Extremes in Southern Hemispheric Zonal Wave‐3 and Their Impact on Antarctic Sea‐Ice Thickness

Abstract Zonal Wave‐3 (ZW3) is a key zonally asymmetric component of the large‐scale extratropical atmospheric circulation, facilitating mass and energy exchanges between middle and high latitudes in the Southern Hemisphere. Despite the crucial role of sea‐ice thickness (SIT) in modulating sea‐ice volume and climate feedbacks, its response to ZW3 variability remains largely unexplored compared to the more widely studied sea‐ice concentration. Our research identifies variability in the ZW3 pattern and assesses its influence on Antarctic SIT and concentration using a combination of reanalysis and data from a coupled climate model. We project a doubling in the mean frequency of extreme ZW3 events under a high emission scenario, which is likely to contribute to a decline in SIT, primarily through dynamic mechanisms. These extreme events drive mechanical displacement of sea‐ice more than direct thermodynamic melting. Such displacements may expose the underlying ocean, potentially enhancing basal melting through ocean thermal influences.