Unlike the Arctic—an ocean basin surrounded by land—the Antarctic is a large continent surrounded by ocean. Because of this geography, sea ice has more room to expand in the winter. But the ice also stretches closer to warmer, lower latitudes, leading to more melting in summer. Antarctic sea ice peaks in September (the end of Southern Hemisphere winter) and retreats to a minimum in February.
These image pairs show Antarctic sea ice during the September maximum (left) and the following February minimum (right) from September 1999 to February 2011. Land is dark gray, and ice shelves—thick slabs of glacial ice grounded along the coast—are light gray. The yellow outline shows the median sea ice extent in September and February from 1979 (when routine satellite observations began) to 2000. Extent is the total area in which ice concentration is at least 15 percent. Themedian is the middle value. Half of the extents over the time period were larger than the line, and half were smaller.
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