The Celtic Sea ( ; ; ; ; ) is the area of the Atlantic Ocean off the south coast of Ireland. It is bounded to the east by Saint George's Channel, the Bristol Channel and the English Channel, as well as adjacent portions of Wales, Cornwall, Devon, and Brittany. The southern and western boundaries are based on the continental shelf.

History

The Celtic heritage of the bounding lands 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 Great Britain. The need for a common name came to be felt because of 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, ; cited in



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 fathom (366 m) marine contour and Ushant.

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 definition, adopted by 1976, uses rhumb lines and extends slightly further south. It is as follows:

• Separated from the Irish Sea to the north by a line from Carnsore Point, County Wexford to Saint David's Head, Pembrokeshire ( )
  • Along the Pembrokeshire coast
• Separated from the Bristol Channel to the east by a line from Saint Govan's Head, Pembrokeshire ( ) to Hartland Point, Devon
  • Along the Devon and Cornwall coast
• Separated from the English Channel to the east by a line from Land's End, Cornwall to ÃŽle Vierge, Finistère ( )
  • Along the Finistère coast
• Separated from the Bay of Biscay to the east by a line from Point Penmarc'h towards Cabo Ortegal in Galicia
• From latitude 46°30’N on this line, northwestwards to
• From there north to
• From there to Mizen Head, County Cork
  • Along the Cork, Waterford, and Wexford coasts to Carnsore Point.

Seabed

The seabed under the Celtic Sea is called the Celtic Shelf, part of the continental shelf of Europe. The northeast portion is c.90–100m deep, increasing towards Saint George's Channel. In the opposite direction, sand ridges pointing southwest have a similar height, separated by troughs c.50m deeper. These ridges were formed by tidal effects when the sea level was lower. South of 50° the topography is more irregular.

See also

• Irish Conservation Box

References

External links

• Coccoliths in the Celtic Sea: a bloom of phytoplankton in the Celtic Sea, visible from outer space in an MISR image, 4 June 2001