Coupled Oscillations in Antarctic Sea Ice, Ocean and Atmosphere

Interannual oscillations with period of about 3-6 years have dominated the winter atmosphericand ice variability in the Weddell, Ross, Amundsen,and Bellingshausen Seas, Antarctica, during 1979-1998. Correlated anomaly signals, evident in ULS-derived sea-ice thickness, satellite-derived ice concentration and satellite-tracked ice drift are observed within the sea-ice pack. Sea ice concentration anomalies at the ice margin result from air-ice-sea interactions involving both the dynamic effect of the anomalous, wind-driven ice motion and the thermodynamic ice growth and melting due to surface air and ocean temperature anomalies. Interannual variability in such anomalies has been commonly reported by several investigators from standard historical sea-ice extent data. However, significant ice thickness anomalies are also generated in locations where satellite-reported 100% ice concentrations are unable to identify dynamically produced winter anomalies. Thickness anomaly signals are shown to circulate around the large gyres, whose formation is linked to large-scale sea level pressure and geostrophic wind anomalies. It is these dynamically produced, periodic ice/freshwater anomalies that are responsible for sustaining the circumpolar ice extent and ocean salinity and temperature anomalies more commonly known as the Antarctic Circumpolar Wave.