Oceanography- 5 | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
OCEANOGRAPHY - 5 
OCEAN CURRENTS 
Ocean currents are like river flow in oceans.  
They represent a regular volume of water in a definite path and 
direction.  
Ocean currents are influenced by two types of forces namely;  
• Primary forces that initiate the movement of water  
• Secondary forces that influence the currents to flow  
 
PRIMARY FORCES  
• Heating by solar energy 
Heating by the solar energy causes the water to expand. That is very 
near the equator, the ocean water is about 8 centimetre higher in 
level than in middle latitude. This causes a very slight gradient and 
water tends to flow down the slope.  
 
• Wind 
Wind blowing on the surface of the ocean pushes the water to move.  
Friction between the wind and the water surface affects the 
movement of the water body in its course . 
Winds are responsible for both magnitude and direction . Monsoon 
winds are responsible for the seasonal reversal of ocean currents in 
the Indian ocean. 
 
• Gravity  
Gravity tends to pull the water down the pile and create gradient 
variation . 
 
Page 2


 
OCEANOGRAPHY - 5 
OCEAN CURRENTS 
Ocean currents are like river flow in oceans.  
They represent a regular volume of water in a definite path and 
direction.  
Ocean currents are influenced by two types of forces namely;  
• Primary forces that initiate the movement of water  
• Secondary forces that influence the currents to flow  
 
PRIMARY FORCES  
• Heating by solar energy 
Heating by the solar energy causes the water to expand. That is very 
near the equator, the ocean water is about 8 centimetre higher in 
level than in middle latitude. This causes a very slight gradient and 
water tends to flow down the slope.  
 
• Wind 
Wind blowing on the surface of the ocean pushes the water to move.  
Friction between the wind and the water surface affects the 
movement of the water body in its course . 
Winds are responsible for both magnitude and direction . Monsoon 
winds are responsible for the seasonal reversal of ocean currents in 
the Indian ocean. 
 
• Gravity  
Gravity tends to pull the water down the pile and create gradient 
variation . 
 
 
• Coriolis force 
 The coriolis force intervenes and causes the water to move to the 
right in the Northern hemisphere and to the left in the southern 
hemisphere. This is large accumulation of water and the flow around 
them are called gyres. These produce large circular currents in all the 
ocean basins . 
One such circular current is the Sargasso Sea. 
 
 
SECONDARY FORCES  
Differences in water density affect the vertical mobility of ocean 
currents  
Water with highest salinity is denser than the water with low salinity 
Cold water is denser than warm water. It into sink by relatively lighter 
water tends to rise.  
 
CLASSIFICATION OF CURRENTS 
 
 BASIS OF DEPTH 
Surface currents: 
They constituent about 10% of all the water in the ocean, these 
waters are the upper 400m of the ocean. 
 
Deep water currents:  
These currents make up the other 90% of the ocean water. These 
water mover around the ocean basins due to  variation in gravity and 
the density. 
 
BASIS OF TEMPERATURE 
Page 3


 
OCEANOGRAPHY - 5 
OCEAN CURRENTS 
Ocean currents are like river flow in oceans.  
They represent a regular volume of water in a definite path and 
direction.  
Ocean currents are influenced by two types of forces namely;  
• Primary forces that initiate the movement of water  
• Secondary forces that influence the currents to flow  
 
PRIMARY FORCES  
• Heating by solar energy 
Heating by the solar energy causes the water to expand. That is very 
near the equator, the ocean water is about 8 centimetre higher in 
level than in middle latitude. This causes a very slight gradient and 
water tends to flow down the slope.  
 
• Wind 
Wind blowing on the surface of the ocean pushes the water to move.  
Friction between the wind and the water surface affects the 
movement of the water body in its course . 
Winds are responsible for both magnitude and direction . Monsoon 
winds are responsible for the seasonal reversal of ocean currents in 
the Indian ocean. 
 
• Gravity  
Gravity tends to pull the water down the pile and create gradient 
variation . 
 
 
• Coriolis force 
 The coriolis force intervenes and causes the water to move to the 
right in the Northern hemisphere and to the left in the southern 
hemisphere. This is large accumulation of water and the flow around 
them are called gyres. These produce large circular currents in all the 
ocean basins . 
One such circular current is the Sargasso Sea. 
 
 
SECONDARY FORCES  
Differences in water density affect the vertical mobility of ocean 
currents  
Water with highest salinity is denser than the water with low salinity 
Cold water is denser than warm water. It into sink by relatively lighter 
water tends to rise.  
 
CLASSIFICATION OF CURRENTS 
 
 BASIS OF DEPTH 
Surface currents: 
They constituent about 10% of all the water in the ocean, these 
waters are the upper 400m of the ocean. 
 
Deep water currents:  
These currents make up the other 90% of the ocean water. These 
water mover around the ocean basins due to  variation in gravity and 
the density. 
 
BASIS OF TEMPERATURE 
 
Cold currents:  
They bring cold water into warm water areas. Cold water ocean currents 
occur when the cold water at the poles thing and slowly moves 
towards the equator . 
These currents are usually found on the west coast of the continents in 
the low and middle latitudes (true in both hemispheres) and on the 
east coast in the higher latitudes in the Northern Hemisphere. 
 
Warm currents: T 
They bring warm water into cold water areas. Warm water currents travel 
out from the equator along the surface flowing towards the poles to 
replace the sinking cold water. 
These are usually observed on the east coast of continents in the low 
and middle latitudes (true in both hemispheres). In the northern 
hemisphere they are found on the west coasts of continents in high 
latitudes. 
 
EFFECTS OF OCEAN CURRENTS 
1. DESERT FORMATION 
Cold ocean currents have a direct effect on desert formation in West 
Coast regions of the Tropical and subtropical continents. There is fog 
and most of the areas are error due to the loss of moisture  
2. RAINS 
- Warm ocean currents bring rain to coastal areas and even interiors  
3. MODERATING EFFECT 
These are responsible for moderate temperature at coasts.  
4. FISHING 
Cold and warm ocean currents mixing brings the richest fishing 
Grounds in the world. 
Page 4


 
OCEANOGRAPHY - 5 
OCEAN CURRENTS 
Ocean currents are like river flow in oceans.  
They represent a regular volume of water in a definite path and 
direction.  
Ocean currents are influenced by two types of forces namely;  
• Primary forces that initiate the movement of water  
• Secondary forces that influence the currents to flow  
 
PRIMARY FORCES  
• Heating by solar energy 
Heating by the solar energy causes the water to expand. That is very 
near the equator, the ocean water is about 8 centimetre higher in 
level than in middle latitude. This causes a very slight gradient and 
water tends to flow down the slope.  
 
• Wind 
Wind blowing on the surface of the ocean pushes the water to move.  
Friction between the wind and the water surface affects the 
movement of the water body in its course . 
Winds are responsible for both magnitude and direction . Monsoon 
winds are responsible for the seasonal reversal of ocean currents in 
the Indian ocean. 
 
• Gravity  
Gravity tends to pull the water down the pile and create gradient 
variation . 
 
 
• Coriolis force 
 The coriolis force intervenes and causes the water to move to the 
right in the Northern hemisphere and to the left in the southern 
hemisphere. This is large accumulation of water and the flow around 
them are called gyres. These produce large circular currents in all the 
ocean basins . 
One such circular current is the Sargasso Sea. 
 
 
SECONDARY FORCES  
Differences in water density affect the vertical mobility of ocean 
currents  
Water with highest salinity is denser than the water with low salinity 
Cold water is denser than warm water. It into sink by relatively lighter 
water tends to rise.  
 
CLASSIFICATION OF CURRENTS 
 
 BASIS OF DEPTH 
Surface currents: 
They constituent about 10% of all the water in the ocean, these 
waters are the upper 400m of the ocean. 
 
Deep water currents:  
These currents make up the other 90% of the ocean water. These 
water mover around the ocean basins due to  variation in gravity and 
the density. 
 
BASIS OF TEMPERATURE 
 
Cold currents:  
They bring cold water into warm water areas. Cold water ocean currents 
occur when the cold water at the poles thing and slowly moves 
towards the equator . 
These currents are usually found on the west coast of the continents in 
the low and middle latitudes (true in both hemispheres) and on the 
east coast in the higher latitudes in the Northern Hemisphere. 
 
Warm currents: T 
They bring warm water into cold water areas. Warm water currents travel 
out from the equator along the surface flowing towards the poles to 
replace the sinking cold water. 
These are usually observed on the east coast of continents in the low 
and middle latitudes (true in both hemispheres). In the northern 
hemisphere they are found on the west coasts of continents in high 
latitudes. 
 
EFFECTS OF OCEAN CURRENTS 
1. DESERT FORMATION 
Cold ocean currents have a direct effect on desert formation in West 
Coast regions of the Tropical and subtropical continents. There is fog 
and most of the areas are error due to the loss of moisture  
2. RAINS 
- Warm ocean currents bring rain to coastal areas and even interiors  
3. MODERATING EFFECT 
These are responsible for moderate temperature at coasts.  
4. FISHING 
Cold and warm ocean currents mixing brings the richest fishing 
Grounds in the world. 
 
5. CLIMATE  
Foggy weather and drizzle in the mixing zones of cold and warm 
currents.  
They pile up warm waters and this warm water is the major force 
behind tropical cyclones. 
6. NAVIGATION 
Ships usually follow routes which are aided by ocean currents and 
winds.