Solar Navigators (those sailors with solar powered boats) should take advantage of trade winds and ocean currents wherever practical by way of an eco compromise route, whereas a steam or diesel powered vessel takes the shortest route to its destination.

Navigation is easier for powerboats, whereas the early European explorers had to discover the pattern of winds and currents that would carry them where they wanted to go. During the age of sail winds and currents determined trade routes.

With a solar and wind powered vessel it makes sense to use natural forces wherever possible. That said, the Elizabeth Swann does not need to tack to take advantage of the wind, where turbines act a rotary sails, compensating for the vector. The efficiency is though greater with following wind.

THE TRADE WINDS

The trade winds and associated ocean currents helped early sailing ships from European and African ports make their journeys to the Americas. Likewise, the trade winds also drive sailing vessels from the Americas toward Asia. Even now, commercial ships use "the trades" and the currents the winds produce to hasten their oceanic voyages. 

How do these commerce-friendly winds form?

Between about 30 degrees north and 30 degrees south of the equator, in a region called the horse latitudes, the Earth's rotation causes air to slant toward the equator in a southwesterly direction in the northern hemisphere and in a northwesterly direction in the southern hemisphere. This is called the Coriolis Effect.

The Coriolis Effect, in combination with an area of high pressure, causes the prevailing winds—the trade winds—to move from east to west on both sides of the equator across this 60-degree "belt."

THE DOLDRUMS

As the wind blows to about five degrees north and south of the equator, both air and ocean currents come to a halt in a band of hot, dry air. This 10-degree belt around Earth's midsection is called the Inter-Tropical Convergence Zone, more commonly known as the doldrums.

Intense solar heat in the doldrums warms and moistens the trade winds, thrusting air upwards into the atmosphere like a hot air balloon. As the air rises, it cools, causing persistent bands of showers and storms in the tropics and rainforests. The rising air masses move toward the poles, then sink back toward Earth's surface near the horse latitudes. The sinking air triggers the calm trade winds and little precipitation, completing the cycle.

THE CLIPPER ROUTE

The clipper route was the traditional route derived from the Brouwer Route and sailed by clipper ships between Europe and the Far East, Australia and New Zealand. The route ran from west to east through the Southern Ocean, in order to make use of the strong westerly winds of the Roaring Forties. Many ships and sailors were lost in the heavy conditions along the route, particularly at Cape Horn, which the clippers had to round on their return to Europe.

The clipper route fell into commercial disuse with the introduction of marine steam engines, and the opening of the Suez and Panama Canals. However, it remains the fastest sailing route around the world, and as such has been the route for several prominent yacht races, such as the Velux 5 Oceans Race and the Vendée Globe.

OCEAN CURRENTS

Coastal currents are affected by local winds. Surface ocean currents, which occur on the open ocean, are driven by a complex global wind system.

Currents travel around 5.6 miles per hour in warmer waters of the northern hemisphere and in the North Pacific moves much slower in cold water at 0.03 to 0.06 miles per hour.

Ocean currents that occur above 100 meters (328 feet) deep are typically classified as surface currents. Surface currents, which include coastal currents and surface ocean currents, are driven primarily by winds.

To understand the effects of winds on ocean currents, one first needs to understand the Coriolis force and the Ekman spiral.

Winds Drive Surface Ocean Currents

Global winds drag on the water’s surface, causing it to move and build up in the direction that the wind is blowing. And just as the Coriolis effect deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, it also results in the deflection of major surface ocean currents to the right in the Northern Hemisphere (in a clockwise spiral) and to the left in the Southern Hemisphere (in a counter-clockwise spiral). These major spirals of ocean-circling currents are called “gyres” and occur north and south of the equator. They do not occur at the equator, where the Coriolis effect is not present (Ross, 1995).

NIGHT LIGHTS - The above satellite map of world routes shows the trade routes most used by modern cargo and passenger vessels. 

Ekman spiral

The Ekman spiral, named after Swedish scientist Vagn Walfrid Ekman (1874-1954) who first theorized it in 1902, is a consequence of the Coriolis effect. When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them. Each layer of water molecules is moved by friction from the shallower layer, and each deeper layer moves more slowly than the layer above it, until the movement ceases at a depth of about 100 meters (330 feet).

Like the surface water, however, the deeper water is deflected by the Coriolis effect - to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. As a result, each successively deeper layer of water moves more slowly to the right or left, creating a spiral effect. Because the deeper layers of water move more slowly than the shallower layers, they tend to “twist around” and flow opposite to the surface current.

In the Northern Hemisphere, that means that the strong trade winds that originate in the northeast and blow westward pull the surface of the ocean along with them near the equator. Thanks to the coastline and the Coriolis effect, the warm-water current then heads north, turning at about 30 degrees north latitude. The westerlies take over then, completing the circuit. Blowing from the west, these winds guide the current eastward and south after they hit land. The two wind patterns create a continual circular pattern of wind flowing clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

These circular wind patterns create spiral ocean currents called gyres. Five major gyres flow both north and south of the equator: the North Atlantic, South Atlantic, North Pacific, South Pacific and Indian Ocean gyres. Smaller gyres also exist at the poles, and one circulates around Antarctica. Short-lasting, smaller currents often spin off both small and large gyres.

The Gulf Stream, a particularly strong current that is part of the North Atlantic gyre, carries warm water north from the Gulf of Mexico up the coast of the eastern United States and over to western Europe.

GLOBAL CONVEYOR BELT

Invisible to us terrestrial creatures, an underwater current circles the globe with a force 16 times as strong as all the world's rivers combined [source: NOAA: "Ocean"]. This deep-water current is known as the global conveyor belt and is driven by density differences in the water. Water movements driven by differences in density are also known as thermohaline circulation because water density depends on its temperature (thermo) and salinity (haline).

The global conveyor belt begins with the cold water near the North Pole and heads south between South America and Africa toward Antarctica, partly directed by the landmasses it encounters. In Antarctica, it gets recharged with more cold water and then splits in two directions -- one section heads to the Indian Ocean and the other to the Pacific Ocean. As the two sections near the equator, they warm up and rise to the surface in what you may remember as upwelling. When they can't go any farther, the two sections loop back to the South Atlantic Ocean and finally back to the North Atlantic Ocean, where the cycle starts again.

The global conveyor belt moves much more slowly than surface currents -- a few centimeters per second, compared to tens or hundreds of centimeters per second. Scientists estimate that it takes one section of the belt 1,000 years to complete one full circuit of the globe. However slow it is, though, it moves a vast amount of water - more than 100 times the flow of the Amazon River. [source: NOAA: "Currents"].

The global conveyor belt is crucial to the base of the world's food chain. As it transports water around the globe, it enriches carbon dioxide-poor, nutrient-depleted surface waters by carrying them through the ocean's deeper layers where those elements are abundant. The nutrients and carbon dioxide from the bottom layers that are distributed through the upper layers enable the growth of algae and seaweed that ultimately support all forms of life. The belt also helps to regulate temperatures. 

RECORD "SUNSHINE" ROUTE

STABILIZED MONOHULL - The diesel powered Cable and Wireless Adventurer was built for the purpose of circumnavigating the world in less than 80 days. This was successfully accomplished in July 1998 in 74 days, 20 hours, 58 minutes, traveling more than 22,600 nautical miles (26,000 miles or 41,855 km). This achievement set a new Guinness World Record for a diesel powered vessel. The nautical mile or knot, is a unit of speed equal to approximately 1.15078 miles per hour on land (1.852 km).