Under the widely used five ocean model, Earth's oceans are the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean and Arctic Ocean. Together they form the interconnected global ocean, which covers roughly 71 percent of Earth's surface and contains the overwhelming majority of the planet's water. The five names are geographical divisions of one connected saltwater system rather than five completely isolated bodies of water.
Ocean boundaries are established through geographical convention, international mapping practices and characteristics such as surrounding continents, latitude and oceanographic conditions. The Pacific lies between Asia and Australia on its western side and the Americas on its eastern side. The Atlantic lies between the Americas and Europe and Africa. The Indian lies between Africa, Asia and Australia. The Southern surrounds Antarctica, and the Arctic occupies the northern polar region.
The Pacific Ocean is the largest and deepest of the five oceans. It stretches from the Arctic region in the north to the Southern Ocean in the south and lies between Asia and Australia and the Americas. Its immense area includes numerous island groups and major marginal seas such as the Philippine Sea, Coral Sea and South China Sea, although these seas are geographically distinct from the Pacific as a whole.
The Pacific contains the Mariana Trench, including the Challenger Deep, the deepest known point in Earth's oceans. It is also a major component of the global climate system and is associated with phenomena such as El Nino and La Nina, which arise from coupled ocean atmosphere processes and influence weather patterns across many regions.
The Atlantic Ocean is the second largest ocean and separates the Americas from Europe and Africa. It has a roughly S shaped configuration and contains major marginal seas and gulfs including the Caribbean Sea, Gulf of Mexico, North Sea and Mediterranean Sea, although these are conventionally treated as subordinate seas rather than separate oceans. The Atlantic is crossed by the Mid Atlantic Ridge, a major underwater mountain system associated with seafloor spreading. Ocean circulation in the Atlantic includes the Atlantic Meridional Overturning Circulation, a large scale system involving the movement of warm surface water and colder deep water. The Atlantic has played a major role in climate, biological exchange, migration, exploration, trade and human history.
The Indian Ocean lies primarily between Africa, Asia, Australia and the Southern Ocean. It is the third largest ocean and is strongly influenced by the seasonal reversal of winds associated with the Asian monsoon system. Major features include the Arabian Sea, Bay of Bengal, Andaman Sea and extensive submarine ridges and basins. The Indian Ocean is important for global heat transport and supports highly productive coastal ecosystems, coral reefs, fisheries and major shipping routes. It also contains islands and island groups including Madagascar, the Maldives and the Seychelles. The ocean connects major economic regions and has long supported maritime trade between East Africa, the Middle East, South Asia and Southeast Asia.
The Southern Ocean is the ocean surrounding Antarctica and is recognised in the five ocean model as a distinct ocean extending generally to 60 degrees south, although historical definitions have differed. Its defining oceanographic feature is the Antarctic Circumpolar Current, which flows continuously around Antarctica and connects the Atlantic, Pacific and Indian Oceans.
The Southern Ocean plays a major role in global climate regulation because it exchanges heat, carbon dioxide and nutrients between the atmosphere, Antarctic waters and the other major ocean basins. It is also strongly affected by seasonal sea ice. The Southern Ocean supports distinctive ecosystems containing organisms such as krill, penguins, seals and numerous whale species, although many species also move beyond its conventional geographical boundaries.
The Arctic Ocean is the smallest and shallowest of the five oceans and occupies the region around the North Pole. It is largely enclosed by Eurasia and North America and is connected to the Atlantic through the Greenland and Norwegian seas and to the Pacific through the Bering Strait. The Arctic Ocean contains extensive seasonal and multiyear sea ice, although the amount and seasonal persistence of sea ice vary substantially over time. Major marginal seas include the Beaufort Sea, Chukchi Sea, Laptev Sea, Kara Sea, Barents Sea and East Siberian Sea. The Arctic is particularly important to climate because its high latitude environment strongly interacts with the atmosphere, sea ice and surrounding land.
Ocean terminology has changed over time. Earlier geographical traditions commonly recognised four oceans, generally the Atlantic, Pacific, Indian and Arctic, while the waters surrounding Antarctica were treated as southern portions of those oceans. The formal recognition of the Southern Ocean as a distinct fifth ocean has become increasingly widespread, including in modern educational and mapping contexts. Some organisations and reference works have historically used different boundaries or terminology, so older sources may describe four oceans. The five ocean model is now a common contemporary framework, but the exact boundaries of ocean basins can still vary according to the authority and purpose involved.
The five oceans are therefore best understood as named regions within a single connected global ocean system. Oceanographers may also use terms such as ocean basin, marginal sea, semi enclosed sea, current, gyre, trench, ridge and continental shelf to describe increasingly specific components of that system. The oceans regulate climate, transport heat, store carbon, support marine ecosystems, provide resources, influence weather and facilitate transportation. Their physical behaviour depends on interactions among wind, Earth's rotation, temperature, salinity, density, tides, sea ice and submarine topography. The five names provide a practical global classification while recognising that the underlying water system is continuous.
