Séminaire
In recent years, contrary to what has been observed in the Arctic, Antarctic sea ice extent has shown on average a small increase. The trend in Antarctic sea ice extent is strongly regional; there are regions where sea ice extent has experienced a marked decrease over the same period. The trend in Antarctic sea ice extent also varies seasonally. The extent of Antarctic sea ice is influenced by largescale atmospheric circulation mechanisms with both tropical and higher latitude origins. At high latitudes, sea ice extent is influenced by the Southern Annular Mode (SAM), zonal wave three (ZW3) and the Amundsen Sea Low (ASL), all three of which exert control on wind speed and direction, which in turn controls advection of energy and mechanical motion of ice. The observed, decadal, positive trend in Antarctic sea ice extent has also been attributed in part to the changes in the high latitude atmospheric circulation that are linked to the stratospheric cooling associated with stratospheric ozone depletion.
This presentation first examines the recorded and simulated variability and change of Antarctic sea ice beginning in the late 20th century. It continues to look at the links between Antarctic sea ice variability and the largescale circulation mechanisms, focusing in particular on the SAM, ZW3 and the ASL and in the process, examine their contribution to the trend in Antarctic sea ice extent. Finally, it will present climate model projections of change in sea ice extent comparing those projections with observations. It will highlight questions that need to be asked and answered so that we understand the processes and mechanisms underlying the contemporary variation in Antarctic sea ice extent.