MEASURING approximately 26.5 million square mi (68.5 million square km), the Indian Ocean includes the 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, Straits of Malacca, Timor Sea, and other tributary water bodies. The ocean is located between Africa, Southern Ocean, Asia, and AUSTRALIA.
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). The Southern Ocean was delineated in a spring 2000 decision by the International Hydrographic Organization, which consolidated a fifth world ocean from the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. This new ocean extends from the coast of ANTARCTICA north to 60 degrees South latitude or the Antarctic Treaty Limit. Five major choke points along commercial sea lanes provide access to the Indian Ocean. These waterways are the Suez Canal (EGYPT), BAB EL MANDEB (DJIBOUTI–YEMEN), Strait of Hormuz (IRAN–OMAN), and Straits of Malacca (INDONESIA–MALAYSIA), and the Lombok Strait (INDONESIA).
The Indian Ocean has held the historic TRADE ROUTES from Occident to Orient since the dawn of maritime commerce in the ancient world. Spices, slaves, and marvelous though modest handcrafts moved among the many ports the Indian Ocean carried by centuries of monsoon winds and currents. This trade now bears the modern manufactured goods of industrialized nations and the petroleum required to fuel the world's economies. Never an insular sea, the Indian Ocean now serves not only the ports of its own shores but the far reaches of the countries of Europe and the Americas.
Historical accounts include the tales of Egyptian, Greek, and Roman commercial and colonial exploits. The settlement of Madagascar by peoples from Indonesia in ancient times points to the reciprocal flow of culture and commerce from the east. Centuries of trade and exploration were carried out by the Islamic merchants and seaman of the Arabian Peninsula, who took their goods and their faith to the lands of the African coast, India, and Southeast Asia. Before the Europeans made good a sea passage to the waters of the Indian Ocean, Admiral Zheng He of the Ming Dynasty of China led several maritime expeditions across these fated waters from 1405 to 1433.
By 1497, Vasco da Gama navigated around the Cape of Good Hope and began the Portuguese fight for domination of the spice trade across the Indian Ocean. This model of bold commercial venture supported by national navies and prestige was followed by the Dutch, French, and British over the next two centuries. European colonial interests in the Indian Ocean LITTORAL continued until after World War II. The independence of regional states from their colonial masters, growth and development among the newly industrialized states, and the increased flows of manufactured goods and petroleum have made the Indian Ocean truly an international sea.
During the Cold War, the Indian Ocean was an arena of competition between East and West. Regional navies were often overshadowed by the number and modern capabilities of the U.S. and Soviet fleets. Establishment of a permanent support and operational base on the island of Diego Garcia, strategically central in the Indian Ocean, was a clear sign of the American intent to remain active in the region. The United States maintains the most active, modern, and capable military forces in the Indian Ocean.
Throughout the long history of foreign economic exploitation and domination, the Indian Ocean has continuously been a rich resource to the peoples of the region. It constantly supplied transportation routes and rich fisheries along the coasts. The Indian Ocean continues to be a major fishing ground with fleets from many nations vying for the limited resource. Fishing stocks are being depleted by a combination of overfishing and pollution along the Indian Ocean coasts. The overexploitation of fish stocks is mostly due to large fishing vessels operating illegally near the coast. The growth of regional populations, particularly in INDIA and Indonesia, will add pressure on the already challenged marine resources.
This population increase and industrial development creates major pollution problems in the most critical fishing areas. Industrial effluents contain heavy metals and chemical wastes. Pesticides and organic wastes flow untreated into the coastal waters from cities and agricultural land. Oil pollution from accidents, ballast dumping, and offshore oil extraction is on the increase. The nations that share the management and use of the Indian Ocean have no comprehensive plan for conservation and management of the resources or uses of this global asset.
Mineral resources and especially offshore petroleum extraction are continuing to grow as a commercial interest to nations. Large reserves of hydrocarbons are being tapped in the offshore areas of SAUDI ARABIA, IRAN, INDIA, and AUSTRALIA. An estimated 40 percent 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. The mining of polymetallic nodules from the seabed remain a tempting, but technologically challenging operation.
Climate and weather patterns are dominated by the annual monsoon. This weather cycle is attributed to low atmospheric pressure over Southwest Asia created by hot, rising summer air, which causes southwest-tonortheast winds and currents during the summer months. A high pressure over North Asia created by cold, falling, winter air results in northeast-to-southwest winds during the winter months.
For half the year (April to October), the winds in this region are from the southwest, reversing in the other half of the year. This monsoon (season) weather pattern dominates the region on land and sea, setting the pace of life onshore and off. Tropical cyclones occur during May/June and October/November in the northern Indian Ocean and January/February in the southern Indian Ocean.
Primary adjoining arms of the Indian Ocean are the Persian Gulf and the Red Sea. The deepest known point is 25,443 ft (7,758 m), off the southern coast of Indonesia in the Java Trench. The Indian Ocean contains numerous islands, the largest of which are MADAGASCAR and SRI LANKA. Smaller islands that constitute independent countries include the MALDIVES, the SEYCHELLES, and MAURITIUS. The major rivers that flow into the Indian Ocean include the waters of the Limpopo and Zambezi rivers from Africa, as well as the IRRAWADDY, Brahmaputra, GANGES, and INDUS from east to west along Asia. The combined waters of the Tigris and Euphrates rivers mix with the Indian Ocean via the Persian Gulf.
The Indian Ocean is of geostrategic interest as it is a transit route for a major portion of the world's oil supply. In addition the commerce flowing by ship from Asia to Europe also sails this sea. Some major ports and harbors of the Indian Ocean are Chennai (Madras; India), Colombo (Sri Lanka), Durban (SOUTH AFRICA), JAKARTA (Indonesia), KOLKATA (Calcutta; India), Melbourne (Australia), MUMBAI (Bombay; India), and Richards Bay (South Africa).
- Atlantic Ocean
- Arctic Ocean
- What Are the Global Patterns of Temperature and Salinity?
- What Causes Water to Rise or Sink?
- How Do Sea-Surface Temperatures Vary from Place to Place and Season to Season?
- What Is the Global Pattern of Surface Currents?
- What Causes Ocean Currents?
- Atmosphere-Ocean-Cryosphere Interactions
- Why Do Temperatures Vary Between Oceans and Continents?