The ratio of the weight of oceanic water and the weight of the substances dissolved in it is called Oceanic Salinity. It is expressed in the form of total amount of solid substances dissolved in one kg. of the oceanic water. Oceanic salinity is expressed in the form of amount of salt present in per thousand grams of water. Among oceanic salts, sodium chloride is found in the maximum amount.
Factors Affecting Oceanic Salinity: Oceanic salinity is not found in the same amount in all the oceans of the world. It varies according to the prevailing conditions.
The factors controlling the extent of oceanic salinity are as follows:
2. Water availability through rainfall.
3. Arrival of river water.
4. Prevailing winds.
5. Oceanic Currents.
6. Transmission of oceanic water.
The description of all these factors is as follows:
1. Evaporation: There is a direct relation between the amount of salinity and evaporation. The more and rapid the evaporation, the more rise in salinity: Lack of humidity in the winds is necessary along with the evaporation. Salinity is more the regions where the temperature is high and the evaporation is more, like – near to the Tropic of Cancer and the Tropic of Capricorn.
2. Water Availability through Rainfall: Salinity reduces due to more availability of clean water. Salinity decreases in the regions where excessive rainfall occurs. Despite of the high temperatures in the equatorial regions, salinity is found to be low due to excessive rainfall.
On the other hand, despite of the low rainfall in tropical parts, salinity is found to be more due to high temperature. In the polar and sub – polar parts, the glaciers formed by excessive snowfall bring snow in the oceans, which reduces the salinity of ocean by melting on reaching the temperate regions.
3. Arrival of River Water: Although the rivers bring salts to the oceans, yet they have so much amount of clean water that they lack salinity near their basin. For example, low salinity is found in the parts of the river basins of the Ganga, Congo, Niger, Amazon, St. Lawrence, etc.
4. Prevailing Winds: In warm and dry regions, evaporation occurs more due to the rapid winds moving towards the oceans. Thus, salinity is found to be more in such parts of the oceans. On the other hand, evaporation occurs less by flow of cold, humid and slow winds.
5. Oceanic Currents: Currents flowing from the regions with low oceanic salinity bring with them the water of low salinity and reduce the amount of salinity on their flow path. On the other hand, salinity is found to be more on the path of the currents flowing from the regions with high oceanic salinity.
6. Transmission of Oceanic Water: Distribution of salinity in the high seas becomes normal by the transmission of ocean water. More saline water gets heavier and settles down and moves in the depth towards low saline water. To take its place, the low saline water moves in the form of surface flow. In this way, the balance of the salinity of ocean water is maintained by this transmission.