As Defiant puts it, the north as well as the south equatorial currents together forms the backbone of the system of currents present in the Atlantic Ocean. The north equatorial current is induced by the northeast-trade winds which drive the tropical waters in a westerly direction.
The north equatorial current receives its water from the currents flowing from the coastal seas of the northwest Africa. The trade winds blowing from the African coast are off-shore winds driving the coastal waters towards the west.
This results in the upwelling of cold and dense water from the intermediate depth of the North Atlantic Ocean. Thus, the trade winds drive the cold water brought down by the Canaries current along the African west coast.
As a matter of fact, the north equatorial current develops all its characteristics as warm and saline ocean current only after it has left the African coast far behind.
The north equatorial current flows in a wide belt with its latitudinal extent from 10°N to 30° N latitude. The motive force behind this current being the northeast trade winds, it affects the water up to a depth of 200 meters.
However, to the south of 20°N latitude the current flows at an average velocity of 15-17 nautical miles per day. But to the north of this latitude the velocity is highly variable.
The most characteristic feature of the north equatorial current is that it is less constant in strength and extent. Its northern boundaries are fluctuating.
According to Schumacher, to the north of 15°N latitude this current, before reaching the Mid-Atlantic Ridge, turning towards right flows towards the north. But after passing over the aforesaid ridge it turns towards the left of its path and starts flowing southward.
Though the Mid-Atlantic Ridge is located 3000 meters below the surface water, yet while crossing it this current deflects more towards the north.
In the western part of the ocean the north equatorial current joins that part of the south equatorial current which flows towards the north after crossing the equator.
This branch of the south equatorial current brings different water mass. Thus, the mixing of different water masses takes place in this region. The waters in the Caribbean Sea are, therefore, intermediate in character.
After reaching the 60° West longitude the north equatorial current bifurcates into two branches. One branch flows into the Caribbean Sea, while the other flowing to the north of the West Indies joins the first branch near 8°N latitude.
The northern branch of the North Equatorial current which flows along the northern side of the Great Antilles is known as the Antilles Current. It carries water which is similar to that of the Sargasso Sea.
It may be stated that the first branch, as referred to above, flowing through the Caribbean Sea enters into the Gulf of Mexico and fills it with the mixed water mass.
Thus, the water level in the gulf is raised. From the Gulf of Mexico the water returns to the Atlantic Ocean through the Florida Strait. At its narrowest, the Strait is only 80 km wide. Thus, hydraulically a swift current is produced, its velocity being more than 2 m sec.
Flowing out from the Florida Strait a strong surface flow extends from the subtropical region well into middle latitudes. This is loosely called the Gulf Stream.
But according to Iselin, the complete set of western currents comprising the Florida Current (between the Florida Strait and Cape Hatteras), the Gulf Steam proper (between Cape Hatteras and the tail of the Grand Banks), and the North Atlantic Current (the continuation of the Gulf Stream eastward from the Grand Banks), is known as the Gulf Stream System. Thus, the Gulf Stream System comprises the following ocean currents.
(i) Florida Current,
(ii) The Gulf Stream, and
(iii) North Atlantic Current/Drift. These currents will be discussed separately.