Oceanography- 2 | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
OCEANOGRAPHY - 2  
TEMPERATURE OF OCEAN WAVES 
- This section deals with the spatial and vertical variations of 
temperature in various oceans  
THE OCEAN WATER IS HEATED BY THREE PROCESSES: 
- Absorption of sun’s radiation. 
- The conventional currents: Since the temperature of the earth increases 
with increasing depth, the ocean water at great depths is heated faster than 
the upper water layers. So, convectional oceanic circulations develop 
causing circulation of heat in water. 
- Heat is produced due to friction caused by the surface wind and the 
tidal currents which increase stress on the water body. 
THE OCEAN WATER IS COOLED BY: 
- Back radiation (heat budget) from the sea surface takes place as the solar 
energy once received is reradiated as long wave radiation (terrestrial 
radiation or infrared radiation) from the seawater. 
- Exchange of heat between the sea and the atmosphere if there is 
temperature difference. 
- Evaporation:  
FACTORS AFFECTING TEMPERATURE DISTRIBUTION 
 
1. LATITUDE 
- The temperature of surface water decreases from the equator 
towards the poles because the amount of insolation decreases 
poleward . 
 
2. UNEQUAL DISTRIBUTION OF LAND AND WATER 
Page 2


 
OCEANOGRAPHY - 2  
TEMPERATURE OF OCEAN WAVES 
- This section deals with the spatial and vertical variations of 
temperature in various oceans  
THE OCEAN WATER IS HEATED BY THREE PROCESSES: 
- Absorption of sun’s radiation. 
- The conventional currents: Since the temperature of the earth increases 
with increasing depth, the ocean water at great depths is heated faster than 
the upper water layers. So, convectional oceanic circulations develop 
causing circulation of heat in water. 
- Heat is produced due to friction caused by the surface wind and the 
tidal currents which increase stress on the water body. 
THE OCEAN WATER IS COOLED BY: 
- Back radiation (heat budget) from the sea surface takes place as the solar 
energy once received is reradiated as long wave radiation (terrestrial 
radiation or infrared radiation) from the seawater. 
- Exchange of heat between the sea and the atmosphere if there is 
temperature difference. 
- Evaporation:  
FACTORS AFFECTING TEMPERATURE DISTRIBUTION 
 
1. LATITUDE 
- The temperature of surface water decreases from the equator 
towards the poles because the amount of insolation decreases 
poleward . 
 
2. UNEQUAL DISTRIBUTION OF LAND AND WATER 
 
- The oceans in the Northern hemisphere receive more heat due to 
their contact with larger extent of land than the oceans in the 
southern hemisphere  
 
3. PREVAILING WIND 
- The winds blowing from the land towards the ocean drive warm 
surface water away from the coast resulting in the upwelling of cold 
water from below  . The replacement of warm water by cold water 
results into longitudinal variation in the temperature in ocean 
 
4. OCEAN CURRENTS 
- Warm ocean currents raise the temperature in Cold areas will the 
cold currents decrease the temperature and warm Ocean areas.  
- Gulf Stream (warm current) raises the temperature near the eastern 
coast of the North America and the West Coast of Europe by the 
labrador current (cold current) lowers the temperature near the 
Northeast Coat of North America. 
 
OTHER FACTORS: 
Heat loss: The loss of energy by reflection, scattering, evaporation 
and radiation. 
 
Albedo: The albedo of the sea (depending on the angle of sun rays).  
 
The physical characteristics of the sea surface: Boiling point of the 
sea water is increased in the case of higher salinity and vice versa 
 
HORIZONTAL AND VERTICAL DSITRIBUTION OF 
TEMPERATURE 
Page 3


 
OCEANOGRAPHY - 2  
TEMPERATURE OF OCEAN WAVES 
- This section deals with the spatial and vertical variations of 
temperature in various oceans  
THE OCEAN WATER IS HEATED BY THREE PROCESSES: 
- Absorption of sun’s radiation. 
- The conventional currents: Since the temperature of the earth increases 
with increasing depth, the ocean water at great depths is heated faster than 
the upper water layers. So, convectional oceanic circulations develop 
causing circulation of heat in water. 
- Heat is produced due to friction caused by the surface wind and the 
tidal currents which increase stress on the water body. 
THE OCEAN WATER IS COOLED BY: 
- Back radiation (heat budget) from the sea surface takes place as the solar 
energy once received is reradiated as long wave radiation (terrestrial 
radiation or infrared radiation) from the seawater. 
- Exchange of heat between the sea and the atmosphere if there is 
temperature difference. 
- Evaporation:  
FACTORS AFFECTING TEMPERATURE DISTRIBUTION 
 
1. LATITUDE 
- The temperature of surface water decreases from the equator 
towards the poles because the amount of insolation decreases 
poleward . 
 
2. UNEQUAL DISTRIBUTION OF LAND AND WATER 
 
- The oceans in the Northern hemisphere receive more heat due to 
their contact with larger extent of land than the oceans in the 
southern hemisphere  
 
3. PREVAILING WIND 
- The winds blowing from the land towards the ocean drive warm 
surface water away from the coast resulting in the upwelling of cold 
water from below  . The replacement of warm water by cold water 
results into longitudinal variation in the temperature in ocean 
 
4. OCEAN CURRENTS 
- Warm ocean currents raise the temperature in Cold areas will the 
cold currents decrease the temperature and warm Ocean areas.  
- Gulf Stream (warm current) raises the temperature near the eastern 
coast of the North America and the West Coast of Europe by the 
labrador current (cold current) lowers the temperature near the 
Northeast Coat of North America. 
 
OTHER FACTORS: 
Heat loss: The loss of energy by reflection, scattering, evaporation 
and radiation. 
 
Albedo: The albedo of the sea (depending on the angle of sun rays).  
 
The physical characteristics of the sea surface: Boiling point of the 
sea water is increased in the case of higher salinity and vice versa 
 
HORIZONTAL AND VERTICAL DSITRIBUTION OF 
TEMPERATURE 
 
 
- Generally the maximum temperature of the oceans is at their 
surfaces  
- This is because they directly receive the heat from the sun and the 
heat is transmitted to the lower sections of the ocean to the process of 
convection  
- This result in to decrease of temperature with the increasing depth 
but the rate of decrease is not uniform throughout. 
- The profile shows a boundary region between the surface waters of 
the ocean and the deeper layers. 
- The boundary usually begin around hundred to 400 metre below the 
sea level and extend hundreds of metre down words.  
- This boundary region from where there is a rapid decrease of 
temperature is called the thermocline . 
- About 90% of total volume of water is Found below the thermocline 
in the deep ocean. 
 
Page 4


 
OCEANOGRAPHY - 2  
TEMPERATURE OF OCEAN WAVES 
- This section deals with the spatial and vertical variations of 
temperature in various oceans  
THE OCEAN WATER IS HEATED BY THREE PROCESSES: 
- Absorption of sun’s radiation. 
- The conventional currents: Since the temperature of the earth increases 
with increasing depth, the ocean water at great depths is heated faster than 
the upper water layers. So, convectional oceanic circulations develop 
causing circulation of heat in water. 
- Heat is produced due to friction caused by the surface wind and the 
tidal currents which increase stress on the water body. 
THE OCEAN WATER IS COOLED BY: 
- Back radiation (heat budget) from the sea surface takes place as the solar 
energy once received is reradiated as long wave radiation (terrestrial 
radiation or infrared radiation) from the seawater. 
- Exchange of heat between the sea and the atmosphere if there is 
temperature difference. 
- Evaporation:  
FACTORS AFFECTING TEMPERATURE DISTRIBUTION 
 
1. LATITUDE 
- The temperature of surface water decreases from the equator 
towards the poles because the amount of insolation decreases 
poleward . 
 
2. UNEQUAL DISTRIBUTION OF LAND AND WATER 
 
- The oceans in the Northern hemisphere receive more heat due to 
their contact with larger extent of land than the oceans in the 
southern hemisphere  
 
3. PREVAILING WIND 
- The winds blowing from the land towards the ocean drive warm 
surface water away from the coast resulting in the upwelling of cold 
water from below  . The replacement of warm water by cold water 
results into longitudinal variation in the temperature in ocean 
 
4. OCEAN CURRENTS 
- Warm ocean currents raise the temperature in Cold areas will the 
cold currents decrease the temperature and warm Ocean areas.  
- Gulf Stream (warm current) raises the temperature near the eastern 
coast of the North America and the West Coast of Europe by the 
labrador current (cold current) lowers the temperature near the 
Northeast Coat of North America. 
 
OTHER FACTORS: 
Heat loss: The loss of energy by reflection, scattering, evaporation 
and radiation. 
 
Albedo: The albedo of the sea (depending on the angle of sun rays).  
 
The physical characteristics of the sea surface: Boiling point of the 
sea water is increased in the case of higher salinity and vice versa 
 
HORIZONTAL AND VERTICAL DSITRIBUTION OF 
TEMPERATURE 
 
 
- Generally the maximum temperature of the oceans is at their 
surfaces  
- This is because they directly receive the heat from the sun and the 
heat is transmitted to the lower sections of the ocean to the process of 
convection  
- This result in to decrease of temperature with the increasing depth 
but the rate of decrease is not uniform throughout. 
- The profile shows a boundary region between the surface waters of 
the ocean and the deeper layers. 
- The boundary usually begin around hundred to 400 metre below the 
sea level and extend hundreds of metre down words.  
- This boundary region from where there is a rapid decrease of 
temperature is called the thermocline . 
- About 90% of total volume of water is Found below the thermocline 
in the deep ocean. 
 
 
LAYERS:  
- The temperature structure of oceans over middle and lower latitude 
can be described as a three layer system from surface to the bottom  
- The first layer represents the top layer of warm oceanic water and it 
is about 500m thick with temperatures ranging between 20° and 25° 
C.  
- This layer, within the tropical region, is present throughout the year 
but in mid-latitudes it develops only during summer. 
- The second layer called the thermocline layer lies below the first layer 
and is characterized by rapid decrease in temperature with 
increasing depth. The thermocline is 500 -1,000 m thick. 
- The third layer is very cold and extends up to the deep ocean floor. 
Here the temperature becomes almost stagnant. 
NOTE: 
- In the Arctic and Antarctic circle the surface water temperature are 
very close to 0 degree Celsius and so the temperature change with the 
depth is very slight.  Here only one layer of cold water exist which 
extends from surface to deep ocean floor . 
- The rate of decrease of temperature with depths is greater at the 
equator than at the poles. 
- The surface temperature and its downward decrease is influenced by 
the upwelling of bottom water 
 
HORIZONTAL TEMPERATURE DISTRIBUTION OF OCEANS 
The average temperature of surface water of the oceans is about 27°C and 
it gradually decreases from the equator towards the poles. 
The rate of decrease of temperature with increasing latitude is generally 
0.5°C per latitude. 
Page 5


 
OCEANOGRAPHY - 2  
TEMPERATURE OF OCEAN WAVES 
- This section deals with the spatial and vertical variations of 
temperature in various oceans  
THE OCEAN WATER IS HEATED BY THREE PROCESSES: 
- Absorption of sun’s radiation. 
- The conventional currents: Since the temperature of the earth increases 
with increasing depth, the ocean water at great depths is heated faster than 
the upper water layers. So, convectional oceanic circulations develop 
causing circulation of heat in water. 
- Heat is produced due to friction caused by the surface wind and the 
tidal currents which increase stress on the water body. 
THE OCEAN WATER IS COOLED BY: 
- Back radiation (heat budget) from the sea surface takes place as the solar 
energy once received is reradiated as long wave radiation (terrestrial 
radiation or infrared radiation) from the seawater. 
- Exchange of heat between the sea and the atmosphere if there is 
temperature difference. 
- Evaporation:  
FACTORS AFFECTING TEMPERATURE DISTRIBUTION 
 
1. LATITUDE 
- The temperature of surface water decreases from the equator 
towards the poles because the amount of insolation decreases 
poleward . 
 
2. UNEQUAL DISTRIBUTION OF LAND AND WATER 
 
- The oceans in the Northern hemisphere receive more heat due to 
their contact with larger extent of land than the oceans in the 
southern hemisphere  
 
3. PREVAILING WIND 
- The winds blowing from the land towards the ocean drive warm 
surface water away from the coast resulting in the upwelling of cold 
water from below  . The replacement of warm water by cold water 
results into longitudinal variation in the temperature in ocean 
 
4. OCEAN CURRENTS 
- Warm ocean currents raise the temperature in Cold areas will the 
cold currents decrease the temperature and warm Ocean areas.  
- Gulf Stream (warm current) raises the temperature near the eastern 
coast of the North America and the West Coast of Europe by the 
labrador current (cold current) lowers the temperature near the 
Northeast Coat of North America. 
 
OTHER FACTORS: 
Heat loss: The loss of energy by reflection, scattering, evaporation 
and radiation. 
 
Albedo: The albedo of the sea (depending on the angle of sun rays).  
 
The physical characteristics of the sea surface: Boiling point of the 
sea water is increased in the case of higher salinity and vice versa 
 
HORIZONTAL AND VERTICAL DSITRIBUTION OF 
TEMPERATURE 
 
 
- Generally the maximum temperature of the oceans is at their 
surfaces  
- This is because they directly receive the heat from the sun and the 
heat is transmitted to the lower sections of the ocean to the process of 
convection  
- This result in to decrease of temperature with the increasing depth 
but the rate of decrease is not uniform throughout. 
- The profile shows a boundary region between the surface waters of 
the ocean and the deeper layers. 
- The boundary usually begin around hundred to 400 metre below the 
sea level and extend hundreds of metre down words.  
- This boundary region from where there is a rapid decrease of 
temperature is called the thermocline . 
- About 90% of total volume of water is Found below the thermocline 
in the deep ocean. 
 
 
LAYERS:  
- The temperature structure of oceans over middle and lower latitude 
can be described as a three layer system from surface to the bottom  
- The first layer represents the top layer of warm oceanic water and it 
is about 500m thick with temperatures ranging between 20° and 25° 
C.  
- This layer, within the tropical region, is present throughout the year 
but in mid-latitudes it develops only during summer. 
- The second layer called the thermocline layer lies below the first layer 
and is characterized by rapid decrease in temperature with 
increasing depth. The thermocline is 500 -1,000 m thick. 
- The third layer is very cold and extends up to the deep ocean floor. 
Here the temperature becomes almost stagnant. 
NOTE: 
- In the Arctic and Antarctic circle the surface water temperature are 
very close to 0 degree Celsius and so the temperature change with the 
depth is very slight.  Here only one layer of cold water exist which 
extends from surface to deep ocean floor . 
- The rate of decrease of temperature with depths is greater at the 
equator than at the poles. 
- The surface temperature and its downward decrease is influenced by 
the upwelling of bottom water 
 
HORIZONTAL TEMPERATURE DISTRIBUTION OF OCEANS 
The average temperature of surface water of the oceans is about 27°C and 
it gradually decreases from the equator towards the poles. 
The rate of decrease of temperature with increasing latitude is generally 
0.5°C per latitude. 
 
The horizontal temperature distribution is shown by isothermal lines, i.e., 
lines joining places of equal temperature. 
Isotherms are closely spaced when the temperature difference is high and 
vice versa.