The Arctic Circle is a significant line of latitude that demarcates the northern polar region of our planet. It is an imaginary boundary line that plays a fundamental role in defining the astronomical and geographical character of the Northern Hemisphere. The name itself is a direct link to the earliest navigators and thinkers who charted the northern sky centuries ago.
Tracing the Name Back to Ancient Greece
The word “Arctic” comes from the ancient Greek word arktikos, meaning “of the Bear” or “near the Bear.” This name is directly linked to the constellation Ursa Major, which the Greeks called Arktos. Ursa Major, often recognized as the Big Dipper, is circumpolar, meaning it remains visible above the horizon all year round for observers in northern latitudes. Ancient Greek navigators used this prominent constellation as a guide for finding true north. The name applies not just to Ursa Major, but also to Ursa Minor, which contains Polaris, the North Star. The region surrounding the North Pole was thus designated as the land “of the Bear.” The term “Antarctic” naturally followed, meaning “opposite the bear,” to describe the southern polar region.
The Astronomical Basis for the Circle
The Arctic Circle is not arbitrarily placed; its precise location is determined by the tilt of the Earth’s axis of rotation relative to its orbital plane around the Sun. This tilt, known as the obliquity of the ecliptic, is currently about 23.44 degrees. The Arctic Circle is fixed at the latitude that is 23.44 degrees south of the North Pole, which places it at approximately 66°33′ North.
This specific latitude marks the southernmost point in the Northern Hemisphere where the Sun can remain continuously above the horizon for a full 24 hours at least once a year. This phenomenon, known as the Midnight Sun, occurs around the summer solstice in June. Conversely, the Arctic Circle also defines the boundary for the Polar Night, which occurs around the winter solstice in December. At this time, the Sun remains continuously below the horizon for a full 24 hours at and north of this latitude.
Geographical Location and Delimitation
The Arctic Circle is an imaginary line that encircles the globe for roughly 16,000 kilometers, encompassing about 4% of the Earth’s surface. It traverses large landmasses, including the Scandinavian Peninsula, North Asia, North America, and the Arctic Ocean. The land within this boundary is shared among eight countries:
- Norway
- Sweden
- Finland
- Russia
- The United States (Alaska)
- Canada
- Denmark (Greenland)
- Iceland
The circle is not a static line; its position slowly shifts over time. The latitude of the Arctic Circle depends on the Earth’s axial tilt, which experiences a minor oscillation over a 41,000-year cycle. This slight wobble, caused primarily by the gravitational pull of the Moon, means the Arctic Circle is currently drifting northward at a rate of about 14.5 meters (48 feet) per year. The island of Grímsey in Iceland, for example, is one of the few places where the circle crosses a small offshore island. The largest city located directly on the Arctic Circle is Salekhard, in Russia.