Indian Ocean (2004) | Southern Ocean (2003) | |
Area | total: 68.556 million sq km
note: includes Andaman Sea, Arabian Sea, Bay of Bengal, Flores Sea, Great Australian Bight, Gulf of Aden, Gulf of Oman, Java Sea, Mozambique Channel, Persian Gulf, Red Sea, Savu Sea, Strait of Malacca, Timor Sea, and other tributary water bodies |
total: 20.327 million sq km
note: includes Amundsen Sea, Bellingshausen Sea, part of the Drake Passage, Ross Sea, a small part of the Scotia Sea, Weddell Sea, and other tributary water bodies |
Area - comparative | about 5.5 times the size of the US | slightly more than twice the size of the US |
Background | The Indian Ocean is the third largest of the world's five oceans (after the Pacific Ocean and Atlantic Ocean, but larger than the Southern Ocean and Arctic Ocean). Four critically important access waterways are the Suez Canal (Egypt), Bab el Mandeb (Djibouti-Yemen), Strait of Hormuz (Iran-Oman), and Strait of Malacca (Indonesia-Malaysia). The decision by the International Hydrographic Organization in the spring of 2000 to delimit a fifth ocean, the Southern Ocean, removed the portion of the Indian Ocean south of 60 degrees south. | A decision by the International Hydrographic Organization in the spring of 2000 delimited a fifth world ocean - the Southern Ocean - from the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. The Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude, which coincides with the Antarctic Treaty Limit. The Southern Ocean is now the fourth largest of the world's five oceans (after the Pacific Ocean, Atlantic Ocean, and Indian Ocean, but larger than the Arctic Ocean). |
Climate | northeast monsoon (December to April), southwest monsoon (June to October); tropical cyclones occur during May/June and October/November in the northern Indian Ocean and January/February in the southern Indian Ocean | sea temperatures vary from about 10 degrees Celsius to -2 degrees Celsius; cyclonic storms travel eastward around the continent and frequently are intense because of the temperature contrast between ice and open ocean; the ocean area from about latitude 40 south to the Antarctic Circle has the strongest average winds found anywhere on Earth; in winter the ocean freezes outward to 65 degrees south latitude in the Pacific sector and 55 degrees south latitude in the Atlantic sector, lowering surface temperatures well below 0 degrees Celsius; at some coastal points intense persistent drainage winds from the interior keep the shoreline ice-free throughout the winter |
Coastline | 66,526 km | 17,968 km |
Disputes - international | some maritime disputes (see littoral states) | Antarctic Treaty defers claims (see Antarctica entry), but Argentina, Australia, Chile, France, NZ, Norway, and UK assert claims (some overlapping), including the continental shelf in the Southern Ocean; several states have expressed an interest in extending those continental shelf claims under the United Nations Convention on the Law of the Sea (LOS) to include undersea ridges; the US and most other states do not recognize the land or maritime claims of other states and have made no claims themselves (the US and Russia have reserved the right to do so); no formal claims have been made in the sector between 90 degrees west and 150 degrees west |
Economy - overview | The Indian Ocean provides major sea routes connecting the Middle East, Africa, and East Asia with Europe and the Americas. It carries a particularly heavy traffic of petroleum and petroleum products from the oilfields of the Persian Gulf and Indonesia. Its fish are of great and growing importance to the bordering countries for domestic consumption and export. Fishing fleets from Russia, Japan, South Korea, and Taiwan also exploit the Indian Ocean, mainly for shrimp and tuna. Large reserves of hydrocarbons are being tapped in the offshore areas of Saudi Arabia, Iran, India, and western Australia. An estimated 40% of the world's offshore oil production comes from the Indian Ocean. Beach sands rich in heavy minerals and offshore placer deposits are actively exploited by bordering countries, particularly India, South Africa, Indonesia, Sri Lanka, and Thailand. | Fisheries in 2000-01 (1 July to 30 June) landed 112,934 metric tons, of which 87% was krill and 11% Patagonian toothfish. International agreements were adopted in late 1999 to reduce illegal, unreported, and unregulated fishing, which in the 2000-01 season landed, by one estimate, 8,376 metric tons of Patagonian and antarctic toothfish. In the 2000-01 antarctic summer 12,248 tourists, most of them seaborne, visited the Southern Ocean and Antarctica, compared to 14,762 the previous year. |
Elevation extremes | lowest point: Java Trench -7,258 m
highest point: sea level 0 m |
lowest point: -7,235 m at the southern end of the South Sandwich Trench
highest point: sea level 0 m |
Environment - current issues | endangered marine species include the dugong, seals, turtles, and whales; oil pollution in the Arabian Sea, Persian Gulf, and Red Sea | increased solar ultraviolet radiation resulting from the Antarctic ozone hole in recent years, reducing marine primary productivity (phytoplankton) by as much as 15% and damaging the DNA of some fish; illegal, unreported, and unregulated fishing in recent years, especially the landing of an estimated five to six times more Patagonian toothfish than the regulated fishery, which is likely to affect the sustainability of the stock; large amount of incidental mortality of seabirds resulting from long-line fishing for toothfish
note: the now-protected fur seal population is making a strong comeback after severe overexploitation in the 18th and 19th centuries |
Environment - international agreements | - | the Southern Ocean is subject to all international agreements regarding the world's oceans; in addition, it is subject to these agreements specific to the Antarctic region: International Whaling Commission (prohibits commercial whaling south of 40 degrees south [south of 60 degrees south between 50 degrees and 130 degrees west]); Convention on the Conservation of Antarctic Seals (limits sealing); Convention on the Conservation of Antarctic Marine Living Resources (regulates fishing)
note: many nations (including the US) prohibit mineral resource exploration and exploitation south of the fluctuating Polar Front (Antarctic Convergence) which is in the middle of the Antarctic Circumpolar Current and serves as the dividing line between the very cold polar surface waters to the south and the warmer waters to the north |
Geographic coordinates | 20 00 S, 80 00 E | 65 00 S, 0 00 E (nominally), but the Southern Ocean has the unique distinction of being a large circumpolar body of water totally encircling the continent of Antarctica; this ring of water lies between 60 degrees south latitude and the coast of Antarctica and encompasses 360 degrees of longitude |
Geography - note | major chokepoints include Bab el Mandeb, Strait of Hormuz, Strait of Malacca, southern access to the Suez Canal, and the Lombok Strait | the major chokepoint is the Drake Passage between South America and Antarctica; the Polar Front (Antarctic Convergence) is the best natural definition of the northern extent of the Southern Ocean; it is a distinct region at the middle of the Antarctic Circumpolar Current that separates the very cold polar surface waters to the south from the warmer waters to the north; the Front and the Current extend entirely around Antarctica, reaching south of 60 degrees south near New Zealand and near 48 degrees south in the far South Atlantic coinciding with the path of the maximum westerly winds |
Location | body of water between Africa, the Southern Ocean, Asia, and Australia | body of water between 60 degrees south latitude and Antarctica |
Map references | Political Map of the World | Antarctic Region |
Natural hazards | occasional icebergs pose navigational hazard in southern reaches | huge icebergs with drafts up to several hundred meters; smaller bergs and iceberg fragments; sea ice (generally 0.5 to 1 meter thick) with sometimes dynamic short-term variations and with large annual and interannual variations; deep continental shelf floored by glacial deposits varying widely over short distances; high winds and large waves much of the year; ship icing, especially May-October; most of region is remote from sources of search and rescue |
Natural resources | oil and gas fields, fish, shrimp, sand and gravel aggregates, placer deposits, polymetallic nodules | probable large and possible giant oil and gas fields on the continental margin, manganese nodules, possible placer deposits, sand and gravel, fresh water as icebergs; squid, whales, and seals - none exploited; krill, fishes |
Ports and harbors | Chennai (Madras; India), Colombo (Sri Lanka), Durban (South Africa), Jakarta (Indonesia), Kolkata (Calcutta; India) Melbourne (Australia), Mumbai (Bombay; India), Richards Bay (South Africa) | McMurdo, Palmer, and offshore anchorages in Antarctica
note: few ports or harbors exist on the southern side of the Southern Ocean; ice conditions limit use of most of them to short periods in midsummer; even then some cannot be entered without icebreaker escort; most antarctic ports are operated by government research stations and, except in an emergency, are not open to commercial or private vessels; vessels in any port south of 60 degrees south are subject to inspection by Antarctic Treaty observers (see Article 7) |
Terrain | surface dominated by counterclockwise gyre (broad, circular system of currents) in the southern Indian Ocean; unique reversal of surface currents in the northern Indian Ocean; low atmospheric pressure over southwest Asia from hot, rising, summer air results in the southwest monsoon and southwest-to-northeast winds and currents, while high pressure over northern Asia from cold, falling, winter air results in the northeast monsoon and northeast-to-southwest winds and currents; ocean floor is dominated by the Mid-Indian Ocean Ridge and subdivided by the Southeast Indian Ocean Ridge, Southwest Indian Ocean Ridge, and Ninetyeast Ridge | the Southern Ocean is deep, 4,000 to 5,000 meters over most of its extent with only limited areas of shallow water; the Antarctic continental shelf is generally narrow and unusually deep, its edge lying at depths of 400 to 800 meters (the global mean is 133 meters); the Antarctic icepack grows from an average minimum of 2.6 million square kilometers in March to about 18.8 million square kilometers in September, better than a sixfold increase in area; the Antarctic Circumpolar Current (21,000 km in length) moves perpetually eastward; it is the world's largest ocean current, transporting 130 million cubic meters of water per second - 100 times the flow of all the world's rivers |
Transportation - note | - | Drake Passage offers alternative to transit through the Panama Canal |