mass balance (SMB), BedMachine ice thickness, and ITS_LIVE annual velocity, we quantify the sensitivity of mass balance estimates to flux gate (FG) location. Results demonstrate that while flux estimates along disparate radar tracks vary by <4%, discrepancies between grounding line and flight-line-based gates can reach 20%, highlighting the importance of flux gate selection. Regional assessments reveal a pronounced regime shift in East Antarctica: basins previously in near-balance or slight loss—including the Amery region and Basins 12–13—transitioned to significant mass accumulation post-2020, primarily driven by a sharp increase in SMB. In contrast, the Amundsen Sea sector in West Antarctica exhibited sustained and accelerating mass loss, with net deficits increasing from −163.9±15.3 Gt a^−1 (2013–2019) to −179.2±15.5 Gt a^−1 (2020–2022). This divergence stems from the dominance of anomalous precipitation in the East versus persistent ice flux acceleration in the West.