Abstract: This study used ERA5 data to conduct composite analysis of wind, air temperature, and sea level pressure in winter over the Ross and Amundsen seas when Southern Annular Mode (SAM) and El Niño-Southern Oscillation (ENSO) events occurred simultaneously, and further analyzed the effects of SAM and ENSO on the Amundsen Sea Low (ASL) in winter. Variational characteristics of regional wind during different periods were explained by Empirical Orthogonal Function (EOF) decomposition of typical regions with consideration of changes in the central position of the ASL. Results showed that SAM and ENSO mainly affect the wind by altering the zonal position of the ASL in the Ross Sea and the western Amundsen Sea. When the positive phase of SAM coincides with a La Niña event, the ASL is displaced eastward, resulting in weakening (strengthening) of southerly winds in the western (eastern) Ross Sea and weakening of easterly winds along the coast of the western Amundsen Sea. In the eastern Amundsen Sea, SAM mainly affects the regional wind by changing the meridional position of the ASL. When SAM is in negative phase, the more northerly position of the ASL leads to stronger easterly winds in the eastern Amundsen Sea. Additionally, positional offset of the ASL changes the regional atmospheric circulation. When the positive phase of SAM coincides with a La Niña event, the ASL is centered close to the western coast of the Amundsen Sea, and cold air flowing from the Antarctic continent dominates the region, resulting in abnormally low air temperatures with maximum reduction of >3°C.

Key words: SAM, ENSO, ASL, Ross Sea, Amundsen Sea, winter climate