Oceans and seas

Balearic Sea

May 13, 2013, 10:30 pm
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Catalonian coast showing intense tourist uses. @ C.Michael Hogan

The Balearic Sea is one of the seas that comprise the western basin of the Mediterranean Sea

Sometimes termed the Catalan Sea, it lies between the Iberian coast and the Balearic Islands (Ibiza, Mallorca, Menorca) in the northwestern Mediterranean.

At its southeastern extremity the Balearic Sea merges with the Alboran Sea, which is the westernmost element of the Mediterranean Sea; it is separated from the Tyrrhenian Sea to the east by Sardinia and Corsica and abuts the sea to the west.

caption Regional setting map of Balearic Sea. Source: Norman Einstein

The bathymetry is dominated by the Balearic Abyssal Plain, which covers over 30,000 square miles, covering the majority of the basin floor at depths ranging from 2700 to 2800 metres. This deep sea plain is bordered to the northwest by the Rhone Fan, a large sedimentary cone.

Geography and Limits

The limits of the Balearic Sea are generally construed as the Alboran Sea to the southwest, the  Balearic Islands to the south and the coast of Spain to the north. More specific limits recognised by the International Hydrographic Association are:

  • At the southwest: A line from Cape San Antonio, Spain 38 degrees 50 minutes N; 0 degrees 12 minutes E, to Cabo Berberia, the Southwest extreme of Formentera within the Balearic Islands
  • At the southeast: The Alboran Sea and the south coast of Formentera, thence a line from Punta Rotja, its eastern extreme, to the southern limit of Cabrera, Balearic Islands, at 39 degrees 7 minutes N; 2 degrees 54 minutes E and to Isla del Aire, off the southern extreme of Minorca.
  • At the northeast: The east coast of Minorca up to Cabo Favaritx, 40 degrees 0 minutes N; 4 degrees 14 minutes E, thence a line to Cabo San Sebastian, Spain, 41 degrees 54 minutes N; 3 degrees 10 minutes E.

Circulation and Hydrography

caption Regional circulation in the Balearic and western Medieterranean
Source: Bergamasco and Malanotte-Rizzoli. 2010

The Balearic Sea circulation can be depicted to first order as a single oblong cyclonic cell with a divergence zone aligned with the shape of the basin. Studies have shown the surface circulation to be strong year–around, and characterised by two permanent density fronts. These are the Catalan Front on the continental shelf slope and the Balearic Front on the Balearic Islands shelf slope, with the former the more active.

The northern area exhibits a near-coastal plume of cold water frequently seen moving southwestward along the continental slope and shedding dipole eddies along its leading edge. A corresponding counterflow current flows generally northeastward along the Balearic Islands coast. Energetic filaments continuously spawned by the Catalan Front are thought to be associated with this plume.

Balearic Channels

The Balearic Channels are the Ibiza Channel, the Mallorca Channel and the deep trough in the Gulf of Valencia, all features found within the Balearic Sea. According to Pinot et al., the Balearic Channels are significant passages for the meridional exchange between the cooler, more saline waters of the northern basin and the warmer, fresher waters of the southern (Algerian) basin of the Alboran Sea (western Mediterranean Basin).

The Northern Current carries northern waters from the Gulf of Lions southward along the continental slope in the Balearic Sea. This current bifurcates where it reaches the northern end of the Ibiza Channel. The main branch proceeds southward and crosses the sill carrying cool and salty water into the Algerian Basin, while the minor one is retroflected cyclonically and returns to the northeast forming the Balearic Current that crosses the continental slope of the islands. This latter current is also fed by warmer, fresher southern waters from the Algerian Basin, which flow northward through both channels. This smooth pattern obtained from climatological analysis was confirmed to be the average picture of a highly fluctuating circulation.

Marine Ecology

As for other parts of the Mediterranean Basin the Balearic Sea is a marine system of relatively low nutrient content. However, there are regular blooms of the harmful dinoflagellate Alexandrium taylorii, particularly in the shallow coastal waters of the Balearic Islands; these yellowish green discolourations may endure for up to two months. Moreover, the intensity of these blooms appears to be increasing, and are thought to be associated with discharge of vessel ballast water.

The Balearic Sea is an important spawining ground for the Bluefin tuna (Thunnus thynnus). There are populations of Loggerhead and Leatherback turtles in the Balearic, especially in the vicinity of the Channel islands; significant numbers of both species are taken as bycatch in  Spanish fishing nets. for example, in one recent year surveyeing only a small part of the fishing fleet, ti was found that 1627 turtles were entrained in the nets.

At the deepest regions (e.g. below 1300 metres in depth) of the Balearic Basin there is a strong resemblance to the Ionian Sea, with respect to a pronouced paucity of megafaunal species. Some dominant species at such great depths are Bathypterois mediterraneus, Chalinura mediterranea and Coryphaenoides guentheri.

Terrestrial Margin

caption Rugged coastal forest, northern Catalonia. @ C.Michael Hogan

See main article: Northeastern Spain and Southern France Mediterranean forests

On both the mainland Balearic coast as well as the Balearic Islands, thick stands of wild olive (Olea europaea) and carob (Ceratonia siliqua) define the Northeastern Spain and Southern France Mediterranean forests; these forests have long been considered a lush locale to inhabit or visit. Some of Europe’s most important littoral wetlands are found here and are teeming with millions of birds of vast diversity. These include the largest colony in the world of Audouin's gull (Larus audouinii) and the largest colony of flamingo (Phoenicopterus ruber) in the Mediterranean. The ecoregion encompasses several centers of plant diversity and has a high floral endemism rate. These natural assets, along with the inviting beaches of the Balearic Sea and other curiosities like the semi-wild Camargue horse and bull, has given the region an appeal that has meant a long history of human pressure on its ecology. Forest fires, urbanization, agriculture, pollution, and intensive water usage all threaten the biodiversity of this ecoregion.

Further Reading

  • Peter Saundry. 2011. Seas of the world. Topic ed. C.Michael Hogan. Ed.-in-chief Cutler J.Cleveland. Encyclopedia of Earth
  • A.Bergamasco and P.Malanotte-Rizzoli. The circulation of the Mediterranean Sea: a historical review of experimental investigations, Advances in Oceanography and Limnology, 1:1, 9 - 22
  • Rhodes W. Fairbridge, editor. The Encyclopedia of Oceanography. Van Nostrand Reinhold Co., 1966.
  • IUCN Centre for Mediterranean Cooperation. 2004. The Mediterranean deep-sea ecosystems: an overview of their diversity, structure, functioning and anthropogenic impacts, with a proposal for their conservation. IUCN. 64 pages
  • Gianfranco d'Onghia, Chrissi Yianna Politou, Anna Bozzano, Domingo Lloris, Guiomar Rotllant, Letizia Sión, Francesco Mastrototaro. 2004. Deep-water fish assemblages in the Mediterranean Sea. Scientia Marina, Vol 68, No S3.
  • Organisation for Economic Co-Operation and Development. 2003. Review of Fisheries in OECD Countries: Policies and Summary Statistics (Google eBook) OECD Publishing. 400 pages
  • J.-M. Pinot, J. L. L´opez-Jurado, and M. Riera. The CANALES experiment (1996–1998). Interannual, seasonal, and mesoscale variability of the circulation in the Balearic Channels. Progress in Oceanography, 55:335–370, 2002.
  • Sergi Tudela. 2004. Ecosystem effects of fishing in the Mediterranean: an analysis of the major threats of fishing gear and practices to biodiversity and marine habitats. General Fisheries Council for the Mediterranean (Food and Agriculture Organization of the United Nations). Food & Agriculture Org. 44 pages
  • Paul A. Tyler. 2003. Ecosystems of the deep oceans. (Google eBook) Elsevier. 569 pages
  • Paul E. La Violette, Joaquin Tintore, and Jordi Font. 1990. The surface circulation of the Balearic Sea. J. Geophys. Res., 95:1559–1568, 1990.
  • J.-M. Pinot and A. Ganachaud. The role of winter intermediate waters in the spring–summer circulation of the Balearic Sea, 1, Hydrography and inverse box modeling. JGR, 104:29,843–29,864, 1999.
  • J.-M. Pinot, J. L. L´opez-Jurado, and M. Riera. The CANALES experiment (1996–1998). Interannual, seasonal, and mesoscale variability of the circulation in the Balearic Channels. Progress in Oceanography, 55:335–370, 2002.
  • Giulio Relini and J.Ryland. 2004. Biodiversity in enclosed seas and artificial marine habitats: proceedings of the 39th European Marine Biology Symposium, held in Genoa, Italy, 21-24 July 2004 (Google eBook) Springer. 271 pages
Glossary

Citation

Hogan, C. (2013). Balearic Sea. Retrieved from http://www.eoearth.org/view/article/150390

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