Seasonal Zonal Asymmetries in the Southern Annular Mode

The structure of the Southern Hemisphere Annular Mode (SAM) during leading positive and negative phases for all seasons is examined. The results demonstrate that the zonal symmetry commonly attributed to the SAM is not strongly apparent when the seasons are considered individually. In many seasons, these zonal asymmetries resemble the Pacific South American Pattern, suggesting a tropical influence. Moreover, these zonal asymmetries suggest that the SAM impacts on temperature, pressure, and precipitation across Antarctica and the Southern Hemisphere midlatitudes are more regional and less zonally symmetric than previously realized. In particular, inter-event differences in the SAM-temperature relationship across the Antarctic Peninsula are observed, which help to explain the variable strength (in both sign and magnitude) of this relationship previously observed using ice cores.