Oceanography thermocline.pptx PRESENTED BY Dr. PK Anthwal

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1. Oceanography Thermocline, halocline, Pycnocline with quiz By Dr. Pramod Kumar Anthwal

2. Physicochemical structure of the oceans 1. Temperature - Isotherms - these are imaginary lines connecting the points of equal temperature running east west parallel to latitude Insolation - amount of solar radiation received by the Earth surface. Latitude controls the distribution of temperature through insolation and it is also subject to variability with respect to seasons . Because temperature is variable with respect to seasons and latitude,   Isotherms shifts are significant in North Pacific and North Atlantic ocean.

3. Thermocline When two water masses are separated from each other by a band of water which have A Sharp temperature gradient .   Or when temperature changes rapidly with depth . Thermocline is a permanent hydrographic feature of temperate and tropical oceans

4. Seasonal Thermocline Forms due to intense solar heating about 40-100 meter in the oceans of mid latitudes.

5. Salinity Function of latitudes and directly depends upon the latitude . Highest salinity value occur between 20 and 30° North and South latitude and decrease towards equator and poles .   Maximum salinity values occur in subtropics whereas minimum values occur near the equator and the polar regions

6. Halocline Layer of rapidly changing salinity which separate two distinct water masses. Indicates sharp salinity gradient existence.

7. Density Depends upon temperature, salinity, pressure of seawater . It controls the vertical structure of water column. As temperature increases, sea water density decreases due to thermal expansion. Salinity increases, then the sea water density increases due to addition of dissolved material which have higher atomic mass than the water molecule. With increase in pressure, water density increases due to compressive effect of pressure

8. A cold saline water is more dense than the warm fresh water. High saline water can overlie low saline water provided the surface temperature is very high.

9. Isopycnocline and pycnocline Line connecting the points of equal density. The density of seawater increase with increasing in depth. Layer of rapidly changing density with depth or sharp density gradient. Pycnocline is absent in polar regions.

10. Density stratification causes 3 layer structure of water column in ocean Surface water- It is about 100 meter thick, 2% of the ocean volume and dense , Warm temperature diurnal seasonal annual fluctuation of salinity and, Water temperature in polar region, is too low, cooling of surface water produce dense water, that will sink, which prevents the formation of pynocline in h igh latitudes.

11. Pycnocline layer- Boundary between surface layer and deep layer. Density gradient exist It is also known as thermocline layer because temperature also control density. It contains 18% of ocean water by volume. In mid latitudes pycnocline coincide with thermocline.

12. Deep layer:- 80% of oceanic water by volume The bulk of this layer originates from high latitudes. Water sink to the ocean bottom and then flows equator ward preventing the formation of pycnocline in high latitudes.

13. Quiz Q1. The word subtropics is used to indicate which number of latitude.... Q2 . The shifting of isotherms is significant in which oceans . Q3. Thermocline is considered as a permanent feature ............ Q4.in low latitude thermocline is - ------and in high latitude thermocline is…….. Q5. The seasonal thermocline is found in   oceans of .............. Q6. The typical depth of seasonal thermocline is........... 07 The maximum salinity value occur in between ...............

14. Isopycnocline line is……… Typical depth of thermocline and pycnocline is…… The average salinity of sea water is………..