Oceans are a vast body of salt water that covers almost three to fourths of the earth's surface. Seas are smaller, found on the margins of the ocean and are partially enclosed by land. Seawater: High density, high heat capacity, colder, salty and slightly compressible (its volume decreases under pressure), thus its density increases with pressure. Why is Ocean Circulation Important? •Similar to winds in the atmosphere, they transfer significant amounts of heat from equatorial areas to the poles and thus play important roles in determining the climates of coastal regions. •The ocean circulation pattern exchanges water of varying characteristics, such as temperature and salinity •ocean currents and atmospheric circulation influence one another. •in addition, they transport nutrients and organisms

1. Ocean Currents
Omer M. Ahmed
MSc, 2016
University of Kerala, India.

2. INTRODUCTION
• Oceans are vast body of salt water that covers almost three
to fourths of the earth's surface.
• Seas are smaller, found on the margins of the ocean and are
partially enclosed by land.
• Seawater:
High density, high heat capacity, colder, salty and slightly
compressible (its volume decreases under pressure), thus its
density increases with pressure.

3. Why is Ocean Circulation Important?
• Similar to winds in the atmosphere, they transfer significant
amounts of heat from equatorial areas to the poles and thus play
important roles in determining the climates of coastal regions.
• The ocean circulation pattern exchanges water of varying
characteristics, such as temperature and salinity
• Ocean currents and atmospheric circulation influence one
another.
• In addition they transport nutrients and organisms

4. Ocean Current
• Stream made up of horizontal and vertical components of the
circulation system of ocean waters that is produced by gravity,
wind friction, and water density variation in different parts of
the ocean.
• There are two type of Ocean Currents:
Surface Currents (Surface Circulation)
From surface — 400 meters, make about 10% of the currents.
Deep Water Currents (Thermo Haline Circulation)
Stared from below 400 M up to the ocean basins, Waters make up
90% of the ocean.

5. Types of the Ocean currents

6. Surface currents
• Generated by wind and solar heating.
• Their patterns are controlled by
 Wind direction.
 Gravity tend to pull the water down the "hill" or pile of
water against the pressure gradient.
 Coriolis force intervenes and cause the water to move to
the right (in the northern hemisphere) and to the left in
the southern hemisphere.

7. Gyres
• Large mounds of water and the flows around them.
• An ocean gyre is a large system of circular ocean currents
formed by global wind patterns and forces created by Earth’s
rotation.
• They are very deep, cold and relatively slow current, but carries
a vast mass of water about twice the volume of the Gulf Stream.
• Forming strong western boundary currents against the eastern
coasts of the continents.
• In the Southern Hemisphere the clockwise circulation of the
gyres creates strong eastern boundary currents against the
western coasts of continents.

8. World Gyres

9. Five main gyres have been recognized
(one in each ocean basin)
1. North Pacific gyre
2. South Pacific gyre
3. North Atlantic gyre
4. South Atlantic gyre
5. Indian gyre
• Generally 4 currents in each gyre
• Centered about 30o north or south latitude
Gyres contin…

10. Ekman Transport (ET)
• Ekman spiral describes speed and direction of
seawater flow at different depths
• Surface currents move at angle to wind 45o.
• 90o to right of wind in Northern hemisphere.
• 90o to left of wind in Southern hemisphere.

11. Ekman Transport (ET)

12. Upwelling
• A very practical and important consequence of the ET is
the vertical upward movement (upwelling) of water that
results from the transport.
• This upwelled water comes from below the surface and is
one of the few ways in which water is exchanged upward
across the thermocline.
• There are two primary locations in which upwelling
occurs:
• Coastal Upwelling
• Equatorial Upwelling

13. • Coastal Upwelling
In the Northern Hemisphere, a steady wind blowing from the north
parallel with a western coastline, in water more than 100 M in
depth may create ET offshore that moves the surface water
horizontally away from the coast. Since there is no substantial
supply of surface water to replace that transported offshore, water
from below 100 m rises to replace it, creating Coastal Upwelling.
• Equatorial Upwelling
Caused by the NE Trade Winds north of the equator and the SE
Trade Winds south of the equator converge at an angle toward the
equator.

14. Upwelling

15. Gulf Stream
• It is like a gigantic river flowing through the ocean,
• Never ending flow of warm water from the Gulf of Mexico all
the way to the Arctic Ocean.
• It is the most famous current in the Atlantic Ocean and keeps
Europe warmer than it really should be.
• At 30 degrees N it splits into two currents with the northern
stream heading to Europe and the southern stream going to
West Africa and then back toward the Caribbean to complete
the process.
• The Gulf Stream is one of the fastest currents in the ocean
flowing at a rate of 2 meters per second.

16. Gulf Stream
.Cold water
.Worm water

17. El Niño
• The phenomena is caused by the arrival of warm water to the
coast of Peru around Christmas time causing abnormally high
surface ocean temperatures.
• Occurs every 2 to 7 years with various degrees of strength,
effects on both climate and weather which is the Southern
Oscillation.
• The Southern Oscillation is a back and forth variation in
atmospheric pressure between a high pressure system in the west
coast of South America and a low pressure system western
Pacific near Indonesia and Australia.
• In the U.S. El Niño conditions result in heavy rains, flooding,
landslides, and tornadoes in greater than normal amounts.

18. La Niña
• Conditions have about the opposite effect of the El Niño
conditions.
• Drier conditions in North and South America, more
hurricanes in the Atlantic.
• And wetter conditions in Australia and Indonesia.

20. Deep water currents
When the surface wind-driven currents generate upwelling currents in
conjunction with landforms, creating deep water currents.
• Decreasing temperature Water molecules cool down, become denser
and sinks.
• Increasing salinity, through the freezing of the surface water or
evaporation and that leads to increase the density.
• Denser water sinks to ocean floor and forms deep currents.
• At high latitudes they sink deep into the ocean basins
• These currents are not fully understood.

21. CONCLUSION
• Two types of the currents made up in the the ocean; surface
currents and deep currents.
• Understanding the role of the ocean in climate change requires
an understanding of the dynamics of ocean circulation changes.
• Ocean currents responsible from many atmospheric conditions
such as : Gyres, Gulf streams, Upwelling, El Niño and
La Niña.

22. REFERENCES :
• John E. Oliver, John J. Hindore (2002), Climatology an atmospheric science, Pearson
Education, Inc, 2nd edition, 410 P.
• http://faculty.montgomerycollege.edu/gyouth/FP_examples/student_examples/connor
_peace/gulfstream.html
• https://www.britannica.com/science/ocean-current
• https://www.earth.usc.edu/~stott/Catalina/Oceans.htm
• http://www4.ncsu.edu/~ceknowle/chapter07/part1.html#Upwelling

23. Thank
omerupto3@gmail.com