The Gulf Stream
By James C. Hobbs
We in South Florida live between two great rivers of the world and each river is unique. On the west we have the Everglades, the river of grass, flowing from the north and draining the greater portion of the southeastern United States. On our eastern shore lies the Gulf Stream, the river within the ocean, flowing to the north. The uniqueness of having two major rivers of the world less than forty miles apart, flowing in opposite directions from each other, exerts a major influence not only on our climate and lives, but also on the food supply or large portions of the world.
The river of grass is comparatively easy to understand--it drains the land of the deep south and the Florida peninsula by funneling the water down to South Florida and out to sea. But how is it possible to have a river in the ocean, and one of such magnitude? Who discovered it, and where does it come from? Where does it go? These are but a few of the many questions that are asked about the Gulf Stream.
The Gulf Stream is bigger than the combined flow of the Mississippi, the Nile, the Congo, the Amazon, the Volga, the Yangtze and many other major rivers of the world. The best technical estimate is that one hundred thousand million tons of warm salt water flow between Florida and the Bahamas every hour. At 235 gallons per ton, we have 235 x 1010 gallons per hour flowing between two and five miles per hour northward. This flow has been estimated to be about twenty times greater than all the fresh water in the world flowing into the oceans of the world from rain, rivers, and melting ice.
This great mass of flowing water, or energy, has no beginning or ending, for its waters flow continuously northward along our east coast then east across the North Atlantic to the coasts of Europe and the United Kingdom, where it turns south and flows along western Europe and Africa, before again turning westward across the South Atlantic to the Caribbean basin. Lake any large river, it has tributaries, counter currents and eddies.
This entire circulation is not called the Gulf Stream; only the portion that flows northward beginning in the Caribbean Islands and flows to the mid-Atlantic at the latitude of the North Sea is so named. There are many other names for the other segments.
How is it possible to have such a continuous source of energy that moves the estimated one hundred thousand million tons of water (100,000,000,000 ) past Miami at the rate of two to five miles per hour? This is perhaps the greatest simple source of power in the world.
Simply explained, the earth rotates counter-clockwise, and the combination of the rotation and the viscous fluids, air and water, produces a pumping action that pushes the water of the South Atlantic westward. The atmosphere, resisting the world's rotation, produces what we call Trade Winds. Because the earth is spinning faster than the surrounding mantle of air, on the surface of the earth the winds blow from the east. Thus, the great expanse of water in the South Atlantic is pushed westward by both the earth's rotation and the less viscous air, until it is thrust against the land masses of Central and South America, and is forced to split into two streams--the Brazil Current, flowing south, and the Gulf Stream, flowing north, the Gulf Stream being greater of the two.
The volume of water returning from Europe and Africa has been calculated to be substantially less than the volume of water of the Gulf Stream between Miami and the Bahamas. Some of this increased volume is attributed to the funnel, or venture, effect, caused by the narrowing of the Gulf Stream between Miami, Bimini and Cat Cay, which increases the Gulf Stream's velocity and drags additional volumes of water along.
There are many doubts about who actually discovered the Gulf Stream. Credit is often given to Anto de Alaminos, the pilot for Ponce de Leon, who sailed to Florida in 1513. Benjamin Franklin has received credit for recognizing, publicizing and naming the current the Gulf Stream in 1770 (see exhibit #23). Walden Hoxton in 1735, however, had already charted and named the Stream, though his work was not published until a later date. Perhaps the discovery and naming of the Gulf Stream is a moot question, but to cartography it becomes important in tracing history, particularly in the Age of Exploration and Discovery of the New World.
From the available records, the title "Gulf Stream" was first used to identify the flowing waters off the southeast coast of Florida in 1768 or 1769 by William Gerand De Brahm, while in the employ of the British Government. In 1771, he requested the opportunity to publish a description of the waters of eastern Florida for the benefit of all ships sailing in these dangerous waters. Permission was granted and his work appeared in 1772. This publication, "The Atlantic Pilot," together with its charts, described the "Gulf Stream" and its flows and eddies. His information was derived from the data he had collected as the Surveyor General of the new colony of East Florida, and as Surveyor General of the newly created Southern District. Since he began to work in St. Augustine, Florida, in January of 1765, the assumption is that his material for the "Atlantic Pilot" was collected between this date and his request for publication in 1771. His research predated Franklin's, though he is not generally considered to have "discovered" the Gulf Stream. (See exhibit #21)
By the middle of the 18th Century, American ships sailing from England to America were completing the voyage as much as two weeks ahead of British Admiralty vessels making the same voyage, and England wanted to know why.
In 1786, Benjamin Franklin, who was then Postmaster General of the North American Colonies, was summoned to England to give a possible explanation. A cousin of Franklin's, a sea captain named Folger, accompanied him. Folger had had much experience sailing the American coastline for fish and whales. Testifying before the Admiralty, he described, by sketching, the flow of water along the coast and the effect this had on shipping. The British Admiralty dismissed his information as of little account, and continued to follow their own, established routes. The rejection of this information may have had a major influence on America's defeat of England during the Revolutionary War, because the information described by Captain Folger gave the American fleet an advantage. Benjamin Franklin published a map in 1770 showing the Gulf Stream. De Brahm's work and maps were published in 1772, although his research was done prior to 1770. Although their objectives were different, both reached substantially the same conclusion about the Gulf Stream.
Many maps and charts followed, although not a great deal was learned about the Gulf Stream for the next hundred and fifty years, except that flow rates, eddies and temperatures were noted, as well as seasonal changes in position. The quantum leap in Gulf Stream knowledge is coming now with the discovery of sonar, radar, and the use of space age satellites. Conditions that have been long suspected are now being validated with the use of these instruments. One of the newest scientific capabilities is the mapping of the ocean floor. Among the most interesting maps will be the Gulf Stream bottom interpreted in three dimensions.