Arctic Circle (북극권) - 알래스카 여행

Arctic Circle (북극권) 

알래스카 여행

알래스카 페어뱅크스에서 출발하는 북극권 (Arctic Circle) 여행 ...

(지난 1월 과기대 학생들이 찍은 사진)

북극권(北極圈)은 지도 위에 표시된 지구의 주요 다섯 위선 중 하나이다. 2011년을 기준으로, 북위 66° 33′ 44″(66.5622°)을 지난다.^[1] 북극권은 여름에 해가 지지 않는 백야와 겨울에 해가 뜨지 않는 극야 현상이 일어나는 남쪽 한계이다.

북극권의 위치는 고정되어 있지 않고, 지구 자전축 기울기의 변화에 따라 40,000년 주기로 2°가량 변한다^[2]. 현재는 1년에 약 15m 가량의 속도로 북쪽으로 움직이고 있다.

Wikipedia  에서 ...

The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. As of 22 January 2016, it runs 66°33′46.1″ ^[1] north of the Equator.

The region north of this circle is known as the Arctic, and the zone just to the south is called the Northern Temperate Zone. The equivalent polar circle in the Southern Hemisphere is called the Antarctic Circle.

The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the sun can remain continuously above or below the horizon for 24 hours (at the June solstice and December solstice respectively). North of the Arctic Circle, 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). On the Arctic Circle those events occur, in principle, exactly once per year, at the June and December solstices, respectively. However, in actuality, because ofatmospheric 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 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.

The position of the Arctic Circle is not fixed. It directly depends on the Earth's axial tilt, which fluctuates within a margin of 2° over a 40,000-year period,^[2] due to tidal forces resulting from the orbit of the Moon. The Arctic Circle is currently drifting northwards at a speed of about 15 m (49 ft) per year (see also Circle of latitude).