What's an Ocean Gyre?

A few years ago, the Gulf Stream swiftly carried me home from the Bahamas while simultaneously tormenting me with waterspouts. It got me thinking...
Author:
Publish date:
ocean_gyre

A few years ago, the Gulf Stream swiftly carried me home from the Bahamas while simultaneously tormenting me with waterspouts. It got me thinking: cruisers often consider currents when determining where to sail, when to leave, and the how best to get there, but what about the bigger picture? 

Here are four things to ponder when sailing (or planning to sail) in the gyres of the North Atlantic and Pacific Ocean. 

Gyres are currents that flow in a circular pattern around the periphery of the major oceans. They are driven by wind and pressure gradients, and directed by the Coriolis effect, which explains how the Earth’s rotation deflects objects. For example, in the North Atlantic, westerly winds push water east across the North Atlantic. Blocked by Europe, the water accumulates until it has more pressure than the surrounding water, so a pressure gradient forms and the water wants to flow down. The Coriolis effect comes into play and makes the water flow south, forming the Canary Current. This pattern continues around the periphery of the ocean, forming a circle of currents called a gyre. 

There are five gyres in the world: North Pacific Gyre, North Atlantic Gyre, South Pacific Gyre, South Atlantic Gyre and Indian Ocean Gyre. All northern hemisphere gyres flow clockwise and all southern hemisphere gyres flow counterclockwise, thanks to the rotation of the Earth. 

Western Boundary Currents are found on the western side of ocean basins and are the deepest and fastest currents. The western boundary current in the North Atlantic is the Gulf Stream. It carries warm water from the equator to northern latitudes to be cooled. Eastern Boundary Currents, such as the California Current, are slow and shallow and carry cool polar water south toward the equator.

Currents moderate the world’s climate by circulating heat from the equator. For example, The Canary Current brings cool northern water south to absorb tropical heat and the Gulf Stream carries warm water back to the poles where it is cooled. This helps the Earth maintain a moderate temperature. Ocean gyres also explain why cities near the same latitude, such as Oakland, California, and Washington DC, have such different climates. Oakland stays cooler in the summer because of the cool air above the California Current while the air above the Gulf Stream warms Washington DC and turns its summers into scorchers.

Related

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell. Got a tip? Send it to sailmail@sailmagazine.com No chafe, safe stay  If you’re leaving the boat unattended for a longish period, there’s a lot to be said for cow-hitching the shorelines, as this sailor did. They’ll never let go, and so long as the ...read more

belize600x

Charter Special: Belize

It would be hard to imagine a more secure spot than the Sunsail base on the outskirts of the beachside community of Placencia, Belize. The entire marina is protected by a robust seawall with a channel scarcely a few boatlengths across. It’s also located far enough up Placencia ...read more

DSC00247

DIY: a Top-to-Bottom Refit

I found my sailing “dream boat” in the spring of 1979 while racing on Lake St. Clair in Michigan. Everyone had heard about the hot new boat in town, and we were anxiously awaiting the appearance of this new Pearson 40. She made it to the starting line just before the race ...read more

01-oysteryachts-regattas-loropiana2016_063

Light-air Sails and How to Handle Them

In the second of a two-part series on light-air sails, Rupert Holmes looks at how today’s furling gear has revolutionized sail handling off the wind. Read part 1 here. It’s easy to look at long-distance racing yachts of 60ft and above with multiple downwind sails set on roller ...read more

HanseCharles

Video Tour: Hanse 348

“It’s a smaller-size Hanse cruiser, but with some big-boat features,” says SAIL’s Cruising Editor, Charles J. Doane. At last fall’s Annapolis Boat Show, Doane had a chance to take a close look at the new Hanse 348. Some of the boat’s highlights include under-deck galleries for ...read more

amalfitown

Charter Destination: Amalfi Coast

Prego! Weeks after returning from our Italian flotilla trip last summer, I was still feeling the relaxed atmosphere of the Amalfi Coast. It’s a Mediterranean paradise, with crystal-clear waters, charming hillside towns and cliffside villages, plenty of delicious food and wine, ...read more

image005

Inside or Outside When Sailing the ICW

Last April, my wife, Marjorie, and I decided to take our Tartan 4100, Meri, north to Maryland from her winter home in Hobe Sound, Florida. This, in turn, meant deciding whether to stay in the “Ditch” for the duration or go offshore part of the way. Although we had both been ...read more

MK1_30542

SailGP: There’s a New Sailing Series in Town

San Francisco was the venue of the biggest come-from-behind victory in the history of the America’s Cup when Oracle Team USA beat Emirates Team New Zealand in 2013, so it seems only fitting that the first American round of Larry Ellison’s new SailGP pro sailing series will be ...read more