Cross-Seasonal Impact of SST Anomalies over the Tropical Central Pacific Ocean on the Antarctic Stratosphere

Abstract. In this study we examine the cross–seasonal effects of boreal winter sea surface temperature (SST) anomalies over the central tropical Pacific (Niño4 region) on Antarctic stratospheric circulation and ozone transport during the subsequent austral winter using ERA5 reanalysis of 45 years (1980–2024). Our analyses show that warm (cold) SST anomalies in Niño4 region during December–February are associated with polar stratospheric warming (cooling), a weakened (strengthened) stratospheric polar vortex (SPV), and enhanced (suppressed) polar ozone concentrations during July–September of the subsequent year. This delayed response is mediated by a Pacific–South America (PSA) teleconnection, which excites planetary waves that propagate upward into stratosphere and modify the Brewer–Dobson circulation. In addition, as the influence of Niño4 SSTs on the PSA teleconnection pattern diminishes during July–September, surface heat feedback at mid and high latitudes becomes critically important for planetary waves. Specifically, persistent South Pacific SST warming and sea-ice loss over the Amundsen and Ross Seas reinforce planetary waves by releasing heat from ocean into atmosphere. A multivariate regression statistical model using predictors of boreal winter Niño4 SST, June PSA, June South Pacific SST, and May–June sea-ice concentration (SIC) indices explain approximately 35 % of the variance in austral winter stratospheric temperatures. These findings highlight a previously underexplored pathway through which tropical Pacific SST anomalies modulate Antarctic stratospheric dynamics and chemistry on seasonal timescales. This implies a new insight into tropical–polar coupling and provides a potential signal for extended–range forecasts of ozone depletion risk.