polcirkeln

Polcirkeln, called the Arctic Circle in English, is the circle of latitude located at about 66°33′ north of the Earth's equator. It marks the southern boundary of the Arctic region and is one of the major circles of latitude used to divide the planet into climatic zones. The position of the circle is determined by the tilt of the Earth's axis relative to its orbit around the Sun.

The latitude is approximately 90° minus the axial tilt, which is about 23.5°. Because the tilt is close to this value, the Arctic Circle lies near 66.5° north. In practice the exact figure is often given as 66°33′44″ north, with small variations over long timescales due to axial precession.

A key characteristic of the polcirkeln is its association with extreme variations in daylight. In summer, places inside the Arctic Circle experience continuous daylight for at least one day and often for several weeks (the midnight sun). In winter, there are periods of continuous darkness (polar night). The phenomena become more pronounced the farther north one goes.

The Arctic Circle crosses several countries and regions. It passes through parts of Norway, Sweden, Finland, Russia, Alaska (United States), Canada, and Greenland (Denmark). It also traverses the Arctic Ocean and adjacent seas, where land presence is limited.

The concept is used in geography, climate science, and regional planning to delineate the Arctic climate zone and its ecological and human implications, including daylight patterns, permafrost, and indigenous communities.