The Arabian Sea () is a region of sea in the northern Indian Ocean, bounded on the west by the Arabian Peninsula, Gulf of Aden and Guardafui Channel, on the northwest by Gulf of Oman and Iran, on the north by Pakistan, on the east by India, and on the southeast by the Laccadive SeaBanse, Karl, and Charles R. McClain. "Winter blooms of phytoplankton in the Arabian Sea as observed by the Coastal Zone Color Scanner." Marine Ecology Progress Series (1986): 201–211. and the Maldives, and on the southwest by Somalia.Pham, J. Peter. "Putting Somali piracy in context." Journal of Contemporary African Studies 28.3 (2010): 325–341. Its total area is and its maximum depth is . The Gulf of Aden in the west connects the Arabian Sea to the Red Sea through the strait of Bab-el-Mandeb, and the Gulf of Oman is in the northwest, connecting it to the Persian Gulf. It is dominated in its south and center by the Arabian Basin, an expansive, relatively flat stretch of seabed reaching depths exceeding 4500 meters in some areas. Most islands and seamounts within the sea are located along its coastal fringes, close to major landmasses.
The straits of Hormuz and Bab-el Mandeb on the northwestern and western ends of the Arabian Sea have historically served as gateways connecting the kingdoms and polities of the Eastern and Western limits of the Old World since the establishment of the region's first international trade networks in the 3rd millennium BC. This produced countless interdependent nodes of regional commerce all operating in tandem with one another, linking merchants in the Mediterranean with their counterparts in the Near East, who thereafter linked to Persia and East Africa, on to India, Southern Africa, Southeast Asia, East Asia, and the Malay Archipelago. This combined activity facilitated the widespread diffusion of concepts, peoples, philosophies, technologies, religions, specie, and various domesticate variants of crops and livestock across the Old World over millennia, most profoundly from and within the confines of the Indian Ocean and Near Eastern worlds.
Trade was historically restricted by the monsoon winds and the currents produced by their interaction with the Indian Ocean Warm Pool. In mid-summer, strong winds carry warm air and moisture northeastwards from the African interior and Indian Ocean, resulting in heavy rains on the northeast shoreline of the Arabian basin, and dry conditions in the Horn of Africa and Arabian Peninsula, though both have seen dramatic fluctuations in their pattern in recent years in favor of more intensive rainfall. Cold, shallow, dry, southwesterly winds from the Karakoram and Himalayas would otherwise predominate in winter and spring.
The Arabian Sea forms the predominance of the Arabian Sea large marine ecosystem, a marine environment stretching from the Laccadive to the Red Sea and the Persian Gulf that is considered to be one of the most, if not the most biologically productive regions on the planet. The region is bounded by the Carlsberg Ridge in the Sea's south. It has been placed under significant strain in recent decades, leading to the listing of a significant number of endangered and critically endangered marine and terrestrial species, owed in large part to overfishing, unintended bycatch, industrial and residential development, pollution, global heating, and accelerating eutrophication in coastal waters.
Notable seaports in the modern era include the Jawaharlal Nehru and Mormugao Ports in India, the Ports of Karachi, Qasim, and Gwadar in Pakistan, Chabahar Port in Iran, and the Port of Salalah in Oman. Among the largest islands in the Arabian Sea are Socotra (Yemen), Masirah (Oman), and Astola (Pakistan). The countries with coastlines on the Arabian Sea are Yemen, Oman, Pakistan, Iran, India and the westernmost islands of the Maldive and Laccadive Archipelagos.
Geography The Arabian Sea's surface area is about . The maximum width of the sea is approximately , and its maximum depth is . The largest river flowing into the sea is the Indus.
The sea has two main arms, the Gulf of Aden in the southwest, connecting it with the Red Sea through the strait of Bab-el-Mandeb; and the Gulf of Oman to the northwest, connecting it with the Persian Gulf. It also bounds the gulfs of Khambhat and Kutch on the Indian Coast, and the Laccadive Sea off the coast of southern India.
Limits The only difference between the National Oceanic and Atmospheric Administration (NOAA) and International Hydrographic Organization (IHO) demarcations of the Arabian Sea is their determination of the sea's limit on its eastern border with India, disputing whether that be Devgad Island or Sadashivgad Village in Karnataka. According to NOAA, the demarcation of the sea is as follows: On the North and the East: From Cape Jiwani in Pakistan () eastward and southward, along the coasts of Pakistan and India, to Devgad Island (), off the western coast of India; thence a line joining Devgad Island southwestward to Cora Divh () and thence southward, along the western side of the Lakshadweep and Maldives Islands, to the southern extremity of Addu Atoll ()
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On the South: A line joining the southern extremity of Addu Atoll northwestward to Cape Hafun () in Somalia.
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On the West: From Cape Hafun northward, along the coast of Somalia, to Cape Asir [Guardafui] (); thence a line joining Cape Asir northeastward to Cape Fartak () in Southern Yemen (the common limit with the Gulf of Aden [...] ), thence from Cape Fartak [...] northeastward, along the coasts of Southern Yemen and Oman, to Cape Al Hadd (), in Oman; and thence a line joining Cape Al Hadd [...] northeastward to Cape Jiwani (), in Pakistan (the common limit with the Gulf of Oman [...])
Geological history
Hydrography In 1959, the International Indian Ocean Expedition was among the first groups to conduct hydrographic surveys in the Arabian Sea. Additionally, "significant bathymetric surveys were also conducted by the Soviet Union during the 1960s".
The Arabian Basin The southern limits of the Sea are dominated by the Arabian Basin, which reaches depths of over , and which maintains a relatively constant depth throughout. The Carlsberg Ridge flanks the southern edge of the basin.
The deepest parts of the Arabian Sea sit in the Alula-Fartak Trough on its western border with the Gulf of Aden. The trough, which reaches depths of over , runs through both bodies. The deepest known point in the Arabian Sea sits at a depth of . Other significant deep points sit within the Arabian Basin, including a deep point off the northern limit of Calrsberg Ridge.
The shelf line and the Indus Fan The continental shelf line is relatively narrow along the Makran, Arabian, and East African coastlines; conversely, its extends greatly from the coast of much of the Indian subcontinent, reaching distances exceeding in some places. The structure of the shelf line played a significant role in the creation of the Indus Fan, which was flooded and submerged along with the rest of the Indian coast at the end of the Last Glacial Maximum (LGM).
Other features The Falaj Valley, discovered in 2009 by French surveyors, is an underwater valley off the eastern coast of Ash Sharqiyah Region in Oman. It is 81 kilometers wide, with a maximum depth of and a relief of , extending out roughly from the shelfline. It is named for the Falaj Irrigation System, a network of conduits, canals, and drainage systems built expansively across eastern Oman in the 5th century to equitably provision and maintain water supplies as groundwater sources depleted in that era.
Owen Fracture Zone The De Covilhăo Trough, discovered in 1930 and named for 15th century Portuguese explorer Pero de Covilhăo, reaches depths exceeding . It and the Murray Ridge on its western border separate the Indus Fan from the Oman Abyssal Plain, which leads on into the Gulf of Oman. The Murray Ridge arguably acts as an extension of the Owen fracture zone, an extensive bathymetric ridge running from the northwestern to southwestern Arabian Sea along a line roughly parallel to the southern Arabian and eastern Somalian coastlines, stretching from the central Makran coast to a point roughly east of the central Somalian coastline. The fracture zone is the intersection point between the Indian and Arabian plates. The zone is characterized by steep slopes reaching heights of nearly relative to the surrounding seabed. The fracture zone has acted as a natural barrier preventing sedimentation from the Indus Fan from extending out into the Oman Basin.
Oceanic fronts and boundaries The Arabian Sea is bounded on its southwest by the Carlsberg Ridge and Horn of Africa, on its west by the Gulf of Aden, on its northwest by eastern Yemen, Oman, and the easternmost point of Iran, on its north by Pakistan and Western India, and on its southeast by the Laccadive Sea and the westernmost islands of Lakshadweep and the Maldives. It consists of 7 ecological oceanic fronts, with the typical and most prominent upwelling fronts resting along the coasts of India and Pakistan. The 4 fronts which sit in or within the immediate environs of the Arabian Sea are delineated as follows: The Gulf of Aden Front (GAF): Forming a concave semicircle running from Burua in Somalia () to the village of Khird in Yemen, 5–10 miles east of Al-Shihr. It's sagitta is roughly . The Oman Coastal Front (OCF): Shielding the coastline from Cape Fartak () to Masirah Island (). The Gulf of Oman Front (GOF): Bordering the coastlines of Iran and the Arabian Sea to produce a three-sided wall around the Oman Abyssal Plain, running from Ras al Hadd to a point at the plain's northwestern limit () near the entrance to the Strait of Hormuz. The area of the Iranian Coast moving east contained within the shield is the principal stretch of coastline contained within this hydrological environment. That mass is then separated on the east by a convex shield stretching roughly from the Ziyarat Peninsula () back to Ras al Hadd, with a sagitta of roughly . The West Indian Shelf-Slope Fronts (WISSF), stretching along the western Indian coastline, additionally containing two separate and hydrologically distinct regions with different outflow, tidal, and sedimentary properties from the wider frontier: The Indian Estuarine Front (IEF): Forming a relatively flat shield stretching from Ras Malan () in Pakistan to the northwestern tip of the Kathiawar Peninsula in India; it encompasses the immediate drainage channels of the Indus River and surrounding source rivers. The West Indian Mid-Shelf Front (WIMSF): Encompassing the watershed of the Gulf of Khambat.
Fronts are largely seasonal, and can be pronounced, exceeding a 5 °C (9 °F) differential in some places. The Arabian Sea LME ultimately ends on a line stretching northwest from south of Cape Comorin in India to midway between Ras Hafun and Cape Guardafui on the eastern Somalian coast, it extends several hundred kilometers north of the Carlsberg Ridge across most of its expanse, only coming within a few hundred kilometers of the uplift zone upon reaching the East African shelf line.
Border and basin countries
Coastline of border and basin countries: – – (Makran Coast) – ~ (No coastline on the Arabian Sea according to IHO delineations) - West coast of westernmost islands (contained by Laccadive Sea) (Excluding Gulf of Oman) - ~ (Including Gulf of Aden) – ~ (Cape Guardafui to Ras Hafun) – ~
Seamounts Prominent sea mounts off the Indian west coast include the Raman and Panikkar Seamounts, named for Nobel Laureate in Physics Sir Chandrasekara Venkata Raman, and N. K. Panikkar, founder of the Indian National Oceanographic Institute, respectively.