- Gulf Stream
The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic
ocean current that originates in theGulf of Mexico , exits through the Strait of Florida, and follows the eastern coastlines of theUnited States and Newfoundland before crossing the Atlantic Ocean. At about 30°W, 40°N, it splits in two, with the northern stream crossing to northernEurope and the southern stream recirculating offWest Africa . It is part of the North Atlantic SubtropicalGyre . The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe. Its presence has led to the development of strongcyclone s of all types, both within theatmosphere and within theocean . The Gulf Stream is also a significant potential source of renewable power generation.Discovery and properties
European discovery of the Gulf Stream dates to the 1513 expedition of
Juan Ponce de León , after which it became widely used by Spanish ships sailing from the Caribbean to Spain. [cite book |last= Fernandez-Armesto |first= Felipe |title= Pathfinders: A Global History of Exploration |year= 2006 |publisher= W.W. Norton & Company |isbn= 0-393-06259-7 |pages= p. 194] In 1786Benjamin Franklin studied and mapped the current in detail. [ [http://www.oceanexplorer.noaa.gov/library/readings/gulf/gulf.html 1785: Benjamin Franklin's "Sundry Maritime Observations"] , NOAA Ocean Explorer] The Gulf Stream proper is a western-intensified current, largely driven by wind stress. [cite journal |last=Wunsch |first=Carl |title=What Is the Thermohaline Circulation? |journal=Science |date=November 8, 2002 |pages=1179–1181 |doi=10.1126/science.1079329 |volume=298 |issue=5596 |url=http://www.sciencemag.org/cgi/content/summary/298/5596/1179 |pmid=12424356 (see also [http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html Rahmstorf] .)] The North Atlantic Drift, in contrast, is largelythermohaline circulation driven. By carrying warm water northeast across the Atlantic, it makesWestern Europe (and especiallyNorthern Europe ) warmer than they otherwise would be. However, the extent of its contribution to the actual temperature differential between North America and Europe is a matter of dispute.cite journal |last=Seager |first=Richard |title=The Source of Europe's Mild Climate |journal=American Scientist Online |date=July–August, 2006 |url=http://www.americanscientist.org/issues/feature/2006/4/the-source-of-europes-mild-climate|accessdate=2008-09-23 ]Behavior
A river of sea water, called the Atlantic North Equatorial Current, flows westward off the coast of northern
Africa . When this current interacts with the northeastern coast ofSouth America , the current forks into two branches. One passes into theCaribbean Sea , while a second, the Antilles Current, flows north and east of the West Indies. These two branches rejoin north of theStraits of Florida , as shown on the accompanying map.Consequently, the resulting Gulf Stream is a strong ocean current. It transports water at a rate of 30 million cubic meters per second (30
sverdrup s) through the Florida Straits. After it passesCape Hatteras , this rate increases to 80 million cubic meters per second. The volume of the Gulf Stream dwarfs all rivers that empty into the Atlantic combined, which barely total 0.6 million cubic meters per second. It is weaker, however, than theAntarctic Circumpolar Current .Typically, the Gulf Stream is convert|80|km|mi to convert|150|km|mi wide and convert|800|m|ft to convert|1200|m|ft deep. The current velocity is fastest near the surface, with the maximum speed typically about convert|2.5|m/s|mph. [cite web |last=Phillips |first=Pamela |title=The Gulf Stream |url=http://fermi.jhuapl.edu/student/phillips/ |publisher=USNA/Johns Hopkins |accessdate=2007-08-02 ]
As it travels
north , the warmwater transported by the Gulf Stream undergoes evaporative cooling andbrine exclusion. The cooling is wind driven: wind moving over the water cools it and also causesevaporation , leaving a saltier brine. In this process, the water increases insalinity and density, and decreases in temperature. These two processes produce water that is denser and colder (or, more precisely, water that is still liquid at a lower temperature). In the NorthAtlantic Ocean , the water becomes so dense that it begins to sink down through less salty and less dense water. (The convective action is not unlike that of alava lamp .) This downdraft of heavy, cold and dense water becomes a part of theNorth Atlantic Deep Water , a southgoing stream.Localized effects
The Gulf Stream is influential on the climate of the Florida peninsula, as east winds during most months of the year move warmer air from over the Gulf Stream inland, [
National Climatic Data Center . [http://www5.ncdc.noaa.gov/documentlibrary/pdf/wind1996.pdf Climatic Wind Data for the United States.] Retrieved on2007-06-02 .] helping to keep temperatures milder across the state than elsewhere across the Southeast during the winter. The Gulf Stream makes the climate of offshore islands of Massachusetts,Martha's Vineyard , andNantucket milder than that of Massachusetts Bay, which is isolated from Gulf Stream effects byCape Cod . [cite web|author=Captain John Lacouture|title=The Gulf Stream Charts of Benjamin Franklin and Timothy Folger|year=1995|publisher=Nantucket Historical Society|accessdate=2008-09-10|url=http://www.nha.org/history/hn/HN-v44n2-gulfstream.htm]The
North Atlantic Current of the Gulf Stream, along with similar warm air currents, helps keepIreland and the western coast ofGreat Britain a couple of degrees warmer than the east. However the difference is most dramatic in the western coastal islands ofScotland . [cite web|author=|title=Satellites Record Weakening North Atlantic Current Impact |publisher=NASA|accessdate=2008-09-10|url=http://oceanmotion.org/html/impact/climate-variability.htm] Parts of Ireland and the west coast of Scotland have a mild enough climate to support palm-like cabbage trees even though they are a degree further north thanMoscow . [cite web |title="Cordyline australis" Cabbage Palm |work=The Garden Flora of Northern Ireland |url=http://www.habitas.org.uk/gardenflora/cordyline1.htm|accessdate=2007-07-20 ]The most spectacular effect of the Gulf Stream and the strong westerly winds (driven by the warm water of the Gulf Stream) on Europe occurs along the Norwegian coast. [cite web|author=Barbie Bischof, Arthur J. Mariano, Edward H. Ryan|title=The North Atlantic Drift Current|year=2003|publisher=The National Oceanographic Partnership Program|accessdate=2008-09-10|url=http://oceancurrents.rsmas.miami.edu/atlantic/north-atlantic-drift.html] Northern parts of
Norway lie close to theArctic zone, most of which is covered with ice and snow in winter. However, almost all of Norway's coast remains free of ice and snow throughout the year.cite book|author=Erik A. Rasmussen, John Turner|title=Polar Lows|year=2003|publisher=Cambridge University Press|page=p. 68|accessdate=2008-09-10]Effect on cyclone formation
The warm water and temperature contrast along the edge of the Gulf Stream often increases the intensity of cyclones, tropical or otherwise. Tropical cyclone generation normally requires water temperatures in excess of convert|26.5|C|F. cite web | author =
Atlantic Oceanographic and Meteorological Laboratory , Hurricane Research Division | title = Frequently Asked Questions: How do tropical cyclones form? | publisher =NOAA | accessdate = 2006-07-26 | url = http://www.aoml.noaa.gov/hrd/tcfaq/A15.html] Tropical cyclone formation is common over the Gulf Stream, especially in the month of July. Storms travel westward through the Caribbean and then, either move in a northerly direction and curve towards the eastern coast of theUnited States , or stay on a north-westward track and enter theGulf of Mexico .National Hurricane Center . [http://www.nhc.noaa.gov/tracks1851to2007_atl_reanal.txt Atlantic Hurricane Database.] Retrieved on2008-06-10 .] Such storms have the potential to create strong winds and extensive damage to the United States' Southeast Coastal Areas. Strongextratropical cyclone s have been shown to deepen significantly along a shallow frontal zone, forced by the Gulf Stream itself during the cold season. [S. Businger, T. M. Graziano, M. L. Kaplan, and R. A. Rozumalski. [http://www.springerlink.com/content/fgec8524arjwth3v/ Cold-air cyclogenesis along the Gulf-Stream front: investigation of diabatic impacts on cyclone development, frontal structure, and track.] Retrieved on2008-09-21 .]Subtropical cyclone s also tend to generate near the Gulf Stream. 75 percent of such systems documented between 1951 and 2000, formed near this warm water current, with two annual peaks of activity occuring during the months of May and October. [David M. Roth . [http://ams.confex.com/ams/pdfpapers/37402.pdf P 1.43 A FIFTY YEAR HISTORY OF SUBTROPICAL CYCLONES.] Retrieved on208-09-21 .] Cyclones within the ocean form under the Gulf Stream, extending as deep as convert|3500|m|ft beneath the ocean's surface. [D. K. Savidge and J. M. Bane. [http://cat.inist.fr/?aModele=afficheN&cpsidt=1914578 Cyclogenesis in the deep ocean beneath the Gulf Stream. 1. Description.] Retrieved on2008-09-21 .]Possible renewable power source
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