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<p>Over recent decades, the Southern Ocean’s westerly winds have intensified and shifted poleward, whereas the Antarctic Circumpolar Current (ACC) transport through the Drake Passage has remained stable. Here using satellite altimetry data, we define the interannual evolution of the ACC’s dynamical boundaries and identify a significant southward shift of its Northern Boundary (NB) over the past three decades, with the most rapid migration (up to 1.1° per decade) occurring in the Southeast Pacific. Ocean reanalysis confirms that volume transport within the ACC’s boundaries remains stable across the circumpolar Southern Ocean, despite a strengthening eastward flow concentrated near the migrating NB. The migrating NB redirects this intensified flow into the subtropical gyre, strengthening the Southern Ocean supergyre while maintaining stable ACC transport. These results resolve the paradox of stronger zonal flows coexisting with stable ACC transport, providing insight into changing Southern Ocean dynamics and their climate implications.</p>

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Southward shift of the Antarctic Circumpolar Current upstream of Drake Passage maintains a stable circumpolar transport

  • 期刊论文

  • 发表日期：

    2025年11月17日

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  • Chunhu Xie,
  • Jiuxin Shi,
  • Dapeng Li,
  • Yongming Sun,
  • Jindong Jiang,
  • Guy D. Williams

摘要

Over recent decades, the Southern Ocean’s westerly winds have intensified and shifted poleward, whereas the Antarctic Circumpolar Current (ACC) transport through the Drake Passage has remained stable. Here using satellite altimetry data, we define the interannual evolution of the ACC’s dynamical boundaries and identify a significant southward shift of its Northern Boundary (NB) over the past three decades, with the most rapid migration (up to 1.1° per decade) occurring in the Southeast Pacific. Ocean reanalysis confirms that volume transport within the ACC’s boundaries remains stable across the circumpolar Southern Ocean, despite a strengthening eastward flow concentrated near the migrating NB. The migrating NB redirects this intensified flow into the subtropical gyre, strengthening the Southern Ocean supergyre while maintaining stable ACC transport. These results resolve the paradox of stronger zonal flows coexisting with stable ACC transport, providing insight into changing Southern Ocean dynamics and their climate implications.