The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), northern Finland (Lapland), Iceland, northern Norway (Finnmark and Svalbard), Russia (Murmansk, Siberia, Nenets Okrug, Novaya Zemlya), northernmost Sweden and the United States (Alaska). Land within the Arctic region has seasonally varying snow and ice cover, with predominantly treeless permafrost (permanently frozen underground ice) containing 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. Definition and etymology The word Arctic comes from the Greek word (arktikos), "near the Bear, northern" and from the word (arktos), meaning bear. The name refers either to the constellation Ursa Major, the "Great Bear", which is prominent in the northern portion of the celestial sphere, or to 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 a number of 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 ; the northernmost tree line roughly follows the isotherm at the boundary of this region. Climate The Arctic 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 . High winds often stir up snow, creating the illusion of continuous snowfall. Average winter temperatures can go as low as , and the coldest recorded temperature is approximately . 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 Arctic sea ice shrinkage, diminished ice in