This section deals with the spatial and vertical variations of temperature in various oceans. Ocean waters get heated up by the solar energy just as land. The process of heating and cooling of the oceanic water is slower than land. UPSC GS paper 1 requires proper understanding of oceans. UPSC aspirants should be understand this topic carefully.

TOPICS

  • Verticle temperature distribution of ocean
  • Horizontal temperature distribution of ocean
  • Factors affecting temperature distribution

VERTICLE TEMPERATURE DISTRIBUTION

The temperature-depth profile for the ocean water shows how the temperature decreases with the increasing depth. The profile shows a boundary region between the surface waters of the ocean and the deeper layers. The boundary usually begins around 100 - 400 m below the sea surface and extends several hundred of metres downward  This boundary region, from where there is a rapid decrease of temperature, is called the thermoclirie. About 90 per cent of the total volume of water is found below the thermocline in the deep ocean. In this zone, temperatures approach 0° C It results into decrease of temperature with the increasing depth, but the rate of decrease is not uniform throughout. The temperature falls very rapidly up to the depth of 200 m and thereafter, the rate of decrease of temperature is slowed down.

A three-layer system

  • 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 characterised by rapid decrease in temperature with increasing depth. The thermocline is 500 -1,000 m thick

  • The third layer is very cold and extends upto the deep ocean floor. In the Arctic and Antartic circles, the surface water temperatures are close to 0° C and so the temperature change with the depth is very slight. Here, only one layer of cold water exists, which extends from surface to deep ocean floor.

HORIZONTAL TEMPERATURE DISTRIBUTION

  • 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 average temperature is around 22°C at 20° latitudes, 14° C at 40° latitudes and 0° C near poles.

  • The oceans in the northern hemisphere record relatively highertemperature than in the southern hemisphere. The highest temperature is not recorded at the equator but slightly towards north of it.

  • The average annual temperatures for the northern and southern hemisphere are around 19° C and 16° C respectively. This variation is due to the unequal distribution of land and water in the northern   and  southern   hemispheres shows the spatial pattern of surface temperature of the oceans.

  • It is a well known fact that the maximum temperature of the oceans is always at their surfaces because they directly receive the heat from the sun and  the  heat is transmitted  to the lower sections of the oceans through the process of convection.

FACTORS AFFECTING TEMPERATURE DISTRIBUTION

  • Latitude : the temperature of surface water decreases from the equator towards the poles because the amount of insolation decreases

  • 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.

  • Prevailing wind: the winds blowing from the land towards the oceans drive warm surface water away form the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature. Contrary to this, the onshore winds pile up warm water near the coast and this raises the temperature.

  • Ocean currents warm ocean currents raise the temperature in cold areas while the cold currents decrease the temperature in warm ocean areas. Gulf stream (warm current) raises the temperature near the eastern coast of North America and the West Coast of Europe while the Labrador current (cold current) lowers the temperature near the north-east coast of North America.

All these factors influence the temperature of the ocean currents locally. The enclosed seas in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas.

This articles discusses the the distributionof temperature in oceans, which plays and important role in decinding the climate of a region. To read more articles on geography, click here