Antarctic climate variability and its linkages to the tropics: A closer look at seasonality, regionality, and frequency dependence

We examine the seasonality, regionality, and frequency dependence of the linkages between Antarctic climate variability and the tropics, focusing on the well-observed period from ~1960 to present. We use a variety of instrumental and proxy datasets from both the tropics and the Antarctic, including monthly sea surface temperature (SST), air temperature, sea level pressure (SLP), precipitation and annually resolved ice core records. Regressions of Antarctic ice core and station data upon global fields of SST, SLP and precipitation reveal strong, physically consistent tropical-high latitude linkages on interannual to decadal time scales. Particularly, the influence of El Niño/Southern Oscillation (ENSO) variability is robust in the Pacific sector of Antarctica and exhibits important seasonal, regional and timescale-dependant variations. Previously not-discussed features of the ENSO signature in the Antarctic include (1) that circulation and temperature anomalies associated with El Niño and La Niña events are not strictly of opposite sign, (2) that the seasonality of teleconnections differs among sites while most show the strongest tropical influence in austral spring and (3) that the frequency information contained in time series from ice core and station data varies considerably from site to site. Outside the Pacific sector, surface air temperature variations are largely caused by atmospheric circulation changes associated with the Southern Annular Mode, particularly on month-to-month time scales, while the tropical SST anomalies over the Atlantic and Indian Ocean also become important on longer time scales. Future work will need to consider how stable these features are in different epochs.