Enhanced Antarctic stratospheric vortex in austral winter: Contributions from regional sea surface temperature

The Antarctic stratospheric polar vortex (SPV) is a crucial feature of the stratospheric system in winter. The variation in the strength of the Antarctic SPV significantly impacts the weather and climate of the Southern Hemisphere (SH). Although previous studies have provided a good understanding of the variations in the strength of the Antarctic SPV and its associated physical mechanisms, the trend of the Antarctic SPV after 2000 has not received sufficient attention. Here, based on observations and reanalysis data, we find that the middle SPV has a strengthening trend in austral winter during 2000–2022. Our findings indicate that warming SST alter atmospheric convection and planetary wave activity, reducing wavenumber-1 planetary waves into the stratosphere and thereby strengthening the polar vortex. Using idealized sea surface temperature (SST) patch experiments with a climate model, we quantified the specific contributions of SST warming in various regions. Among these, the tropical Atlantic, North Indian Ocean, West Pacific warm pool, and East Pacific contributed 106.86 %, −52.67 %, −40.72 %, and 36.94 %, respectively, to the cooling of the polar vortex from 2000 to 2022. On decadal timescales, the variability of tropical SST patterns, particularly in the Atlantic and Pacific basins, has been critical in shaping the observed trends and fluctuations in the Antarctic SPV during recent decades.