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Antarctic Circle

An imaginary line that delimits the northern boundary of Antarctica. It is a distinctive parallel of latitude at approximately 66°30' south. Thus it is located about 4590 mi (7345 km) south of the Equator and about 1630 mi (2620 km) north of the south geographic pole.

All of Earth's surface south of the Antarctic Circle experiences one or more days when the Sun remains above the horizon for at least 24 h. The Sun is at its most southerly position on or about December 21 (slightly variable from year to year). This date is known as the summer solstice in the Southern Hemisphere and as the winter solstice in the Northern Hemisphere. At this time, because Earth is tilted on its axis, the circle of illumination reaches 23.50° to the far side of the South Pole and stops short 23.50° to the near side of the North Pole.

The longest period of continuous sunshine at the Antarctic Circle is 24 h, and the highest altitude of the noon Sun is 47° above the horizon at the time of the summer solstice. The long days preceding and following the solstice allow a season of about 5 months of almost continuous daylight.

Six months after the summer solstice, the winter solstice (Southern Hemisphere terminology) occurs on or about June 21 (slightly variable from year to year). On this date the Sun remains below the horizon for 24 h everywhere south of the Antarctic Circle; thus the circle of illumination reaches 23.50° to the far side of the North Pole and stops short 23.50° to the near side of the South Pole. Arctic Ocean

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From McGraw-Hill Concise Encyclopedia of Environmental Science. The Content is a copyrighted work of McGraw-Hill and McGraw-Hill reserves all rights in and to the Content. The Work is © 2008 by The McGraw-Hill Companies, Inc.
 
 
 
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