There is good reason to learn everything we can about the Gulf Stream, and to learn it now. This river in the ocean is vulnerable to changes that are already underway, and what happens to it will affect us all-boaters and non-boaters alike. To this end, and to have some fun as well, we're trying an experiment. We set 20 floats adrift in the heart of the current somewhere off Florida, and we had readers help find them. With their help, we hope to learn where the Stream has taken these little orange cruisers.
Where will the floats end up? We polled the saltiest Gulf Stream experts out there, including scientists, fishermen, and freighter captains, and the consensus was..."Who knows?"
The Gulf Stream is a restless beast, shifting in size, temperature, and location every decade, every year, every hour. For all the studies that have been done over the centuries, and will be done in the future, we will probably remain at a loss to fully understand this slippery character. A worrisome fact, and there are signs that we might not have much longer to get to know the Gulf Stream as our environment is going through some rapid changes. In the meantime, here's what we do know and why we are concerned.
ORANGE BLOSSOM SPECIAL
Floridians define the gulf stream as loosely as they define "presidential election." What they call the Gulf Stream starts as a jet of water known as the Florida Current that rips eastward between Cuba and the Keys. About 12 miles off Miami it's joined by the Antilles Current, which has been charging westward, funneling between the Bahamas and the island of Hispaniola. The Florida Current, now doing about four knots, then arches around Ft. Lauderdale before moving back to within five miles of West Palm Beach. This flow doesn't become the actual Gulf Stream, at least in scientific terms, until it deepens and picks up speed up off the Carolinas, where it can reach almost seven knots.
That top speed only occurs in the middle of the Stream, with the current slowing on both sides. "In our computer models, if you put a drifter in the high-velocity core it will stay there," explains Tom Rossby, Ph.D., of the University of Rhode Island, one of the country's premier Gulf Stream researchers. So it's likely our floats will remain trapped between the slower-moving edge currents, rather than go ashore. Rossby believes the floats will travel almost 125 miles a day, which means they would be approaching Cape Hatteras off North Carolina about two weeks after they were set adrift. The problem is, according to Rossby, "If they get 20 miles past Cape Hatteras, they'll probably never be found." At least not by someone on this continent.
Just north of Cape Hatteras, between 10 and 20 miles offshore, the Gulf Stream shoulders up against the much colder Labrador Current, which snakes down around Newfoundland and edges along the Atlantic shore. Meandering strands of the Stream break off here and sometimes peel away to form immense eddies 50 miles across. Cold-core eddies, which trap cold coastal water, can extend 12,000 feet to the bottom of the ocean. Warm-core eddies don't go as deep, but are considered prime fishing sites-almost like drifting aquariums for warm-water fish-as they swirl to the southwest.
"I think the floats will get caught up in the eddies, where the two currents meet," is yet another possible outcome, this one provided by Mark Laboccetta, who waits off North Carolina with his speargun for the Gulf Stream to deliver fish like dorado and wahoo. "Some-times the current boundary is so sharp, the bow of my boat is in warm water and the stern in cold," he says.
A WINTER'S CROSSING
Once you have a reason to study the Gulf Stream, you find yourself being pulled along in its flow as if some wonder of the universe awaits downstream. That's how it felt on the bridge of the M/V Oleander last December as it made its weekly run from New York to Bermuda. Oleander, a 387' cargo carrier, is one of a global network of merchant vessels known by scientists as "ships of opportunity." Since it crosses the Gulf Stream on the same headings on a regular basis, oceanographers from NOAA and the University of Rhode Island have installed an instrument package onboard that has been registering the Gulf Stream's speed, temperature, and salinity for the last 20 years.
After dropping off the New York harbor pilot, Capt. Johan Vrolyk sets his usual 137-degree course for Bermuda, 705 nautical miles to the southeast. The latest satellite imagery shows the Gulf Stream 129 miles away. The personable Dutch skipper says we should enter it about 7:30 the next morning.
I'm anticipating crossing from cold green water into the bright blue of the Stream. Instead what I see at dawn is a rolling gunmetal gray ocean turning pearly.
The Gulf Stream is most easily found by looking for the more or less permanent fog bank that lives along its western and northern edges. Today's weather forecast off the continental shelf is for the fog to clear, northeast winds at 15 to 25 knots, reaching 30 knots near the Gulf Stream. "You always add 15 to 20 percent to the winds and seas for the Gulf Stream," Capt. Vrolyk explains. "It can get really, really bad here."
In the radio room off the bridge, a couple of old 486 computers constantly record data from the instrument package containing the Acoustic Doppler Current Profiler (ADCP) built into the ship's hull. Sonar beams are emitted through four transducers, and the current is computed by measuring the Doppler shift on the returning echoes. At 6:45 a.m. the water temperature drops from 62.6 to 57.2 degrees. "We're in the small strands on the edge of the Stream now," says first mate Philippe Cannicioni, who is now at the helm.
As we approach the Stream's infamous north wall, we get lucky. The wind has definitely increased due to the atmospheric turbulence created by the warmer water, but it's out of the northwest, blowing across the Stream rather than directly into it from the northeast. "If you get a nor'easter in the Stream, you must avoid this place," Cannicioni advises in his thick Corsican accent.
Oleander is now rolling in 11-second intervals, hardover to hardover, as the current kicks in. "This isn't so bad," says Cannicioni. "You should have been here last week. We had 25-foot seas. The water temperature was 78 degrees, the air 38. It created sea smoke. On the horizon it looked like trees growing up into the clouds."
At 7:15 the water temperature is back up to 61.8, and we're steering 143 to be able to maintain a 137-degree course. At about 7:30 a pod of porpoise bursts out of the east like a fusillade of torpedoes headed directly for the ship, then takes up station on our bow wave. At 7:40 Cannicioni sets the gyro compass to 144, angling harder to starboard into the current. At 8:00 the water temperature is up to 68, and at 8:30 it goes to 73.9, climbing 12 degrees in only 18 miles. The seas have smoothed out. We've crossed the north wall and are into the heart of the Stream, beyond the continental shelf. An hour later we adjust our course again, as the current wheels around and is now pushing on our port side. We've either entered a bending elbow of the Stream, sweeping southward for a short distance, or perhaps one of the countercurrents that oppose the flow. At 10:30 the southward nudge is even stronger, and the water temperature is down to 67.1-a cold-core eddy outside the main path of the Stream. The eddy is clearly marked on the satellite imagery downloaded from the Web that morning. "It's a different world east of the Gulf Stream, no?" Cannicioni points out. Yes, it is.
PASS THE SALT
The Gulf Stream is literally a barrier protecting the colder coastal waters from the warmer, listless Mid-Atlantic. It's also a warm-water delivery system allowing Parisians to forget they share the same latitude as Fargo, North Dakota. Since its discovery by Ponce de Leon in 1513, the Gulf Stream has played major roles in world commerce, and even helped hide our submarines in underwater spy ops during the cold war.
The flow is so constant that it's tempting to believe it's unstoppable. But, in fact, scientists are now thinking the unthinkable-the Gulf Stream could someday shut down, triggering an ice age. And this time we're the mastodons.
One theory of global warming we are now experiencing predicts more rain in Northern Europe and the faster melting of ice in Greenland and the Arctic Ocean. Most of this fresh water would find its way into the North Atlantic, which could hinder the Stream's flow.
As the Gulf Stream travels northward, surface water evaporates, making it saltier and denser. Millions of tons of this entrained water sinks, circulating back down to the south along the sea bottom. It eventually spreads out, rises to the surface, and is drawn back north once again by the sinking waters.
But in our nightmare scenario, "All that new fresh water could dilute the saltier water so it wouldn't sink, essentially shutting down the conveyor belt," explains Arthur Mariano, Ph.D., a University of Miami physical oceanographer who has worked on Gulf Stream studies for the U.S. Navy. "It sounds dramatic, but the physical processes aren't that wild. It would only take a very small reduction in salinity in the North Atlantic." The end result would be no more Gulf Stream as we know it. And no more moderate winters or good fishing.
It's still an open question about how far north the current would get if this happened. The Gulf Stream is a major part of the clockwise North Atlantic gyre. It begins with the northeast trade winds, which, along with the Coriolis effect of the spinning Earth, creates the westward flowing north equatorial current. Water piles up into the Caribbean Sea and the Gulf of Mexico, where, as we have seen, it all meets off Miami to head north.
If the Gulf Stream's part of the Atlantic gyre breaks down because of diminished salinity, its equatorial warmth would no longer make it north. Europe and the eastern U.S. would get cold and snowy. Solar energy would radiate back from the snow cover, further cooling the planet. Adversely affected ocean currents would also mean a reduction in evaporation, and that would mean a colder atmosphere due to the reduction of greenhouse gases. What started as a moderate trend in global warming could get out of hand in short order.
This isn't fantastical science fiction. Ben Franklin, who commissioned the first map of the Gulf Stream in 1770, proposed during the American Revolutionary War to build a giant levy to alter the course of the Stream and plunge Britain into an ice age. "It's happened before," says Mariano. There was a mini-ice age that chilled the northern hemisphere about 12,500 years ago. The temperatures plummeted within 10 years and stayed that way for another 1,300 years. It's still unclear what caused it, but one thing is certain: The Gulf Stream was part of it and therefore bears close watching.
Check back for an update on what readers found in their small part to help save the Gulf Stream. Thanks.