Mechanisms Forcing Antarctic Sea Ice Variability

The dominant mode of variability in Antarctic sea ice cover exhibits a dipole pattern with anomalies of one sign in the Pacific and of the opposite sign in the Atlantic. This mode of variability has been documented in observations. Here we examine 600 years of a control simulation of the Community Climate System Model 2 to determine the simulated sea ice area variability and the mechanisms driving this variability. The dominant modes of simulated variability compare very well to the observations both in their spatial distribution and magnitude. These variations in the ice cover have limited intra-basin eastward propagation which appears to be related to the observed Antarctic circumpolar wave.

The mechanisms driving the simulated sea ice variability are examined. In particular, the interplay of dynamic and thermodynamic processes in forcing the ice variability is discussed. Additionally, how these processes relate to atmosphere and ocean conditions, including those associated with the southern oscillation and the southern annular mode, are investigated. The relationships found are consistent with the atmosphere and ocean forcing the sea ice variability, with different processes dominating in the different basins. There are also indications that positive feedbacks associated with the sea ice conditions influence the atmosphere and ocean temperatures in the regions. This acts to prolong the life of the anomalies, particularly in the Pacific.