Temperature of the Ocean Water and its Importance

Importance of Ocean Temperature

• The temperature of the oceanic water is important for marine organisms including Phytoplanktons and Zooplanktons.

• It is important factor in controlling the movements of large masses of ocean water and their characteristics.

• It is also affects the climate of coastal lands and plants and animals therein.

• The standard type of thermometer is used to measure the surface temperature while reversing thermometers and Thermographs are used to measure the sub-surface temperature.

• With respect to temperature, there are 3 layers of warm oceans from surface to the bottom in the tropics viz.

a) Epilimlion layer &ndash it represents the top layer of warm oceanic water and is 500 m thick with temperature ranging between 20⁰ and 25⁰ c.

b) Thermocline layer &ndash it represents vertical zone of oceanic water below the first layer and is characterized by rapid rate of decrease of temperature with increasing depth.

c) Hypolimlion layer &ndash it is very cold and extends upto the deep ocean floor.

Source of the temperature

• The major source of the temperature of the oceanic water is the sun.

• Some energy, though insignificant is also received from below the bottom and through the compression of sea water.

• The amount of insolation to be received at the sea surface depends on :

I. Angle of sun’s rays

II. Length of day

III. Distance of the earth from the sun

IV. Effects of the atmosphere.

Process of heating and cooling

• There are two process of heating :

- By absorption of radiation from the sun

• - By convection of heat through the ocean bottom from the interior of the earth.

• There are three main processes of cooling :

- By back radiation of heat from the sea surface.

- By convection.

- By evaporation.

Some factors affecting the distribution of temperature of ocean water

1. Latitudes

2. Unequal distribution of land and water

3. Ocean currents

4. Minor factors like submarine ridges, local weather, location and shape of the sea.

5. Prevailing wind.

The temperature of surface water between 40⁰N and 40⁰ S is lower than air temperature but it becomes higher than air temperature between 40⁰latitudes and poles in both the hemispheres.

Horizontal distribution of temperature

• On an average, the temperature of surface water of the ocean is 26.7⁰ c.

• The temperature gradually decreases from equator towards the poles.

• The rate of decrease of temperature with increasing latitudes is generally 0.5⁰F per latitude.

• The oceans in the northern hemisphere records relatively higher average temperature than in the southern hemisphere.

Vertical distribution of temperature

• Maximum temperature of the ocean is always at their surface because it directly receives the Insolation.

• The temperature decreases from the ocean surface with increasing depth.

The oceans are vertically divided into two zones

Photic or euphotic zone &ndash it represents the upper surface upto the depth of 200 m and receives solar radiation.

Aphotic zone &ndash it extends from 200 m depth to the bottom and does not receive solar rays.

Avg. annual temperature of Ocean &ndash 17.2⁰ c
Avg. annual temperature of Surface Water &ndash 26.7⁰ c
Avg. annual temperature for North Hemisphere &ndash 19.4⁰ c
Avg. annual temperature for south Hemisphere - 16.1⁰ c
Avg. annual temperature of Pacific Ocean &ndash 19.10⁰ c
Avg. annual temperature of Atlantic Ocean &ndash 16.91⁰ c
Avg. annual temperature of Indian Ocean &ndash 17⁰ c

This article is shared by Priyanka Duta. Priyanka is a Guest Lecturer of Geography at New Alipore College, Kolkata.