Antarctic sea ice expanded pre–2015 1–3 and declined rapidly post–2015 4 , a regime shift generally attributed to a combination of factors, including sudden Southern Annular Mode transition 5 and tropospheric teleconnections associated with the Pacific 4,6–8 . Yet, mechanisms responsible for the decadal variability remain unresolved. We demonstrate that stratosphere–troposphere coupling can potentially contribute to transmitting late austral winter Pacific Decadal Oscillation (PDO) forcing to subsequent summer Antarctic sea ice. The positive PDO phase excites dual pathways: (1) tropospheric Rossby waves strengthening both the Amundsen and Dumont d’Urville Sea Lows (ASL/DSL); and (2) planetary waves modulating the stratospheric polar vortex, whose downward influence amplifies ASL anomalies. The strengthened ASL and DSL generate warm advection anomalies that ultimately promote subsequent summer sea ice melt. Furthermore, analysis of the Coupled Model Intercomparison Project Phase 6 (CMIP6) ensembles supports the role of stratospheric pathways in capturing the observed PDO–ASL linkages. Thus, accurately representing stratosphere–troposphere interactions is beneficial for simulating Antarctic sea ice’s decadal variability.
Wang et al. (Thu,) studied this question.