Arabian Sea

The Arabian Sea is a vast marginal sea of the northern Indian Ocean, located between the Arabian Peninsula to the west and the Indian subcontinent to the east, with borders extending to Pakistan in the north, India in the east, Somalia in the southwest via the Guardafui Channel and Gulf of Aden, and connections to the Laccadive Sea in the southeast.^[1] It spans approximately 3.9 million square kilometers, features an average depth of 2,734 meters, and reaches a maximum depth of 5,803 meters at the Wheatley Deep, with deep waters extending close to the continental margins and no significant mid-sea islands.^[2]^[1] The sea's physical oceanography is dominated by seasonal monsoon winds, which drive a reversal in surface circulation: during the northeast monsoon (December to February), northeasterly winds promote southward flow along the Somali Coast, while the southwest monsoon (June to September) generates powerful northward currents, including the Somali Current and the Great Whirl eddy between 5° and 10°N, along with intense coastal upwelling off Oman and Somalia.^[3] This upwelling system, one of the world's most intense, brings nutrient-rich deep waters to the surface, classifying the Arabian Sea as a highly productive Large Marine Ecosystem with primary productivity exceeding 300 grams of carbon per square meter per year (as of assessments in the early 2000s).^[4] The sea also hosts a prominent oxygen minimum zone, contributing to the world's largest dead zone in the adjacent Gulf of Oman, spanning about 63,700 square miles, where low oxygen levels severely limit marine life.^[5] Ecologically, the Arabian Sea supports exceptional biodiversity, including over 1,200 fish species, 330 coral species (accounting for 1.84% of global coral reefs), 500 mollusc species, 200 crab species, 20 marine mammal species such as whale sharks and dolphins, and diverse habitats like coral reefs, seaweed forests, and seamounts (0.62% of the world's total) (as of early 2000s data).^[4]^[6] Monsoon-driven nutrient influx sustains key pelagic species like Indian oil sardine and tunas, while coastal areas feature mudskippers, ghost crabs, lobsters, and sea turtles; however, the ecosystem faces threats from overfishing, where 50% of fish stocks were overexploited by 2004, and pollution hotspots with elevated oil hydrocarbons and heavy metals.^[4]^[6] Human activities underscore the sea's strategic significance, with small-scale fisheries landing around 2 million tonnes annually in the early 2000s, valued at approximately 1.6 billion USD, primarily within exclusive economic zones of bordering nations and supporting food security for a coastal population exceeding 1.2 billion (as of 2002).^[4] The region serves as a vital shipping corridor for global trade, linking the Persian Gulf's oil exports to international routes via the Gulf of Oman and Strait of Hormuz, while artisanal fishing remains a cornerstone of livelihoods along the coasts of India, Pakistan, Oman, and Yemen.^[1] Only 0.21% of the sea was protected as of the early 2000s, highlighting ongoing needs for enhanced conservation amid growing pressures from habitat modification and climate change.^[4]

Geography

Extent and Boundaries

The Arabian Sea constitutes the northeastern extension of the Indian Ocean, serving as a distinct marginal sea bounded by the Arabian Peninsula to the north, the Horn of Africa to the west, and the Indian subcontinent to the east.^[7] This positioning places it within the northern Indian Ocean, separating the major landmasses of South Asia and the Middle East while facilitating maritime connections to adjacent gulfs and seas.^[8] According to the International Hydrographic Organization's definitions, the northern boundary runs from Ras al Hadd on the eastern tip of the Arabian Peninsula (approximately 22°32'N, 59°47'E) to Ras Jiyuni on the Pakistani coast (approximately 24°50'N, 61°43'E), marking the entrance to the Gulf of Oman and Persian Gulf at around 24°N.^[7] The western boundary follows the eastern limit of the Gulf of Aden northward along the East African coast from Ras Hafun in Somalia (10°26'N, 51°25'E).^[7] The southern boundary is delineated by a line connecting the southern extremity of Addu Atoll in the Maldives (00°42'S, 73°06'E) to Ras Hafun, effectively merging with the broader Indian Ocean around 10°N.^[7] The eastern boundary aligns with the western limit of the Laccadive Sea, tracing the Indian coastline from near Cape Comorin (Kanyakumari) in the south northward to Mumbai and beyond toward Pakistan.^[7] The sea spans a surface area of approximately 3,862,000 km², with dimensions reaching about 3,800 km in north-south length and up to 2,400 km in east-west width.^[9] Its bathymetry features an average depth of 2,734 m, while the maximum depth measures 4,652 m at the Wheatley Deep in the central basin.^[1]

Physical Characteristics

The Arabian Sea's physical landscape is dominated by expansive deep basins interspersed with ridges and a varied continental margin. The central Arabian Basin forms the sea's deepest region, with depths up to 4,652 meters, particularly in its southern extent at the Wheatley Deep. The basin is bisected by the Carlsberg Ridge, a seismically active mid-ocean ridge.^[2] This basin is bounded to the northeast by the Laxmi Ridge and to the north by the Murray Ridge, a seismically active submarine feature that delineates the boundary between the Indian and Arabian tectonic plates and rises prominently from surrounding seafloors.^[10] The Laxmi Basin, located in the eastern Arabian Sea between the Indian continental shelf and the main Arabian Basin, is comparatively shallower, reflecting its transitional crustal nature.^[11] The continental shelves along the Arabian Sea's margins vary significantly in width and topography. Along the Indian west coast, the shelf is relatively narrow, averaging about 100 kilometers in width, though it broadens to up to 345 kilometers off the northern Gujarat region near Daman and narrows to around 60 kilometers off southern Kerala.^[12] In contrast, the shelf off Pakistan is wider, extending up to 200 kilometers northward from Karachi before tapering to less than 50 kilometers westward along the Balochistan coast.^[13] These shelves slope gently from coastal depths, supporting sediment accumulation and occasional shallow-water features. Surface characteristics include low-relief coastal plains fringed by riverine deltas and localized biogenic structures. The Indus Delta, at the sea's northern edge in Pakistan, exemplifies a major depositional plain where the Indus River discharges vast sediment loads into the Arabian Sea, forming extensive mangrove-lined wetlands and tidal flats.^[14] In shallower coastal zones, particularly around the Gulf of Kutch in India and off the Omani coast, scattered coral reefs develop on suitable substrates, contributing to the sea's marginal biodiversity hotspots despite the region's generally sediment-dominated shelves.^[15] A key sedimentary feature is the Indus Fan, the world's second-largest submarine fan system, which extends southward from the Indus Delta across the northern and central Arabian Sea. Spanning over 1,500 kilometers in length and accumulating sediments up to 10 kilometers thick in places, this fan results from long-term deposition of terrigenous materials eroded from the Himalayan and Karakoram ranges via the Indus River.^[16]^[17] Its leveed channels and lobes shape the seafloor topography, influencing sediment distribution across adjacent basins.

Hydrography

The hydrography of the Arabian Sea is characterized by elevated salinity levels, averaging 36.5 practical salinity units (psu), with values exceeding this threshold in the northern regions due to intense year-round evaporation and minimal freshwater influx from rivers or precipitation.^[18] This high-salinity water mass, known as Arabian Sea High Salinity Water (ASHSW), forms through evaporative processes that concentrate salts, particularly during the dry winter months when cool northeasterly winds enhance surface cooling and salt flux.^[18] Salinity gradients are further amplified by limited runoff from surrounding arid landmasses, resulting in spatial variability where northern waters can reach up to 37 psu or higher.^[19] Surface temperatures in the Arabian Sea exhibit pronounced seasonal fluctuations, typically ranging from 22°C to 30°C, with the lower end occurring during the southwest monsoon period from June to September when upwelling brings cooler subsurface waters to the surface.^[20] In contrast, inter-monsoon periods and winter months see warmer surface layers, often exceeding 28°C, driven by solar heating and reduced vertical mixing.^[20] These thermal variations influence water density and stratification, with cooler monsoon temperatures promoting deeper mixing in coastal upwelling zones.^[21] The sea's water masses are significantly shaped by inflows from adjacent marginal seas, including the high-salinity Persian Gulf Water (PGW), which outflows through the Strait of Hormuz and spreads southward as a dense subsurface layer, and the warm, saline Red Sea Water (RSW) entering via the Gulf of Aden.^[22] PGW, characterized by salinities often above 40 psu, contributes to the maintenance of high-salinity conditions in the northern and western basins, while RSW adds heat and salt to intermediate depths, altering the overall thermohaline structure. These influences create a complex layering where ASHSW overlies the denser PGW and RSW, affecting vertical stability and nutrient distribution.^[19] Evaporation dominates the hydrological balance, averaging about 1.5 meters per year across the basin, far exceeding precipitation rates of approximately 0.5 meters per year and leading to a net water loss of around 1 meter per year that drives dense water formation and export to the Indian Ocean.^[23] In northern areas, evaporation can approach 2 meters per year during peak dry seasons, intensifying the salinity surplus and contributing to the convective overturning of ASHSW.^[23] This imbalance underscores the Arabian Sea's role as a significant evaporative basin, with the excess salt and heat influencing broader Indian Ocean circulation.^[24]

Adjacent Regions

Coastal Countries

The Arabian Sea is bordered by seven countries: India, Pakistan, Iran, Oman, Yemen, Somalia, and the Maldives. These nations share approximately 10,000 km of coastline along the sea, influencing regional maritime dynamics and resource management. Somalia possesses the longest stretch, followed by India, with the others varying in extent based on geographic configuration.^[25]

Country	Coastline Length (km)	Key Coastal Regions
India	~2,500	Gujarat to Kerala
Pakistan	~1,046	Sindh and Balochistan
Iran	~850 (Gulf of Oman coast)	Sistan and Baluchestan Province
Oman	~2,000	Dhofar and Al Wusta Governorates
Yemen	~1,482	Hadhramaut and Socotra
Somalia	~3,025	Puntland and Galmudug
Maldives	N/A (island nation)	EEZ overlap in central sea

The coastlines exhibit diverse geomorphic features shaped by tectonic activity, monsoons, and sediment deposition. India's Arabian Sea margin features extensive sandy beaches and barrier spits, particularly along Gujarat and Maharashtra, supporting tourism and fisheries.^[25] In contrast, Oman's southern shores include rugged rocky cliffs and limestone formations, especially near Salalah, which contribute to unique marine habitats.^[30] Pakistan's coastal zone, particularly in Sindh, is characterized by mangrove swamps and tidal creeks in the Indus Delta, vital for biodiversity but vulnerable to erosion.^[31] These countries assert territorial claims through exclusive economic zones (EEZs) extending up to 200 nautical miles from their baselines, collectively encompassing over 3 million km² in the Arabian Sea region and enabling control over fisheries, hydrocarbons, and navigation.^[4] Notable disputes include the India-Pakistan maritime boundary in the northern Arabian Sea, stemming from the unresolved Sir Creek land border, which affects EEZ delineations and resource allocation in an area potentially rich in oil and gas.^[32] The Maldives' EEZ, spanning about 900,000 km², overlaps with central Arabian Sea waters, influencing transboundary conservation efforts.^[33]

Surrounding Landmasses

The Arabian Peninsula forms the northwestern boundary of the Arabian Sea, characterized by extensive arid landscapes and rugged topography. The Rub' al-Khali, also known as the Empty Quarter, is the largest continuous sand desert in the world, covering approximately 650,000 square kilometers across southern Saudi Arabia, Yemen, Oman, and the United Arab Emirates, and acting as a major barrier to moisture influx from the sea.^[34] Along the southeastern edge, the Hajar Mountains rise sharply, extending over 700 kilometers from the Musandam Peninsula to Ras al-Hadd in Oman, with peaks reaching up to 3,000 meters and influencing local drainage patterns toward the sea.^[35] To the northeast, the Indian Subcontinent encircles the sea with diverse geological features, including the Thar Desert, a vast arid expanse spanning about 200,000 square kilometers across northwestern India and southeastern Pakistan, which contributes to aeolian dust transport into the marine environment.^[36] The Western Ghats, a UNESCO World Heritage site, form a continuous mountain range along the western edge of the subcontinent, rising to over 2,600 meters and trapping monsoon rains while channeling rivers toward the Arabian Sea.^[37] Inland, the Deccan Plateau, a basaltic upland covering much of peninsular India, slopes eastward but feeds significant sediment through major rivers such as the Indus and Narmada; the Indus, originating in the Himalayas, delivers one of the world's largest sediment loads to the sea, building extensive deltaic features, while the Narmada erodes the plateau to supply terrigenous materials to coastal zones.^[38]^[39] The southwestern margin is defined by the Horn of Africa, where the Somali Plateau—a broad, elevated tableland averaging 500 to 1,000 meters—dominates the landscape of Somalia and influences arid climatic conditions through its rain shadow effect.^[40] Adjacent to it, the Ethiopian Highlands, rising to over 4,000 meters, serve as a critical watershed, sourcing rivers like the Shebelle, which flows southeastward across the plateau into Somalia and intermittently reaches the sea, contributing freshwater and sediment pulses.^[41] The surrounding landmasses profoundly shape the Arabian Sea's climate through differential heating, driving the South Asian monsoon system. Large elevated areas like the Deccan Plateau and Ethiopian Highlands heat rapidly in summer, creating low-pressure zones that draw moist southwest winds across the sea from June to September, while winter cooling over the same landmasses reverses flows to northeast trades, resulting in seasonal wind reversals and upwelling.^[42]^[43] This land-sea thermal contrast amplifies precipitation patterns over adjacent regions, sustaining the sea's dynamic circulation.^[44]

Oceanography

Ocean Currents and Circulation

The circulation in the Arabian Sea is predominantly driven by the seasonal reversal of monsoon winds, resulting in distinct patterns of surface currents and gyres that vary between summer and winter. During the southwest monsoon (June–September), the Findlater Jet—a narrow, low-level atmospheric jet with winds peaking at around 15 m/s—induces strong anticyclonic wind stress curl over the basin, promoting an overall anticyclonic gyre circulation.^[45]^[46] This leads to the formation of prominent features like the Great Whirl, an anticyclonic eddy south of Socotra with transports exceeding 70 Sv, and the Southern Gyre near the equator. The Southwest Monsoon Current flows northeastward across the western and central Arabian Sea at speeds of 0.5–1 m/s, transporting warm surface waters toward the Indian coast while contributing to the broader anticyclonic loop.^[45]^[46] The Somali Current, serving as the western boundary current of this anticyclonic system, intensifies during the southwest monsoon, flowing northward along the Somali and Omani coasts at velocities up to 2 m/s and transports of 20–70 Sv.^[46]^[45] This strong inflow, part of the larger Indian Ocean Gyre, drives Ekman transport southward (approximately 20 Sv) and fosters coastal upwelling zones off Oman and Somalia, where nutrient-rich waters from depths of 200–300 m rise to the surface, cooling sea surface temperatures to 15–23°C in intense events.^[45]^[46] The upwelling is particularly pronounced along the Somali margin due to the alignment of the Findlater Jet with the coastline, enhancing vertical mixing and offshore Ekman advection.^[3] In contrast, the northeast monsoon (November–February) weakens the winds and shifts the stress curl to cyclonic, establishing a basin-wide cyclonic gyre with reduced intensities compared to summer.^[47]^[45] The Somali Current reverses direction, flowing southward at lower speeds (transports around 5 Sv in the upper 150 m) as part of the equatorward Northeast Monsoon Current, which drifts westward across the sea before merging with the South Equatorial Current.^[45]^[46] Ekman transport in this period is northward (also ~20 Sv), diminishing upwelling and allowing warmer waters to dominate the surface, though residual eddies from the prior season may persist.^[45] Overall, these monsoon-driven reversals integrate the Arabian Sea into the Indian Ocean's subtropical gyre, with interannual variations linked to wind strength fluctuations.^[48]

Oxygen Minimum Zone

The Oxygen Minimum Zone (OMZ) in the Arabian Sea is a prominent mid-water feature characterized by severely depleted dissolved oxygen levels, typically below 0.5 ml/L, occurring primarily between depths of 150 and 1,200 meters. This layer represents one of the world's thickest and most intense OMZs, with the core often exhibiting near-anoxic conditions (≤0.1 ml/L or ~4.5 μmol/L) between approximately 250 and 750 meters. The zone's persistence stems from the region's unique oceanographic conditions, making it a critical area for studying global deoxygenation processes.^[49]^[50] The formation of the Arabian Sea OMZ is driven by a combination of high biological oxygen demand and limited physical replenishment. Intense monsoon-driven upwelling and seasonal blooms lead to elevated export of organic matter to depth, where microbial decomposition consumes oxygen through remineralization, creating a high oxygen demand. This is compounded by sluggish ventilation and strong stratification in the water column, which restrict the influx of oxygen-rich waters from the surface or adjacent regions, resulting in poor renewal of intermediate waters. The OMZ's distribution is further modulated by regional ocean currents that influence oxygen supply variability, including contributions from Persian Gulf water providing an average of 1.3 Tmol of oxygen per year.^[49]^[51]^[50]^[52] In terms of extent, the OMZ encompasses approximately 2.5 × 10¹⁵ m³ of water volume, representing about 24% of the Arabian Sea's total water column volume of roughly 1.07 × 10¹⁶ m³, and it is the largest contributor (around 80%) to the northern Indian Ocean's hypoxic waters. The zone is most pronounced in the northern and northeastern regions, particularly off the coasts of Pakistan and Oman, where oxygen minima approach zero and the layer thickens due to enhanced productivity and reduced ventilation. This spatial variability underscores the OMZ's role as a hotspot for biogeochemical transformations.^[49]^[50]^[53] Recent observations indicate a historical decline in oxygen levels within the OMZ, with concentrations decreasing by 0.1–0.2 ml/L per decade since the 1960s, as documented in analyses from the 2020s drawing on historical datasets, exceeding 6% per decade in some northern sectors during the late 20th century. However, more recent data from 2022–2023 show a reversal with increased oxygenation, where average dissolved oxygen concentrations rose 2–2.5 times from 2019 levels (from ~10.31 μmol/kg). This deoxygenation trend up to the early 2020s, and subsequent oxygenation, reflects broader patterns of reduced solubility from warming and altered circulation, with short-term variability influenced by winds and eddies, highlighting the sensitivity of the Arabian Sea OMZ to environmental shifts as of 2025.^[49]^[51]^[54]^[55]^[56]

Undersea Features

The Arabian Sea's undersea topography is characterized by a variety of submarine geological formations, including prominent seamounts that rise from the basin floor. The Raman Seamount, located approximately 300 km west of Mumbai, India, stands as a notable feature in the Laxmi Basin, reaching a height of about 2,000 meters above the surrounding seafloor and exhibiting elongated morphology with dendritic gully patterns indicative of erosional processes.^[57] Nearby, the Sindbad Seamount, situated in the central-western Arabian Sea at around 16° N, 58.6° E, forms part of a chain of volcanic edifices, with its summit influencing local bathymetric variations.^[58] These seamounts are connected to the broader Laccadive-Chagos Ridge chain, an aseismic volcanic ridge extending over 2,000 km from the Indian continental margin southward toward the Chagos Archipelago, formed through hotspot-related magmatism and featuring elevated plateaus up to 1,500 meters high.^[59] Major ridges and fracture zones further define the basin's structure, with the Owen Fracture Zone serving as a transform fault boundary between the Arabian and Indian plates, stretching over 800 km along the southeastern margin of the Arabian Peninsula and accommodating dextral strike-slip motion at rates of about 2 mm per year.^[60] The Carlsberg Ridge, a segment of the Central Indian Ridge system, bisects the southern Arabian Sea as an active mid-ocean ridge, propagating northward since the Eocene and contributing to the basin's maximum depths of over 4,600 meters through seafloor spreading.^[61] The Arabian Abyssal Plain occupies much of the central basin at depths averaging around 4,000 meters, covered by thick sediment layers that preserve records of late Quaternary turbidite sequences and tectonic events, as revealed by core samples showing interbedded silty clays and sands from regional slumping.^[62] Submarine volcanic activity in the Arabian Sea is primarily linked to the Réunion hotspot plume, which has influenced the formation of seamount chains like the Laccadive-Chagos Ridge through anomalous magmatism intersecting ancient spreading centers, with evidence from bathymetric surveys indicating multiphased eruptions dating back to the late Cretaceous.^[63]

Islands

Major Archipelagos

The major archipelagos in the Arabian Sea are predominantly coral or volcanic in origin, shaped by the tectonic movements of the Indian Ocean plates, including hotspot volcanism and ridge formations that have influenced their emergence over millions of years.^[64] These island groups fringe the sea's margins and are closely proximate to the coastal countries of India, the independent nation of Maldives, and Yemen.^[65] The Lakshadweep Archipelago, located off the southwestern coast of India, comprises 36 coral islands organized into 12 atolls, with a total land area of 32 km².^[66]^[67] These islands formed atop the Chagos-Laccadive Ridge, a submarine volcanic chain resulting from ancient tectonic activity associated with the Indian plate's northward drift. The atolls feature shallow lagoons encircled by reef rings, characteristic of coral buildup on subsiding volcanic foundations. The Maldives Archipelago consists of 1,192 coral islands distributed across 26 atolls, spanning approximately 90,000 km² of ocean waters.^[68] Its formation stems from subsidence of volcanic bases, where coral reefs grew upward as the underlying structures sank due to isostatic adjustments in the Indian Ocean's tectonic framework.^[69] This process, aligned with Charles Darwin's classic subsidence theory, has created a low-lying chain of ring-shaped atolls with minimal elevation above sea level. The Socotra Archipelago, off the coast of Yemen near the Arabian Sea's entrance to the Gulf of Aden, includes four main islands covering a total area of 3,796 km².^[70] Unlike the coral-dominated groups to the east, Socotra features unique geological formations of granite basements overlain by limestone plateaus, remnants of an ancient microplate separated during the breakup of Gondwana.^[71]^[72] Designated as a UNESCO World Heritage Site in 2008, it highlights exceptional tectonic isolation that preserved its distinct lithological diversity.^[65]

Notable Individual Islands

Astola Island, located off the coast of Balochistan in Pakistan, spans approximately 6.7 km² and features prominent limestone karst formations that contribute to its unique topography, including rugged hills and sea caves.^[73]^[74] This uninhabited island serves as an important bird sanctuary, hosting breeding populations of species such as the Socotra cormorant and supporting diverse seabird colonies, which led to its designation as Pakistan's first Marine Protected Area in 2017.^[75] Karanja Island, situated near Mumbai in India, spans approximately 83 km² (13 km long by 6.4 km broad) and is characterized by extensive mangrove forests that provide critical coastal protection and habitat for marine species. These mangroves, dominated by species like Avicennia marina, face pressures from development but remain vital for ecological stability in the region.^[76] The island hosts oil terminals that facilitate the transfer of petroleum products, leveraging its strategic position in the Mumbai Harbour for lighterage operations.^[77] Perim Island, off the southwestern coast of Yemen, measures around 13 km² and owes its formation to volcanic activity, with basaltic rocks dating back to the Miocene epoch exposed across its barren landscape.^[78] Positioned at the southern entrance to the Bab-el-Mandeb Strait, it divides the waterway into two channels, enhancing its geological and navigational significance in connecting the Red Sea to the Arabian Sea.^[79] Masirah Island, the largest off the coast of Oman at approximately 682 km², exposes significant ophiolite sequences representing fragments of ancient ocean crust from the Proto-Indian Ocean, formed during the Late Jurassic to Early Cretaceous.^[80] These ophiolites, including peridotites and gabbros, provide key insights into mid-ocean ridge processes, with the island's thin crustal section (about 2 km thick) distinguishing it from other regional formations.^[81] The exposures highlight tectonic obduction events that thrust oceanic material onto the continental margin.^[82]

Human Activity

Historical and Modern Trade Routes

The Arabian Sea has been a pivotal artery for maritime trade since the 3rd millennium BCE, when early routes linked the Indus Valley Civilization with Mesopotamia through the Arabian Peninsula, forming the foundational Maritime Silk Road for exchanging goods like timber, shells, and metals.^[83] These ancient pathways relied on monsoon winds to facilitate voyages across the sea, enabling the transport of raw materials such as conch shells from the Arabian coast to Mesopotamian ports.^[84] By the Roman era, trade expanded significantly, with direct routes connecting Red Sea ports like Berenike to Muziris on India's Malabar Coast, where Roman ships carried pepper, spices, and textiles in exchange for Eastern luxuries, supported by over 6,000 Roman coins unearthed at the site.^[85] This network, peaking in the 1st to 2nd centuries CE, integrated the Arabian Sea into a broader Indo-Mediterranean exchange system, with voyages timed to the southwest monsoon for efficient passage.^[86] In the medieval period, Arab dhows dominated the Arabian Sea, ferrying spices from India, textiles from the Deccan, and aromatics like frankincense across monsoon-driven circuits to East Africa and the Persian Gulf, sustaining a vibrant Islamic mercantile economy from the 7th to 15th centuries.^[87] The Portuguese disrupted this hegemony in 1498 when Vasco da Gama's expedition rounded the Cape of Good Hope, establishing the first European ocean route to Calicut and redirecting spice flows toward Lisbon, which spurred fortified outposts along the Indian coast.^[88] Today, the Arabian Sea hosts primary north-south corridors from the Persian Gulf into the broader Indian Ocean and east-west lanes linking India's west coast to East Africa, carrying diverse cargoes including oil, containers, and bulk goods amid a surge in global trade volumes.^[89] These routes accommodate substantial annual vessel traffic, with over 50,000 ships entering the Persian Gulf alone for energy transport, underscoring the sea's role in connecting Eurasian markets.^[90] Critical chokepoints include the Strait of Hormuz, which channels about 20% of global seaborne oil trade—roughly 21 million barrels per day—and the Bab el-Mandeb Strait, which facilitated around 8.7 million barrels per day en route to the Suez Canal prior to 2023 disruptions, but averaged about 4.0 million barrels per day in 2024 due to Houthi attacks, with volumes remaining suppressed into 2025.^[91] Since late 2023, Houthi attacks in the Red Sea have disrupted traffic through the Bab el-Mandeb Strait, forcing many vessels to reroute around the Cape of Good Hope, increasing transit times and costs for Arabian Sea-linked trade.^[92]

Major Ports and Shipping

The Arabian Sea hosts several major ports that serve as critical hubs for international trade, particularly along the coastlines of India, Pakistan, Oman, and Yemen. Jawaharlal Nehru Port (JNPA) in India, located near Mumbai, is the country's largest container port, with a capacity exceeding 10 million twenty-foot equivalent units (TEUs) as of early 2025, handling a significant portion of India's containerized exports and imports.^[93] The Port of Karachi in Pakistan achieved a record cargo throughput of 54 million tons in fiscal year 2025, supported by expansions that boost its annual capacity to 125 million tons, focusing on bulk, container, and general cargo.^[94]^[95] Port Sultan Qaboos in Muscat, Oman, plays a key role in oil transshipment and general cargo, benefiting from national port expansions that increased container handling by 11.7% in the first half of 2025.^[96] The Port of Aden in Yemen serves as a strategic refueling and bunkering station due to its position near major shipping lanes, with ongoing expansions aiming to raise container capacity to nearly 1 million TEUs despite regional challenges.^[97] Shipping in the Arabian Sea is dominated by energy transport, with routes through the Strait of Hormuz accounting for more than 25% of global seaborne oil trade volumes in early 2025, equivalent to over 20 million barrels per day.^[98] Container throughput in the region has shown steady growth, with ports in bordering countries like Saudi Arabia (adjacent via the Gulf of Aden) reporting increases of 12-13% year-on-year in 2025, reflecting broader trends in maritime trade recovery.^[99]^[100] Overall, the sea facilitates vital trade links, including brief connections to established routes from the Indian Ocean to Europe and East Asia. Port infrastructure along the Arabian Sea emphasizes deep-water capabilities to accommodate large vessels, with many berths offering drafts up to 18 meters to handle ultra-large crude carriers and container ships.^[101] Qatar's Ras Laffan Port features extensive LNG terminals, including the world's largest export facility, supporting regasification and loading for global energy markets.^[102] In India, automation trends are advancing at Arabian Sea ports like JNPA, incorporating digital systems for berth management and cargo tracking to enhance efficiency amid rising volumes.^[103] These ports collectively contribute to the economic vitality of bordering nations, with India's maritime sector, valued at nearly $1 trillion as of 2025, supporting trade that bolsters national GDP through logistics and related industries.^[104]^[105] In Oman, the logistics sector, driven by ports like Sultan Qaboos, has shown increasing alignment with GDP growth through diversified cargo handling.^[106] Overall, maritime activities around the Arabian Sea generate substantial employment and revenue, underpinning regional economic stability.

Fisheries and Natural Resources

The Arabian Sea supports a significant marine fishery, with total capture production reaching approximately 5.6 million tonnes as of 2020, with no comprehensive updates available for subsequent years despite ongoing pressures, primarily from coastal and small-scale operations.^[107] This output is dominated by small pelagic species such as sardines (particularly the Indian oil sardine, Sardinella longiceps) and mackerel (including the Indian mackerel, Rastrelliger kanagurta), which constitute a major portion of landings due to their abundance in upwelling zones along the Indian and Pakistani coasts.^[108] India accounts for the largest share, contributing about 58% of the regional catch, followed by Pakistan as a key player with substantial fleets operating in the northern and eastern sectors.^[108] Overfishing poses a growing threat to sustainability, with stocks of key species like tuna and shrimp showing notable declines. In the western Indian Ocean, which encompasses the Arabian Sea, Penaeidae shrimp populations are classified as overfished, with management measures implemented to address excessive pressure.^[107] Tuna stocks in the region have experienced a 20-30% biomass reduction since 2000, driven by increased industrial fishing and inadequate regulation, as documented in FAO assessments of Indian Ocean fisheries.^[109] Beyond fisheries, the Arabian Sea harbors valuable non-living resources, including offshore oil and gas fields. The Bombay High field, located in the northern basin off India's west coast, produces around 131,000 barrels of oil per day as of 2025, supporting a significant portion of India's domestic energy needs despite production declines from its historical peak. Deeper basins also contain potential deposits of polymetallic nodules rich in manganese, nickel, cobalt, and copper, with India actively exploring these in its exclusive economic zone through geological surveys.^[110] The sea's waters further offer desalination potential for coastal nations facing water scarcity, leveraging reverse osmosis technologies to convert saline inflows into freshwater, though large-scale implementation remains limited by energy costs.^[111] Aquaculture is emerging as a complementary sector, with initiatives focused on high-value marine species. In Oman, a pilot pearl oyster farming project launched in 2025 at Masirah Island marks the first such effort in the region, targeting species like Pinctada radiata for sustainable pearl production.^[112] India has similarly expanded pearl oyster cultivation along its Arabian Sea coastline, integrating it with broader marine farming to reduce pressure on wild stocks.^[113] Seaweed farming is also gaining traction, with Oman's upwelling zones identified as ideal for species like Sargassum and Gracilaria, supported by pilot projects to boost the blue economy.^[114] In India, national programs aim to cultivate over 30,000 tonnes of dry seaweed annually from coastal areas, including the Arabian Sea, emphasizing economic and environmental benefits.^[115]

Ecology and Environment

Biodiversity and Marine Life

The Arabian Sea hosts a rich array of marine life, supported by its dynamic oceanographic conditions including seasonal upwelling that enhances nutrient availability and fosters high biological productivity. This environment sustains diverse ecosystems, from coastal coral reefs to open-ocean pelagic zones, harboring thousands of species across various taxa. The sea's biodiversity is particularly notable for its mix of tropical and subtropical elements, with significant contributions from migratory populations that utilize its waters seasonally.^[116] Marine mammals are prominent components of the Arabian Sea's fauna, with approximately 21 cetacean species recorded, including five baleen whales and 16 odontocetes. Notable among these are migratory blue whales (Balaenoptera musculus), which traverse the region as part of their Indo-Pacific range, and Indo-Pacific humpback dolphins (Sousa plumbea), often observed in coastal and nearshore habitats. Dugongs (Dugong dugon), herbivorous sirenians, inhabit seagrass meadows along the continental shelves, particularly off the coasts of Oman and Pakistan, where they graze on benthic vegetation. These species highlight the sea's role as a critical habitat for both resident and transient large vertebrates.^[117]^[118]^[119] The ichthyofauna of the Arabian Sea is exceptionally diverse, encompassing over 1,000 fish species that span reef, pelagic, and demersal niches. Reef-associated fishes, such as groupers (Epinephelus spp.), dominate coral habitats and contribute to the ecological complexity of these systems. Invertebrates are equally abundant, including a variety of crustaceans, mollusks, and echinoderms that form the base of food webs. The Lakshadweep archipelago's coral reefs, fringing these low-lying atolls, support more than 170 scleractinian coral species, creating biodiverse habitats that shelter numerous reef fishes and invertebrates.^[120]^[121]^[122] Plankton communities thrive due to upwelling-driven nutrient influx, particularly during the southwest monsoon, yielding primary productivity rates of 200–260 gC/m²/year in these zones and supporting a robust base for higher trophic levels. Phytoplankton blooms, dominated by diatoms and dinoflagellates, sustain zooplankton populations that, in turn, feed pelagic fishes and marine mammals. Avian biodiversity includes migratory seabirds that exploit these productive waters; sooty terns (Onychoprion fuscatus), for instance, forage extensively across the tropical Indian Ocean, including the Arabian Sea, during their non-breeding migrations.^[123]^[124] Endemism is evident in species adapted to the Arabian Sea's oxygen minimum zone (OMZ), where low-oxygen conditions (below 0.5 mL/L) prevail between 150–1,500 m depth along the continental margin, influencing distributions but also fostering specialized adaptations. Certain jellyfish, such as those in the genus Crambionella (e.g., C. orsini), exhibit tolerance to hypoxic waters and form dense aggregations in OMZ-influenced areas, contributing to unique midwater communities. Coral reefs in the region have experienced bleaching events, notably in 2010 and during recent global heatwaves, yet some areas show recovery through juvenile recruitment and survivor growth, restoring cover within 10–15 years in less stressed locales.^[125]^[126]^[127]

Environmental Challenges

The Arabian Sea faces significant pollution threats from oil spills, plastic debris, and industrial effluents. In June 2025, a major oil spill occurred in the Gulf of Oman following a collision between two large tankers, creating an oil slick spanning approximately 1,500 hectares and threatening marine ecosystems connected to the broader Arabian Sea.^[128] Plastic debris enters the sea primarily through rivers draining from densely populated South Asian catchments, with the Indian Ocean region receiving substantial inputs from sources like the Indus River, contributing to widespread marine litter accumulation.^[129] Heavy metals such as lead, cadmium, and chromium contaminate coastal waters from industrial runoff, particularly along the shores of Pakistan and India, where untreated effluents from urban centers like Karachi discharge over 269 million gallons of waste daily into the sea.^[130] Habitat degradation exacerbates these issues, with mangrove forests along the Arabian Sea coastline experiencing notable losses since the 1990s due to coastal development, pollution, and dredging activities. In Pakistan's Indus Delta, for instance, mangrove coverage has declined sharply from historical levels, driven by reduced freshwater flows and industrial pressures. Coral reefs in Somali waters, part of the Arabian Sea's eastern margin, suffer destruction from dynamite fishing, a destructive practice that shatters reef structures and reduces habitat for marine species.^[131]^[132] Geopolitical challenges compound environmental pressures, including piracy in the Gulf of Aden, which, while declining sharply after 2012 due to international naval patrols, remains a sporadic threat to safe maritime operations in the region. Illegal, unreported, and unregulated (IUU) fishing by foreign trawlers, often using banned gear like drift nets, depletes fish stocks and damages seafloor habitats; nearly 200 Iranian and Pakistani vessels were detected engaging in such activities off Somalia and Yemen in recent years. These activities indirectly harm biodiversity by overexploiting key species and disrupting food webs. Conservation efforts aim to mitigate these threats through protected areas and cooperative frameworks. The Chagos Archipelago, encompassing over 640,000 square kilometers in the central Indian Ocean adjacent to the Arabian Sea, was designated a no-take marine protected area in 2010, banning all commercial fishing to safeguard reefs and pelagic ecosystems. Under the UNEP Regional Seas Programme, initiatives like the Nairobi Convention for the Western Indian Ocean promote regional cooperation on pollution control and habitat protection, including protocols to reduce marine litter and enforce sustainable fishing in Arabian Sea waters.^[133]^[134]

Climate Change Impacts

The Arabian Sea has undergone notable warming trends, with sea surface temperatures increasing by approximately 0.5°C over the past four decades based on satellite observations from 1980 to 2021, exceeding the global average rate of about 0.1°C per decade during the same period.^[135] This acceleration is evident in the northern and northeastern regions, where rates reach up to 0.7°C per decade, driven by enhanced stratification and reduced vertical mixing, as confirmed by 2020s interim satellite data extensions.^[136] These changes build on baseline hydrographic warming patterns, intensifying marine heatwaves that have increased by roughly 20 days per decade since the 1980s.^[137] Sea level rise in the Arabian Sea averages 3–5 mm per year, contributing to heightened risks for low-lying coastal areas such as the Indus Delta in Pakistan.^[138] Projections indicate potential submersion of up to 0.3–0.5 m in the region by 2050 under moderate emissions scenarios, exacerbating erosion and saltwater intrusion that threaten mangrove ecosystems and agricultural lands spanning hundreds of square kilometers.^[139] Ocean acidification has led to a surface pH decline of about 0.1 units since pre-industrial times, affecting shell-forming organisms like pteropods and foraminifera across the basin.^[140] Concurrent deoxygenation is expanding the oxygen minimum zone (OMZ) by intensifying hypoxia in subsurface waters, with observational data showing a volume increase of up to 20% over recent decades due to warmer temperatures and reduced oxygen solubility.^[51] These climatic shifts are driving ecosystem alterations, including widespread coral bleaching events in 2010 and 2024 along the UAE and Omani coasts, where elevated temperatures expelled symbiotic algae from reefs.^[141] Species are migrating poleward in response to warming, with pelagic fish and zooplankton shifting distributions northward at rates of tens to hundreds of kilometers per decade.^[142] Fisheries yields are projected to decline by 10–20% by 2030 in tropical regions like the Arabian Sea, as habitat compression and reduced productivity impact key commercial stocks such as sardines and mackerel.