The Arctic consists of ocean surrounded by continental land masses and islands. The central Arctic Ocean is ice-covered year-round, and snow and ice are present on land for most of the year.
The southern limit of the arctic region is commonly placed at the Arctic Circle (latitude 66 degrees, 32 minutes North). The Arctic Circle is an imaginary line that marks the latitude above which the sun does not set on the day of the summer solstice (usually 21 June) and does not rise on the the day of the winter solstice (usually 21 December). North of this latitude, periods of continuous daylight or night last up to six months at the North Pole.
Arctic researchers also define the Arctic region as:
- The area north of the treeline (the northern limit of upright tree growth)
- Locations in high latitudes where the average daily summer temperature does not rise above 10 degrees Celsius