Celtic Sea
Encyclopedia
The Celtic Sea is the area of the Atlantic Ocean
off the south coast of Ireland
bounded to the east by Saint George's Channel; other limits include the Bristol Channel
, the English Channel
, and the Bay of Biscay
, as well as adjacent portions of Wales
, Cornwall
, Devon
, and Brittany
. The southern and western boundaries are delimited by the continental shelf
, which drops away sharply.
ic heritage of the bounding lands to the north and east gives the sea its name, first proposed by E. W. L. Holt
at a 1921 meeting in Dublin of fisheries experts from England, Ireland, Scotland and France. The northern portion of this sea had previously been considered as part of Saint George's Channel and the southern portion as an undifferentiated part of the "Southwest Approaches
" to Britain
. The need for a common name came to be felt because of the common marine biology
, geology
and hydrology
. It was adopted in France before being common in the English-speaking countries. It was adopted by marine biologists and oceanographers, and later by oil exploration firms. It is named in a 1963 British atlas, but a 1972 article states "what British maps call the western approaches, and what the oil industry calls the Celtic Sea [...] certainly the residents on the western coast [of Great Britain] don't refer to it as such."
(366 m) marine contour
and the island of Ushant
off the tip of Brittany.
The definition approved by 1974 by the Hydrographer
of the Royal Navy
for use in Admiralty
Charts was "bounded roughly by lines joining Ushant, Land's End
, Hartland Point
, Lundy Island, St. Govan's Head and Rosslare
, thence following the Irish coast south to Mizen Head
and then along the 200-metre isobath to approximately the latitude of Ushant."
The International Hydrographic Organization
defines the limits of the Celtic Sea as follows:
of Europe
. The northeast portion has a depth of between 90m and 100m, increasing towards Saint George's Channel. In the opposite direction, sand ridges pointing southwest have a similar height, separated by troughs approximately 50m deeper. These ridges were formed by tidal effects when the sea level was lower. South of 50°
the topography is more irregular.
Oil and gas exploration in the Celtic Sea has had limited commercial success. The Kinsale Head gas field
supplied much of the Republic of Ireland
in the 1980s and 1990s.
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
off the south coast of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
bounded to the east by Saint George's Channel; other limits include the Bristol Channel
Bristol Channel
The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Severn to the North Atlantic Ocean...
, the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
, and the Bay of Biscay
Bay of Biscay
The Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
, as well as adjacent portions of Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
, Devon
Devon
Devon is a large county in southwestern England. The county is sometimes referred to as Devonshire, although the term is rarely used inside the county itself as the county has never been officially "shired", it often indicates a traditional or historical context.The county shares borders with...
, and Brittany
Brittany
Brittany is a cultural and administrative region in the north-west of France. Previously a kingdom and then a duchy, Brittany was united to the Kingdom of France in 1532 as a province. Brittany has also been referred to as Less, Lesser or Little Britain...
. The southern and western boundaries are delimited by the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
, which drops away sharply.
History
The CeltCelt
The Celts were a diverse group of tribal societies in Iron Age and Roman-era Europe who spoke Celtic languages.The earliest archaeological culture commonly accepted as Celtic, or rather Proto-Celtic, was the central European Hallstatt culture , named for the rich grave finds in Hallstatt, Austria....
ic heritage of the bounding lands to the north and east gives the sea its name, first proposed by E. W. L. Holt
Ernest William Lyons Holt
Ernest William Lyons Holt was an eminent English marine naturalist and biologist specialized in ichthyology, the study of fish...
at a 1921 meeting in Dublin of fisheries experts from England, Ireland, Scotland and France. The northern portion of this sea had previously been considered as part of Saint George's Channel and the southern portion as an undifferentiated part of the "Southwest Approaches
Southwest Approaches
The Southwest Approaches is the name given to the offshore waters to the southwest of Great Britain. The area includes the Celtic Sea, the Bristol Channel and sea areas off southwest Ireland...
" to Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
. The need for a common name came to be felt because of the common marine biology
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
. It was adopted in France before being common in the English-speaking countries. It was adopted by marine biologists and oceanographers, and later by oil exploration firms. It is named in a 1963 British atlas, but a 1972 article states "what British maps call the western approaches, and what the oil industry calls the Celtic Sea [...] certainly the residents on the western coast [of Great Britain] don't refer to it as such."
Limits
There are no land features to divide the Celtic Sea from the open Atlantic Ocean to the south and west. For these limits, Holt suggested the 200 fathomFathom
A fathom is a unit of length in the imperial and the U.S. customary systems, used especially for measuring the depth of water.There are 2 yards in an imperial or U.S. fathom...
(366 m) marine contour
Contour line
A contour line of a function of two variables is a curve along which the function has a constant value. In cartography, a contour line joins points of equal elevation above a given level, such as mean sea level...
and the island of Ushant
Ushant
Ushant is an island at the south-western end of the English Channel which marks the north-westernmost point of metropolitan France. It belongs to Brittany and is in the traditional region of Bro-Leon. Administratively, Ushant is a commune in the Finistère department...
off the tip of Brittany.
The definition approved by 1974 by the Hydrographer
Hydrography
Hydrography is the measurement of the depths, the tides and currents of a body of water and establishment of the sea, river or lake bed topography and morphology. Normally and historically for the purpose of charting a body of water for the safe navigation of shipping...
of the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
for use in Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
Charts was "bounded roughly by lines joining Ushant, Land's End
Land's End
Land's End is a headland and small settlement in west Cornwall, England, within the United Kingdom. It is located on the Penwith peninsula approximately eight miles west-southwest of Penzance....
, Hartland Point
Hartland Point
Hartland Point is a high rocky outcrop of land on the northwestern tip of the Devon coast in England. It is three miles north-west of the village of Hartland. The point marks the western limit of the Bristol Channel with the Atlantic Ocean continuing to the west...
, Lundy Island, St. Govan's Head and Rosslare
Rosslare
The name Rosslare may refer to:*Rosslare Strand, a village in County Wexford, Ireland* Rosslare Harbour, a village in County Wexford, Ireland*The Rosslare Europort at Rosslare Harbour...
, thence following the Irish coast south to Mizen Head
Mizen Head
Mizen Head , is located at the extremity of a peninsula in the district of Carbery in County Cork, Ireland. It is one of the extreme points of the island of Ireland and is a major tourist attraction, noted for its dramatic cliff scenery...
and then along the 200-metre isobath to approximately the latitude of Ushant."
The International Hydrographic Organization
International Hydrographic Organization
The International Hydrographic Organization is the inter-governmental organisation representing the hydrographic community. It enjoys observer status at the UN and is the recognised competent authority on hydrographic surveying and nautical charting...
defines the limits of the Celtic Sea as follows:
On the North. The Southern limit of the Irish SeaIrish SeaThe Irish Sea separates the islands of Ireland and Great Britain. It is connected to the Celtic Sea in the south by St George's Channel, and to the Atlantic Ocean in the north by the North Channel. Anglesey is the largest island within the Irish Sea, followed by the Isle of Man...
[a line joining St David's Head to Carnsore PointCarnsore PointCarnsore Point is a headland in the very South East corner of County Wexford, Ireland. This headland is Ireland's southern limit point of the Irish Sea....
], the South coast of Ireland, thence from Mizen Head a line drawn to a position 51°0′N 11°30′W.
On the West and South. A line from the position 51°0′N 11°30′W South to 49°N
49th parallel northThe 49th parallel north is a circle of latitude that is 49 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
, thence to latitude 46°30'N on the Western limit of the Bay of BiscayBay of BiscayThe Bay of Biscay is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish...
[a line joining Cape Ortegal to Penmarch PointPoint Penmarc'hPoint Penmarc'h, often spelled Point Penmarch, or in French Pointe de Penmarc'h, is the extremity of a small peninsula in Finistère department in Brittany in northwestern France, and the northern limit of the Bay of Biscay....
], thence along that line to Penmarch Point.
On the East. The Western limit of the English Channel [a line joining Île Vierge
Île ViergeÎle Vierge is an islet lying off the north-west coast of Brittany, opposite the village of Lilia. It is in the commune of Plouguerneau, in the département of Finistère. It is the location of the tallest stone lighthouse in Europe, and the tallest "traditional lighthouse" in the world...
to Land's End] and the Western limit of the Bristol Channel [a line joining Hartland Point to St. Govan's Head].
Seabed
The seabed under the Celtic Sea is called the Celtic Shelf, part of the continental shelfContinental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. The northeast portion has a depth of between 90m and 100m, increasing towards Saint George's Channel. In the opposite direction, sand ridges pointing southwest have a similar height, separated by troughs approximately 50m deeper. These ridges were formed by tidal effects when the sea level was lower. South of 50°
50th parallel north
The 50th parallel north is a circle of latitude that is 50 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
the topography is more irregular.
Oil and gas exploration in the Celtic Sea has had limited commercial success. The Kinsale Head gas field
Kinsale Head gas field
The Kinsale Head gas field is an offshore natural gas field off the southern coast of Ireland discovered in 1973 near Old Head of Kinsale, in the Celtic Sea and met Ireland's gas need until 1996...
supplied much of the Republic of Ireland
Republic of Ireland
Ireland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
in the 1980s and 1990s.
External links
- Coccoliths in the Celtic Sea: a bloom of phytoplanktonPhytoplanktonPhytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
in the Celtic Sea, visible from outer spaceOuter spaceOuter space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
in an MISRMISRThe Multi-angle Imaging SpectroRadiometer is a scientific instrument on the Terra satellite launched by NASA on December 18, 1999. This device is designed to measure the intensity of solar radiation reflected by the Earth system in various directions and spectral bands; it became operational in...
image, 4 June 2001