In the central part of the North Atlantic Ocean a vast oval-shaped area is formed by the North Equatorial Current, the Gulf Stream and the Canaries Current. All these currents flow in a clockwise direction. Within this almost circular area the ocean is calm and stable.
The water movement, if any, is very slow. On the surface of the ocean a sea-weed belonging to the Sargassum species is found floating in abundance. That is why this sea has been named as the Sargasso Sea.
In the central part of this sea the thickness of the sea-weed is greater than that at the margins. It is estimated that this particular sea-weed covers about 11,000 km2. It may be stated that this sea-weed is rootless, so it is confined to the sea-surface only.
Though various theories have been developed regarding the origin of this weed, it is an established fact that this special type of weed develops only in the open seas. However, it is to be kept in mind that in no other ocean such a type of weed is found.
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Even the boundaries of the Sargasso Sea are controversial. In Marmer’s opinion, the latitudinal as well as the longitudinal extent of this sea is between 20° and 40° N latitudes, and 35°W and 75° W longitudes.
Since this sea is located in the subtropical high-pressure region, it is characterized by high temperature and higher rate of evaporation. Due to these factors the salinity of the surface water is 37%o – more than the average salinity of the open ocean water.
Being surrounded by ocean currents on all sides, the water of this sea cannot mix with the low-salinity waters of the open ocean. Besides, the supply of fresh water from the inflow of rivers, from the precipitation or the melt-water is also not possible.
Under these conditions, salinity remains high throughout the year. However, the Sargasso Sea offers ideal conditions for the laying of eggs by some special types of fish. This sea is, however, conspicuous by the absence of sea birds.