The Southern Ocean, also called the Antarctic Ocean, includes the waters farthest south in the world's oceans, usually considered to be south of 60° S latitude and surrounding Antarctica. It covers an area of 21,960,000 km (8,480,000 mi) and is the second-smallest of the five main ocean regions. It is smaller than the Pacific, Atlantic, and Indian oceans, but larger than the Arctic Ocean.

The deepest part of the Southern Ocean, based on the definition that it lies south of the 60th parallel, was measured during the Five Deeps Expedition in early February 2019. 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, James Cook's voyages showed that waters exist in the southern parts of the globe. However, geographers have often debated whether the Southern Ocean should be defined as the area bounded by the Antarctic Convergence—a zone where cold, northward-moving Antarctic waters mix with warmer Subantarctic waters—or if its waters should instead be considered the southern edges of the Pacific, Atlantic, and Indian oceans. In 2000, the International Hydrographic Organization (IHO) resolved this debate after recognizing the importance of the Southern Ocean's overturning circulation. Now, the term "Southern Ocean" refers to the body of water located south of the northern edge of this circulation.

The Southern Ocean overturning circulation is important because it is 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 ocean stratification and may cause the circulation to slow or even collapse. Such a collapse 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 was the earlier version of the IHO, held the First International Conference to agree on borders and names for oceans and seas. The IHO later published these agreements in its book Limits of Oceans and Seas, with the first edition released in 1928. Over time, the boundaries of the Southern Ocean have moved farther south. Since 1953, the Southern Ocean has not been officially included in the IHO’s publications, and local map-making offices have been responsible for defining their own limits.

In 2000, the IHO included the Southern Ocean in its revisions, defining it as the waters south of the 60th parallel south. However, this definition has not been officially accepted due to disagreements, such as the naming dispute over the Sea of Japan. The 2000 definition was shared as a draft in 2002 and is used by some groups, including the CIA World Factbook and Merriam-Webster.

The Australian Government considers the Southern Ocean to be the area directly south of Australia. In 2021, the National Geographic Society officially recognized the Southern Ocean. Before this, its maps showed the Pacific, Atlantic, and Indian Oceans extending to Antarctica, without clearly labeling the Southern Ocean. Map publishers like Hema Maps and GeoNova include the Southern Ocean on their maps.

The term “Southern Ocean” was once used for the Pacific Ocean or South Pacific, named by Spanish explorer Vasco Núñez de Balboa. An older synonym is “South Seas.” A British law from 1745 referred to “the Western and Southern Ocean of America.”

Historically, different people used varying limits for the Southern Ocean. For example, James Cook’s writings suggested New Caledonia bordered it, while others, like Peacock and John Payne, used different lines. In 1835, the Family Magazine divided the “Great Southern Ocean” into the “Southern Ocean” and the “Antarctick Ocean” along the Antarctic Circle.

In 1834, the UK’s South Australia Act described the southern boundary of the new province as “the Southern Ocean.” In 1881, the Colony of Victoria’s Legislative Council Act described part of the Bairnsdale division as extending to “the Southern Ocean.”

In the 1928 first edition of Limits of Oceans and Seas, the Southern Ocean was defined by land-based limits: Antarctica to the south and South America, Africa, Australia, and Broughton Island, New Zealand, to the north. Specific land limits included Cape Horn in Chile, Cape Agulhas in Africa, and parts of Australia’s coast. The boundary followed the coast of mainland Australia from Cape Leeuwin to Cape Otway, then across Bass Strait to Cape Grim, Tasmania. From there, it continued along Tasmania’s west coast to the South East Cape, then to Broughton Island, New Zealand, and back to Cape Horn.

In the 1937 second edition, the northern limits of the Southern Ocean were moved farther south. The ocean extended from Antarctica northward to 40°S between Cape Agulhas and Cape Leeuwin, and to 55°S between New Zealand’s Auckland Islands and Cape Horn.

Before the 2002 edition, ocean boundaries did not include seas within them. The Great Australian Bight was unnamed in the 1928 edition and was described in the 1937 edition. By 1937, it was no longer part of any adjacent ocean. In the 2002 draft, the IHO classified seas as parts of oceans, which would have kept the Bight within the Southern Ocean if the 2002 rules had been in place earlier.

The Southern Ocean was not included in the 1953 third edition. Instead, the Atlantic, Indian, and Pacific Oceans were extended southward, and the Great Australian Bight and Tasman Sea’s southern limits were moved northward.

In 2000, the IHO asked its 68 member nations about the Southern Ocean. Of the 28 responses, all except Argentina supported redefining it, emphasizing the importance of ocean currents. The name “Southern Ocean” received 18 votes, more than the alternative “Antarctic Ocean.” Half of the votes supported defining the northern limit at the 60th parallel south, while others supported lower latitudes.

A draft fourth edition of Limits of Oceans and Seas was shared in 2002 but has not been published due to naming disputes, such as the Sea of Japan issue. Some countries, like Australia, raised concerns about the Southern Ocean’s limits. The third edition, which did not define the Southern Ocean, remains the official version.

Despite this, the 2002 draft is used by some nations, scientists, and organizations, including the U.S. (via the CIA World Factbook) and Merriam-Webster. Some countries, like the UK, use the 55th parallel south as a boundary. Others, such as Encyclopædia Britannica, describe the Southern Ocean as extending north to South America, while its description of the Indian Ocean conflicts with this. The National Geographic Society also shows the Southern Ocean on its maps.

History of exploration

Exploration of the Southern Ocean began because people believed a large landmass called Terra Australis existed in the far south of the globe to balance the northern lands of Eurasia and North Africa. This idea was first mentioned by Ptolemy. In 1487, Bartolomeu Dias sailed around the Cape of Good Hope, bringing explorers closer to the cold of Antarctica and showing that an ocean separated Africa from any land that might exist in the south. In 1520, Ferdinand Magellan passed through the Strait of Magellan and thought the islands of Tierra del Fuego were part of this unknown southern land. In 1564, Abraham Ortelius made a map called Typus Orbis Terrarum and showed a region called Regio Patalis with Locach as a northern part of Terra Australis, reaching as far as New Guinea.

European mapmakers continued to connect Tierra del Fuego with New Guinea and imagined a large continent called Terra Australis Incognita ("Unknown Southern Land") stretching into the tropics. Finding this land became a major goal for explorers in the 16th and early 17th centuries.

In 1603, Spanish explorer Gabriel de Castilla claimed to see "snow-covered mountains" beyond 64° S, and is considered the first person to discover Antarctica, though his discovery was ignored at the time. In 1606, Pedro Fernández de Quirós claimed lands in Australia del Espiritu Santo (New Hebrides) and said he would find lands "even to the Pole."

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 sailed to the southern tip of Tierra del Fuego and named it Cape Horn, proving the Tierra del Fuego archipelago was small and not connected to a southern continent. In 1642, Abel Tasman showed that New Holland (Australia) was separated by sea from any southern continent.

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

In 1700, Edmond Halley sailed on the Paramour to study Earth's magnetic field and met pack ice at 52° S, his farthest point south. In 1730, French explorer Jean-Baptiste Charles Bouvet de Lozier searched for "South Land" and discovered Bouvet Island at 54°10′ S, navigating ice-covered seas near 55° S.

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

Alexander Dalrymple, a hydrographer, strongly believed in the existence of an undiscovered southern continent. In 1769, the Royal Society sent James Cook on a voyage to study the Transit of Venus in Tahiti. In 1772, Cook sailed south with two ships, searching for Bouvet Island and exploring latitudes as far as 67° 15′ S. He crossed the Antarctic Circle for the first time and reached 67° 15′ S by 39° 35′ E before ice blocked his path.

Cook later searched for French Southern and Antarctic Lands but missed them due to a miscalculation. He sailed as far south as 71° 10′ S before returning north. In 1774, Cook reached 71° 10′ S, the farthest south any ship had gone in the 18th century. He then returned to Tahiti and later explored the South Pacific, proving there was no habitable southern continent.

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

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

Geography

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

The Southern Ocean has a northern boundary at 60°S. Unlike other oceans, its largest boundary does not touch a landmass. Instead, it connects with the Atlantic, Indian, and Pacific Oceans.

One reason the Southern Ocean is considered a separate ocean is that much of its water differs from water in other oceans. The Antarctic Circumpolar Current helps move water quickly around the Southern Ocean. 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 typically has depths between 4,000 and 5,000 meters (13,000 to 16,000 feet) over most of its area, with only a few shallow regions. Its deepest point, 7,236 meters (23,740 feet), is located at the southern end of the South Sandwich Trench, near 60°00'S, 024°W. The Antarctic continental shelf is generally narrow and unusually deep, with its edge at depths up to 800 meters (2,600 feet), compared to an average of 133 meters (436 feet) globally.

Each year, the Antarctic ice pack changes in size due to the sun's seasonal influence. It reaches its smallest average size of about 2.6 million square kilometers (1.0 × 10^6 square miles) in March and grows to about 18.8 million square kilometers (7.3 × 10^6 square miles) in September.

Oceans are divided into regions such as seas, straits, bays, channels, and gulfs. The 2002 draft of the IHO publication Limits of Oceans and Seas proposed several subdivisions of the Southern Ocean, though this draft was never officially approved. These regions, listed in clockwise order, include:

• Weddell Sea (57°18'W – 12°16'E)
• King Haakon VII Sea (20°W – 45°E)
• Lazarev Sea (0° – 14°E)
• Riiser-Larsen Sea (14° – 30°E)
• Cosmonauts Sea (30° – 50°E)
• Cooperation Sea (59°34' – 85°E)
• Davis Sea (82° – 96°E)
• Mawson Sea (95°45' – 113°E)
• Dumont D'Urville Sea (140°E)
• Somov Sea (150° – 170°E)
• Ross Sea (166°E – 155°W)
• Amundsen Sea (102°20′ – 126°W)
• Bellingshausen Sea (57°18' – 102°20'W)
• Part of the Drake Passage (54° – 68°W)
• Bransfield Strait (54° – 62°W)
• Part of the Scotia Sea (26°30' – 65°W)

Some of these regions, like the Cosmonauts Sea, Cooperation Sea, and Somov Sea, are not included in the currently valid 1953 IHO document. These names were introduced after 1962 and are not used in major geographic references, such as the 2014 World Atlas by National Geographic or the 2014 Times Atlas of the World. However, Soviet and Russian maps do include them.

The Southern Ocean may contain large oil and gas reserves along its continental margin. Valuable minerals like gold, formed by natural processes, may also be present. Manganese nodules, which are rock formations made of layers of iron and manganese around a core, are expected in the Southern Ocean. These nodules were of interest to 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. Ideas to move these icebergs to drier regions, like Australia, have been proposed but are not yet practical.

Icebergs can appear at any time of year in the Southern Ocean. Some are hundreds of meters deep, and smaller icebergs or sea ice (0.5 to 1 meter thick) can pose risks to ships. The deep continental shelf has varied glacial deposits.

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. These conditions are worsened by icebergs, especially from May to October. The region's remoteness limits access to rescue services.

Physical oceanography

The Southern Ocean is the second smallest of Earth's oceans. It contains the Antarctic Circumpolar Current, a powerful and unique current that flows continuously eastward, forming a loop. This current is the longest in the world, stretching 21,000 kilometers (13,000 miles). It moves 130 million cubic meters of water every second (4.6 × 10^9 cubic feet per second), which is 100 times the combined flow of all the world's rivers.

In the Southern Ocean, special water masses form along Antarctica's coast that are not found elsewhere in the Southern Hemisphere. 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 zone around Antarctica where cold, northward-flowing Antarctic waters meet warmer subantarctic waters. The colder Antarctic waters sink beneath the subantarctic waters, creating areas of mixing and upwelling that are rich in nutrients. These nutrients support large amounts of phytoplankton, which feed copepods and Antarctic krill. This, in turn, supports food chains that include fish, whales, seals, penguins, albatrosses, and many other species.

The Antarctic Convergence is widely recognized as the best natural boundary marking the northern edge of the Southern Ocean.

Strong westerly winds around Antarctica drive water northward, creating large-scale upwelling. This process occurs because there are no continents in the region between South America and the Antarctic Peninsula, allowing deep water to rise to the surface. In many scientific models, this upwelling is the main way deep, dense water reaches the surface. Similar, shallower upwelling also happens near the west coasts of North and South America, Africa, and Australia, where subtropical high-pressure systems influence ocean currents.

Two gyres, the Ross Gyre and Weddell Gyre, exist 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 are shaped by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf.

Sea ice has been observed in the center of the Ross Gyre. Some studies suggest that global warming has caused a decrease in 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, leading to Ekman transport away from the center of the Weddell Gyre. This process brings cold, nutrient-rich water to the surface, making these areas highly productive.

The Southern Ocean Observing System (SOOS) coordinates research in the Southern Ocean. It provides access to metadata for much of the data collected in the region over the past decades, including measurements of ocean currents and water properties. The system focuses on data related to Essential Ocean Variables (EOVs) for areas south of 40°S.

Climate

Sea temperatures range from about -2°C to 10°C (28°F to 50°F). Cyclonic storms move eastward around the continent and often become strong due to the temperature difference between ice and open water. The ocean between about 40°S latitude and the Antarctic Circle has the strongest average winds on Earth. In winter, the ocean freezes outward to 65°S latitude in the Pacific and 55°S latitude in the Atlantic, lowering surface temperatures 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 (SMOC) or Antarctic overturning circulation, is part of a global ocean current system that connects different ocean basins. Its northern counterpart is the Atlantic Meridional Overturning Circulation (AMOC). This circulation works when some 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 significantly affect 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 accounted for over 90% of global heating since 1971. Much of this warming has occurred in the Southern Hemisphere ocean south of 30°S. In West Antarctica, the upper ocean layer has warmed by 1°C (1.8°F) since 1955, and the Antarctic Circumpolar Current (ACC) is warming faster than the global average. This warming changes the movement of warm and cold water in the overturning circulation and reduces sea ice cover (which reflects sunlight, increasing Earth’s albedo) in the Southern Hemisphere. It also affects 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 status of the circulation than on 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 1,100–1,500 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 separated and stable, which has the biggest impact on the long-term properties of the ocean’s circulation. These changes speed up the upper part of the circulation, increasing the flow of major currents, while slowing down the lower part, 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 circulation has strengthened by 3–4 sverdrup (Sv; 1 million cubic meters per second), or 50–60% of its flow, while the lower circulation has weakened by a similar amount. However, these changes were not fully 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 also influenced by ocean warming and meltwater from the shrinking Greenland ice sheet. It is possible that both circulations may not just weaken but could collapse to a much weaker state, which would be hard to reverse and could be an example of tipping points in the climate system. Paleoclimate evidence shows that the overturning circulation was weaker in the past during both warmer and colder periods. 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 have estimated the level of global warming that could cause the AMOC to collapse, fewer studies have focused on the Southern Ocean overturning circulation as of the early 2020s. Some estimates suggest its collapse may occur between 1.7°C (3.1°F) and 3°C (5.4°F), but this is less certain than for other tipping points.

The effects of Southern Ocean overturning circulation collapse have been studied less, but 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. Lower marine productivity would also reduce the ocean’s ability to absorb carbon (though not in the 21st century), which could increase long-term warming from human emissions and prolong warming on geological timescales. There may also be reduced rainfall in Southern Hemisphere countries like Australia, with increased rainfall in the Northern Hemisphere. However, the collapse of the AMOC would have similar but opposite effects, and the two would counteract each other to some extent. These impacts would also occur alongside other climate change effects on water cycles and fisheries.

Biodiversity

Marine animals in the Southern Ocean depend on phytoplankton, either directly or indirectly. Antarctic wildlife includes penguins, blue whales, orcas, colossal squids, and fur seals. The emperor penguin is the only penguin that breeds during 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. Antarctic krill, which forms large groups, is a key species in the Southern Ocean ecosystem. Krill is a primary food source for whales, seals, squid, penguins, albatrosses, and many other animals.

The seafloor near Antarctica has diverse and dense communities, with up to 155,000 animals in one square meter. Because the seafloor environment is similar around Antarctica, hundreds of species live there, which is unusual for such a large area. Many deep-sea animals are unusually large, a phenomenon called deep-sea gigantism.

A study of marine life during the International Polar Year, involving 500 researchers, was completed in 2010. This research found that over 235 marine species live in both polar regions. Some large animals, like whales and birds, travel between the poles each year. Smaller animals, such as worms and snails, also live in both regions. Uniform ocean temperatures and ocean currents help these species spread across the globe. Studies have shown that some species previously thought to be the same are actually closely related but distinct species.

Rocky shores in Antarctica and nearby islands provide nesting areas for over 100 million birds each spring. These birds include albatrosses, petrels, skuas, gulls, and terns. The South Georgia pipit, a bird that eats insects, lives only on South Georgia and nearby islands. Freshwater ducks are found on South Georgia and the Kerguelen Islands.

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

Few fish species live in the Southern Ocean, grouped into a few families. The most common family is snailfish, followed by cod icefish and eelpouts. These groups make up nearly 90% of the 320 known fish species in the Southern Ocean. Snailfish live in deep water, while icefish can be found in shallower areas.

Cod icefish and related species have special proteins in their blood that help them survive in very cold water. Some fish, like the crocodile icefish, have no red blood cells, making their blood colorless. These fish were once very common but were overfished.

Two fish species, the Antarctic toothfish and the Patagonian toothfish, live on the seafloor and can grow up to 2 meters long. The Antarctic toothfish lives near Antarctica, while the Patagonian toothfish lives in warmer waters. These fish are fished commercially, and their populations have declined due to overfishing.

Another group of fish, the genus Notothenia, also has antifreeze proteins in their bodies. The Antarctic silverfish is the only fish that lives far from the seafloor in the Southern Ocean.

Seven types of seals live in Antarctica. The largest, the elephant seal, can weigh up to 4,000 kilograms, while the smallest, the Antarctic fur seal, weighs about 150 kilograms. Some seals live on sea ice and form groups, while others live alone. These seals are important because they make up about half of the world’s seal population.

Ten types of whales and dolphins live in the Southern Ocean. The blue whale, the largest animal on Earth, can grow to 24 meters long and weigh 84 tonnes. Many of these species migrate to warmer waters during winter.

Five types of krill, small crustaceans, live in the Southern Ocean. Antarctic krill is the most numerous species, with a total weight of about 500 million tonnes. Each krill is 6 centimeters long and weighs over 1 gram. Krill form large groups that can turn the water red. These groups move to the surface at night to feed on plankton. Many larger animals depend on krill for survival. During winter, when food is scarce, adult krill may struggle to find enough to eat.

Environment

Increased harmful sunlight from the Antarctic ozone hole has decreased the amount of marine plants and algae (phytoplankton) by up to 15%. This sunlight has also begun to harm the DNA of some fish. Illegal, unreported, and unregulated fishing, especially catching about five to six times more Patagonian toothfish than allowed, may threaten the survival of this fish population. Long-line fishing for toothfish causes many seabirds to die.

All international agreements 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°S latitude (south of 60°S latitude between 50°W and 130°W). Japan does not accept this rule because it claims the sanctuary violates the IWC charter. Since the sanctuary only limits commercial whaling, Japan continues to hunt whales for scientific research and commercial purposes. On March 31, 2014, the International Court of Justice ruled that Japan’s whaling program, which Japan claims is for scientific reasons, was actually a cover for commercial whaling. No more permits for whaling will be issued.

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 began on April 7, 1982, with the goal of protecting marine life and the environment near Antarctica. This agreement was created because concerns grew that catching too much krill in the Southern Ocean could harm other marine animals that depend on krill for food.

Many countries stop exploring or using mineral resources south of the Antarctic Convergence. This line separates very cold polar waters to the south from warmer waters to the north. The Antarctic Treaty covers the area south of 60°S latitude and stops new claims to Antarctica.

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

Economy

From July 1, 1998, to June 30, 1999, fisheries caught 119,898 tonnes (118,004 long tons; 132,165 short tons) of fish. Of this total, 85% was krill and 14% was Patagonian toothfish. In late 1999, international agreements were put into effect to reduce illegal, unreported, and unregulated fishing. During the 1998–99 season, these illegal fishing activities caught five to six times more Patagonian toothfish than the regulated fishery.

Ports and harbors

Important 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 shore areas usable only during short periods in midsummer. Some areas 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 ship in a port south of 60 degrees south must be checked 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 ships to dock during summer. Operation Deep Freeze personnel built the first ice pier at McMurdo in 1973.

According to the original 1928 IHO map (and the 1937 map if the Great Australian Bight is included), Australian ports and harbors between Cape Leeuwin and Cape Otway on the mainland and along the west coast of Tasmania 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 races claim their routes pass through the Southern Ocean, the actual routes do not enter the geographical boundaries of the Southern Ocean. Instead, the routes travel through the South Atlantic, South Pacific, and Indian Oceans.