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. Its southern equivalent is the Antarctic Circle.

The Arctic Circle marks the southernmost latitude at which, on the December solstice, the shortest day of the year in the northern hemisphere, the sun will not rise all day, and on the June solstice, the longest day of the year in the northern hemisphere, the sun will not set. These phenomena are referred to as polar night and midnight sun respectively, and the further north one progresses, the more pronounced these effects become. For example, in the Russian port city of Murmansk, three degrees above the Arctic Circle, the sun does not rise for 40 successive days in midwinter.

The position of the Arctic Circle is not fixed and currently runs north of the Equator. Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, owing to tidal forces resulting from the orbit of the Moon. Consequently, the Arctic Circle is currently drifting northwards at a speed of about per year.

Etymology

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

Midnight sun and polar night

The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the center 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 center of the sun is visible at local midnight, and at least once the center is not visible at local noon.

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 (′) () 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

The largest communities north of the Arctic Circle are situated in Russia, Norway, and Sweden: Murmansk (population 295,374) and Norilsk (178,018) in Russia; Tromsø (75,638) in Norway, Vorkuta (58,133) in Russia, Bodø (52,357), and Harstad (24,703) in Norway; and Kiruna, Sweden (22,841). Rovaniemi (62,667) in Finland is the largest settlement in the immediate vicinity of the Arctic Circle, lying south of the line. Salekhard (51,186) in Russia is the only city in the world located directly on the Arctic Circle.

In contrast, the largest North American community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,000 inhabitants. In the United States, Utqiaġvik, 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 3,137 people living there.

Geography

The Arctic Circle is roughly in circumference. The area north of the Circle is about and covers roughly 4% of Earth's surface.

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

The climate north of 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 , while the winter temperatures frequently fall below .

Sites along the Arctic Circle

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

File:2016-11-20 01 Arctic Circle marker on the island of Vikingen Norway.jpg, Northern Polar Circle Globe on Vikingen island marking the Arctic Circle in Norway
File:Polarkreis inlandsbanan.jpg, Arctic Circle sign by the Inland Line railway, Sweden
File:Rovaniemi-SantaClausVillage.jpg, The white borderline of the Arctic Circle at the Santa Claus Village in Rovaniemi, Finland
File:Полярный круг, Россия.jpg, Arctic Circle sign in the Republic of Karelia, Russia
File:Россия, ЯНАО, Полярный круг..JPG, Arctic Circle sign by the Yamalo-Nenets Autonomous Okrug, Russia
File:Круиз Якутск - Ленские столбы - Тикси - Якутск, 2017 (364).jpg, A sign in the Sakha Republic (Yakutia), Russia
File:Iceland2008-Grimsey.arctic.circle.JPG, Arctic Circle marker on island of Grímsey in Iceland

See also

* 60th parallel north
* Antarctic Circle
* Arctic cooperation and politics
* Arctic haze
* Circumpolar star
* Equator
* Scott Polar Research Institute
* Territorial claims in the Arctic
* Tropic of Cancer
* Tropic of Capricorn

References

External links

Terra Incognita: Exploration of the Canadian Arctic
��Historical essay about early expeditions to the Canadian Arctic, illustrated with maps, photographs and drawings


Download: Epoch v2009.xls (modify D4)


See: Obliquity of the ecliptic

{{geographical coordinates

Geography of the Arctic
Circles of latitude