The Gulf Stream: A River In The Ocean

The Gulf Stream is not born in the Gulf of Mexico as its name suggests. Rather, its waters have traveled across the Atlantic as part of an ocean-wide system. Along the Equator, the elements of the Gulf Stream begin to take shape. Flowing from the east, the South Equatorial Current splits in two when it hits the tip of Brazil. One-half of the current moves north along the coast of South America where it is joined by the full force of the North Equatorial Current.

Continuing northwest, the huge push of water again branches as it approaches the Caribbean Basin. The larger branch, the Antilles Current, moves north and east along the Antilles and Hispanola. The other runs west, past the Caribbean Islands and Cuba and through the Yucatan Channel and into the Gulf of Mexico. It is this branch of the current that helps give the Gulf Stream its distinctive characteristics.

Warmed by the sun in the shallow waters of the gulf, the water rushes east through its only escape, the narrow Straits of Florida. The straits, only 50 miles wide and 2,500 feet deep in places, help to increase the speed and force of the water. Like a thumb over a garden hose, the narrow straits push the water ahead, sometimes reaching speeds of up to 10 miles per hour. This current -- the Florida Current -- is faster than any other Atlantic Current, carrying a billion cubic feet of water every second past Miami. Deflected to the north by the Bahama Islands, the Florida Current joins the Antilles Current. The Gulf Stream System, as it is now known, triples in volume and pushes north.

The flow of the current moves north along the southeastern United States, slowing as it runs toward Cape Hatteras where it gradually turns toward the east. But the huge wheel of the North Atlantic continues to turn, pushing the still-warm waters off the New England coast and the cold water of the Labrador Current. Off the Grand Banks of Newfoundland, the Gulf Stream and Labrador currents collide, creating heavy fog and often-violent weather conditions. The ocean water temperature changes can be dramatic. One boat reported a 20-degree temperature difference from bow to stern as it crossed from one current to the other.

The cold water of the Labrador Current sinks below the Gulf Stream as it drops off the Continental Shelf, robbing the warmer current of energy and cooling and slowing its speed as it continues east. Most scientists consider this to be the end of the Gulf Stream, preferring to call the current that flows on the North Atlantic Current. The North Atlantic Current continues to flow east and then south, joining with the Canaries Current of the western coast of Europe. There the currents combine to form the North Equatorial Current and completing the ocean-sized outlines of the North Atlantic wheel.

The benefits of the Gulf Stream were discovered early by sea captains. Spanish galleons, laden with the treasure of the New World, used the current as an expressway as they made their passages back to Europe. Early maps of the Gulf Stream were closely guarded secrets handled with the utmost care. Pirates and privateers knew to keep on the lookout for Atlantic armadas along the southeastern United States.

Throughout the colonial era, the Gulf Stream remained the principal ocean route along the southern coast of North America. Trade in rum, sugar and spices fortified the young colonies and was vital to the economic needs of the growing markets. Although the current was a benefit to some ships, it proved detrimental to others pushing west to the New England colonies from Britain.

In 1768, when Benjamin Franklin, then-postmaster general for the American colonies, traveled to London, he was questioned by British authorities about why letters took much longer to get to New York than to New England ports when the two locations were ''scarcely a day's sail apart.'' Franklin asked his cousin, Timothy Folger, an American whaling captain, if he knew why.

Folger said American whalers were well-acquainted with the Gulf Stream. They knew whales could be found along its plankton-rich boundaries. They also knew travel back to New England whaling ports could be hastened by sailing north of the powerful push of the current. Folger said Americans had frequently told British captains about the futility of fighting the current, and how to avoid it, but that they had ignored the advice. ''They were too wise to be counselled [sic] by simple American fishermen,'' Folger dryly told him.

Franklin asked Folger to sketch the current on a map, which he then had printed and presented to the Lords of the Treasury, who in turn passed it along to their captains. British ships soon began to steer clear of the current when heading west.