The document discusses the physical structure of oceans, including temperature, salinity, density, and how they vary with depth and location. It introduces key concepts like thermocline (layer with a sharp temperature gradient), halocline (layer with a sharp salinity gradient), and pycnocline (layer with a sharp density gradient). The oceans have three main layers - a surface layer that is warm, saline and experiences fluctuations; a pycnocline layer that separates the surface and deep layers and contains a density gradient; and a deep layer that originates from high latitudes and flows equatorward. Thermocline typically coincides with pycnocline in mid-latitudes.

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

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

9. 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

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

14. 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

15. • 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.

16. 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.

18. Density stratification causes 3 layer structure
of water column in ocean
1. 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 high latitudes.

19. • 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.

20. • 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.

22. 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...............

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