Published: 
September 2008

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Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic

Stan Ulanski

Copyright (c) 2008 by the University of North Carolina Press.
All rights reserved.



Stan Ulanski, author of The Gulf Stream, on the Atlantic Ocean's superhighway.

Q: What is the Gulf Stream, and why doesn't the public know more about it?

A: The Gulf Stream is a powerful ocean current that transports water, heat, and organisms from the steamy tropics to the colder, higher latitudes. As part of a large, clockwise circulation known as the North Atlantic gyre, the Gulf Stream flows hundreds of miles along the Atlantic seaboard and is the western boundary of the oceanic gyre.

Although the Gulf Stream has been studied for centuries by scientists, mariners, and merchants, a visitor to the Cape Hatteras National Seashore rarely has direct contact with this current. This same visitor might be surprised to find out that this current, though not visible from the shore, is less than forty miles from the coast.

Q: Why did you decide to take an interdisciplinary approach in writing this book?

A: While it is true that many previous accounts of the Gulf Stream have taken a one-dimensional approach to this subject, generally from a scientific perspective, I have come to view the Gulf Stream, the nexus of this story, as the link between the natural and cultural world. Hopefully, understanding these complex connections will give readers a greater appreciation of this unique natural phenomenon. The whole story of the Gulf Stream would be incomplete if I had ignored the five-hundred-year relationship between humankind and this oceanic river.

Q: What were some of the misconceptions we once had about the Gulf Stream?

A: The general populace and the academic community have long held the belief that the Gulf Stream warms Europe and accounts for its relatively mild climate. This idea may date back to Matthew Maury (1806-1873), commonly referred to as the "father of modern oceanography," who waxed eloquent about how the Gulf Stream "makes Erin the Emerald Isle of the Sea." However, recent studies by climatic scientists have shown that the moderating influence of the current is overstated. Though the Gulf Stream does indeed transport heat from the tropics to the shores of England, only 10 percent of England's winter warming comes directly from the Gulf Stream.

Q: What role did Benjamin Franklin play in revealing the properties of the Gulf Stream?

A: Franklin took water temperature measurements on three crossings of the Gulf Stream and meticulously recorded them. From these readings, he was able to delineate the main axis of the current as well as its boundaries. With the aid of his cousin, Timothy Folger, Franklin published one of the detailed charts of the nature of the Gulf Stream. The average path, boundaries, width, and speed of this current as we know it today are accurately represented on the Franklin-Folger chart.

Q: What powers the Gulf Stream?

A: The Gulf Stream is driven by a combination of atmospheric and oceanic factors: wind drag across the ocean surface, pressure gradients in the ocean, and the influence of a rotating Earth. Add these together, inject some physical and mathematical insight into the coupling between the atmosphere and the ocean, and what emerges is a realistic picture of ocean circulation.

Q: What recent discovery about the Gulf Stream seems most striking to you?

A: Scientists are increasingly recognizing the Gulf Stream as the "weather maker" of the western Atlantic. The western edge of the Gulf Stream is where this incessant current clashes with the atmosphere to form a meteorological battlefield. In particular, North Carolina's offshore waters are the breeding grounds for a fierce winter storm called a nor'easter.

Q: Does the Gulf Stream have an official boundary? If so, what determines it?

A: The Gulf Stream, an oceanic river, is like no river on land. Though its "banks" are fluid ocean, not soil and rock, the Gulf Stream can move surprisingly long distances within well-defined boundaries, marked by changes in temperature, current speed, and water color.

Q: Why is the Gulf Stream considered one of the last vestiges of wilderness on Earth?

A: The answer to this question can be elusive because a wilderness, at its core, is a region of bewildering vastness. In this regard, the Gulf Stream is indeed a wilderness of surprising degree, stretching from the torrid tropics to the polar seas, with boundaries that are not rigid in space and time. In addition, my feelings about the wilderness aspect of the Gulf Stream fall in line with the arguments of Ernest Hemingway: "The Gulf Stream and other great ocean currents are the last wild country that is left. Once you are out of sight of land and the other boats you are more alone than you can ever be hunting and the sea is the same as it has been since men ever went on it in boats."

Q: What kinds of biological life are particularly dependent on the Gulf Stream?

A: All kinds of riders accompany the Gulf Stream on its northward journey through the western Atlantic. These include passive organisms, which literally go with the flow, such as the floating sargassum weed. This brown algae is a critical source of food, shelter, and substrate for a multitude of marine organisms. At the other end of the spectrum of Gulf Stream travelers is the giant bluefin tuna, which spawns in the Gulf of Mexico and undertakes prodigious feeding migrations of more than two thousand miles.

Q: What role did the Gulf Stream play in the building and prosperity of the American colonies?

A: The sea paths to the Americas blazed by early European explorers would forever transform the New World, allowing for unprecedented migration and settlement. The Gulf Stream made possible an enormously lucrative trade in spices, sugar, and rum during the colonial era. Horribly, it also floated ships filled with African slaves, whose forced labor is now acknowledged as having been essential to the building and prosperity of the American colonies.

Q: How did buccaneers and pirates use this sea highway?

A: Beginning in 1561 and lasting until 1726, a convoy of ships would annually depart from Spain to plunder the wealth of the West Indies and South America. When the vessels were loaded with treasures, they returned home via the Gulf Stream. Lurking within the web of islands, cays, and reefs of the Bahamas, pirate ships, known for their speed and agility, relentlessly preyed upon Spanish shipping. Sailing in the Gulf Stream, these pirate sloops could easily overtake a merchant ship and escape pursuit by the heavier man-of-war.

Q: What attracts game fish to the Gulf Stream?

A: The "place" is at the essence of locating and catching fish. Wherever there is a concentration of prey, hungry predators are present and ready to play their role in the marine food chain. To Gulf Stream game fish, the thermal fronts of the Gulf Stream—boundaries separating the warm water of the current from the cooler but fertile coastal waters—mean food and plenty of it. Thermal fronts, especially those with well-defined edges, can act as barriers to the movement of game fish such as tuna and marlin. Seeking their thermal comfort on the warm side, the fish will cruise along these edges instead of crossing them.

Q: How does global warming threaten the Gulf Stream?

A: Today there is some concern within the scientific community that global warming may trigger a sudden climatic shift: a tipping point will be reached, resulting in a complete shutdown of the Gulf Stream, disrupting its heat transport and initiating a new ice age.

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