Thursday, June 2, 2016

The Gulf Stream - Part II

Continuing from the previous post regarding a question asked us from a reader regarding the Gulf Stream and if it was affected by the onetime Panama Throughway before the Panama Isthmus rose to its present position. 
We also need to keep in mind that the Gulf Stream is a comparatively new area of knowledge, and wasn’t even known before 1513, when Juan Ponce de León (left), who was a close friend and neighbor to Vasco de Gama and may have accompanied Columbus on his second voyage, discovered it quite by accident while exploring the coast of what he named Florida (meaning “flowery”)—a very strong, warm ocean current that would help future Spanish ships maneuver their way home from the New World.
    A summary of 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.” However it was the Italian historian, Peter Martyr d’Anghiera who was the first to realize the significance of it, making his “Decades” of great value in the history of geography and discovery. It was learned that the stream is a powerful current in the Atlantic Ocean, starting in the Gulf of Mexico and flows into the Atlantic at the tip of Florida, accelerating along the eastern coastlines of the United States and Newfoundland.  It is part of the North Atlantic Subtropical Gyre, one of the five major oceanic gyres, which are large systems of circular currents and powerful winds.
    The Gulf Stream is a western boundary current with its movement determined by the North American coastline. Trade winds from Africa drive water in the Atlantic westward until it hits the coastline and gets pushed northward. In turn, the Gulf Stream affects the climate of the areas closest to the current by transferring tropical heat toward the northern latitudes. There is a consensus among scientists that the climate of Western and Northern Europe is warmer than it would be otherwise because of the North Atlantic Current, one of the branches of the Gulf Stream.
It was not until Anton de Alaminos (left), however, who had sailed with Columbus on his last voyage, and was the chief pilot aboard Ponce de Leon’s ship on his earlier trip, who six years later set sail for Spain from Vera Cruz, Mexico, using the Gulf Stream by following the Florida coastline before turning eastward to Europe. His route was then followed by all the other European mariners sailing form the New World back to Europe. Thus the Gulf Stream was instrumental in the colonization of the Americas, for it altered sailing patterns and shaved time off a typically long and treacherous trip. Most sea voyages to Virginia southward, as an example, chose the southern route across the Atlantic pioneered by Columbus, even though it was 2000 miles to 3000 miles out of the way, but the returning voyages took Alaminos’ route saving that distance and speeding their journey.
    It was Benjamin Franklin, in his role as deputy postmaster of the British American colonies, who had a keen interest in the North Atlantic Ocean circulation patterns as a way to streamline communication between the colonies and England. 
During a 1768 visit to England, Franklin (left) discovered that it took British packets several weeks longer to reach New York from England than it took an average American merchant ship to reach Newport, Rhode Island. Franklin’s cousin Timothy Folger, a Nantucket whaling captain, explained that merchant ships routinely crossed the then-unnamed Gulf Stream while the mail packet captains ran against it. The merchant ships tracked whale behavior, measurement of the water's temperature and the speed of bubbles on its surface and changes in the water's color to follow the speedier route.
    Franklin worked with Folger and other experienced ship captains to chart the Gulf Stream and giving it the name by which it is still known today.  His Gulf Stream chart was published in 1770 in England—where it was ignored—and subsequent versions were printed in France in 1778 and the United States in 1786.
    It was years before the British finally took Franklin's advice on navigating the current but once they did, they were able to shave two weeks off the sailing time between Europe and the United States.
    Another important factor that only recently has been discovered is that the waters feeding into the Gulf Stream begin flowing off the west coast of Northern Africa, and not just from the Gulf of Mexico as earlier thought. While the Gulf Stream is classified as a western boundary current, it literally means that the current is affected by the coastline of North America (United States and Canada), not so much by the Gulf of Mexico, though that it where it gets its warmth.
The Gulf Stream as it originates off the coast of West Africa (red arrows) and flows across the Atlantic toward Florida, up the coast of North America and back across the Atlantic and up the coast of England toward Norway, where it feeds the Norwegian Current and moves the relatively warm water along the west coast of Europe. The impact of the Gulf of Mexico is minimal
    As the current flows across the Atlantic, coming off the South Atlantic Gyre into the North Atlantic Gyre, it reaches the American continents where it splits into two currents, one of which is the Antilles Current. These currents are then funneled through the islands of the Caribbean and through the Yucatan Channel between Mexico and Cuba, and the other is the Gulf Stream current that flows northward along the North American eastern coast.
    Because these areas are often very narrow, the current is able to compress and gather strength. As it does so, it begins circulating in the Gulf of Mexico’s warm waters. Once it gains enough strength after circulating in the Gulf of Mexico, the Gulf Stream then moves east, rejoins the Antilles Current, and exits the area through the Straits of Florida. It is here that the Gulf Stream becomes noticeably visible on satellite images so it is said that the current originates in this area; however it actually originates along the western shores of Africa.
    In any event, these warm currents mix with the African current, heating up the waters that then are forced eastward around Florida and pick up the other half of the current, the Gulf Stream. Here, the Gulf Stream is a powerful underwater river that transports water at a rate of 30 million cubic meters per second (30 Sverdrups). It then flows parallel to the east coast of the United States and later flows into the open ocean near Cape Hatteras but continues moving north. While flowing in this deeper ocean water, the Gulf Stream is its most powerful (at about 150 Sverdrups), forms large meanders, and splits into several currents, the largest of which is the North Atlantic Current.
If the Gulf was not enclosed, as it is now, the currents moving into the Gulf of Mexico from the Panama Throughway would merely force the Gulf waters into the Gulf Stream in an even faster current, moving upward and eventually back across the Atlantic toward Great Britain in a somewhat faster current than now occurs, since the current now, once it turns eastward, begins to slow down considerably
    The Gulf Stream, like all other ocean currents is mainly caused by wind as it creates friction when moving over the water. This friction then forces the water to move in the same direction. Because it is a western boundary current, the presence of land along the Gulf Stream’s edges also aids in its movement. The northern branch of the Gulf Stream, the North Atlantic Current, is deeper and is caused by thermohaline circulation resulting from density differences in the water.
    Because ocean currents circulate water of different temperatures all over the globe, they often have a significant impact on the world’s climate and weather patterns. The Gulf Stream is one of the most important currents in this regard since its waters mix with the warm tropical waters of the Caribbean and the Gulf of Mexico. As such, it keeps sea surface temperatures warm, causing the areas around it to be warm and more hospitable. Florida and much of the Southeastern United States for instance is mild all year round as a result of this Gulf Stream.
The temperature of the Gulf Stream cools as it crosses the Atlantic and moves up the coast of Europe; however, it still remains warmer than the surrounding waters and effectively warms the European coastal areas
    The greatest impact, however, that the Gulf Stream has on climate is found in Europe. Since it flows into the North Atlantic Current, it too is warmed (though at this latitude the sea surface temperatures are cooled considerably), and it is believed that it helps keep places like Ireland and England much warmer than they would otherwise be at such a high latitude. For example, the average low in London in December is 42°F while in St. John’s, Newfoundland, the average is 27°F. The Gulf Stream and its warm winds are also responsible for keeping northern Norway’s coast free of ice and snow.
    So we see, that even with the Panama Throughway, this current coming off western Africa would still flow in he same manner and accomplish the same purpose it now does. And the currents coming up the west coast of South America, the Humbolt Current, would still act the same way since the west coast shelf would still be sufficiently raised both above and beneath the surface as to direct these currents. The bulge of Peru would still direct the current back out into the Pacific in the South Pacific Gyre, and the throughway would have little impact on anything other than currents immediately within the Gulf of Mexico, between Central America and Cuba.

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