Enhanced Meridional Transport in the Antarctic Circumpolar Current under Global Warming

Abstract The prevailing view posits that the meridional transport of the Antarctic Circumpolar Current (ACC) is predominantly driven by wind stress curl instigated by the Southern Hemisphere's westerly winds. However, this perspective, often rooted in model simulations under preindustrial conditions, might not be entirely applicable to the contemporary era, characterized by rapid greenhouse gas emissions. Analysis of observational and Reanalyzed datasets during 1993–2020 reveals a paradox: while the strength of the Southern Hemisphere westerly winds has intensified, the corresponding wind stress curl has diminished. Instead, a significant fraction of the energy transferred to the ocean by the wind is absorbed by eddies, increasing eddy potential vorticity anomalies. The escalation in positive potential vorticity anomalies, transported by mesoscale eddies, triggers an acceleration in the meridional transport. This phenomenon counteracts and even overshadows the effects of diminishing wind stress curl, potentially exerting a substantial influence on global climate dynamics. Our findings illuminate the intricate dynamics governing the ACC and underscore its critical role in ice melt and climate regulation.