How Has the Ferrel Cell Contributed to the Maintenance of Antarctic Sea Ice at Low Levels Since 2016?

This study investigates the specific circulation anomalies that have sustained the low Antarctic sea ice state since 2016. Firstly, we find a significant strengthening and southward shift in the Ferrel Cell during 2016–2022, resulting in a marked increase in zonally southward transport of heat and moisture. Secondly, this enhanced Ferrel Cell is closely associated with a stronger circumpolar wave pattern (CWP) over the same period. This pattern is zonally asymmetric and greatly amplifies the poleward advections of heat and moisture, leading to the increased downward longwave radiation, more liquid precipitation and sea ice retreat in specific regions, including the western Pacific and Indian Ocean sectors, eastern Ross and northern Weddell Seas. The strong correlation between the Ferrel Cell and CWP was reproduced by the Community Earth System Model - Large Ensemble. As global warming continues, the potential southward shift of the Ferrel Cell poses a major threat to sea ice retreat.