|
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 at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean. The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America. At about , it splits in two, with the northern stream crossing to Northern Europe and the southern stream recirculating off West Africa. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe. Although there has been recent debate, there is consensus that the climate of Western Europe and Northern Europe is warmer than it would otherwise be due to the North Atlantic drift, one of the branches from the tail of the Gulf Stream. It is part of the North Atlantic Gyre. Its presence has led to the development of strong cyclones of all types, both within the atmosphere and within the ocean. The Gulf Stream is also a significant potential source of renewable power generation. The Gulf Stream is typically 100 kilometres (62 mi) wide and 800 metres (2,600 ft) to 1,200 metres (3,900 ft) deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second (5.6 mph). == History == European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de León, after which it became widely used by Spanish ships sailing from the Caribbean to Spain. A summary of Ponce de León's voyage log, on April 22, 1513, noted, "A current such that, although they had great wind, they could not proceed forward, but backward and it seems that they were proceeding well; at the end it was known that the current was more powerful than the wind." Its existence was also known to Peter Martyr d'Anghiera, and to Sir Humphrey Gilbert at that time.〔Source: Explanations and Sailing Directions to Accompany the Wind and Current Charts, 1853, p.53, by Matthew Fontaine Maury〕 Benjamin Franklin became interested in the North Atlantic Ocean circulation patterns. In 1768, while in England, Franklin heard a curious complaint from the Colonial Board of Customs: Why did it take British packets several weeks longer to reach New York from England than it took an average American merchant ship to reach Newport, Rhode Island, despite the merchant ships leaving from London and having to sail down the River Thames and then the length of the English Channel before they sailed across the Atlantic, while the packets left from Falmouth in Cornwall?〔Tuchman, Barbara W. ''The First Salute: A View of the American Revolution'' New York: Ballantine Books, 1988. pp.221–222.〕 Franklin asked Timothy Folger, his cousin twice removed (Nantucket Historical Society), a Nantucket whaling captain, for an answer. Folger explained that merchant ships routinely crossed the then-unnamed Gulf Stream—identifying it by whale behavior, measurement of the water's temperature and the speed of bubbles on its surface, and changes in the water's color—while the mail packet captains ran against it.〔 Franklin worked with Folger and other experienced ship captains, learning enough to chart the Gulf Stream and giving it the name by which it is still known today. He offered this information to Anthony Todd, secretary of the British Post Office, but it was ignored by British sea captains.〔 Franklin's Gulf Stream chart was published in 1770 in England, where it was mostly ignored. Subsequent versions were printed in France in 1778 and the U.S. in 1786. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gulf Stream」の詳細全文を読む スポンサード リンク
|