| Abstract: | This paper documents a decadal strengthened co-variability of the Antarctic Oscillation (AAO) and ENSO in austral spring after the mid-1990s. During the period 1979-93, the ENSO (AAO) spatial signatures are restricted to the tropics-midlatitudes (Antarctic-midlatitudes) of the Southern Hemisphere (SH), with a weak connection between the two oscillations. Comparatively, after the mid-1990s, the El Niño-related atmospheric anomalies project on a negative AAO pattern with a barotropic structure in the mid-high latitudes of the SH. The expansion of El Niño-related air temperature anomalies have a heightened impact on the meridional thermal structure of the SH, contributing to a weakened circumpolar westerly and strengthened subtropical jet. Meanwhile, the ENSO-related southern three-cell circulations expand poleward and then strongly couple the Antarctic and the tropics. Numerical simulation results suggest that the intensified connection between ENSO and SST in the South Pacific since the mid-1990s is responsible for the strengthened AAO-ENSO relationship. |
