Arctic Circle

The Arctic Circle is one of the two polar circles and the most northerly of the five major circles of latitude as shown on maps of Earth. It marks the northernmost point at which the centre of the noon sun is just visible on the December solstice and the southernmost point at which the centre of the midnight sun is just visible on the June solstice.[1][2] The region north of this circle is known as the Arctic, and the zone just to the south is called the Northern Temperate Zone.

This article is about one of the five major circles of latitude. For other uses, see Arctic Circle (disambiguation).

Map of the Arctic, with the Arctic Circle in blue and the 10°C July  mean isotherm in red

As seen from the Arctic, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at midnight) and below the horizon for 24 continuous hours at least once per year (and therefore not visible at noon). This is also true in the Antarctic region, south of the equivalent Antarctic Circle.

The position of the Arctic Circle is not fixed and currently runs 66°33′48.4″ north of the Equator.[3] 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.[4] Consequently, the Arctic Circle is currently drifting northwards (shrinking) at a speed of about 15 m (49 ft) per year.

Etymology

The word arctic comes from the Greek word ἀρκτικός (arktikos: "near the Bear, northern")[5] and that from the word ἄρκτος (arktos: "bear").[6]

Midnight sun and polar night
Relationship of Earth's axial tilt (ε) to the tropical and polar circles
At night, bright aurora borealis are a fairly common sight in the Arctic Circle. The picture of the northern lights in Rovaniemi.
Further information: Midnight sun and Polar night

The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the centre of the sun can remain continuously above or below the horizon for twenty-four hours; as a result, at least once each year at any location within the Arctic Circle the centre of the sun is visible at local midnight, and at least once the centre is not visible at local noon.[7]

Directly on the Arctic Circle these events occur, in principle, exactly once per year: at the June and December solstices, respectively. However, because of atmospheric refraction and mirages, and also because the sun appears as a disk and not a point, part of the midnight sun may be seen on the night of the northern summer solstice up to about 50 minutes (′) (90 km (56 mi)) south of the Arctic Circle; similarly, on the day of the northern winter solstice, part of the sun may be seen up to about 50′ north of the Arctic 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.

Human habitation
Cylindrical projection showing the Arctic Circle in red
Further information: Circumpolar peoples

Only four million people live north of the Arctic Circle due to the climate; nonetheless, some areas have been settled for thousands of years by indigenous peoples, who today make up 10% of the region's population.[8] The largest communities north of the Arctic Circle are situated in Russia, Norway and Sweden: Murmansk (population 295,374), Norilsk (178,018), Tromsø (75,638), Vorkuta (58,133), and Kiruna (22,841). Rovaniemi (62,667) in Finland is the largest settlement in the immediate vicinity of the Arctic Circle, lying 6 km (4 mi) south of the line.

In contrast, the largest North American community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,000 inhabitants. In the United States, Utqiagvik, Alaska is the largest settlement north of the Arctic Circle with about 4,000 inhabitants. The largest such community in Canada is Inuvik in the Northwest Territories, with 3,200 people living there.

Geography

The Arctic Circle is roughly 16,000 km (9,900 mi) long.[9] The area north of the Circle is about 20,000,000 km2 (7,700,000 sq mi) and covers roughly 4% of Earth's surface.[10]

The Arctic Circle passes through the Arctic Ocean, the Scandinavian Peninsula, North Asia, Northern America, and Greenland. The land within the Arctic Circle is divided among eight countries: Norway, Sweden, Finland, Russia, the United States (Alaska), Canada (Yukon, Northwest Territories, and Nunavut), Denmark (Greenland), and Iceland (where it passes through the small offshore island of Grímsey).

Climate
Further information: Climate of the Arctic

The climate inside the Arctic Circle is generally cold, but the coastal areas of Norway have a generally mild climate as a result of the Gulf Stream, which makes the ports of northern Norway and northwest Russia ice-free all year long. In the interior, summers can be quite warm, while winters are extremely cold. For example, summer temperatures in Norilsk, Russia will sometimes reach as high as 30 °C (86 °F), while the winter temperatures frequently fall below −50 °C (−58 °F).

Sites along the Arctic Circle

Starting at the prime meridian and heading eastwards, the Arctic Circle passes through:

Co-ordinates Country, territory, or ocean Notes
66°34′N 0°0′E  Atlantic Ocean Norwegian Sea
66°34′N 12°3′E  Norway Islands and skerries of Træna, Nordland County
66°34′N 12°18′E Atlantic Ocean Trænfjorden, Norwegian Sea
66°34′N 12°29′E  Norway Islands and skerries of Nesøya, Nordland County
66°34′N 12°41′E Atlantic Ocean Nesøyfjorden, Norwegian Sea
66°34′N 12°49′E  Norway Islands and skerries of Storseløya, Nordland County
66°34′N 12°52′E Atlantic Ocean Kvarøyfjorden, Norwegian Sea
66°34′N 12°57′E  Norway Islands and skerries of Rangsundøya, Nordland County, including Vikingen Island
66°34′N 13°3′E Atlantic Ocean Værangfjorden, Norwegian Sea
66°34′N 13°12′E  Norway Nordland County
66°34′N 15°33′E  Sweden Norrbotten County (Provinces of Lapland and Norrbotten)
66°34′N 23°51′E  Finland Lapland Region, crosses Rovaniemi Airport
66°34′N 29°28′E  Russia Republic of Karelia
66°34′N 31°36′E Murmansk Oblast
66°34′N 32°37′E Republic of Karelia
66°34′N 33°10′E Grand Island, Murmansk Oblast
66°34′N 33°25′E Arctic Ocean Kandalaksha Gulf, White Sea, Barents Sea
66°34′N 34°28′E  Russia Kola Peninsula, Murmansk Oblast — for about 7 km (4.3 mi)
66°34′N 34°38′E Arctic Ocean Kandalaksha Gulf, White Sea, Barents Sea
66°34′N 35°0′E  Russia Kola Peninsula, Murmansk Oblast
66°34′N 40°42′E Arctic Ocean White Sea, Barents Sea
66°34′N 44°23′E  Russia Nenets Autonomous Okrug
66°34′N 50°51′E Komi Republic
66°34′N 63°48′E Yamalo-Nenets Autonomous Okrug
66°34′N 71°5′E Arctic Ocean Gulf of Ob, Kara Sea
66°34′N 72°27′E  Russia Yamalo-Nenets Autonomous Okrug
66°34′N 83°3′E Krasnoyarsk Krai
66°34′N 106°18′E Yukaghir Highlands, Sakha Republic
66°34′N 158°38′E Anadyr Highlands and Chukotka Mountains, Chukotka Autonomous Okrug
66°34′N 171°1′W Arctic Ocean Chukchi Sea
66°34′N 164°38′W  United States Seward Peninsula, Alaska
66°34′N 163°44′W Arctic Ocean Kotzebue Sound, Chukchi Sea
66°34′N 161°56′W  United States Alaska—passing through Selawik Lake
66°34′N 141°0′W  Canada Yukon
66°34′N 133°36′W Northwest Territories, passing through Great Bear Lake
66°34′N 115°56′W Nunavut
66°34′N 82°59′W Arctic Ocean Foxe Basin
66°34′N 73°25′W  Canada Nunavut (Baffin Island), passing through Nettilling Lake and Auyuittuq National Park (sign location)
66°34′N 61°24′W Atlantic Ocean Davis Strait
66°34′N 53°16′W  Greenland passing through Kangerlussuaq Fjord and Schweizerland
66°34′N 34°9′W Atlantic Ocean Denmark Strait
66°34′N 26°18′W Greenland Sea
66°34′N 18°1′W  Iceland Island of Grímsey
66°34′N 17°59′W Atlantic Ocean Greenland Sea
66°34′N 12°32′W Norwegian Sea
A sign along the Dalton Highway marking the location of the Arctic Circle in Alaska
Arctic Circle line in Rovaniemi, Finland c.1865
Aurora Borealis above Arctic Circle sign along the Dempster Highway in Yukon at 66°33′55″N 136°18′26″W

See also

References
  1. Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Retrieved 28 September 2015.
  2. NB: This refers to the true geometric centre which actually appears higher in the sky because of refraction by the atmosphere.
  3. "Obliquity of the Ecliptic (Eps Mean)". Neoprogrammics.com. Retrieved 13 May 2014.
  4. Berger, A. L. (1976). "Obliquity and Precession for the Last 5000000 Years". Astronomy and Astrophysics. 51 (1): 127–135. Bibcode:1976A&A....51..127B.
  5. Liddell, Henry; Scott, Robert. "Arktikos". A Greek–English Lexicon. Perseus Digital Library.
  6. Liddell, Henry; Scott, Robert. "Arktos". A Greek–English Lexicon. Perseus Digital Library.
  7. Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Retrieved 28 September 2015.
  8. "Arctic Population". www.athropolis.com.
  9. Nuttall, Mark (2004). Encyclopedia of the Arctic Volumes 1, 2 and 3. Routledge. p. 115. ISBN 978-1579584368.
  10. Marsh, William M.; Kaufman, Martin M. (2012). Physical Geography: Great Systems and Global Environments. Cambridge University Press. p. 24. ISBN 978-0-521-76428-5.
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