Atmospheric teleconnections involving the Southern Ocean

Abstract

I review the characteristics patterns of low-frequency (interannual and subdecadal) variation in atmospheric circulation over the Southern Hemisphere (SH) extratropics and their climatic associations (e.g., temperature, precipitation, winds, sea surface temperatures (SSTs), and sea ice conditions) for the Southern Ocean. The considerable spatial and temporal limitations of the observational database have strongly conditioned the pace of our understanding of SH teleconnections, particularly for the Pacific sector, where the tropical El Niño-Southern Oscillation (ENSO) exerts a dominant influence: an ENSO signal appears in the intensity interannual variations of the Amundsen Sea mean low pressure (ASL), jet streams, and long waves. These variations comprise the so-called Pacific-South America (PSA) teleconnection. Patterns of low-frequency variability in SH circulation that are mostly extratropical in origin, but which can interact with ENSO, are dominated by the zonally symmetric "high-latitude mode" or Antarctic Oscillation (AAO). The AAO involves an alternation of atmospheric mass between middle and high southern latitudes. A zonally asymmetric mode of wave number 1 is represented by an oscillation in pressure/ height between Australian and South American sectors, depicted by a "Trans-Polar" circulation index. A significant wave number 2 oscillation in the coupled atmosphere-ocean-ice system or Antarctic circumpolar wave (ACW) has a similar periodicity to ENSO and is strongest in the Pacific-SW Atlantic sectors. Atmospheric teleconnections involving the Southern Ocean, including those to ENSO, show evidence of recent changes, and the climatic implications of these are discussed.