1. Mass movements of water in the ocean

2. Formation of Surface Currents
Currents = The forces that move water to produce ocean currents are caused by:
Rotation of the earth
Winds
Water density Differences

3. Effect of a Rotating Earth
Turns from west to east.
Velocity of rotation at its surface is greatest at the equator and least at the poles.
This is called the Coriolis effect.
Click here
What is the Coriolis effect?
Answer: the phenomenon that causes fluids (water and air) to curve as they travel across the earths surface.
Which way does earth spin?
Answer: Clockwise, west to east.
Why do storms spin in a certain location and why do they spin in different directions?

4. In the Northern Hemisphere, ocean currents are deflected to the right, in a clockwise motion. In the Southern Hemisphere, ocean currents are pushed to the left, in a counterclockwise motion. 
Click here –VIDEO
Caution, this video might make you dizzy.
CLICK HERE

5. Gyres – circular flow of water
Flow clockwise in the northern hemisphere
Flow counterclockwise in the southern hemisphere
There are 5 Major Gyres
North Atlantic
South Atlantic
South Pacific
North Pacific
Indian
Gyres = A natural phenomenon of a rotating current system.

6. What is stuck in the Gyres?
Click here- Video
If you were to take a trip out to a Gyre, what do you think (specifically) you would you find?
Take 3 min and discuss this with your neighbor.

7. Coriolis Effect Recap
Simply is the Earth rotation causes a phenomena on free moving objects. Video
Northern Hemisphere right,
Southern Hemisphere deflect to the left.

8. Recap Gyres – circular flow of water
There are 5 Major Gyres
North Atlantic
South Atlantic
South Pacific
North Pacific
Indian

9. Ekman Transport Coriolis effect – spinning of the earth
Water flows to the right of the direction of the wind
Water in each water column flows a little more to the right as you go down
A down flowing spiral occurs

10. Western and Eastern Boundary Currents
5 major ocean gyres flow in relation to the spin of the earth – geostrophic currents.
Currents on the western boundary of the ocean flow from the equator to the poles
Currents on the eastern boundary of the ocean flow from the poles to the equator
Western boundary currents are narrower, faster and deeper than other currents.

11. Western Boundary Currents
Western boundary currents are:
faster than their eastern counterparts
fastest surface currents in the ocean
The Coriolis effect is stronger in the latitudes of the westerlies than the trade winds.

12. Western Boundary Currents Cont.
Water moving toward the western boundary of the ocean basins causes the ocean-surface slope to be steeper on the western side (versus eastern side) of a gyre (in either hemisphere).
A steeper ocean-surface slope translates into a faster geostrophic flow on that side of the gyre.

13. Eastern Boundary Currents
Are relatively shallow, broad and slow-flowing.
Found on the eastern side of oceanic basins.
Subtropical eastern boundary currents flow equatorward, transporting cold water from higher latitudes to lower latitudes;
examples include the:
Benguela Current
Canary Current
Humboldt Current
California Current

15. Stop Here Each person will be completing the Surface Current Map.
With one partner you will match the correct number for the corresponding location of the current on your map, as well as record whether the current in warm by placing a (W) or Warm and a (C) for Cold.

16. Countercurrents and Undercurrents
Countercurrent - water at the equator where lack of wind allows them to flow in the opposite direction of the current next to it.
Undercurrent – water flows beneath and opposite of the current over it.
Both return excess water to their source
Undercurrents are why the galapogos islands are in cold water even though they are in the tropics
Coastal upwelling often brings nutrient-rich water into eastern boundary current regions, making them productive areas of the ocean.

17. Upwellings and Downwellings
Form when winds parallel to shore force water away from shore; west coast of continents.
Water from the bottom (max depth of a few 100 meters deep) is brought up to replace the moved water
Water brings with it nutrients from the ocean bottom
Downwellings
Form when winds parallel to shore force water into shore; east coast of continents
Extra water is forced down towards the bottom

19. Heat transport and Climate
Currents redistribute heat throughout the globe
Without these, Earth would have more extreme weather.
Cold water from the poles keeps the Galapogos Islands cool even though they are in the tropics
Warm water from Gulf Stream, warms the air above and keeps much of Europe warmer than other places at similar latitudes.
** This phenomena is called Thermohaline Circulation.

20. Gravitational Currents
Two forces that explain vertical movement in the ocean:
Gravitational Force (G)
Buoyant Force (B)
G > B – downward movement = sinking
B >G – upward movement = rising
G = B – no movement = floating at surface
G = B – no movement = floating neutrally buoyant
Cold water molecules are packed more tightly together then warm water making cold water more dense.
Density currents form at the north and South pols: Cold air at the poles makes the surface water temperature coolerr making the dense water molecules sink.
When ice forms in saltwater it leaves behind salt, increasing the salinity making the polor water salter.
Evaporation also increase salinity. In the Mediterranean sea, where there is little rainfall and lots of heat the water becomes more dense and sinks to the bottom.

21. Thermohaline Circulation and how it works:

22. Deep Ocean Currents
Thermohaline circulation, also known as the ocean's “conveyor belt”, refers to the deep ocean density-driven ocean basin currents.
Video
These currents, which flow under the surface of the ocean and are thus hidden from immediate detection, are called submarine rivers.
Thermo = tempretaure
Haline = salinity

23. Density Current
Cold water molecules are packed more tightly together then warm water molecules making cold water more dense.
Density currents form at the North and South poles:
Cold air at the poles makes the surface water temperature cooler making the dense water molecules sink.
Ocean Odyssey -

24. Density Current cont.
When ice forms in saltwater it leaves behind salt, increasing the salinity making the water salter.
Evaporation also increase salinity.
For example: In the Mediterranean sea, where there is little rainfall and lots of heat, the water becomes more dense and sinks to the bottom.
Deep water only forms in 2 places:
NADW = North Atlantic Deep Water (off Greenland)
AABW = Antarctic Bottom Water

25. What causes Thermohaline Circulation?
Denser water sinks causing a downward flow.
Other water must then rise to replace it causing an upward flow.
Water density differences drive the slow circulation of deep water.

26. Deep Water Flow Patterns
Dense water descends quickly into deep areas
As deep or bottom water is mixed upward, it warms
Rises to surface and is carried by surface currents to poles where it cools and sinks repeating the process
Takes about 1,000 years for a water mass to complete the cycle

28. Thermohaline Circulation
Water movement caused by differences in temperature and salinity.
Processes that decrease salinity:
Precipitation
Freshwater run-off
Processes that increase salinity:
Evaporation
Freezing

29. The interconnected flow of currents that redistribute heat is called the “Ocean Conveyor Belt” or the Earth’s “Air Conditioner”  

30. Deep ocean currents are driven by density and temperature gradients.
These deep currents are currently being researched by a fleet of underwater robots called Argo.

31. ARGO
A system for observing temperature, salinity, and currents in the Earth's oceans for climate and oceanographic research.
Consists of a fleet of approximately 3700 drifting profiling floats deployed worldwide
How it works:
Probes drift at a depth of 1000 metres and every 10 days they change their buoyancy and dive to metres. Then they move to the sea-surface, measuring conductivity and temperature profiles as well as pressure.

32. ARGO at work

33. Deep Ocean Currents Remember:
Deep ocean currents are driven by density and temperature gradients.