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Arctic Circle
Map of the Arctic, with the Arctic Circle in blue and the July 10 °C mean isotherm in red[timeframe?]
The Arctic Circle is 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.
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; as of 1 January 2019, it runs 66°33′47.4″ 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 at a speed of about 15 metres (49 feet) per year.
Contents
1 Etymology
2 Midnight sun and polar night
3 Human habitation
4 Geography
4.1 Climate
4.2 Sites along the Arctic Circle
5 See also
6 References
7 External links
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
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 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
Only four million people live north of the Arctic Circle due to the severe 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] Tens of thousands of years ago, waves of people migrated from eastern Siberia across the Bering Strait into North America to settle.
The largest communities north of the Arctic Circle are situated in Russia, Norway and Sweden: Murmansk (population 307,257), Norilsk (175,365), Tromsø (71,295), Vorkuta (59,231) and Kiruna (18,148). Rovaniemi (61,329) in Finland is the largest settlement in the immediate vicinity of the Arctic Circle, lying 6 kilometres (4 miles) south of the line.
In contrast, the largest North American community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,000 inhabitants. Of the Canadian and American Arctic communities, Utqiagvik, Alaska is the largest settlement with about 4,000 inhabitants.
Geography
The Arctic Circle is roughly 16,000 kilometres (9,900 mi).[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 8 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
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:
|  A sign along the Dalton Highway marking the location of the Arctic Circle in Alaska  Arctic Circle line in Rovaniemi, Finland  Aurora Borealis above Arctic Circle sign along the Dempster Highway in Yukon at 66°33′55″N 136°18′26″W / 66.565325°N 136.307169°W / 66.565325; -136.307169 |
A sign on the Vikingen island marking the Arctic Circle in Norway
The Arctic Circle on Grímsey in Iceland
Arctic Circle sign by the Inland Line railway, Sweden
The Arctic Circle in the Republic of Karelia, Russia
Arctic Circle sign by the Yamal-Nenets Autonomous District, Russia
A sign in Yakutia, Russia
See also
- Antarctic Circle
- Arctic Cooperation and Politics
- Arctic haze
- Circumpolar circle
- Scott Polar Research Institute
- Territorial claims in the Arctic
- Tropic of Cancer
- Tropic of Capricorn
References
^ Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Retrieved 28 September 2015..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
^ NB: This refers to the true geometric centre which actually appears higher in the sky because of refraction by the atmosphere.
^ "Obliquity of the Ecliptic (Eps Mean)". Neoprogrammics.com. Retrieved 13 May 2014.
^ Berger, A. L. (1976). "Obliquity and Precession for the Last 5000000 Years". Astronomy and Astrophysics. 51: 127–135. Bibcode:1976A&A....51..127B.
^ Liddell, Henry; Scott, Robert. "Arktikos". A Greek–English Lexicon. Perseus Digital Library.
^ Liddell, Henry; Scott, Robert. "Arktos". A Greek–English Lexicon. Perseus Digital Library.
^ Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Retrieved 28 September 2015.
^ "Arctic Population". www.athropolis.com.
^ Nuttall, Mark (2004). Encyclopedia of the Arctic Volumes 1, 2 and 3. Routledge. p. 115. ISBN 978-1579584368. Retrieved 26 July 2016.
^ 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.
External links
 | Wikimedia Commons has media related to Arctic Circle. |
 | Look up arctic circle in Wiktionary, the free dictionary. |
Terra Incognita: Exploration of the Canadian Arctic—Historical essay about early expeditions to the Canadian Arctic, illustrated with maps, photographs and drawings
Temporal Epoch Calculations ©2006 by James Q. Jacobs Download: Epoch v2009.xls (modify D4)
Useful constants" See: Obliquity of the ecliptic
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WikiProjectCircles of latitude / meridians | |
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