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<p>The Antarctic sea ice Dipole (ADP), the leading mode of sea ice variability in the Southern Ocean in austral spring and summer, has been found to be negatively correlated with the Southern Annular Mode (SAM), the leading mode of southern extratropical atmosphere variability. Whether the ADP affects SAM variability remains unclear, whereas the SAM has been widely shown to drive ADP-related sea ice anomalies. Based on sensitivity experiments using the Community Atmosphere Model version 5 (CAM5) and a dry Atmospheric General Circulation Model (AGCM) developed by Princeton University, this study investigates the feedback of ADP on the SAM and the underlying mechanisms. The results indicate that the negative-phase ADP—featured by decreased sea ice in the eastern Ross Sea to Amundsen Sea but enhanced sea ice in the Weddell Sea—triggers a negative SAM response, whereas the positive-phase ADP produces the opposite circulation and thermal anomalies. Mechanistically, the ADP drives a zonal “east-colder and west-warmer” thermal anomaly, which induces an atmospheric stationary wave anomaly, subsequently modulating transient eddy momentum and heat flux feedback and favoring the formation and maintenance of the negative SAM. This not only provides a dynamical framework for understanding the observed ADP-SAM connection, but also offers a benchmark for evaluating climate models simulated transient eddy feedback and zonal-asymmetric thermal gradients induced by sea-ice anomalies.</p>

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Simulated atmospheric seasonal responses of the southern annular mode to the Antarctic sea ice dipole in austral spring and summer

  • 期刊论文

  • 发表日期：

    2026年6月17日

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  • Hui Cai,
  • Shuanglin Li,
  • Sijing Huang,
  • Chao Zhang

摘要

The Antarctic sea ice Dipole (ADP), the leading mode of sea ice variability in the Southern Ocean in austral spring and summer, has been found to be negatively correlated with the Southern Annular Mode (SAM), the leading mode of southern extratropical atmosphere variability. Whether the ADP affects SAM variability remains unclear, whereas the SAM has been widely shown to drive ADP-related sea ice anomalies. Based on sensitivity experiments using the Community Atmosphere Model version 5 (CAM5) and a dry Atmospheric General Circulation Model (AGCM) developed by Princeton University, this study investigates the feedback of ADP on the SAM and the underlying mechanisms. The results indicate that the negative-phase ADP—featured by decreased sea ice in the eastern Ross Sea to Amundsen Sea but enhanced sea ice in the Weddell Sea—triggers a negative SAM response, whereas the positive-phase ADP produces the opposite circulation and thermal anomalies. Mechanistically, the ADP drives a zonal “east-colder and west-warmer” thermal anomaly, which induces an atmospheric stationary wave anomaly, subsequently modulating transient eddy momentum and heat flux feedback and favoring the formation and maintenance of the negative SAM. This not only provides a dynamical framework for understanding the observed ADP-SAM connection, but also offers a benchmark for evaluating climate models simulated transient eddy feedback and zonal-asymmetric thermal gradients induced by sea-ice anomalies.