The
Arctic (ˈɑrktɪk or ˈɑrtɪk) is a
polar region located at the northernmost part of the
Earth. The Arctic consists of the
Arctic Ocean and parts of
Canada,
Russia,
Denmark (
Greenland),
Norway, the
United States (
Alaska),
Sweden,
Finland, and
Iceland. The Arctic region consists of a vast,
ice-covered ocean, surrounded by treeless
permafrost. The area can be defined as north of the
Arctic Circle (66° 33'N), the approximate limit of the
midnight sun and the
polar night. Alternatively, it can be defined as the region where the average temperature for the warmest month (July) is below 10 °C; the northernmost
tree line roughly follows the
isotherm at the boundary of this region.
Socially and politically, the Arctic region includes the northern territories of the eight Arctic states, although by
natural science definitions much of this territory is considered
subarctic. The Arctic region is a unique area among Earth's ecosystems. The cultures in the region and the Arctic
indigenous peoples have adapted to its cold and extreme conditions. In recent years the extent of the sea ice has declined. Life in the Arctic includes organisms living in the ice,
zooplankton and
phytoplankton, fish and
marine mammals, birds, land animals, plants and human societies.