GULF STREAM

GULF STREAM. A powerful, warm, surface current in the North Atlantic Ocean, east of North America, the Gulf Stream is one of the strongest known currents. It originates in the Gulf of Mexico as the Florida Current, with an approximate temperature of 80 degrees Fahrenheit, a breadth of no more than fifty miles and a depth of a mile or more. It passes through the Straits of Florida and up along the eastern coast of the United States to the Grand Banks of Newfoundland, Canada, driven northward by southwest winds.

As the Gulf Stream reaches Cape Hatteras, North Carolina, the cold Labrador Current that flows from the north separates it from the coast. At this confluence, the warm Gulf Stream waters combine with the cold winds accompanying the Labrador Current, forming one of the densest concentrations of fog in the world. Because of this immense heat transfer, atmospheric storms tend to intensify in this region. Also at this location, the Gulf Stream is split into two currents: the Canary Currents, which are diverted southeast and carry cooler waters to the Iberian Peninsula and northwestern Africa; and the North Atlantic Drift, which flows northwest toward western Europe, providing temperate waters to the western coastal areas of Europe. The water temperature decreases with the northward flow and the breadth of the current spans several hundred miles at its widest. The average speed of the Gulf Stream is four miles per hour, slowing to one mile per hour as the current widens to the north. The Gulf Stream transports as much as 3.99 billion cubic feet of water per second, an amount greater than that carried by all of the world's rivers combined. The current's core, or jet, follows the contours of the continental rise.

The Spanish explorer Juan Ponce de León was the first to describe the Gulf Stream in 1513 as he searched for the fountain of youth in what is now Florida. The Gulf Stream played a major role in the settling of southeastern regions of the United States. North America's oldest city, St. Augustine, sits on the coast of eastern Florida where the Gulf Stream flows. It was founded during the Spanish period, fifty years or so after De León's trek. When the United States acquired Florida, land speculators quickly moved in and formed large plantations. Tourism in the region escalated soon after, and continued to thrive in the early 2000s, especially along Florida's Treasure Coast. The Gulf Stream was also popularized in art, as evidenced in Winslow Homer's 1899 painting The Gulf Stream.

Another major contribution of the Gulf Stream is its warming effect on the climates of adjacent land areas that it passes, especially in northern latitudes, where the coastal weather is quite temperate, even in winter. The Gulf Stream is known as a western-boundary current, a current that is located on the western side of every ocean basin. It is part of a clockwise-rotating system of currents in the North Atlantic. The Gulf Stream is the most extensively studied ocean current in the world, but many questions about it remain unanswered.

BIBLIOGRAPHY

Groves, Donald G., and Lee M. Hunt. The Ocean World Encyclopedia. New York: McGraw-Hill, 1980.

Mary AnneHansen

See alsoClimate ; Grand Banks ; Oceanography .

Gulf Stream The Gulf Stream is a western boundary current and is part of the North Atlantic Gyre (Fig. 1). The name ‘Gulf Stream’ is commonly applied to the entire northern branch of the gyre, but the current is in fact made up of at least three individual parts: the Florida Current, which flows from the Caribbean to approximately 37° N, the Gulf Stream proper between 37° N to approximately 40° W, and then the extension of the current towards Europe, which is the North Atlantic Drift. The velocity of the Gulf Stream is strongest just south of Cape Hatteras and can reach 2.5 m s⁻¹. At this point the current is constrained to the continental shelf and limited to approximately 800 m in depth. Meanders in the current are common but only of approximately 50 km in amplitude. Just north of Cape Hatteras the current leaves the shelf and moves over the deeper water of the North Atlantic, slowing to velocities that are typically 0.7 m s⁻¹. The northern boundary of the current usually corresponds to a sharp gradient in temperature with cold water on the northern side. The southern boundary is typically more diffuse.

The slowing down of the current as it moves away from Cape Hatteras and the lack of topographic steering allows meanders of up to 350 km in amplitude to develop. These large meanders can break from the main current to form eddies called Gulf Stream rings, which can typically be 200 km in diameter. Because of the temperature gradient on either side of the current, the meanders can form rings with either cold or warm water in their centres (‘cold-core’ or ‘warm-core’) and can extend to full ocean depth. The eddies can be re-absorbed by the current or can exist independently for up to a year, and at any one time there may be up to ten rings in existence. Similar rings have been observed forming in other western boundary currents such as the Agulhas and the Kuroshio (see ocean currents).

The reason for the existence of the Gulf Stream and the North Atlantic Gyre is principally Ekman drift (see ocean currents) coupled with the latitudinal variation of the Coriolis force. The prevailing wind field across the North Atlantic is zonal (see Walker circulation), being from the west above approximately 30° N and to the east south of this towards the Equator. These prevailing winds generate currents which are deflected to the right by the rotation of the Earth and result in a general inflow of water into the subtropic convergence (that is the centre of the gyre). The pool of water which develops in the centre causes a decrease in vorticity, and because of the conservation of angular momentum an anticyclonic gyre develops across the basin. The intensification of the western boundary of the gyre (i.e. the formation of the Gulf Stream) results from the fact that the Coriolis force changes with latitude, coupled with the conservation of vorticity across the whole gyre.

Mark A. Brandon

Bibliography

Apel, J. R. (1987) Principles of ocean physics. International Geophysics Series, Vol. 38. Academic Press, London.

Gulf Stream The most important ocean-current system in the northern hemisphere, which stretches from Florida to north-western Europe. It incorporates several currents: the Florida Current; the Gulf Stream itself; and an eastern extension, the North Atlantic Drift. The Florida Current is fast, deep, and narrow, but after passing Cape Hatteras the Gulf Stream becomes less effective at depth and develops a series of large meanders which form, detach, and reform in a complicated manner. After passing the Grand Banks (off Newfoundland) the flow forms the diffuse, shallow, slower-moving North Atlantic Drift. The temperature (18–20°C) and salinity (36 parts per thousand) tend to be seasonally constant, unlike neighbouring coastal water masses.

Gulf Stream The most important ocean-current system in the northern hemisphere, which stretches from Florida to north-western Europe. It incorporates several currents: the Florida Current, the Gulf Stream itself, and an eastern extension, the North Atlantic Drift. The Florida Current is fast, deep, and narrow, but after passing Cape Hatteras the Gulf Stream becomes less effective at depth and develops a series of large meanders which form, detach, and reform in a complicated manner. After passing the Grand Banks (off Newfoundland), the flow forms the diffuse, shallow, slower-moving N. Atlantic Drift. The temperature (18–20 °C) and salinity (36 parts per thousand) tend to be seasonally constant, unlike neighbouring coastal water masses.

Gulf Stream Relatively fast-moving current of the n Atlantic Ocean. It flows from the straits of Florida, USA, along the e coast of North America, then e across the Atlantic (as the North Atlantic Drift) to the nw European coast. The current warms coastal climates along its course.