Oceanography- 3 | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
OCEANOGRAPHY - 3 
SALINITY OF OCEAN WATERS 
- All waters in nature whether the rain water or ocean water contain 
dissolved mineral salt  
- Salinity is the term used to define the total content of dissolved salts in 
sea water.  
- It is calculated and the amount of salt dissolved in thousand gram of 
sea water  
- It is usually expressed as parts per thousand.  
FACTORS AFFECTING OCEAN SALINITY 
- The salinity of water in the surface layer of oceans depend mainly on 
evaporation and precipitation  
- Surface salinity is greatly influenced in coastal regions by the fresh 
water flow from rivers  
- Surface salinity in polar regions is influenced by process of freezing 
and thawing of ice, inflow of Glacier etc.  
- Wind also influences salinity of an area by transferring water to 
other areas.  
- Ocean currents too contribute to the salinity variations  
 
Page 2


 
OCEANOGRAPHY - 3 
SALINITY OF OCEAN WATERS 
- All waters in nature whether the rain water or ocean water contain 
dissolved mineral salt  
- Salinity is the term used to define the total content of dissolved salts in 
sea water.  
- It is calculated and the amount of salt dissolved in thousand gram of 
sea water  
- It is usually expressed as parts per thousand.  
FACTORS AFFECTING OCEAN SALINITY 
- The salinity of water in the surface layer of oceans depend mainly on 
evaporation and precipitation  
- Surface salinity is greatly influenced in coastal regions by the fresh 
water flow from rivers  
- Surface salinity in polar regions is influenced by process of freezing 
and thawing of ice, inflow of Glacier etc.  
- Wind also influences salinity of an area by transferring water to 
other areas.  
- Ocean currents too contribute to the salinity variations  
 
 
 
 
 
ADDITIONAL INFO: 
IN TROPICS 
- The salinity is higher where the addition of fresh water through rain 
fall, rivers and ice melt is lesser and the rate of evaporation is higher. 
- Conversely the salinity is low in areas receiving a lot of freshwater 
through rainfall, icemelt or rivers and where the loss of water is 
through evaporation is lower  
 
IN POLAR REGIONS 
- The lowest salinity in polar areas in on a count of two factors: 
• rate of evaporation here is very low 
• a large amount of water is added through ice melt  
Page 3


 
OCEANOGRAPHY - 3 
SALINITY OF OCEAN WATERS 
- All waters in nature whether the rain water or ocean water contain 
dissolved mineral salt  
- Salinity is the term used to define the total content of dissolved salts in 
sea water.  
- It is calculated and the amount of salt dissolved in thousand gram of 
sea water  
- It is usually expressed as parts per thousand.  
FACTORS AFFECTING OCEAN SALINITY 
- The salinity of water in the surface layer of oceans depend mainly on 
evaporation and precipitation  
- Surface salinity is greatly influenced in coastal regions by the fresh 
water flow from rivers  
- Surface salinity in polar regions is influenced by process of freezing 
and thawing of ice, inflow of Glacier etc.  
- Wind also influences salinity of an area by transferring water to 
other areas.  
- Ocean currents too contribute to the salinity variations  
 
 
 
 
 
ADDITIONAL INFO: 
IN TROPICS 
- The salinity is higher where the addition of fresh water through rain 
fall, rivers and ice melt is lesser and the rate of evaporation is higher. 
- Conversely the salinity is low in areas receiving a lot of freshwater 
through rainfall, icemelt or rivers and where the loss of water is 
through evaporation is lower  
 
IN POLAR REGIONS 
- The lowest salinity in polar areas in on a count of two factors: 
• rate of evaporation here is very low 
• a large amount of water is added through ice melt  
 
 
IN EQUATOR REGION 
- The chief cause of lowest salinity in the equatorial regions is a large 
amount of rainfall here and the number of large rivers flowing into 
the seas  
- Also the cloudy weather of these regions restricts the rate of water 
loss through evaporation  
HORIZONTAL DISTRIBUTION OF SALINITY 
- The salinity for normal open Ocean ranges between 33 and 37%  
- In the land locked Red Sea, it is as highest 41% why in the estuaries and 
the earth take it fluctuates from 0 to 35 seasonally.  
- In hot and dry regions where evaporation is high, the salinity 
sometimes reaches to 70%  
- Salinity and gradually decreases from the tropics as we move 
northwards. 
- The average salinity of the Indian Ocean is 35 o/oo. The low salinity 
trend is observed in the Bay of Bengal due to influx of river water by 
the river Ganga.  
- On the contrary, the Arabian Sea shows higher salinity due to high 
evaporation and low influx of fresh water 
VERTICAL DISTRIBUTION OF SALINITY 
- Salinity changes with depth, but the weight changes depends upon 
the location of the sea  
- At the surface it increases by the loss of water To evaporation or 
decrease by the input of freshwater such as from the rivers  
- At depth, it is more or less fixed, because there is no way the water is 
lost or more salt is added.  
- There is a marked Difference in the salinity between the surface 
zones and the deep zones of the oceans  
Page 4


 
OCEANOGRAPHY - 3 
SALINITY OF OCEAN WATERS 
- All waters in nature whether the rain water or ocean water contain 
dissolved mineral salt  
- Salinity is the term used to define the total content of dissolved salts in 
sea water.  
- It is calculated and the amount of salt dissolved in thousand gram of 
sea water  
- It is usually expressed as parts per thousand.  
FACTORS AFFECTING OCEAN SALINITY 
- The salinity of water in the surface layer of oceans depend mainly on 
evaporation and precipitation  
- Surface salinity is greatly influenced in coastal regions by the fresh 
water flow from rivers  
- Surface salinity in polar regions is influenced by process of freezing 
and thawing of ice, inflow of Glacier etc.  
- Wind also influences salinity of an area by transferring water to 
other areas.  
- Ocean currents too contribute to the salinity variations  
 
 
 
 
 
ADDITIONAL INFO: 
IN TROPICS 
- The salinity is higher where the addition of fresh water through rain 
fall, rivers and ice melt is lesser and the rate of evaporation is higher. 
- Conversely the salinity is low in areas receiving a lot of freshwater 
through rainfall, icemelt or rivers and where the loss of water is 
through evaporation is lower  
 
IN POLAR REGIONS 
- The lowest salinity in polar areas in on a count of two factors: 
• rate of evaporation here is very low 
• a large amount of water is added through ice melt  
 
 
IN EQUATOR REGION 
- The chief cause of lowest salinity in the equatorial regions is a large 
amount of rainfall here and the number of large rivers flowing into 
the seas  
- Also the cloudy weather of these regions restricts the rate of water 
loss through evaporation  
HORIZONTAL DISTRIBUTION OF SALINITY 
- The salinity for normal open Ocean ranges between 33 and 37%  
- In the land locked Red Sea, it is as highest 41% why in the estuaries and 
the earth take it fluctuates from 0 to 35 seasonally.  
- In hot and dry regions where evaporation is high, the salinity 
sometimes reaches to 70%  
- Salinity and gradually decreases from the tropics as we move 
northwards. 
- The average salinity of the Indian Ocean is 35 o/oo. The low salinity 
trend is observed in the Bay of Bengal due to influx of river water by 
the river Ganga.  
- On the contrary, the Arabian Sea shows higher salinity due to high 
evaporation and low influx of fresh water 
VERTICAL DISTRIBUTION OF SALINITY 
- Salinity changes with depth, but the weight changes depends upon 
the location of the sea  
- At the surface it increases by the loss of water To evaporation or 
decrease by the input of freshwater such as from the rivers  
- At depth, it is more or less fixed, because there is no way the water is 
lost or more salt is added.  
- There is a marked Difference in the salinity between the surface 
zones and the deep zones of the oceans  
 
- It really increases with depth and there is a zone called the halocline 
where salinity increases sharply . 
- Other factors being constant, increasing salinity of sea water causes its 
density to increase  
- High salinity sea water generally sinks below the Lower salinity water. 
This leads to stratification by salinity