The Arctic Circle marks the southernmost latitude for which at the December solstice (winter) the Sun does not rise and at the June solstice (summer) the Sun does not set. These phenomena are referred to as polar night and midnight sun, respectively, and the closer to the pole one goes, the longer that situation persists. For example, in the Russian port city of Murmansk (three degrees north of the Arctic Circle) the Sun stays below the horizon for 20 days before and after the winter solstice, and above the horizon for 20 days before and after the summer solstice.[2][3][4]
The positions of the Arctic and Antarctic Circles vary slightly from year to year. Currently the Arctic Circle is 66°33′50.9″ north of the Equator.[5] Its latitude depends on Earth's axial tilt, which fluctuates by a margin of some 2° over a 41,000-year period due to tidal forces resulting from the orbit of the Moon.[6] Consequently, in the current epoch the Arctic Circle is drifting toward the North Pole, while the Antarctic Circle drifts towards the South Pole, each at a speed of about 14.5m (48ft) per year.
Etymology
The word arctic comes from the Greek word ἀρκτικός (arktikos: "near the Bear, northern")[7] and that from the word ἄρκτος (arktos: "bear").[8]
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 centre of the Sun is visible at local midnight, and at least once the centre is not visible at local noon.[3]
Directly on the Arctic Circle these events occur, in principle, exactly once per year: at the June and Decembersolstices, 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 is visible, on the night of the northern summer solstice, at a latitude of about 50 minutes of arc (′) (90km (56mi)) 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.
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). In Finland, the largest settlement in the immediate vicinity of the Arctic Circle is Rovaniemi (62,667), lying 6km (4mi) south of the line. Salekhard (51,186) in Russia is the only city in the world located directly on the Arctic Circle.[9]
In contrast, the largest Danish community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,600 inhabitants. In the United States, Utqiagvik, Alaska (formerly known as Barrow) is the largest settlement north of the Arctic Circle with about 5,000 inhabitants. The largest such community in Canada is Inuvik in the Northwest Territories, with 3,137 inhabitants.
Under international law, including the United Nations Convention on the Law of the Sea (UNCLOS), the North Pole and the surrounding high seas of the Arctic Ocean are not owned by any country. Sovereignty in the region is managed through established maritime zones, though the "Arctic Five" (Canada, Denmark, Norway, Russia, and the U.S.) maintain specific rights over their respective continental shelves and EEZs.
The Arctic Circle is roughly 16,000km (9,900mi) in circumference.[10] The area north of the Circle is about 20,000,000km2 (7,700,000sqmi) and covers roughly 4% of Earth's surface.[11]
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 30°C (86°F), while the winter temperatures frequently fall below −50°C (−58°F).
↑Liddell, Henry; Scott, Robert. "Arktos". A Greek–English Lexicon. Perseus Digital Library.
↑Всеволод Липатов (26 April 2011). "Город на Полярном круге". ToGeo.ru (in Russian). Archived from the original on 8 August 2014. Retrieved 23 July 2021.
.jpg)
.jpg)
