Arctic

The Arctic (/ˈɑːr(k)tɪk/; from Ancient Greek ἄρκτος (árktos) 'bear') is the polar region of Earth that surrounds the North Pole, lying north of the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway (Nordland, Troms, Finnmark, Svalbard and Jan Mayen), northernmost Sweden (Västerbotten, Norrbotten and Lappland), northern Finland (North Ostrobothnia, Kainuu and Lappi), Russia (Murmansk, Siberia, Nenets Okrug, Novaya Zemlya), the United States (Alaska), Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), and northern Iceland (Grímsey and Kolbeinsey), along with the Arctic Ocean and adjacent seas.

Land within the Arctic region has seasonally varying snow and ice cover, with predominantly treeless permafrost under the tundra. Arctic seas contain seasonal sea ice in many places.

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. Life in the Arctic includes zooplankton and phytoplankton, fish and marine mammals, birds, land animals, plants, and human societies. Arctic land is bordered by the subarctic.

The word Arctic comes from the Greek word ἀρκτικός arktikos "near the Bear, northern" and from the word ἄρκτος arktos meaning "bear" for either to the constellation known as Ursa Major, the "Great Bear", which is prominent in the northern portion of the celestial sphere, or the constellation Ursa Minor, the "Little Bear", which contains the celestial north pole (currently very near Polaris, the current north Pole Star, or North Star).

There are several definitions of what area is contained within the Arctic. The area can be defined as north of the Arctic Circle (about 66° 34'N), the approximate southern limit of the midnight sun and the polar night. Another definition of the Arctic, which is popular with ecologists, is the region in the Northern Hemisphere where the average temperature for the warmest month (July) is below 10 °C (50 °F); the northernmost tree line roughly follows the isotherm at the boundary of this region.

The climate of the Arctic region is characterized by cold winters and cool summers. Its precipitation mostly comes in the form of snow and is low, with most of the area receiving less than 50 cm (20 in). High winds often stir up snow, creating the illusion of continuous snowfall. Average winter temperatures can go as low as −40 °C (−40 °F), and the coldest recorded temperature is approximately −68 °C (−90 °F). Coastal Arctic climates are moderated by oceanic influences, having generally warmer temperatures and heavier snowfalls than the colder and drier interior areas. The Arctic is affected by current global warming, leading to climate change in the Arctic, including Arctic sea ice decline, diminished ice in the Greenland ice sheet, and Arctic methane emissions as the permafrost thaws. The melting of Greenland's ice sheet is linked to polar amplification.

Due to the poleward migration of the planet's isotherms (about 56 km (35 mi) per decade during the past 30 years as a consequence of global warming), the Arctic region (as defined by tree line and temperature) is currently shrinking. Perhaps the most alarming result of this is Arctic sea ice shrinkage. There is a large variance in predictions of Arctic sea ice loss, with models showing near-complete to complete loss in September from 2035 to sometime around 2067.

Arctic life is characterized by adaptation to short growing seasons with long periods of sunlight, and cold, dark, snow-covered winter conditions.