Marginal sea of the South Pacific off the northeast coast of Australia
The Coral Sea () is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends down the Australian northeast coast. Most of it is protected by the French Natural Park of the Coral Sea () and the Australian Coral Sea Marine Park. The sea was the location for the Battle of the Coral Sea, a major confrontation during World War II between the navies of the Empire of Japan, and the United States and Australia.
The sea contains numerous islands and reefs, as well as the world's largest reef system, the Great Barrier Reef (GBR), which was declared a World Heritage Site by UNESCO in 1981. All previous oil exploration projects were terminated at the GBR in 1975, and fishing is restricted in many areas. The reefs and islands of the Coral Sea are particularly rich in birds and aquatic life and are a popular tourist destination, both domestically and internationally.
Geography.
It is bounded in the west by the east coast of Queensland, thereby including the Great Barrier Reef, in the east by Vanuatu (formerly the New Hebrides) and by New Caledonia, and in the northeast approximately by the southern extremity of the Solomon Islands. In the northwest, it reaches to the south coast of eastern New Guinea, thereby including the Gulf of Papua. It merges with the Tasman Sea in the south, with the Solomon Sea in the north and with the Pacific Ocean in the east. On the west, it is bounded by the mainland coast of Queensland, and in the northwest, it connects with the Arafura Sea through the Torres Strait.
The sea is characterised by its warm climate, with frequent rains and tropical cyclones.
Extent.
While the Great Barrier Reef with its islands and cays belong to Queensland, most reefs and islets east of it are part of the Coral Sea Islands Territory. In addition, some islands west of and belonging to New Caledonia are also part of the Coral Sea Islands in a geographical sense, such as the Chesterfield Islands and Bellona Reefs.
The International Hydrographic Organization defines the limits of the Coral Sea as follows:
"On the North." The South coast of New Guinea from the entrance to the Bensbach River (141°01'E) to Gadogadoa Island near its Southeastern extreme (), down this meridian to the 100 fathom line and thence along the Southern edges of Uluma Reef and those extending to the Eastward as far as the Southeast point of Lawik Reef () off Tagula Island, thence a line to the Southern extreme of Rennell Island (Solomon Islands) and from its Eastern point to Cape Surville, the Eastern extreme of San Cristobal Island [Makira], Solomons; thence through Nupani Island, the Northwestern of the Santa Cruz Islands () to the Northernmost Island of the Duff Islands ().
"On the Northeast." From the Northernmost island of the Duff Islands, through these islands to their Southeastern extreme, thence a line to Méré Lava, Vanuatu Islands() and down the Eastern coasts of the islands of this Group to Anatom Island () in such a way that all the islands of these Groups, and the straits separating them, are included in the Coral Sea.
"On the Southeast." A line from the Southeastern extreme of Anatom Island to Nokanhoui (reefs) () off the Southeast extreme of New Caledonia, thence through the East point of Middleton Reef to the Eastern extreme of Elizabeth Reef () and down this meridian to Latitude 30° South.
"On the South." The parallel of 30° South to the Australian coast. (Bordering the Tasman Sea.)
"On the West." The Eastern limit of the Arafura Sea [The entrance to the Bensbach River (141°01'E), and thence a line to the Northwest extreme of York Peninsula, Australia ()] and the East Coast of Australia as far south as Latitude 30° South.
Geology.
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New Guinea
Solomon         Islands
Coral  Sea
D'Entrecasteaux  Basin
Australia
Zealandia
NewCaledonia
 Coral Sea and surrounds topography with Zealandia outlined 
The fairly deep Coral Sea basin was formed between 58 million and 48 million years ago when the Queensland continental shelf was uplifted, forming the Great Dividing Range, and continental blocks subsided at the same time. The sea has been an important source of coral for the Great Barrier Reef, both during its formation and after sea level lowering.
The geological formation processes are still proceeding, as partly evidenced by the seismic activity. Several hundred earthquakes with the magnitude between 2 and 6 were recorded in the period 1866–2000 along the Queensland coast and in the Coral Sea. However this seismic activity is much less than to the east or north of the sea, and most of the area under the sea can be regarded as now tectonically inactive except for sedimentation. On 2 April 2007, the Solomon Islands were struck by a major earthquake followed by a several metres tall tsunami. The epicentre of this magnitude earthquake was northwest of Honiara, at a depth of . It was followed by more than 44 aftershocks of a magnitude 5.0 or greater. The resulting tsunami killed at least 52 people and destroyed more than 900 homes.
The sea received its name because of its numerous coral formations. They include the Great Barrier Reef, which extends about along the northeast coast of Australia and includes approximately 2,900 individual reefs and 1000 islands. The Chesterfield Islands and Lihou Reef are the largest atolls of the Coral Sea.
Topography.
To the east of the north Australian coast is the Great Barrier Reef on the continental shelf. To its east is a plateau that is host to the Coral Sea Islands Territory that is known as either the Coral Sea Plateau or the Queensland Plateau. To the north of the Great Barrier Reef the Eastern and Papuan Plateaus continue the southern continental shelf of New Guinea. The Coral Sea Basin, while being the main oceanic basin of the sea, is associated with much more geologically complex and younger basins situated to the seas's east and south. It is separated to the east from these younger basins by the Louisiade Plateau. To the east of the Louisiade Plateau is what has been named geologically as the Rennell Basin, south-west of Rennell Island, but is gazetted as being known as either the Rennell or Rennel Trough. To the east of this Rennell Basin is the Rennell Island Ridge (Rennel Island Ridge) which contains both Rennell Island and the Indispensable Reefs. To the southeast of the Rennell Island Ridge is the South Rennell Trough, quite a deep spreading center linear structure extending from northeast to southwest extending along the south east border of the Mellish Rise. The main eastern basins are the north the Santa Cruz Basin and to its south the D'Entrecasteaux Basin which is delimited to its south by the undersea D'Entrecasteaux Ridge. South of the D'Entrecasteaux Ridge is the North Loyalty Basin (gazetted as the Loyalty Basin as an alternative name), which is bordered on its southwest by the Loyalty Ridge that contains the Loyalty Islands. This ridge is the north east border of the submerged continent of Zealandia and all the structures on the sea floor of the Coral Sea to its south east are related to this area of continental crust. In turn going to the south west they are the South Loyalty Basin, the New Caledonia Nappe, the New Caledonia Trough (previously known as the New Caledonia Basin) and to its south west the Bellona Plateau.
Hydrology.
Major Coral Sea currents form a counter-clockwise gyro which includes the East Australian Current. It brings warm nutrient-poor waters from the Coral Sea down the east coast of Australia to the cool waters of the Tasman Sea. This current is the strongest along the Australian coasts and transforms 30 million m3/s of water within a flow band of about 100 kilometres wide and 500 metres deep. The current is strongest around February and weakest around August.
The major river flowing into the sea is the Burdekin River, which has its delta southeast of Townsville. Owing to the seasonal and annual variations in occurrence of cyclones and in precipitation (typically between 200 and 1600 mm/year), its annual discharge can vary more than 10 times between the two succeeding years. In particular, in the period 1920–1999, the average flow rate near the delta was below 1000 m3/s in 1923, 1931, 1939, 1969, 1982, 1985, 1987, 1993 and 1995; it was above 25,000 m3/s in 1927, 1940, 1946, 1950, 1951, 1959, 1968, 1972, 1974 and 1991, and reached about 40,000 m3/s in 1946. This irregularity results in concomitant fluctuations of the sea water composition near the river delta.
The surface water temperature varies on the south of the sea from 19 °C in August to 24 °C in February. It is rather warm and stable at 27–28 °С in the north all through the year. Water salinity is 34.5–35.5‰ (parts per thousand). The water is mostly very clear, with the visibility of about 30 metres (100 ft) near the reefs.
History.
The Coral Sea takes its name from its coral formations of the Great Barrier Reef, the largest known reef system in the world.
In May 1942, a battle between Allied and Imperial Japanese naval units took place in the Coral Sea, which resulted in the prevention of the Japanese sea-borne invasion of Port Moresby.
Climate.
The sea has a subtropical climate and is frequently hit by tropical cyclones, especially between January and April. This range extends to November–May in the areas south to 10°S. Between 1969 and 1997, the GBR experienced 80 cyclones, 90% which were of category 1 or 2 (winds 17–33 m/s, central pressure 970–1000 hPa) and only 10% of category 3 (winds ;33 m/s, pressure ;970 hPa). The cyclone frequency decreased between 1997 and 2005 to 1.5 per year (12 in total).
Annual rainfall typically ranges between 1,000 and 3,000 mm depending on the area. Most rains fall between December and March, in bursts of 30–60 days. The number of clear days per year varies approximately between 80 and 125, and the typical temperature variation through the year are 18–27 °C.
Climate change made it 175 times more likely that the surface waters of the Coral Sea would reach the record-breaking temperatures March 2016 that bleached reefs, modelling analysis showed.
Winds.
Winds in the Coral Sea can be classified by season, longitude and latitude. Southeasterly trade winds dominate through all sea areas and all seasons, especially between 20°S and 25°S, west of the meridian of 155°E. However, between September and December they change to northerly and northwesterly winds in this region, and the direction is mostly southwestern in May–August. West of 155°E, gales are common between January and August and are less frequent in September–December.
In January, the northwest monsoon may occur between the parallels of 15°S and 20°S, west of the 150°E meridian. Gales are rare in this region most of the year except for June–August, when strong southeasterly winds occur a few days per month.
The southeasterly trades are also strong north of 15°S between March and November. They weaken and often change to westerly winds in December and to northerly and northwesterly winds in January
and February.
Flora.
The Australian shore of the Coral Sea is mostly composed of sand. The GBR is too far away to provide significant coral deposits, but it effectively screens the coast from the ocean waves. As a result, most land vegetation spreads down to the sea, and the coastal waters are rich in underwater vegetation, such as green algae. The most common genera of seagrasses are "Halophila" and "Halodule".
The islands of the GBR contain more than 2,000 plant species, and three of these are endemic. The northern islands have 300–350 plant species which tend to be woody, whereas the southern islands have 200 which are more herbaceous; the Whitsunday region is the most diverse, supporting 1,141 species. The plants are spread by birds.
Fauna.
The sea hosts numerous species of anemones, sponges, worms (e.g. "Spirobranchus giganteus" shown in the photograph), gastropods, lobsters, crayfish, prawns and crabs. Red algae "Lithothamnion" and "Porolithon" colour many coral reefs purple-red and the green alga "Halimeda" is found throughout the sea. The coastal plants consisting of only about 30–40 species, and mangroves occur in the northern part of the sea. Four hundred coral species, both hard corals and soft corals inhabit the reefs. The majority of these spawn gametes, breeding in mass spawning events that are triggered by the rising sea