The Southern Ocean, also called the Antarctic Ocean, is the area of water in the southernmost part of the world's oceans. It is usually considered to be the area south of 60° S latitude, surrounding Antarctica. The Southern Ocean covers about 21,960,000 square kilometers (8,480,000 square miles), making it the second-smallest of the five major ocean regions. It is smaller than the Pacific, Atlantic, and Indian oceans, but larger than the Arctic Ocean.

In early February 2019, the Five Deeps Expedition measured the deepest part of the Southern Ocean, which is located south of the 60th parallel. Using multibeam sonar technology, the team found the deepest point at coordinates 60° 28' 46"S, 025° 32' 32"W, with a depth of 7,434 meters (24,390 feet). The expedition leader, Victor Vescovo, suggested naming this location "Factorian Deep" after the submersible DSV Limiting Factor, which he used to reach the bottom for the first time on February 3, 2019.

In the 1770s, explorer James Cook proved that the Southern Ocean connects the southern parts of the globe. However, scientists have long debated whether the Southern Ocean should be considered a separate body of water, bounded by the Antarctic Convergence—a zone where cold Antarctic waters mix with warmer Subantarctic waters—or if it should instead be seen as the southern edge of the Pacific, Atlantic, and Indian oceans. In 2000, the International Hydrographic Organization (IHO) decided to recognize the Southern Ocean as a distinct region after studying its role in ocean circulation. The Southern Ocean is now defined as the area south of the northern boundary of this circulation.

The Southern Ocean overturning circulation is a key part of the global thermohaline circulation, which includes the well-known Atlantic meridional overturning circulation (AMOC). Like AMOC, this circulation has been significantly affected by climate change. These changes have increased the separation of ocean layers, and could lead to the circulation slowing or even collapsing. If this happens, it could harm global weather patterns and marine ecosystems, with effects lasting for centuries. The warming of the ocean is already altering marine life in this region.

Definition and term use

In 1919, the International Hydrographic Bureau, which later became the IHO, held the First International Conference to agree on borders and names for oceans and seas. The IHO published these agreements in its book Limits of Oceans and Seas, with the first edition released in 1928. Over time, the northern boundary of the Southern Ocean has gradually moved farther south. From 1953 onward, the Southern Ocean was no longer included in the official publication, and local hydrographic offices were left to define its limits.

In 2000, the IHO included the Southern Ocean in its revised definitions, describing it as the waters south of the 60th parallel south. However, this definition has not been officially accepted due to ongoing disagreements, such as the naming of the Sea of Japan. A draft version of this definition was shared in 2002 and is used by some organizations, including the CIA World Factbook and Merriam-Webster.

The Australian Government defines the Southern Ocean as the area directly south of Australia. In 2021, the National Geographic Society officially recognized the Southern Ocean. Before this, it did not show the Southern Ocean on its maps, instead extending the Pacific, Atlantic, and Indian Oceans to Antarctica. Map publishers like Hema Maps and GeoNova now include the Southern Ocean on their maps.

The term "Southern Ocean" was once used to describe the Pacific Ocean or South Pacific. It was first used by the Spanish explorer Vasco Núñez de Balboa in the 1500s. "South Seas" is another older term for the same region. A British law from 1745 mentioned "the Western and Southern Ocean of America" when discussing a Northwest Passage.

Historically, different people used varying limits for the Southern Ocean. For example, James Cook’s writings suggested New Caledonia was near its edge. In 1795, a dictionary said the Southern Ocean was south of America and Africa. Other sources used different latitudes, such as 40°S or 50°S, as northern limits. In 1835, a magazine divided the "Great Southern Ocean" into two parts: the "Southern Ocean" and the "Antarctic Ocean," with the boundary along the Antarctic Circle.

In 1834, a British law called the waters south of South Australia the "Southern Ocean." In 1881, a law in Victoria, Australia, described a region’s boundary as reaching the "Southern Ocean."

In the 1928 edition of Limits of Oceans and Seas, the Southern Ocean was defined by land borders: Antarctica to the south, and South America, Africa, Australia, and Broughton Island, New Zealand, to the north. Specific land-based limits included Cape Horn in Chile, Cape Agulhas in Africa, and parts of Australia’s coast, such as Cape Leeuwin and Cape Otway. From there, the boundary followed the coast of Australia, crossed Bass Strait, and reached Broughton Island, New Zealand, before returning to Cape Horn.

In 1937, the IHO moved the northern limits of the Southern Ocean farther south. The ocean was then defined as extending northward to 40°S between Cape Agulhas in Africa and Cape Leeuwin in Australia, and to 55°S between New Zealand and Cape Horn in South America.

Before the 2002 edition, the IHO’s definitions did not include seas within oceans. The Great Australian Bight was not named in the 1928 edition and was defined differently in the 1937 edition. This meant it was part of the Southern Ocean in 1928 but not officially inside any adjacent ocean by 1937.

In the 2002 draft edition, the IHO proposed that seas are subdivisions of oceans. If this rule had been in place in 1937, the Great Australian Bight would still have been part of the Southern Ocean. Comparing old and new definitions requires understanding how the 2002 changes in terminology affect these comparisons.

The Southern Ocean was not included in the 1953 edition of Limits of Oceans and Seas. A note in the publication stated that most countries believed the term "Ocean" was not appropriate for the Southern Ocean due to unclear northern boundaries. Instead, the Atlantic, Indian, and Pacific Oceans were extended southward to touch Antarctica. The Great Australian Bight and Tasman Sea were also redefined.

In 2000, the IHO asked its 68 member nations about the Southern Ocean. Of the 28 responding countries, all except Argentina supported redefining it. The name "Southern Ocean" received the most votes, beating "Antarctic Ocean." Half of the votes supported defining the northern limit at 60°S, while others supported 50°S or even 35°S. The Southern Ocean Observing System collects data from areas south of 40°S.

A draft fourth edition of Limits of Oceans and Seas was shared in 2002 but has not been officially published. Some countries raised concerns about naming issues, such as the Sea of Japan dispute. Changes included renaming 60 seas and updating the publication’s title. Australia also expressed concerns about the Southern Ocean’s definition. The third edition, which excluded the Southern Ocean, remains in use.

Despite this, the 2002 draft definition is used by some countries, scientists, and organizations, such as the U.S. (the CIA World Factbook includes "Southern Ocean," though not all new sea names within it, like "Cosmonauts Sea").

History of exploration

Exploration of the Southern Ocean was inspired by the idea of a Terra Australis, a large landmass in the far south of the globe to balance the northern lands of Eurasia and North Africa. This belief existed since the time of Ptolemy. In 1487, Bartolomeu Dias sailed around the Cape of Good Hope, bringing explorers closer to the cold of Antarctica and proving that an ocean separated Africa from any land that might exist in the south. Ferdinand Magellan, who passed through the Strait of Magellan in 1520, thought the islands of Tierra del Fuego were part of this unknown southern land. In 1564, Abraham Ortelius published his first map, Typus Orbis Terrarum, an eight-leaved wall map of the world, showing Regio Patalis with Locach as a northward extension of Terra Australis, reaching as far as New Guinea.

European geographers continued to connect the coast of Tierra del Fuego with the coast of New Guinea on their maps. They imagined a vast unknown land in the southern Atlantic, Indian, and Pacific oceans, drawing the outline of Terra Australis Incognita, a large continent stretching into the tropics. The search for this southern land was a major goal for explorers in the 16th and early 17th centuries.

In 1603, the Spaniard Gabriel de Castilla claimed to have seen "snow-covered mountains" beyond 64° S. He is recognized as the first explorer to discover Antarctica, though no one believed him at the time. In 1606, Pedro Fernández de Quirós claimed all lands he discovered in Australia del Espiritu Santo (the New Hebrides) and those he would find "even to the Pole" for the king of Spain.

Francis Drake, like earlier Spanish explorers, thought there might be an open channel south of Tierra del Fuego. In 1615, Willem Schouten and Jacob Le Maire discovered the southern tip of Tierra del Fuego and named it Cape Horn, proving the archipelago was small and not connected to a southern land. In 1642, Abel Tasman showed that New Holland (Australia) was separated from any southern continent by sea.

In 1675, Anthony de la Roché visited South Georgia, the first discovery of land south of the Antarctic Convergence, in the Southern Ocean or Antarctic. Cartographers later named this land "Roché Island" to honor him. James Cook knew of this discovery when he mapped the island in 1775.

Edmond Halley’s voyage in the HMS Paramour to study magnetism in the South Atlantic reached 52° S in 1700, where he encountered pack ice. French naval officer Jean-Baptiste Charles Bouvet de Lozier searched for the "South Land" described by a legendary figure named "sieur de Gonneyville." His efforts led to the discovery of Bouvet Island in 54°10′ S and navigation through ice-covered seas near 55° S in 1730.

In 1771, Yves Joseph Kerguelen sailed from France to search for a large continent. He found a land at 50° S, naming it South France, and believed it was the center of the southern continent. Later, he renamed it the Isle of Desolation, but it was eventually called Kerguelen Island.

The search for the unknown continent reached its peak with Alexander Dalrymple, a hydrographer who led the Royal Society’s Transit of Venus expedition to Tahiti in 1769. Captain James Cook was chosen to lead the expedition. In 1772, Cook sailed with the Resolution and Adventure, searching for Bouvet Island and exploring latitudes as far south as 67° 15′ S. He crossed the Antarctic Circle for the first time in history.

Cook then searched for French Southern and Antarctic Lands but missed them due to an error in longitude. He continued south, reaching 71° 10′ S before ice blocked his path. In 1774, Cook’s farthest point was 71° 10′ S, the southernmost position reached in the 18th century. He later discovered the South Sandwich Islands and confirmed there was no land connection between New Zealand and Tierra del Fuego. Cook’s voyages disproved the idea of a habitable southern continent.

Before 1770, no voyagers had reached the Antarctic Circle. In 1822–1824, James Weddell sailed to the South Orkneys, seeking seals. On 20 February 1823, he reached 74°15′ S, the southernmost point any ship had reached at the time. He theorized the sea extended to the South Pole.

In 1819, William Smith discovered Livingston Island, the first land south of 60° S latitude.

Geography

The Southern Ocean is the youngest ocean on Earth. It formed about 30 million years ago when Antarctica and South America moved apart, creating the Drake Passage. This movement allowed the Antarctic Circumpolar Current to form, which flows around Antarctica.

The Southern Ocean has a northern boundary at 60°S. Unlike other oceans, its northern edge does not touch land. Instead, it meets the Atlantic, Indian, and Pacific Oceans. This is different from earlier maps that showed a land boundary.

One reason the Southern Ocean is considered a separate ocean is because its water is different from water in other oceans. The Antarctic Circumpolar Current moves water around the Southern Ocean quickly. For example, water near New Zealand and water near South America are more similar to each other than to water in the Pacific Ocean.

The Southern Ocean is deep in most areas, with typical depths between 4,000 and 5,000 meters (13,000 to 16,000 feet). Its deepest point is 7,236 meters (23,740 feet) at the South Sandwich Trench. The Antarctic continental shelf is narrow and unusually deep, with edges reaching 800 meters (2,600 feet), much deeper than the global average of 133 meters (436 feet).

The Antarctic ice pack changes size with the seasons. It reaches its smallest size of about 2.6 million square kilometers (1.0 × 10^6 square miles) in March and its largest size of about 18.8 million square kilometers (7.3 × 10^6 square miles) in September.

Oceans are divided into sections like seas, straits, bays, and gulfs. The 2002 draft of the IHO publication Limits of Oceans and Seas proposed many sections of the Southern Ocean, such as the "Cosmonauts Sea" and "Cooperation Sea." These names are not included in the current IHO document from 1953. Major maps, like the 2014 National Geographic and British Times Atlas, do not use these names, but some Soviet and Russian maps do.

The Southern Ocean may contain large oil and gas reserves along its edges. It may also have placer deposits, which are valuable minerals like gold formed by natural processes. Manganese nodules, which are rock formations made of layers of iron and manganese, are expected to exist in the Southern Ocean. These nodules were studied by mining groups in the 1960s and 1970s.

Icebergs that form in the Southern Ocean hold enough fresh water to meet the needs of all people on Earth for several months. Some ideas have been proposed to move icebergs to dry regions, like Australia, but none have worked yet.

Icebergs can appear in the Southern Ocean at any time of year. Some icebergs are very deep, while smaller ones and sea ice (about 0.5 to 1 meter thick) can be dangerous to ships. The ocean floor near Antarctica has layers of glacial deposits that change quickly over short distances.

Sailors refer to latitudes between 40°S and 70°S as the "Roaring Forties," "Furious Fifties," and "Shrieking Sixties" because of strong winds and large waves. Icebergs, especially between May and October, make this area even more dangerous. The remote location of the Southern Ocean makes search and rescue efforts difficult.

Physical oceanography

The Southern Ocean is the second smallest ocean, but it has a unique and powerful current called the Antarctic Circumpolar Current. This current flows continuously eastward around Antarctica, forming the longest ocean current in the world at 21,000 kilometers (13,000 miles) in length. It moves 130 million cubic meters of water every second, which is 100 times the combined flow of all the world's rivers.

Along the coast of Antarctica, several processes create water types found only in the Southern Ocean. One example is Antarctic Bottom Water, a very cold and salty water that forms under sea ice. Another is Circumpolar Deep Water, a mix of Antarctic Bottom Water and North Atlantic Deep Water.

The Antarctic Circumpolar Current is linked to the Antarctic Convergence, a boundary where cold waters from Antarctica meet warmer subantarctic waters. At this boundary, Antarctic waters sink below subantarctic waters, creating areas of mixing and upwelling. These areas are rich in nutrients, supporting large amounts of phytoplankton, copepods, and Antarctic krill. These organisms form the base of food chains that support fish, whales, seals, penguins, albatrosses, and many other species.

The Antarctic Convergence is considered the best natural marker for the northern edge of the Southern Ocean.

Strong westerly winds around Antarctica drive water northward, creating a type of coastal upwelling. Since there are no continents between South America and the Antarctic Peninsula, some of this water rises from great depths. In many studies, this upwelling is the main way deep water reaches the surface. Similar upwelling occurs near the west coasts of North and South America, Africa, and Australia, all connected to oceanic high-pressure systems.

The Ross Gyre and Weddell Gyre are two large, circular ocean currents in the Southern Ocean. The Ross Gyre is in the Ross Sea, and the Weddell Gyre is in the Weddell Sea. Both gyres rotate clockwise and form due to interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf.

Sea ice has been observed in the center of the Ross Gyre. Some evidence suggests that global warming has slightly reduced the salinity of the Ross Gyre’s waters since the 1950s.

The Coriolis effect in the Southern Hemisphere causes water to move to the left, creating upwelling of cold, nutrient-rich water in the Weddell Gyre. This upwelling makes these areas very productive.

The Southern Ocean Observing System (SOOS) coordinates research on the Southern Ocean. It provides access to data collected over many years, including information about ocean currents and water conditions. This data focuses on key ocean measurements for the region south of 40°S.

Climate

Sea temperatures range from about −2 to 10 °C (28 to 50 °F). Cyclonic storms move eastward around the continent and often become strong due to the temperature difference between ice and open ocean. The ocean between about 40° south latitude and the Antarctic Circle has the strongest average winds on Earth. In winter, the ocean freezes outward to 65° south latitude in the Pacific region and 55° south latitude in the Atlantic region, causing surface temperatures to drop below 0 °C. At some coastal areas, strong drainage winds from the interior prevent shoreline ice from forming during winter.

The Southern Ocean overturning circulation (also called the Southern Meridional Overturning Circulation or Antarctic Overturning Circulation) is part of a global thermohaline circulation that connects different ocean basins worldwide. Its northern counterpart is the Atlantic Meridional Overturning Circulation (AMOC). This circulation works when certain currents carry warm, oxygen-rich, nutrient-poor water into the deep ocean (downwelling), while cold, oxygen-poor, nutrient-rich water rises (upwelling) at specific locations. Thermohaline circulation moves large amounts of warm and cold water across the planet, as well as dissolved oxygen, organic carbon, and nutrients like iron. Both parts of the circulation greatly influence Earth's energy balance and ocean carbon cycle, playing a key role in Earth's climate system.

As human-caused greenhouse gas emissions increase, one major effect of climate change on oceans is the rise in ocean heat content, which has absorbed over 90% of global warming since 1971. Much of this warming has occurred in the Southern Hemisphere ocean south of 30°S. In West Antarctica, the upper layer of the ocean has warmed 1 °C (1.8 °F) since 1955, and the Antarctic Circumpolar Current (ACC) is warming faster than the global average. This warming affects the movement of warm and cold water masses in the overturning circulation and reduces sea ice cover (which reflects sunlight and increases Earth's albedo) in the Southern Hemisphere. It also impacts the mass balance of Antarctica's ice shelves and glaciers. For these reasons, climate models show that the year global warming reaches 2 °C (3.6 °F) depends more on the state of the circulation than any other factor, except emissions themselves.

Greater warming of ocean water increases ice loss from Antarctica and produces more fresh meltwater at a rate of 1100–1500 billion tons (GT) per year. This meltwater mixes back into the Southern Ocean, making its water fresher. This freshening causes layers in the Southern Ocean to become more stable and separated, which has the largest impact on the long-term properties of its circulation. These changes speed up the upper cell of the circulation, increasing the flow of major currents, while slowing down the lower cell, which relies on highly saline Antarctic bottom water. This water has already weakened due to freshening, despite some recovery in the 2010s. Since the 1970s, the upper cell has strengthened by 3–4 sverdrup (Sv; 1 million cubic meters per second), or 50–60% of its flow, while the lower cell has weakened by a similar amount. However, these changes were not only caused by climate change, as the natural Interdecadal Pacific Oscillation cycle also played a role.

Similar processes affect the Atlantic Meridional Overturning Circulation (AMOC), which is influenced by ocean warming and meltwater from the shrinking Greenland ice sheet. It is possible that both circulations may weaken further in response to warming and freshening, or eventually collapse to a much weaker state, which would be hard to reverse and represent tipping points in the climate system. Paleoclimate evidence shows the overturning circulation was weaker during past periods that were both warmer and colder than today. However, the Southern Hemisphere is home to only 10% of the world's population, and the Southern Ocean overturning circulation has historically received less attention than the AMOC. While many studies estimate the level of global warming that could cause AMOC collapse, less research exists for the Southern Ocean overturning circulation as of the early 2020s. Some suggest its collapse may occur between 1.7 °C (3.1 °F) and 3 °C (5.4 °F), but this estimate is less certain than for other tipping points.

The effects of Southern Ocean overturning circulation collapse have been studied less, though scientists expect them to unfold over centuries. One example is the loss of nutrients from Antarctic bottom water, which could reduce ocean productivity and harm Southern Ocean fisheries, potentially leading to fish species extinction and marine ecosystem collapse. Reduced marine productivity would also mean the ocean absorbs less carbon (though not in the 21st century), which could increase long-term warming from human emissions or extend the time warming lasts before declining on geological timescales. There may also be less rainfall in Southern Hemisphere countries like Australia, with more rainfall in the Northern Hemisphere. However, a collapse of the AMOC would have similar but opposite effects, and the two would counteract each other to some extent. Both impacts would occur alongside other climate change effects on water cycles and fisheries.

Biodiversity

Many marine animals live in the Southern Ocean and depend on phytoplankton, tiny plants that float in the water. Antarctic wildlife includes penguins, blue whales, orcas, colossal squids, and fur seals. The emperor penguin is the only penguin that breeds during the winter in Antarctica. The Adélie penguin breeds farther south than any other penguin. The rockhopper penguin has unique feathers around its eyes that look like eyelashes. King penguins, chinstrap penguins, and gentoo penguins also breed in Antarctica.

The Antarctic fur seal was hunted heavily in the 18th and 19th centuries for its fur by people from the United States and the United Kingdom. The Weddell seal is named after Sir James Weddell, a British explorer who led sealing expeditions in the Weddell Sea. Antarctic krill, a small crustacean that swims in large groups, is the most important species in the Southern Ocean ecosystem. Krill is a main food source for whales, seals, squid, penguins, albatrosses, and many other animals.

The seafloor in Antarctica has many different types of life, with as many as 155,000 animals found in one square meter. Because the seafloor environment is similar around Antarctica, hundreds of species live in the same area, which is unusual for such a large group. Many deep-sea animals in Antarctica are unusually large, a phenomenon called deep-sea gigantism.

A study of sea life conducted during the International Polar Year involved about 500 researchers and was completed in 2010. This research was part of the global Census of Marine Life (CoML) and found that over 235 marine species live in both the Arctic and Antarctic regions, despite the 12,000-kilometer distance between them. Large animals like whales and birds travel between the poles each year, while smaller animals such as mudworms and snails also live in both regions. Factors like similar deep ocean temperatures and ocean currents that carry eggs and larvae help these species spread across the world. Studies of small marine animals often show that they are closely related but different species, not a single species found in both poles.

The rocky shores of Antarctica and nearby islands are home to over 100 million birds each spring. These birds include albatrosses, petrels, skuas, gulls, and terns. The South Georgia pipit, a bird that eats insects, is only found on South Georgia and nearby islands. Freshwater ducks live on South Georgia and the Kerguelen Islands.

All penguins live in the Southern Hemisphere, with the highest number near Antarctica. Four of the 18 penguin species live on the Antarctic mainland and nearby islands, and four more live on subantarctic islands. Emperor penguins have four layers of feathers that help them stay warm. They are the only Antarctic animals that breed during the winter.

There are few fish species in the Southern Ocean, grouped into a small number of families. The most diverse family is the snailfish (Liparidae), followed by the cod icefish (Nototheniidae) and eelpout (Zoarcidae). Together, these fish make up nearly nine-tenths of the 320 known fish species in the Southern Ocean, with many more species yet to be discovered, especially among snailfish. Snailfish are usually found in deep water, while icefish live in shallower areas.

Cod icefish (Nototheniidae) and other families belong to the Notothenioidei suborder, sometimes called icefish. These fish have special proteins in their blood that prevent freezing, allowing them to live in water near or below 0°C. Similar proteins are also found in snailfish.

Crocodile icefish (family Channichthyidae), also called white-blooded fish, are only found in the Southern Ocean. These fish lack red blood cells, so their blood is colorless. One species, the mackerel icefish, was once the most common fish in shallow coastal waters but was overfished in the 1970s and 1980s. Icefish spend the day near the seafloor and swim higher in the water at night to eat plankton and small fish.

Two species in the Dissostichus genus, the Antarctic toothfish and the Patagonian toothfish, live on the seafloor at depths of 100–3,000 meters. These fish can grow up to 2 meters long and weigh 100 kilograms, living up to 45 years. The Antarctic toothfish lives near the Antarctic mainland, while the Patagonian toothfish lives in warmer subantarctic waters. Both species are fished commercially, and overfishing has reduced their numbers.

Another group of fish, the genus Notothenia, also has antifreeze proteins in their bodies, like the Antarctic toothfish.

The Antarctic silverfish (Pleuragramma antarcticum) is a unique icefish that lives in open ocean waters near Antarctica, unlike most other icefish.

Seven types of seals, called pinnipeds, live in Antarctica. The largest, the elephant seal, can weigh up to 4,000 kilograms, while the smallest, the Antarctic fur seal, weighs only 150 kilograms. Elephant seals and Antarctic fur seals live north of the sea ice and breed on beaches. The other four seal species live on sea ice. Crabeater seals and Weddell seals form groups to breed, while leopard seals and Ross seals live alone. These seals hunt underwater but breed on land or ice, as they have no land predators.

The four seal species that live on sea ice make up about half of the world’s seal population. Crabeater seals number

Environment

Increased sunlight from the Antarctic ozone hole has harmed marine life, reducing the amount of tiny ocean plants called phytoplankton by up to 15%. This sunlight has also begun to damage the DNA of some fish. Illegal fishing, which involves catching far more Patagonian toothfish than allowed, may harm the long-term survival of this species. Fishing methods like long-line fishing for toothfish often cause many seabirds to die.

All international rules about the world's oceans apply to the Southern Ocean. This area is also covered by several regional agreements:

The Southern Ocean Whale Sanctuary, created by the International Whaling Commission (IWC), bans commercial whaling south of 40 degrees south (and between 50 and 130 degrees west south of 60 degrees south). Japan does not accept this rule, claiming it violates the IWC charter. Since the sanctuary only restricts commercial whaling, Japan has continued to hunt whales in the area for scientific research. In 2014, the International Court of Justice ruled that Japan's whaling program, which Japan claimed was for scientific purposes, was actually a way to hide commercial whaling. No further permits for whaling were allowed.

The Convention for the Conservation of Antarctic Seals is part of the Antarctic Treaty System. It was signed on February 11, 1972, during a meeting in London.

The Convention for the Conservation of Antarctic Marine Living Resources is also part of the Antarctic Treaty System. It started on April 7, 1982, with the goal of protecting marine life and the environment near Antarctica. This agreement was created because scientists were worried that catching too much krill (a small shrimp-like creature that many animals depend on for food) in the Southern Ocean could harm other marine species.

Many countries have banned searching for and using minerals south of the Antarctic Convergence, a line of water that separates cold polar waters from warmer waters. The Antarctic Treaty covers the area south of 60 degrees south and stops new claims to Antarctica.

The Convention for the Conservation of Antarctic Marine Living Resources applies to the area south of 60° South latitude and also includes areas north of that line up to the Antarctic Convergence.

Economy

Between 1 July 1998 and 30 June 1999, fisheries caught 119,898 tonnes (118,004 long tons; 132,165 short tons) of fish, with 85% being krill and 14% being Patagonian toothfish. In late 1999, international agreements were introduced to reduce illegal, unreported, and unregulated fishing. During the 1998–99 season, illegal fishing activities caught five to six times more Patagonian toothfish than the legal fishery allowed.

Ports and harbors

Major operational ports in Antarctica include Rothera Station, Palmer Station, Villa Las Estrellas, Esperanza Base, Mawson Station, McMurdo Station, and offshore anchorages.

Few ports or harbors exist along the southern (Antarctic) coast of the Southern Ocean because ice conditions make most shores usable only for short periods during midsummer. Even then, some locations require icebreaker ships to help vessels enter. Most Antarctic ports are managed by government research stations and are closed to commercial or private ships unless an emergency occurs. Any vessel in a port south of 60 degrees south must be inspected by Antarctic Treaty observers.

The southernmost port in the Southern Ocean is McMurdo Station, located at 77°50′S 166°40′E. Winter Quarters Bay, on the southern tip of Ross Island, has a small harbor where a floating ice pier allows port operations during summer. Operation Deep Freeze personnel built the first ice pier at McMurdo in 1973.

Based on the original 1928 IHO definition of the Southern Ocean (and the 1937 definition if the Great Australian Bight is included), Australian ports and harbors between Cape Leeuwin and Cape Otway on the mainland and along Tasmania’s west coast would also be considered part of the Southern Ocean. These include larger ports such as Albany, Thevenard, Port Lincoln, Whyalla, Port Augusta, Port Adelaide, Portland, Warrnambool, and Macquarie Harbour.

Although some yacht race organizers describe their routes as passing through the Southern Ocean, the actual paths of these races do not enter the geographical boundaries of the Southern Ocean. Instead, the routes pass through the South Atlantic, South Pacific, and Indian Oceans.