The southern boundary (SB) of the Antarctic Circumpolar Current, the southernmost extent of the upper overturning circulation, regulates the Antarctic thermal conditions. The SB’s behavior remains unconstrained because it does not have a clear surface signature. Revisited hydrographic data from off East Antarctica indicate full-depth warming from 1996 to 2019, concurrent with an extensive poleward shift of the SB subsurface isotherms (>50 km), which is most prominent at 120°E off the Sabrina Coast. The SB shift is attributable to enhanced upper overturning circulation and a depth-independent frontal shift, generally accounting for 30 and 70%, respectively. Thirty years of oceanographic data corroborate the overall and localized poleward shifts that are likely controlled by continental slope topography. Numerical experiments successfully reproduce this locality and demonstrate its sensitivity to mesoscale processes and wind forcing. The poleward SB shift under intensified westerlies potentially induces multidecadal warming of Antarctic shelf water.

南极环极流的南部边界（SB）是上部翻转环流的最南端，调节南极的热条件。SB 的行为不受约束，因为它没有明确的表面特征。来自东南极洲海域的重新审视的水文数据表明，从 1996 年到 2019 年，全深度变暖，同时伴随着 SB 地下等温线（> 50 公里）的广泛向极移，这在萨布丽娜海岸外的 120°E 最为突出。SB 偏移归因于上部翻转环流增强和与深度无关的锋面偏移，通常分别占 30% 和 70%。三十年的海洋学数据证实了可能受大陆坡地形控制的整体和局部极地转移。数值实验成功地再现了这个地方，并证明了它对中尺度过程和风力的敏感性。在加强的西风下的极地 SB 移动可能会导致南极大陆架水的数十年变暖。