The Influence of Extreme Amundsen Sea Low (ASL) Events on Antarctica's Climate

Abstract

Antarctica’s climate is strongly influenced by different atmospheric circulation features. One of the most prominent of these is the Amundsen Sea Low (ASL), which is a climatological, mobile low-pressure center located in the Pacific sector of the Southern Ocean (SO). Atmospheric circulation features like the ASL can influence changes in sea surface temperature (SST), surface winds, surface temperature, sea ice concentration (SIC), and the direction and speed of sea ice drift around Antarctica. This research project uses European Center for Medium-Range Weather Forecast (ECMWF) Reanalysis version 5 (ERA5) data to study extreme ASL events and their effect on Antarctica's climate. We use an ASL index to identify the date, location, and intensity of the ASL from 1979 to present day. Using timeseries analysis, we select those ASL events with the strongest and weakest intensities based on the central pressure. We then use the ERA5 reanalysis data to select the mean sea level pressure, SST, surface winds, surface temperature and SIC associated with extreme occurrences of the ASL. These are examined to determine the impact of the ASL. Results suggest that very intense ASLs may be associated with the larger scale components of the atmospheric circulation such as the Southern Annular Mode or Zonal Wave Three. It may also reflect variation only in regions where the Low is dominant. Intense ASLs also influence the surface temperature as well as the distribution of sea ice, i.e the sea ice concentration.