The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab el Mandeb strait and the Gulf of Aden. The Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez (leading to the Suez Canal) lie north. It is underlain by the Red Sea Rift, part of the Great Rift Valley.
The Red Sea has a surface area of roughly 438,000 km2 (169,100 mi2), is about 2250 km (1398 mi) long, and – at its widest point – 355 km (220.6 mi) wide. It has an average depth of 490 m (1,608 ft), and in the central Suakin Trough, it reaches its maximum depth of 3,040 m (9,970 ft).
The sea is the habitat of over 1,000 invertebrate species and 200 soft and hard coral types. It is the world’s northernmost tropical sea and is designated a Global 200 ecoregion. The Red Sea also has extensive shallow shelves, noted for their marine life and corals.
The International Hydrographic Organization defines the limits of the Red Sea as follows:
- On the North. The Southern limits of the Gulfs of Suez, A line running from Ràs Muhammed (27°43’N) to the South point of Shadwan Island (34°02’E) and thence Westward on a parallel (27°27’N) to the coast of Africa] and Aqaba, A line running from Ràs al Fasma Southwesterly to Requin Island (27°57′N 34°36′E) through Tiran Island to the Southwest point thereof and thence Westward on a parallel (27°54’N) to the coast of the Sinai Peninsula.
- In the South. A line joining Husn Murad (12°40′N 43°30′E) and Ras Siyyan (12°29′N 43°20′E).
The Red Sea is a direct translation of the Greek Erythra Thalassa (Ερυθρὰ Θάλασσα). The sea itself was once referred to as the Erythraean Sea by Europeans. As well as Mare Rubrum in Latin (alternatively Sinus Arabicus, literally “Arabian Gulf”), the Romans called it Pontus Herculis (Sea of Hercules). Other designations include the Arabic: البحر الأحمر, romanized: Al-Baḥr Al-Aḥmar (alternatively بحر القلزم Baḥr Al-Qulzum, literally “the Sea of Clysma”), the Coptic ⲫⲓⲟⲙ ̀ⲛϣⲁⲣⲓ Phiom ̀nšari, ܝܡܐ ܣܘܡܩܐ Yammāʾ summāqā, Somali Badda cas and Tigrinya Qeyyiḥ bāḥrī (ቀይሕ ባሕሪ).
The name of the sea may signify the seasonal blooms of the red-coloured Trichodesmium erythraeum near the water’s surface. A theory favoured by some modern scholars is that the name red refers to the direction south, just as the Black Sea’s name may refer to the north. The basis of this theory is that some Asiatic languages use colour words to refer to the cardinal directions. Herodotus, on one occasion, uses the Red Sea and Southern Sea interchangeably.
The name in Hebrew Yam Suph (Hebrew: ים סוף, lit. ’Sea of Reeds’) is of biblical origin. The name in Coptic: ⲫⲓⲟⲙ `ⲛϩⲁϩ Phiom Enhah (“Sea of Hah”) is connected to the Ancient Egyptian root ḥ-ḥ which refers to water and sea (for example the names of the Ogdoad gods Heh and Hauhet).
Historically, Western geographers also know it as Mare Mecca (Sea of Mecca) and Sinus Arabicus (Gulf of Arabia). Some ancient geographers called the Red Sea the Arabian Gulf or Gulf of Arabia.
The association of the Red Sea with the biblical account of the Israelites crossing the Red Sea is ancient and was made explicit in the Septuagint translation of the Book of Exodus from Hebrew to Koine Greek in approximately the third century BC. In that version, the Yam Suph (Hebrew: ים סוף, lit. ’Sea of Reeds’) is translated as Erythra Thalassa (Red Sea).
The Red Sea is one of four seas named in English after standard colour terms – the others being the Black Sea, the White Sea and the Yellow Sea. The direct rendition of the Greek Erythra Thalassa in Latin as Mare Erythraeum refers to the north-western part of the Indian Ocean and a region on Mars.
The earliest known exploration of the Red Sea was conducted by ancient Egyptians as they attempted to establish commercial routes to Punt. One such expedition took place around 2500 BC, and another around 1500 BC (by Hatshepsut). Both involved long voyages down the Red Sea. The biblical Book of Exodus tells the account of the Israelites’ crossing of a body of water, which the Hebrew text calls Yam Suph (Hebrew: יַם סוּף). Yam Suph was traditionally identified as the Red Sea. Rabbi Saadia Gaon (882‒942), in his Judeo-Arabic translation of the Pentateuch, identifies the crossing place of the Red Sea as Baḥar al-Qulzum, meaning the Gulf of Suez.
In the 6th century BC, Darius the Great of Persia sent reconnaissance missions to the Red Sea, improving and extending navigation by locating many hazardous rocks and currents. A canal was built between the Nile and the northern end of the Red Sea at Suez. In the late 4th century BC, Alexander the Great sent Greek naval expeditions down the Red Sea to the Indian Ocean. Greek navigators continued to explore and compile data on the Red Sea. Agatharchides collected information about the sea in the 2nd century BC. The Periplus of the Erythraean Sea (“Periplus of the Red Sea”), a Greek periplus written by an unknown author around the 1st century, contains a detailed description of the Red Sea’s ports and sea routes. The Periplus also describes how Hippalus first discovered the direct route from the Red Sea to India.
The Red Sea was favoured for Roman trade with India starting with the reign of Augustus, when the Roman Empire gained control over the Mediterranean, Egypt, and the northern Red Sea. The route had been used by previous states but grew in traffic volume under the Romans. From Indian ports, goods from China were introduced to the Roman world. Contact between Rome and China depended on the Red Sea, but the route was broken by the Aksumite Empire around the 3rd century AD.
Middle Ages and modern era
The Red Sea was an essential part of the spice trade route during the Middle Ages. In 1183, Raynald of Châtillon launched a raid down the Red Sea to attack the Muslim pilgrim convoys to Mecca. The possibility that Raynald’s fleet might sack the holy cities of Mecca and Medina caused fury throughout the Muslim world. However, it appears that Reynald’s target was the lightly armed Muslim pilgrim convoys rather than the well-guarded cities of Mecca and Medina, and the belief in the Muslim world that Reynald was seeking to sack the holy cities was due to the proximity of those cities to the areas that Raynald raided.
In 1513, trying to secure that channel to Portugal, Afonso de Albuquerque laid siege to Aden but was forced to retreat. They cruised the Red Sea inside the Bab al-Mandab, as the first fleet from Europe in modern times to have sailed these waters. Later in 1524, the city was delivered to Governor Heitor da Silveira as an agreement for protection from the Ottomans. In 1798, France ordered General Napoleon to invade Egypt and take control of the Red Sea. Although he failed in his mission, the engineer Jean-Baptiste Lepère, who took part in it, revitalised the plan for a canal which had been envisaged during the reign of the Pharaohs.
The Suez Canal was opened in November 1869. Several canals were built in ancient times from the Nile to the Red Sea along or near the present Sweet Water Canal line, but none lasted long. After the Second World War, the Americans and Soviets exerted their influence whilst the volume of oil tanker traffic intensified. However, the Six-Day War culminated in the closure of the Suez Canal from 1967 to 1975. Today, despite patrols by the major maritime fleets in the waters of the Red Sea, the Suez Canal has never recovered its supremacy over the Cape route, which is believed to be less vulnerable to piracy.
The Red Sea is between arid land, desert and semi-desert. The Red Sea water mass exchanges its water with the Arabian Sea and the Indian Ocean via the Gulf of Aden. Reef systems are better developed along the Red Sea mainly because of their greater depths and efficient water circulation patterns. These physical factors reduce the high salinity caused by evaporation in the north and relatively hot water in the south.
The Red Sea climate results from two monsoon seasons; a northeasterly monsoon and a southwesterly monsoon. Monsoon winds occur because of differential heating between the land and the sea. Very high surface temperatures and high salinities make this one of the world’s warmest and saltiest bodies of seawater. The average surface water temperature of the Red Sea during the summer is about 26 °C (79 °F) in the north and 30 °C (86 °F) in the south, with only about two °C (3.6 °F) variation during the winter months. The overall average water temperature is 22 °C (72 °F). Temperature and visibility remain good to around 200 m (656 ft). The sea is known for its strong winds and unpredictable local currents.
The rainfall over the Red Sea and its coasts are deficient, averaging 60 mm (2.36 in) per year. The rain is mostly short showers, often with thunderstorms and occasionally with dust storms. The scarcity of rainfall and no primary source of freshwater to the Red Sea result in excess evaporation as high as 2,050 mm (81 in) per year and high salinity with minimal seasonal variation. A recent underwater expedition to the Red Sea offshore from Sudan and Eritrea found surface water temperatures 28 °C (82 °F) in winter and up to 34 °C (93 °F) in the summer.
Still, despite that extreme heat, the coral was healthy with much fish life with very little sign of coral bleaching, with only 9% infected by Thalassomonas loyana, the white plague agent. Favia favus coral harbours a virus, BA3, which kills T. loyana. Scientists are investigating the unique properties of these coral and their commensal algae to see if they can be used to salvage bleached coral elsewhere.
The Red Sea is one of the saltiest bodies of water globally, owing to high evaporation and low precipitation; no significant rivers or streams drain into the sea, and its southern connection to the Gulf of Aden, an arm of the Indian Ocean, is narrow. Its salinity ranges between ~36 ‰ in the south part and 41 ‰ in the northern region around the Gulf of Suez, with an average of 40 ‰. (Average salinity for the world’s seawater is ~35 ‰ on the Practical Salinity Scale or PSU; that translates to 3.5% of actually dissolved salts.).
In general, the tide ranges between 0.6 m (2.0 ft) in the north, near the mouth of the Gulf of Suez and 0.9 m (3.0 ft) in the south near the Gulf of Aden, but it fluctuates between 0.20 m (0.66 ft) and 0.30 m (0.98 ft) away from the nodal point. The central Red Sea (Jeddah area) is therefore almost tideless, and as such, the annual water level changes are more significant. Because of the small tidal range, the water during high tide inundates the coastal sabkhas as a thin sheet of water up to a few hundred metres rather than flooding the sabkhas through a network of channels. However, south of Jeddah in the Shoiaba area, the water from the lagoon may cover the adjoining sabkhas as far as 3 km (2 mi), whereas north of Jeddah in the Al-Kharrar area, the sabkhas are covered by a thin sheet of water as far as 2 km (1.2 mi).
The prevailing north and northeast winds influence water movement in the coastal inlets to the adjacent sabkhas, especially during storms. Winter mean sea level is 0.5 m (1.6 ft) higher than in summer. Tidal velocities passing through constrictions caused by reefs, sand bars and low islands commonly exceed 1–2 m/s (3–6.5 ft/s). Coral reefs in the Red Sea are near Egypt, Eritrea, Israel, Saudi Arabia, and Sudan.
Detailed information regarding current data is lacking, partially because the currents are weak and both spatially and temporally variable. The variation of temporal and spatial currents is as low as 0.5 m (1.6 ft)[clarification needed] and is governed by the wind. During the summer, NW winds drive surface water south for about four months at a velocity of 15–20 cm/s (6–8 in/s), whereas in winter, the flow is reversed, resulting in the inflow of water from the Gulf of Aden into the Red Sea. The net value of the latter predominates, resulting in an overall drift to the north end of the Red Sea. Generally, the velocity of the tidal current is between 50 and 60 cm/s (20–23.6 in/s) with a maximum of 1 m/s (3.3 ft/s) at the mouth of the al-Kharrar lagoon. However, the range of the north-northeast current along the Saudi coast is 8–29 cm/s (3–11.4 in/s).