Arabian Sea

The Arabian Sea, a marginal sea of the Indian Ocean, lies between the Arabian Peninsula on the west and the Indian subcontinent on the east. Encompassing roughly 3.86 million km², it is bounded by Saudi Arabia, Yemen, Oman, the United Arab Emirates, Iran, Pakistan, and India, and links to the Gulf of Aden via the Bab al‑Mandab Strait and to the Persian Gulf through the Gulf of Oman and the Strait of Hormuz. Its strategic position as a conduit for a substantial share of global oil trade, coupled with rich fisheries and distinctive monsoonal dynamics, makes the Arabian Sea a focal point of economic, ecological, and geopolitical interest.

Geography and Physical Characteristics

The sea’s bathymetry is marked by a broad continental shelf that gives way to a steep slope plunging to an average depth of 2,734 m. The deepest recorded point, near the Oman–Iran basin, reaches approximately 4,652 m. Surface temperatures range from 22 °C in winter to 30 °C in summer, while salinity hovers around 35 psu, reflecting the balance between riverine inflow from the Indus and monsoonal precipitation. The seasonal southwest monsoon, strongest between June and September, drives a pronounced upwelling along the western coast, enhancing nutrient concentrations and supporting high primary productivity.

Geological History and Formation

The Arabian Sea basin originated in the Late Cretaceous as the Indian Plate collided with Eurasia, closing the Tethys Ocean and reshaping continental margins. Seismic surveys reveal thick sedimentary sequences up to 5 km on the continental slope, composed largely of terrigenous material delivered by the Indus and other rivers. Tectonic activity along the Makran subduction zone continues to generate modest seismicity, exemplified by the M 6.4 Makran earthquake of 2013, which underscored the region’s ongoing geodynamic evolution.

Economic and Strategic Significance

Oil and gas dominate the sea’s economic profile; the Strait of Hormuz alone saw an estimated 21 million barrels of crude oil transit daily in 2022, accounting for roughly 30 % of the world’s petroleum flow. Major ports such as Mumbai, Karachi, and Muscat handle combined cargo volumes exceeding 1 billion tonnes per year, facilitating trade in minerals, textiles, and perishables. The fisheries sector contributes about 2.5 million tonnes of catch annually (FAO, 2020), supporting livelihoods for coastal communities across six nations and supplying a significant portion of regional protein intake.

Ecology, Biodiversity, and Environmental Challenges

Biologically, the Arabian Sea hosts over 2,000 fish species, including commercially vital sardines, mackerel, and tuna, alongside at least 30 cetacean species such as the blue whale (Balaenoptera musculus) and the Indo‑Pacific humpback dolphin (Sousa chinensis). The monsoon‑driven upwelling sustains phytoplankton blooms that can reach 2.5 g C m⁻² d⁻¹, fostering a food web that supports seabirds and sea turtles. However, rapid industrialization has introduced challenges: plastic debris concentrations near the coast have risen to 1.2 million particles km⁻², and oil spill incidents—most notably the 2019 Al‑Mansour spill—have threatened marine habitats. Overfishing, particularly of sardine stocks, prompted regional management plans in 2018 that imposed catch limits of 1.2 million tonnes to curb depletion.