Antarctica

Antarctica is the fifth-largest continent. Its roughly 14.2 million square kilometres surround the South Pole, with the Antarctic Peninsula extending north toward South America. The continent is conventionally divided into East Antarctica and West Antarctica, separated by the Transantarctic Mountains. Most of its underlying land is hidden beneath ice, so maps of the surface often depict the ice sheet and its floating margins as much as the bedrock below.

Unlike the Arctic, which is an ocean surrounded by land, Antarctica is a landmass surrounded by the Southern Ocean. This difference shapes their geography, ecosystems and climate.

Antarctica is the coldest, highest, driest and windiest continent. A continental ice sheet, several kilometres thick in places, covers nearly all of its surface. Snowfall is low over much of the interior; accumulated snow gradually compacts into ice, which flows outward through glaciers. At the coast, some glaciers extend over the sea as floating ice shelves. Sea ice around the continent expands and contracts seasonally, affecting the surrounding ocean and atmosphere.

The ice sheet stores a very large share of Earth's land-based freshwater. Satellite observations from NASA's GRACE and GRACE Follow-On missions show that Antarctica's ice sheet has lost mass since 2002. Meltwater from land ice enters the ocean and contributes to sea-level rise; the scale and timing of future change depend on how the ice sheet and climate evolve.

Life on the continent is concentrated in small ice-free areas and is adapted to severe cold, dryness and limited liquid water. Lichens, mosses and liverworts are among the common land plants; only two native flowering plants are known from the Antarctic Peninsula. The continent has no naturally occurring terrestrial mammals, reptiles or amphibians.

The surrounding Southern Ocean is much richer in animal life. Antarctic krill form a key part of its food web, supporting fish, seabirds, penguins, seals and whales. Most Antarctic animal life is associated with the sea or its margins rather than the frozen interior. Marine ecosystems are studied and managed internationally, including because fishing and environmental change can affect species that depend on krill.

Antarctica has no native human population or permanent cities. Researchers and support staff from many countries work at stations for limited periods; the number of people present varies greatly between summer and winter. The remoteness, extreme conditions and ice cover make much of the continent difficult to reach, so satellites and remote sensing complement field research.

International cooperation is central to human activity there. The Antarctic Treaty was signed in 1959 by countries active in Antarctic science during the International Geophysical Year of 1957–58 and entered into force in 1961. It provides for peaceful use, freedom of scientific investigation and exchange of scientific observations and results. The treaty framework is distinct from the continent's physical geography, but it shapes how research and other human activities are conducted.