The Zonal Wave-3 Mode Impacts Antarctic Dense Water Formation

Abstract

At the Antarctic margins, dense water masses form as sea ice develops, driving the Antarctic branch of the global meridional overturning circulation. Previous studies found that large-scale climate modes such as the Southern Annular Mode and El Niño Southern do not fully account for the interannual variability of dense water formation. Here, we investigate the influence of the overlooked Zonal Wave-3 (ZW3) mode, characterized by three alternating cyclone–anticyclone pairs in the Southern Hemisphere mid-latitudes. Simulations with ZW3 perturbations of different phases show multi-year impacts on dense water formation and export. The PC1 phase exerts the strongest influence in the Ross Sea, while the PC2 phase can nearly shut down or double dense water formation in the Weddell Sea. A simulation with interannually varying atmospheric forcing confirms ZW3 correlates with dense water formation in both regions. Our results highlight that ZW3 is a key driver of Antarctic dense water dynamics. Show more