Salinity of the Oceans
Salinity - Salinity is the proportion of dissolved salts in 1000 grams of sea water. It is measured in parts per thousand (ppt) with the symbol of (‰).
The average salinity of the Earth's Ocean is 35 ppt.
Sources of Ocean's Salinity
- Continents (through rivers, rain waters, winds and other agents of erosion deposited minerals into the seas)
- Volcanic eruptions within the oceans.
- Evaporation of water along the ocean surface which leaves the salt behind (it will help in increasing the salt content/salinity).
Composition (different types of salts dissolved in Sea water)
- Chlorine - 18.97 grams of salt in 1 kg of sea water
- Sodium - 10.47 grams of salt in 1 kg of sea water.
- Sulphate - 2.65 grams of salt in 1 kg of sea water
- Magnesium - 1.28 grams of salt in 1 kg of sea water
- Calcium - 0.41 grams of salt in 1 kg of sea water
- Potassium - 0.38 grams of salt in 1 kg of sea water
- Bicarbonate - 0.14 grams of salt in 1 kg of sea water
- Bromine - 0.06 grams of salt in 1 kg of sea water
- Borate - 0.02 grams of salt in 1 kg of sea water
- Strontium - 0.01 grams of salt in 1 kg of sea water
Factors affecting Salinity
1. Temperature
- Increase in temperature leads to increase in evaporation and thus increase in Salinity.
2. Wind Speed
- Wind speed ↑ 🠞 ↑ Evaporation 🠞 ↑ Salinity
- This is the reason why Equatorial region has low salinity (Equatorial region - Calm climatic condition)
3. River
- ↑ River 🠞 brings more fresh water 🠞 ↓ Salinity
- Example - Low salinity is experienced along the deltas of Ganga and Amazon.
4. Ice & Snow
- When Sea Water freezes, it leaves behind the salts. Thus, increases the salinity.
- Whereas when the ice melts, it adds more fresh water. Thus, decreases the salinity.
- Example - Formation of ice near to the polar regions increases the salinity whereas melting of ice decreases the salinity.
5. Ocean Currents & Circulations
- Ocean currents helps in distribution of salinity across the globe and maintains a balance.
Vertical distribution of Salinity
- In Equatorial region, low evaporation and high precipitation leads to low salinity in the upper layer and it increases with depth and finally becomes uniform.
- Along the Sub-tropics, high evaporation leads to high salinity along the surface and it decreases sharply and becomes uniform after certain depth.
- Along the Polar region, low temperature and low evaporation makes the water low in salinity. In addition to this melting of ice adds fresh water near to the surface resulting in low salinity. The salinity increases with depth and becomes uniform after certain depth.
Horizontal distribution of Salinity
Salinity along Sub-tropics ﹥Salinity along Equatorial region﹥Salinity along Polar region.
Characteristics of water bodies having higher Salinity than normal
- They are found near to Sub-tropics.
- They are surrounded by land on almost all sides.
- For example - Mediterranean sea, Red sea, Persian Gulf, etc.
Characteristics of water bodies having Salinity below normal
- They are found in Temperate or Polar region.
- For example - North sea, Baltic sea, Bering sea, Gulf of San Florence (Canada), Arctic Ocean, etc.
Water bodies having exceptionally high salinity
- Lake Van, Turkey - (330 ppt)
- Dead Sea - (240 ppt)
- Great Salt Lake - (220 ppt)
Previous Article - Temperature of the Oceans
Next Article - Ocean deposits & Coral reefs
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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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