Red Sea State Map of Sudan

Measuring about 1,930 km in length with a width of about 18 km, it stretches between the Egyptian city of the Suez and the Bab el-Mandeb Strait to the Indian Ocean to connect the Mediterranean world to the Indian Ocean via the Suez Canal and the Gulf of Aden. The basin is widest at 305 km across and deepest in the vicinity of 3,040 m. Geographically, the Great Basin separates Egypt, Sudan and Eritrea to the north of Africa and Saudi Arabia and Yemen to the south. On the southern side, two gulfs- the Gulf of Suez and the Gulf of Aqaba extend north towards the Mediterranean and the barren land that is the Levant respectively. All these aspects of orientation are important since they also determine the climate and circulation patterns of the region, and its human exploitation.

A young oceanic rift which is still opening

One of the greatest natural laboratories of the earth in terms of rifting- the process of splitting and forming new oceanic crusts- is located here. The basin is situated on a huge rift valley that is enclosed by Arabia and northeast Africa, among others, which connects down to the East African Rift and other further away rifts in the Gulf of Aden. Indisputable evidence of spreading at very slow rates is more than 50 km long sections of the Northern spreading centre where modern geodesy and seafloor mapping have demonstrated that true spreading is already in progress. Rates of full spreading estimated by bathymetry, gravity and earthquakes are approximately a few millimeters per year or perhaps 8-15 millimeters per year, which is typical of the ultra-slow mid-ocean ridges. This also makes sense of the row of central-trough volcanic highs, of an upper layer of young basalts beneath young deep brine pools under thick Miocene evaporites.

The history of the rift has occurred in stages since the beginning of the Cenozoic, and the main events occurred around 30 million years ago (deformation of the Gulf of Suez and the northern sector) and about 3-4 million years ago, which accelerated deformation of the southern one and at the Aqaba branch. It is not a purely academic story because extension and magmatism that has been continually occurring in recent times as evidenced by volcanism and earthquakes, still occurs and still shapes the seafloor and coastal geomorphology in the present.

An evaporation-dominated sea with unusual water masses

Climatically dry coasts and clear skies create amplified evaporation rates- on the order of about two metres a year in traditional maritime syntheses- which dwarf all the precipitation and river input. Such a high evaporative loss pulls in lower-salinity surface water at Bab el-Mandeb and out of the Gulf of Aden and causes denser, saltier intermediate and deep water to flow southward beneath it, returning back over the sill into the Gulf of Aden. At depths below 90–120 m, however, conditions are truly homogeneous: deep water temperatures are around 22°C and salinity is around 41‰, and the entire water column is replaced in a period of about every ten years. The overall circulation and budgets have also been examined over many decades, and are consistent with more recent observations: high evaporation, north-south flow through wind driving, and a two-layer exchange over the Bab el-Mandeb, which is itself only 115-120 m deep (about 380 ft).

Coral reefs which push the boundary of physiology

Huge areas of coastline and hundreds of islands are rimmed by fringing and barrier reefs. What this region has in common with many other global reef provinces is how hot and salty these waters are-- and yet how well some of the corals in the north branch are tolerating that heat. Experimental and in-situ observations in the Gulf of Aqaba documented extreme tolerance to temperatures: common reef constructors such as Stylophora pistillata survived months at 1-2 °C above local summer maxima without undergoing bleaching, and others have reported tolerance windows up to +5 °C above normal maxima. This renders the northern reefs (Jordan/Eilat-Aqaba region) a global hotspot of climate-resilient reef research and a conservation priority that is often cited as reefs of hope.

The resilience is finite Although extreme heatwaves themselves may still produce significant biological effects, the larger literature indicates that significant biological effects often follow when various metrics of heat stress (i.e., degree-heating weeks) exceed certain thresholds. To give reefs in these regions the best possible chance in a warmer climate, it is critical to preserve water quality and eliminate local sources of stress coastal construction, sedimentation, overfishing, etc. In this basin, remote sensing and modeling efforts are now being used to trace multi-decadal changes in live coral cover in order to identify areas of risk and refuge with greater precision.

Coasts, gulfs and the strait connecting it with the world

Geographically, the basin reduces in size moving southwards to the Bab el-Mandeb, where there is a chokepoint which passes into the Gulf of Aden and the Arabian Sea. To the north exists the Gulf of Suez (shallow and characterized by wide shelves) and the steep-sided Gulf of Aqaba (up to 1,700 m) leading to two very diverse marine environments that nonetheless rest on the same tectonic regime. The branches also form separate national coastlines; the Suez branch belongs completely within Egyptian borders; the Aqaba coastline borders Egypt, Israel, Jordan and Saudi Arabia.

A sea route- and vulnerability point in the world trade system

This corridor is one of the great trade routeways to the world because the Suez Canal (opened in 1869) provides a direct sea-level passage between the Mediterranean and the Indian Ocean. Ordinarily, about 12-15 percent of world trade in volume can be considered to transit the canal and an even greater share of east-west containerized trade. Even small disruptions can ricochet throughout a supply chain, as in 2023-2025 when hijackings and maritime security threats on the other side of the Suez Canal caused carriers to switch to the Cape of Good Hope, reducing Suez traffic by as much as 50 percent during certain periods and decimating Egyptian revenues on the canal. Such impacts on macroeconomic factors have been recounted by UNCTAD, the IMF, and others as the effects of longer routes increase the duration of deliveries, include fuel expenditures, and in some cases the prices of energy and consumer products.

Strategically this is of value to not only Europe and Asia but also East Africa and the Arabian Peninsula. The constrained Bab el-Mandeb sill ensures traffic is narrowed into limited lanes with maritime security, pilotage and weather windows being kept in check. This vulnerability explains why ports and logistics points along both coasts, including Jeddah, Yanbu, Port Sudan and Safaga as well as the twin ports of Eilat and Aqaba, become the centre of gravity in regional economies.

Life on the verge of tolerance- and the pressure it is exposed to

Contrary to popular belief that many seas are extremely salty and hot, biodiversity is high: corals, seagrass meadows, mangroves, reef fish, sharks, and charismatic megafauna attract scientists and divers. In the case of the basin, the main factor is the environmental gradients cooler, slightly less saline waters in the south, increasing the dryness and salinity as one reaches north, and which produces distinct ecological provinces along the length of the basin. Direct anthropogenic impacts are coastal development, sedimentation, and eutrophication associated with poorly treated wastewater and the added risk of shipping (oil spillage, groundings on reefs and vessel introductions of ballast water or biological invasions). Desalination impact is also not small in a few embayments; modeling of the northern gulf shows that brine releases now form a significant part of the natural evaporation budget and in the light of increasing desalination plant number, they can further raise salinity unless restrained by intake/outfall placement and basin-scale flow.

Responses to conservation include the local marine protected areas and global approaches. Through UNESCO and partner programs the resilience of the reefs in the northern gulf has been featured and heritage listings and transboundary approaches supported to protect corridors of connectivity. These initiatives are also moving toward satellite surveillance, self-regulating sensors, and local caretaking which is particularly helpful in an extensive, river-starved shoreline where ground-level patrol may be not very practical.

Why does the water appear red sometimes?

On most days the surface is blue-green but seasonal plankton blooms of nitrogen-fixing cyanobacterium Trichodesmium erythraeum may display red and brown tinges as the blooms die off and pigments oxidize. Historic descriptions, and the modern ocean color data, suggest that this phenomenon is by far the most credible explanation of why the sea is So-called, rather than quite literal suspended grains or the reflection of denizens like the deserts.

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