The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at solar midnight) and the centre of the Sun (ignoring refraction) is below the horizon for 24 continuous hours at least once per year (and therefore not visible at solar noon); this is also true within the Arctic Circle, the Antarctic Circle’s counterpart in the Northern Hemisphere.
The position of the Antarctic Circle is not fixed and, not taking account of the nutation, currently runs 66°33′50.3″ south of the Equator. This figure may be slightly inaccurate because it does not allow for the effects of astronomical nutation, which can be up to 10″. Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, due to tidal forces resulting from the orbit of the Moon. Consequently, the Antarctic Circle is currently drifting southwards at a speed of about 14.5 m (48 ft) per year.
Midnight sun and polar night
The Antarctic Circle is the northernmost latitude in the Southern Hemisphere at which the centre of the sun can remain continuously above the horizon for twenty-four hours; as a result, at least once each year at any location within the Antarctic Circle the centre of the sun is visible at local midnight, and at least once the centre of the sun is below the horizon at local noon.
Directly on the Antarctic Circle these events occur, in principle, exactly once per year: at the December and June solstices, respectively. However, because of atmospheric refraction and mirages, and because the sun appears as a disk and not a point, part of the midnight sun may be seen on the night of the southern summer solstice up to about 50 minutes (′) (90 km (56 mi)) north of the Antarctic Circle; similarly, on the day of the southern winter solstice, part of the sun may be seen up to about 50′ south of the Antarctic Circle. That is true at sea level; those limits increase with elevation above sea level, although in mountainous regions there is often no direct view of the true horizon. Mirages on the Antarctic continent tend to be even more spectacular than in Arctic regions, creating, for example, a series of apparent sunsets and sunrises while in reality the sun remains below the horizon.
Human habitation
There is no permanent human population south of the Antarctic Circle, but there are several research stations in Antarctica operated by various nations that are inhabited by teams of scientists who rotate on a seasonal basis. In previous centuries some semi-permanent whaling stations were established on the continent, and some whalers would live there for a year or more. At least eleven children have been born in Antarctica, albeit in stations north of the Antarctic Circle.
Geography
The circumference of the Antarctic Circle is roughly 16,000 kilometres (9,900 mi). The area south of the Circle is about 20,000,000 km2 (7,700,000 sq mi) and covers roughly 4% of Earth's surface. Most of the continent of Antarctica is within the Antarctic Circle.
Sites along the Circle
Starting at the prime meridian and heading eastwards, the Antarctic Circle passes through:
See also
- Antarctic Convergence
- Tropic of Cancer
- Tropic of Capricorn
References
- "Obliquity of the Ecliptic (Eps Mean)". Neoprogrammics.com. Archived from the original on 2017-06-12. Retrieved 2014-05-13.
- Berger, A.L. (1976). "Obliquity and Precession for the Last 5000000 Years". Astronomy and Astrophysics. 51 (1): 127–135. Bibcode:1976A&A....51..127B.
- Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Archived (PDF) from the original on 6 August 2023. Retrieved 28 September 2015.
- NB: This refers to the true geometric centre which actually appears higher in the sky because of refraction by the atmosphere.
- "World record Baby, it's cold outside". International Antarctic Centre. Retrieved 2024-02-18.
- Nuttall, Mark (2004). Encyclopedia of the Arctic Volumes 1, 2 and 3. Routledge. p. 115. ISBN 978-1579584368. Archived from the original on 15 January 2023. Retrieved 26 July 2016.
- William M. Marsh; Martin M. Kaufman (2012). Physical Geography: Great Systems and Global Environments. Cambridge University Press. p. 24. ISBN 978-0-521-76428-5. Archived from the original on 2023-01-15. Retrieved 2021-11-27.
External links
- Map of the Antarctic Circle (archived 13 October 2007)
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth The region south of this circle is known as the Antarctic and the zone immediately to the north is called the Southern Temperate Zone South of the Antarctic Circle the Sun is above the horizon for 24 continuous hours at least once per year and therefore visible at solar midnight and the centre of the Sun ignoring refraction is below the horizon for 24 continuous hours at least once per year and therefore not visible at solar noon this is also true within the Arctic Circle the Antarctic Circle s counterpart in the Northern Hemisphere Map of the Antarctic with the Antarctic Circle in blue The position of the Antarctic Circle is not fixed and not taking account of the nutation currently runs 66 33 50 3 south of the Equator This figure may be slightly inaccurate because it does not allow for the effects of astronomical nutation which can be up to 10 Its latitude depends on the Earth s axial tilt which fluctuates within a margin of more than 2 over a 41 000 year period due to tidal forces resulting from the orbit of the Moon Consequently the Antarctic Circle is currently drifting southwards at a speed of about 14 5 m 48 ft per year Midnight sun and polar nightRelationship of Earth s axial tilt e to the tropical and polar circles The Antarctic Circle is the northernmost latitude in the Southern Hemisphere at which the centre of the sun can remain continuously above the horizon for twenty four hours as a result at least once each year at any location within the Antarctic Circle the centre of the sun is visible at local midnight and at least once the centre of the sun is below the horizon at local noon Directly on the Antarctic Circle these events occur in principle exactly once per year at the December and June solstices respectively However because of atmospheric refraction and mirages and because the sun appears as a disk and not a point part of the midnight sun may be seen on the night of the southern summer solstice up to about 50 minutes 90 km 56 mi north of the Antarctic Circle similarly on the day of the southern winter solstice part of the sun may be seen up to about 50 south of the Antarctic Circle That is true at sea level those limits increase with elevation above sea level although in mountainous regions there is often no direct view of the true horizon Mirages on the Antarctic continent tend to be even more spectacular than in Arctic regions creating for example a series of apparent sunsets and sunrises while in reality the sun remains below the horizon Human habitationAn iceberg near the Antarctic Circle north of Detaille Island There is no permanent human population south of the Antarctic Circle but there are several research stations in Antarctica operated by various nations that are inhabited by teams of scientists who rotate on a seasonal basis In previous centuries some semi permanent whaling stations were established on the continent and some whalers would live there for a year or more At least eleven children have been born in Antarctica albeit in stations north of the Antarctic Circle GeographyMap all coordinates using OpenStreetMap Download coordinates as KML GPX all coordinates GPX primary coordinates GPX secondary coordinates The circumference of the Antarctic Circle is roughly 16 000 kilometres 9 900 mi The area south of the Circle is about 20 000 000 km2 7 700 000 sq mi and covers roughly 4 of Earth s surface Most of the continent of Antarctica is within the Antarctic Circle Sites along the Circle Starting at the prime meridian and heading eastwards the Antarctic Circle passes through Co ordinates approximate Country territory or sea Notes66 34 S 0 0 E 66 567 S 0 000 E 66 567 0 000 Prime Meridian Southern Ocean North of Queen Maud Land and Enderby Land66 34 S 50 32 E 66 567 S 50 533 E 66 567 50 533 Antarctica Antarctica Enderby Land Territory claimed by Australia66 34 S 57 19 E 66 567 S 57 317 E 66 567 57 317 Southern Ocean Southern Ocean North of the Amery Ice Shelf66 34 S 82 6 E 66 567 S 82 100 E 66 567 82 100 Antarctica Antarctica Territory claimed by Australia66 34 S 89 14 E 66 567 S 89 233 E 66 567 89 233 Southern Ocean Southern Ocean66 34 S 91 29 E 66 567 S 91 483 E 66 567 91 483 Antarctica Antarctica Territory claimed by Australia66 34 S 92 21 E 66 567 S 92 350 E 66 567 92 350 Southern Ocean Southern Ocean66 34 S 93 52 E 66 567 S 93 867 E 66 567 93 867 Antarctica Antarctica Territory claimed by Australia66 34 S 107 45 E 66 567 S 107 750 E 66 567 107 750 Southern Ocean Southern Ocean Vincennes Bay66 34 S 110 12 E 66 567 S 110 200 E 66 567 110 200 Antarctica Antarctica Wilkes Land Territory claimed by Australia66 34 S 116 35 E 66 567 S 116 583 E 66 567 116 583 Southern Ocean Southern Ocean66 34 S 121 31 E 66 567 S 121 517 E 66 567 121 517 Antarctica Antarctica Wilkes Land Territory claimed by Australia66 34 S 127 9 E 66 567 S 127 150 E 66 567 127 150 Southern Ocean Southern Ocean66 34 S 129 38 E 66 567 S 129 633 E 66 567 129 633 Antarctica Antarctica Wilkes Land Territory claimed by Australia66 34 S 136 0 E 66 567 S 136 000 E 66 567 136 000 Antarctica Antarctica Adelie Land Territory claimed by France66 34 S 138 56 E 66 567 S 138 933 E 66 567 138 933 Southern Ocean Southern Ocean66 34 S 162 44 E 66 567 S 162 733 E 66 567 162 733 Balleny Islands Borradaile Island Territory claimed by New Zealand66 34 S 162 45 E 66 567 S 162 750 E 66 567 162 750 Southern Ocean Southern Ocean Passing just north of Adelaide Island claimed by Argentina Chile and United Kingdom 66 34 S 65 44 W 66 567 S 65 733 W 66 567 65 733 Antarctica Antarctica Antarctic Peninsula Graham Land and Larsen Ice Shelf Territory claimed by Argentina Chile and United Kingdom66 34 S 60 21 W 66 567 S 60 350 W 66 567 60 350 Southern Ocean Southern Ocean Passing through the Weddell Sea and into an unnamed part of the oceanSee alsoGeography portalAntarctic Convergence Tropic of Cancer Tropic of CapricornReferences Obliquity of the Ecliptic Eps Mean Neoprogrammics com Archived from the original on 2017 06 12 Retrieved 2014 05 13 Berger A L 1976 Obliquity and Precession for the Last 5000000 Years Astronomy and Astrophysics 51 1 127 135 Bibcode 1976A amp A 51 127B Burn Chris The Polar Night PDF The Aurora Research Institute Archived PDF from the original on 6 August 2023 Retrieved 28 September 2015 NB This refers to the true geometric centre which actually appears higher in the sky because of refraction by the atmosphere World record Baby it s cold outside International Antarctic Centre Retrieved 2024 02 18 Nuttall Mark 2004 Encyclopedia of the Arctic Volumes 1 2 and 3 Routledge p 115 ISBN 978 1579584368 Archived from the original on 15 January 2023 Retrieved 26 July 2016 William M Marsh Martin M Kaufman 2012 Physical Geography Great Systems and Global Environments Cambridge University Press p 24 ISBN 978 0 521 76428 5 Archived from the original on 2023 01 15 Retrieved 2021 11 27 External linksMap of the Antarctic Circle archived 13 October 2007 66 33 50 S 0 0 0 W 66 56389 S 0 00000 E 66 56389 0 00000 Prime Meridian
