rT HE areal extent and variability of sea ice is one of the most important of the numerous components that interact to produce global climatic patterns, even for areas far removed from the polar zones. Sea ice in the south-polar region exhibits significant seasonal and interannual variations that from a practical viewpoint are important for Antarctic coastal navigation and fishery operations. The impact of these variations on global climate can have other far-reaching consequences. The presence of an ice cover effectively halts the exchanges of energy and mass between ocean and atmosphere and, therefore, must influence the behavior of the atmosphere. The sea ice becomes, as far as interface processes are concerned, an extension of the Antarctic continental ice sheet. During the time of minimum ice extent (usually March), ice occupies approximately 6 percent of the total hemispheric area; at the time of maximum extension (usually September), ice covers nearly 33 million square kilometers, or almost 13 percent of total hemispheric area. Fluctuations of this magnitude must profoundly influence the global energy balance and associated circulation patterns. Any global or hemispheric climate model should therefore contain sea-ice cover as a variable.