TheSargasso Sea (/sɑːrˈɡæsoʊ/) is a region of theAtlantic Ocean bounded by fourcurrents forming anocean gyre.[1] It is the only namedsea without land boundaries.[2][3][4] It is distinguished from other parts of the Atlantic Ocean by its characteristic brownSargassum seaweed and often calm blue water.[1]
The sea is bounded on the west by theGulf Stream, on the north by theNorth Atlantic Current, on the east by theCanary Current, and on the south by theNorth Atlantic Equatorial Current, the four together forming a clockwise-circulating system of ocean currents termed theNorth Atlantic Gyre. It lies between 20° and 35° north and 40° and 70° west and is approximately 1,100 kilometres (600 nautical miles) wide by 3,200 km (1,750 nmi) long.Bermuda is near the western fringes of the sea. While all of the above currents deposit marine plants and refuse into the sea, ocean water in the Sargasso Sea is distinctive for its deep blue color and exceptional clarity, with underwater visibility of up to 60 m (200 ft).[5]
A chart drawn by the Spanish cartographerGabriel de Vallseca ofMallorca has been interpreted to indicate that theAzores were first discovered byDiogo de Silves in 1427. In 1431,Gonçalo Velho was dispatched with orders to determine the location of "islands" first identified by de Silves. Velho apparently got as far as theFormigas, in the eastern archipelago, before having to return to Sagres, probably due to bad weather.
By this time, the Portuguese navigators had also reached the Sargasso Sea (western North Atlantic region), naming it after theSargassum seaweed growing there (sargaço orsargasso in Portuguese).[6] Later in 1492,Christopher Columbus wrote about seaweed that he feared would trap his ship and potentially hide shallow waters that could run them aground, as well as a lack of wind that he feared would trap them.[7]
The sea may have been known to earliermariners, as a poem by 4th-century authorAvienius describes a portion of the Atlantic as being covered with seaweed and windless, citing a now-lost account by the 5th century BCCarthaginianHimilco the Navigator. Columbus was aware of this account and thought Himilco had reached the Sargasso Sea, as did several other explorers. However, modern scholars consider this unlikely.[8]
In 1609, the English vesselSea Venture was blown to the shore ofBermuda. The sea has also been the site of whaling and fishing.[9]
The 1920–1922Dana expeditions, led byJohannes Schmidt, determined that theEuropean eel's breeding sites were in the Sargasso Sea.[10][11] The sea has played a role in a number of other pioneering research efforts, includingWilliam Beebe andOtis Barton's 1932 dive where they conducted observations of animals and radio broadcasts,John Swallow's work on theSwallow float in the late 1950s, the discovery ofProchlorococcus by a team of researchers in the 1980s, and various oceanographic data gathering programs such as those ofHenry Stommel.[12]
The sea is bounded on the west by theGulf Stream, on the north by theNorth Atlantic Current, on the east by theCanary Current, and on the south by theNorth Atlantic Equatorial Current, the four together forming a clockwise-circulating system of ocean currents termed theNorth Atlantic Gyre.[13] It lies between 20° to 35° N and 40° and 70° W and is approximately 1,100 km (600 nmi) wide by 3,200 km (1,750 nmi) long.[14][15] Bermuda is near the western fringes of the sea.[16]
Because the Sargasso Sea is bordered by oceanic currents, its borders may change. The Canary Current in particular is widely variable, and often the line utilized is one west of theMid-Atlantic Ridge. A 2011 report based the sea's boundaries on several variables including currents, presence of seaweed, and the topography of the ocean floor, and determined that the specific boundaries of the sea were "between 22°–38°N, 76°–43°W and centred on 30°N and 60°W" for a total of around 4,163,499 km2 (1,213,882 sq nmi).[17]
The Sargasso Sea is home toseaweed of the genusSargassum, which floats en masse on the surface.[18] TheGreat Atlantic Sargassum Belt is the largest such mass in the world.[19] The sargassum masses generally are not a threat to shipping, and historic incidents of sailing ships being trapped there are due to the often-calm winds of thehorse latitudes.[18]
The Sargasso Sea plays a role in themigration ofcatadromous eel species, such as theEuropean eel, theAmerican eel, and theAmerican conger eel. Thelarvae of these species hatch within the sea, and as they grow they travel to Europe or the east coast of North America. Later in life, the matured eel migrates back to the Sargasso Sea to spawn and lay eggs. It is also believed that after hatching, youngloggerhead sea turtles use currents such as the Gulf Stream to travel to the Sargasso Sea, where they use the sargassum as cover from predators until they are mature.[20][21] Thesargassum fish is a species offrogfish specially adapted to blend in among the sargassum seaweed.[22] Millions of European eel babies are born there and then make a three-year journey back toUK waters; many seabird species also fly and feed across it on their way to Britain.[23]
In the early 2000s, the Sargasso Sea was sampled as part of theGlobal Ocean Sampling Expedition, to evaluate its diversity of microbial life throughmetagenomics. Contrary to previous theories, results indicated the area has a wide variety ofprokaryotic life.[24] Commonly called seaweed,Sargassum is a type ofmacroalgae. Like all algae, it produces oxygen. Based on 1975 measurements of oxygen production, and estimates of the total mass ofSargassum in the sea, it can be calculated that the Sargasso Sea may produce 2.2 billion litres of O2 per hour,[25] making the sea one of the primary sources of atmospheric oxygen.
The Sargasso Sea, like many unique ocean ecosystems, is under various threats, such asindustrial-scale fishing,plastic waste pollution,oil drilling, anddeep-sea mining.[26][23] Owing to surface currents, the Sargasso accumulates a high concentration of non-biodegradable plastic waste.[27][28] The area contains the hugeNorth Atlantic garbage patch.[29] Several nations and nongovernmental organizations have united to protect the Sargasso Sea.[30] These organizations include the Sargasso Sea Commission[31] established in 2014 by the governments of the Azores (Portugal), Bermuda (United Kingdom), Monaco, the United Kingdom and the United States.
Bacteria that consume plastic have been found in the plastic-polluted waters of the Sargasso Sea; however, it is unknown whether these bacteria ultimately clean up poisons or simply spread them elsewhere in the marine microbial ecosystem. Plastic debris can absorb toxic chemicals fromocean pollution, potentially poisoning anything that eats it.[32] Human activity in the Sargasso Sea has negatively affected it, such as over-fishing and shipping.[33]
The Sargasso Sea is often portrayed in literature and the media as an area of mystery.[34] It is often depicted in fiction as a dangerous area where ships are mired in weed for centuries, unable to escape.[35] Outer-space equivalents are a recurring motif inscience fiction.[36][37]
Ezra Pound'sPortrait d'une Femme opens with the line: "Your mind and you are our Sargasso Sea", suggesting that the woman addressed in the poem is a repository of trivia and disconnected facts.[38]
Dennis Wheatley's Uncharted Seas (1938), a fantasy novel about a tramp steamer trapped in the Sargasso Sea surrounded by killer seaweed, murderous crustaceans, and previously marooned descendants of SpanishConquistadores and pirates. This was made into an adventure film,The Lost Continent (1968), byHammer Films andSeven Arts.
Doc Savage visited the Sargasso Sea in his adventure "The Sargasso Ogre." The novel described the Sargasso as a graveyard of stranded ships marooned in vast beds of sargassum, and was used by (then) modern-day pirates as a storage location for ships they had plundered.
Sargasso Sea is featured prominently inAlexander Belyaev's adventure novel The Shipwreck Island (1926).
^"What's the Difference between an Ocean and a Sea?".Ocean Facts. Silver Spring MD: National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA). 25 March 2014. Retrieved7 January 2017 – via OceanService.NOAA.gov.
