Adapted from a NOAA Base Map



A River in the Ocean

photo by Geoff Dennis

This coconut likely traveled more than a thousand miles by the current of the Gulf Stream before washing ashore on a Rhode Island beach. Photo by Geoff Dennis.

Last summer, beachcombers in Rhode Island came across coconuts washed up on the beach, still in their husks after having floated more than 1,000 miles from the tropics. Two years earlier, 14-year–old Michael Kearney found a coconut on the beach on the southwestern coast of Ireland, more than 4,000 miles from where scientists believe it came from!

The buoyant tropical fruits were likely carried to these far–flung beaches by the Gulf Stream, that famous “river in the ocean” that starts in the Gulf of Mexico and Caribbean and travels north and east along the East Coast before turning towards Europe across the Atlantic Ocean. The powerful current transports more water through the ocean than all of the world’s rivers combined, and its warm temperature is responsible for moderating the climate in coastal New England, Bermuda, Western Europe and even as far north as Norway, where the air over the ocean in winter is an astonishing 40° F (22° C) warmer than is typical for that latitude.

The Franklin–Folger Map of the Gulf Stream.

The Franklin–Folger Map of the Gulf Stream. Franklin published three editions of this map, each with new information. This is the third version, published in 1786. It was used by mariners to plan their routes across the Atlantic. Courtesy by Library of Congress.


Ship captains were the first to discover it. Spanish explorer Juan Ponce de Leon was sailing towards Florida in 1513 when he encountered a current so strong that it pushed his ship backwards. The first person to study and document its path was none other than Benjamin Franklin. Franklin wore many hats in his role as an American Founding Father, as well as work as a scientist and inventor, but he first became interested in the Gulf Stream when he was working as the Deputy Postmaster General of the American colonies. He wanted to know why ships carrying mail took weeks longer to get across the Atlantic when sailing east–to–west vs. west–to–east.

He consulted his cousin, Timothy Folger, a Nantucket sea captain, who told him about the strong current in the Atlantic that can speed up or slow down a ship’s progress considerably, depending which way it was sailing. The two men worked together to produce the first–ever map that showed the path of the Gulf Stream—and it was the first to name it as such. Franklin’s goal was to help ship captains plan their routes to take advantage of its speed or to avoid it altogether when traveling in the opposite direction.

Since then, the Gulf Stream has been studied at length by scientists and is a topic of intense analysis. Modern technology—satellites, research vessels, remote sensing instruments, etc.—allows us to collect data with greater precision, related to temperature, weather and climate, and track.

If you are on a boat entering the Gulf Stream, it actually looks like a river. Its bright cobalt–blue color is dramatically different from gray–green–blue of the rest of the Atlantic Ocean it flows through. Mariners sampling water temperatures as they proceed notice a dramatic increase in water temperature as they enter the Gulf Stream, not to mention the strong current that may be pushing them along or holding them back.

These days, mail goes by air, so letters you send to Europe won’t get there in less time than you’d get a reply. And the Gulf Stream still doesn’t warm Europe enough for coconuts with wanderlust to sprout new groves in Galway Bay or on the edges of Norwegian fjords. But, if you put a message in a bottle and drop it in the ocean, that steady, reliable river in the ocean might just find you a new pen–pal on the other side of the Atlantic. Just be sure they send their reply by airmail or email—the Gulf Stream only goes one way.

— Deirdre O’Regan

Did You Know?

Einstein On Sailboat Billard Smoke Pipe

Albert Einstein loved to sail and he sailed his whole life.

Renowned as one of the greatest mathematicians and physicists of all time, by most accounts Einstein was also a terrible sailor! Making a boat go in a particular direction is a very interesting bit of science, so you wouldn’t think he would have had any trouble with it—but you’d be wrong.

What’s the secret to sailing any place you want to go, no matter which way the wind is blowing?

Read more at Albert Einstein, Sailor