1. Chapter 3 Chemical and Physical Features of the Oceans Why study this?
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2. Part Two: Ocean Circulation
Perpetual Ocean Video
Currents move and mix ocean waters
Transport/Move around:

3. Surface Circulation ___________ drives strongest ocean currents
occur in surface layer
Wind and surface currents:
Driven by:
Influenced by:

4. Coriolis Effect
Because Earth is rotating, anything that moves over the surface tends to turn a little rather than in a straight line
Deflects large-scale motions like winds and currents
N. Hemis:
S. Hemis:

5. Coriolis Effect
Simulation

6. Winds driven by heat energy from sun.
Wind Patterns
Winds driven by heat energy from sun.
3 types of winds:
1) Trade Winds
2) Westerlies
3)Polar Easterlies
Global Wind Patterns

7. Wind Patterns: Trade Winds

8. The trade winds, meet at the Intertropical Convergence Zone (also called the doldrums) between 5 degrees North and 5 degrees South latitude, where the winds are calm.

9. Wind Patterns: Westerlies
At middle latitudes

10. Wind Patterns: Polar Easterlies
Polar easterlies at high latitudes

11. The wind fields are pictured here as they would look if whole Earth covered in water.
In actuality, modified by the influence of continents.

12. Surface Currents Winds push the sea surface creating currents
Surface current moves off 45° b/c Coriolis
Top layer pushes on layer below & again Coriolis Effect come into play:
Second layer moves slightly to right and slower and is repeated down the water column
Process =

13. Surface Currents-Ekman Transport
lower waters move progressively at greater angles from wind
effect of wind decrease with depth
100 m no wind is felt
affected layer = Ekman layer
Taken as a whole, the Ekman layer moves at 90⁰ from wind
=Ekman Transport
upper part of water column moves perpendicular to wind direction -- right N. Hemisphere & left in S. Hemisphere

14. Equatorial Currents and Gyres
Trade winds move toward equator
The equatorial currents created by trade winds, move parallel to equator because of Coriolis Effect
All currents combine into huge gyres = huge circular systems

15. Major Surface Currents
West side of gyres carry:
Cold current flows
**Remember , water has a high heat capacity***
Affects organisms:

16. Major Surface Currents
Currents shown are AVERAGE patterns over large distances and a long time span.
Currents shift with
Currents affected by the
Remember: Surface currents!

17. The role of surface currents in transporting heat is reflected in the sea surface temperatures, seen below.

18. Thermohaline Circulation and the Great Ocean Conveyor
Ocean water stratified
Cold water more dense on the bottom
Warmer water less dense on top
Three layers
Surface/mixed layer
Intermediate layer
Deep and bottom layers
So those were surface currrents, not onto deeper waters.

19. The Three-layered Ocean
Surface layer or mixed layer 100 to 200m thick
Mixed by wind, waves and currents
Intermediate layer depth of 1000 to 1500m
Main thermocline in open ocean
A zone of transition between warm surface water and cold water below
Rarely breaks down
Deep or bottom layers
Below 1500 m
Uniformly cold, typically less than 4°C
Stable
Surface = mixed
Int = thermocline
Deep = stable

20. As temp approaches zero, density ________________.
LOW stability
HIGH stability
Cold water is denser.
As temp approaches zero, density ________________.
Deep oceans are stable
Density and Temperature are correlated

21. Stability and Overturn
Water column with less dense water on top and dense water on bottom with no mixing is stable.
How stable?
depends on the difference in densities between layers
If density difference is large, lots of energy needed to mix layers, high stability.
If density difference is small not much energy is needed to mix the water, low stability

22. Stability depends on the difference in densities between layers
LOW stability
HIGH stability
Water column with less dense water on top and dense water on bottom with no mixing is stable.
Stability depends on the difference in densities between layers
If density difference is large, lots of energy needed to mix layers, high stability.
If density difference is small not much energy is needed to mix the water, low stability

23. Downwelling Occurs when top layers become more dense, sink
The sinking water displaces the deeper water, bringing it the top
Call the sinking water = water mass
What shape is the temperature profile when downwelling is happening? Straight line
What shape do you expect the density to be? A straight line
This tends to happen in certain places in the ocean, Northern Atlantic.

24. Water Mass & Thermohaline Circulation
Sinking water mass now has a “fingerprint”
When it sinks, keeps characteristics it had at surface
This “fingerprint” allows oceanographers to follow the movement of the water mass, its CIRCULATION.
Because this form of circulation is driven by density changes, (determined by temperature and salinity) the circulation is called thermohaline circulation
Thermo = temp Haline =salt

25. The Great Ocean Conveyor
Water mass sinks, spreads through Atlantic and other ocean basins.
Eventually rises somewhere else, returns to Atlantic
Sinks again, cycle repeats
Cycle called The Great Ocean Conveyor
Takes 4,000 years to mix ocean
The Great Ocean Conveyor:
Regulates climate
Alterations in circulation hypothesized to have produced rapid climate changes (ie ice ages)
Bring dissolved oxygen to deep sea

26. The Great Ocean Conveyor
A few locations where water masses sink all the way to the bottom
1) North Atlantic, south of Greenland
2) South Atlantic, north of Antarctica

27. The Great Ocean Conveyor
Regulates climate
Alterations in circulation hypothesized to have produced rapid climate changes (ie ice ages)
Bring dissolved oxygen to deep sea