Water is a renewable resource. Water undergoes a cycle from ocean to land and land to ocean. Water is unevenly distributed on the earth. Some countries have plenty, while others have water in very limited quantity.
There are five oceans: Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean and Southern Ocean.
The ocean floor can be divided into four major divisions:
Deep sea plain
The minor relief features of ocean floor are:
Ocean waters get heated up by the solar energy as land. Process of heating and cooling is slower than on the land. The factors affecting temperature distribution are:
Unequal distribution of land and water
Temperature decreases with the increasing depth in the ocean waters. The boundary from where there is a rapid decrease of temperature is called ‘thermocline’.
Average annual temperatures for Northern and Southern Hemispheres are around 19°C and 16°C, respectively. Variation is due to the unequal distribution of land and water in both the hemispheres.
Salinity is used to define the total content of dissolved salts in sea water. It is calculated as the amount of salt dissolved in 1000 gm of sea water. It is expressed as parts per thousand or ppt.
Salinity ranges between 33 parts per thousand and 37 parts per thousand for the normal, open ocean ranges. Salinity changes with the depth. The way it changes, depends on the location of the sea. Salinity increases at the surface by the loss of water. Salinity at the depth is fixed.