Red Sea

Related subjects: Geography of the Middle East

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Location of the Red Sea

The Red Sea is a salt water inlet of the Indian Ocean between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb sound and the Gulf of Aden. In the north are the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez (leading to the Suez Canal). The Red Sea is a Global 200 ecoregion.

Occupying a part of the Great Rift Valley, the Red Sea has a surface area of about 438,000 km² (169,100 square miles ). It is roughly 2250 km (1398 mi) long and, at its widest point at 355 km (220.6 miles) wide. It has a maximum depth of 2211 m (7254 ft) in the central median trench and an average depth of 490 m (1,608 feet ), but there are also extensive shallow shelves, noted for their marine life and corals. The sea is the habitat of over 1,000 invertebrate species and 200 soft and hard corals and is the world's northernmost tropical sea.

Name

Eilat and the Red Sea with Jordan on the other side

Red Sea is a direct translation of the Greek Erythra Thalassa (Ερυθρά Θάλασσα), Latin Mare Rubrum, Arabic Al-Baḥr Al-Aḥmar (البحر الأحمر), and Tigrinya Qeyyiḥ bāḥrī (ቀይሕ ባሕሪ).

The name of the sea may signify the seasonal blooms of the red-coloured cyanobacteria Trichodesmium erythraeum near the water's surface. Some suggest that it refers to the mineral-rich red mountains nearby which are called Harei Edom (הרי אדום). Edom, meaning "ruddy complexion", is also an alternative Hebrew name for the red-faced biblical character Esau (brother of Jacob), and the nation descended from him, the Edomites, which in turn provides yet another possible origin for Red Sea.

Another hypothesis is that the name comes from the Himyarite, a local group whose own name means red.

Yet another theory favored by some modern scholars is that the name red is referring to the direction south, the same way the Black Sea's name may refer to north. The basis of this theory is that some Asiatic languages used colour words to refer to the cardinal directions. Herodotus on one occasion uses Red Sea and Southern Sea interchangeably.

A final theory suggests that it was named so because it borders the Egyptian Desert which the ancient Egyptians called the Dashret or "red land"; therefore it would have been the sea of the red land.

The association of the Red Sea with the Biblical account of the Exodus, in particular in the Passage of the Red Sea, goes back to the Septuagint translation of the book of Exodus from Hebrew into Koine, in which Hebrew Yam Suph (ים סוף), meaning Reed Sea, is translated as Erythra Thalassa (Red Sea). Yam Suph is also the name for the Red Sea in modern Hebrew.

History

The earliest known exploration expeditions of the Red Sea were conducted by Ancient Egyptians seeking to establish commercial routes to Punt. One such expedition took place around 2500 BC and another around 1500 BC. Both involved long voyages down the Red Sea.

The Biblical book of Exodus tells the story of the Israelites' miraculous crossing of a body of water which the Hebrew text calls Yam Suph, traditionally identified as the Red Sea. The account is part of the Israelites' escape from slavery in Egypt, and is told in Exodus 13:17--15:21. (For another possible translation of Yam Suph, see Sea of Reeds.)

In the 6th century BC Darius I 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, written sometime around the 1st century AD, contain 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 favored 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 the volume of traffic 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.

During medieval times the Red Sea was an important part of the Spice trade route.

In 1798, France charged General Bonaparte with invading Egypt and capturing the Red Sea. Although he failed in his mission, the engineer J.B. Lepere, who took part in it, revitalised the plan for a canal which had been envisaged during the reign of the Pharaohs. Several canals were built in ancient times, but none lasted for long. The Suez Canal was opened in November 1869. At the time, the British, French, and Italians shared the trading posts. The posts were gradually dismantled following the First World War. 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, in spite of 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.

Oceanography

Bathymetric map of the Red Sea

The Red Sea lies between arid land, desert and semi-desert. The main reasons for the better development of reef systems along the Red Sea is because of its greater depths and an efficient water circulation pattern, The Red Sea water mass exchanges its water with the Arabian Sea, Indian Ocean via the Gulf of Aden. These physical factors reduce the effect of high salinity caused by evaporation and cold water in the north and relatively hot water in the south.

Climate: The climate of the Red Sea is the result of two distinct monsoon seasons; a northeasterly monsoon and a southwesterly monsoon. Monsoon winds occur because of the differential heating between the land surface and sea. Very high surface temperatures coupled with high salinities makes this one of the hottest and saltiest bodies of seawater in the world. 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 2 °C (3.6 °F) variation during the winter months. The overall average water temperature is 22 °C (72 °F). The rainfall over the Red Sea and its coasts is extremely low averaging 0.06 m (2.36 in) per year; the rain is mostly in the form of showers of short spells often associated with thunderstorms and occasionally with dust storms. The scarcity of rainfall and no major source of fresh water to the Red Sea result in the excess evaporation as high as 205 cm (81 in) per year and high salinity with minimal seasonal variation.

Salinity: The Red Sea is one of the most saline water bodies in the world, due to the effects of the water circulation pattern, resulting from evaporation and wind stress. Salinity ranges between 3.6 and 3.8%.

Tidal range: In general 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 meters rather than inundating 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 northeastern winds influence the movement of water 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).

Current: In the Red Sea detailed current data is lacking, partially because they are weak and variable both spatially and temporally. Temporal and spatial currents variation is as low as 0.5 m (1.6 ft) and are governed mostly by wind. In 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 northern end of the Red Sea. Generally the velocity of the tidal current is between 50-60 cm/s (20–23.6 in/s) with a maximum of 1 m/s (3.3 ft). at the mouth of the al-Kharrar Lagoon. However, the range of north-northeast current along the Saudi coast is 8-29 cm/s (3–11.4 in/s).

Wind Regime: With the exception of the northern part of the Red Sea, which is dominated by persistent north-west winds, with speeds ranging between 7 km/h (4.3 mph) and 12 km/h (7.5 mph)., the rest of the Red Sea and the Gulf of Aden are subjected to the influence of regular and seasonally reversible winds. The wind regime is characterized by both seasonal and regional variations in speed and direction with average speed generally increasing northward.

Wind is the driving force in the Red Sea for transporting the material either as suspension or as bedload. Wind induced currents play an important role in the Red Sea in initiating the process of resuspension of bottom sediments and transfer of materials from sites of dumping to sites of burial in quiescent environment of deposition. Wind generated current measurement is therefore important in order to determine the sediment dispersal pattern and its role in the erosion and accretion of the coastal rock exposure and the submerged coral beds.

Geology

Dust storm over the Red Sea

The Red Sea formed by Arabia splitting from Africa due to plate tectonics. This split started in the Eocene and accelerated during the Oligocene. The sea is still widening and it is considered that the sea will become an ocean in time (as proposed in the model of John Tuzo Wilson).

Sometime during the Tertiary period the Bab el Mandeb closed and the Red Sea evaporated to an empty hot dry salt-floored sink. Effects causing this would be:-

A "race" between the Red Sea widening and Perim Island erupting filling the Bab el Mandeb with lava.
The lowering of world sea level during the Ice Ages due to much water being locked up in the ice caps.

Today surface water temperatures remain relatively constant at 21–25 °C (70–77 °F) and temperature and visibility remain good to around 200 m (656 ft), but the sea is known for its strong winds and unpredictable local currents.

In terms of salinity, the Red Sea is greater than the world average, approximately 4 percent. This is due to several factors: 1) high rate of evaporation and very little precipitation, 2) a lack of significant rivers or streams draining into the sea, and 3) limited connection with the Indian Ocean (and its lower water salinity).

A number of volcanic islands rise from the centre of the sea. Most are dormant, but in 2007, Jabal al-Tair island erupted violently.

Desalination plants

There is extensive demand of desalinated water to meet the requirement of the population and the industries along the Red Sea.

There are at least 18 desalination plants along the Red Sea coast of Saudi Arabia which discharge warm brine and treatment chemicals (chlorine and anti-scalants) that may cause bleaching and mortality of corals and diseases to the fish stocks. Although this is only a localized phenomenon, it may intensify with time and have a profound impact on the fishing industry.

The water from the Red Sea is also utilized by oil refineries and cement factories for cooling purposes. Used water drained back into the coastal zones may cause harm to the nearshore environment of the Red Sea.

Facts and figures at a glance

Length: ~2,250 km (1,398.1 mi) - 79% of the eastern Red Sea with numerous coastal inlets
Maximum Width: ~ 306–355 km (190–220 mi)– Massawa (Eritrea)
Minimum Width: ~ 26–29 km (16–18 mi)- Bab el Mandeb Strait (Yemen)
Average Width: ~ 280 km (174.0 mi)
Average Depth: ~ 490 m (1,607.6 ft)
Maximum Depth: ~2,211 m (7,253.9 ft)
Surface Area: 438-450 x 10² km² (16,900–17,400 sq mi)
Volume: 215–251 x 10³ km³ (51,600–60,200 cu mi)

Approximately 40% of the Red Sea is quite shallow (under 100 m/330 ft), and about 25% is under 50 m (164 ft) deep.
About 15% of the Red Sea is over 1,000 m (3,300 ft) depth that forms the deep axial trough.
Shelf breaks are marked by coral reefs
Continental slope has an irregular profile (series of steps down to ~500 m/1,640 ft)
Centre of Red Sea has a narrow trough (~ 1,000 m/3,281 ft; some deeps may exceed 2,500 m/8,202 ft)

Some of the research cruises in the Red Sea

Numerous research cruises have been conducted:

Arabia Felix (1761-1767)
Vitiaz (1886-1889)
Valdivia (1898-1894)
Pola (1897-98) Southern Red Sea and (1895/96 – Northern Red Sea
Ammiraglio Magnaghi (1923/24)
Snellius (1929 –1930)
Mabahiss (1933-1934 and 1934-1935)
Albatross (1948)
Manihine (1849 and 1952)
Calypso (1955)
Atlantis and Vema (1958)
Xarifa (1961)
Meteor (1961)
Glomar Challenger (1971)
Sonne (1997)
Meteor (1999)

Tourism

The sea is known for its spectacular dive sites such as Ras Mohammed, SS Thistlegorm (shipwreck), Elphinstone, The Brothers, Dolphin Reef and Rocky Island in Egypt and less known sites in Sudan such as Sanganeb, Abington, Angarosh and Shaab Rumi (see photo above).

The Red Sea became known a sought-after diving destination after the expeditions of Hans Hass in the 1950s, and later by Jacques-Yves Cousteau. Popular tourist resorts include El Gouna, Hurghada, Safaga, Marsa Alam, on the western shore of the Red Sea, and Sharm-El-Sheikh, Dahab, and Taba on the Egyptian side of Sinaï, as well as Eilat, in Israel in an area known as the Red Sea Riviera.

Tourism in the South of Red Sea is presently considered risky because of the presence of pirates originating from uncontrolled zones of Eritrea and Somalia. Large vessels such as cargoes are sometimes attacked by high-speed boats heavily armed. The situation is even worse in the Gulf of Aden between Somalia and Yemen.