No. 24: Nov-Dec 1982
"Polyna" is a Russian word meaning "an enclosed area of unfrozen water surrounded by ice." Polynas form for some unknown reason in the Southern Ocean surrounding Antarctica. These transient ice-free "lakes" may cover 300,000 square kilometers, inferring a substantial influx of heat countering the frigid polar temperatures. Although small coastal polynas can be blown free of ice by strong Antarctic winds, the open-ocean polynas are much larger and do not seem to owe their origins to wind.
One suggested explanation is that warm subsurface water rises suddenly to the surface, but it takes a lot of heat to keep hundreds of thousands of square kilometers ice-free. The most recent polyna opened up a region of the Weddell Sea for about three years (1973-1976).
(Simon, C.; "Polynas Surrounded by Ice and Mystery," Science News, 122:183, 1982.)