Celtic Sea

Map of the Celtic Sea, an arm of the Atlantic.

Coccoliths in the Celtic Sea. [1]

The Celtic Sea (Template:Lang-ga; Template:Lang-cy; Cornish An Mor Keltek; Breton: Ar Mor Keltiek) 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 Celtic heritage of the bounding lands give the sea its name, first proposed by E. W. L. Holt in 1921. The northern portion of this sea had previously been considered part of Saint George's Channel and the southern part had no common name; the need for a common name came to be felt because of common geology and hydrology. The name is now commonly used by workers in the oil and fishing industries.

The southern and western boundaries are less clearly defined. Holt suggested the 200 fathom (366 m) marine contour and Ushant; the International Hydrographic Organization definition uses rhumb lines and extends slightly further south.