Arctic• The Arctic is a region located at the northern-most part of theEarth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia,Greenland, the United States, Norway, 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° 33N), 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 (50 °F); 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 Earths 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.
Antarctica• Antarctica is Earths southernmost continent, encapsulating the South Pole. It is situated in the Antarcticregion of the Southern Hemisphere, almost entirely south of theAntarctic Circle, and is surrounded by the Southern Ocean. At 14.0 million km2 (5.4 million sq mi), it is the fifth-largest continent in area after Asia, Africa, North America, and South America. For comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages at least 1 mile (1.6 km) in thickness.• Antarctica, on average, is the coldest, driest, and windiest continent, and has the highest average elevation of all the continents. Antarctica is considered a desert, with annualprecipitation of only 200 mm (8 inches) along the coast and far less inland. The temperature in Antarctica has reached −89 °C (−129 °F). There are no permanent human residents, but anywhere from 1,000 to 5,000 people reside throughout the year at the research stations scattered across the continent. Only cold-adapted organisms survive there, including many types of algae, animals (for example mites, nematodes,penguins, seals and tardigrades), bacteria, fungi, plants, andprotista. Vegetation where it occurs is tundra.• Although myths and speculation about a Terra Australis("Southern Land") date back to antiquity, the first confirmed sighting of the continent is commonly accepted to have occurred in 1820 by the Russian expedition of Fabian Gottlieb von Bellingshausen and Mikhail Lazarev. The continent, however, remained largely neglected for the rest of the 19th century because of its hostile environment, lack of resources, and isolation. The Antarctic Treaty was signed in 1959 by 12 countries; to date, 47 countries have signed the treaty. The treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear power, supports scientific research, and protects the continents ecozone. Ongoing experiments are conducted by more than 4,000 scientists of multiple nationalities.