1. Ocean Circulation

2. Ocean Circulation Key Points:
I can discuss the importance of ocean circulation.
I can describe the circulation of wind in a non-rotating vs. a rotating Earth.
I can discuss the physical properties of the atmosphere.
I can begin to understand the Coriolis effect.

3. Why is Ocean Circulation Important?
Transport ~ 20% of latitudinal heat
Equator to poles
Transport nutrients and organisms
Influences weather and climate
Influences commerce
4 th century BC ,Pytheas of Massalia, a Greek ship captain, explored eastern Atlantic
Okeanos (Greek for “Great River”) because he found the ocean flowing south (Canary Current) and thought it was a river too wide to cross.

4. Non-rotating Earth Convection cell model
Non rotating model- when the density of air is lower than normal, the atms pressure drops--- low pressure zone
When the density of air is higher than normal, the pressure increases--- high pressure zone

5. Add rotation and add landmasses
unequal heating and cooling of the Earth You Tube Link
YouTube Link #2

6. Physical properties of the atmosphere: Density
Warm, low density air rises
Cool, high density air sinks
Creates circular- moving loop of air (convection cell)

7. Physical properties of the atmosphere: Water vapor
Cool air cannot hold much water vapor, so is typically dry
Warm air can hold more water vapor, so is typically moist
Water vapor decreases the density of air

8. Physical properties of the atmosphere: Pressure
A column of cool, dense air causes high pressure at the surface, which will lead to sinking air
A column of warm, less dense air causes low pressure at the surface, which will lead to rising air

9. The Coriolis effect The Coriolis effect
The Coriolis effect
Is a result of Earth’s rotation
Causes moving objects to follow curved paths:
In Northern Hemisphere, curvature is to right
In Southern Hemisphere, curvature is to left
Changes with latitude:
No Coriolis effect at Equator
Maximum Coriolis effect at poles
Coriolis Effect: Coriolis effect is an inertial force described by the 19th-century French engineer-mathematician Gustave-Gaspard Coriolis in Coriolis showed that, if the ordinary Newtonian laws of motion of bodies are to be used in a rotating frame of reference, an inertial force--acting to the right of the direction of body motion for counterclockwise rotation of the reference frame or to the left for clockwise rotation--must be included in the equations of motion.
The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system. The object does not actually deviate from its path, but it appears to do so because of the motion of the coordinate system.

10. The Coriolis effect on Earth
As Earth rotates, different latitudes travel at different speeds
The change in speed with latitude causes the Coriolis effect

11. Ocean Currents Recap Key Points:
I can discuss the importance of ocean circulation.
I can describe the circulation of wind in a non-rotating vs. a rotating Earth.
I can discuss the physical properties of the atmosphere.
I can begin to understand the Coriolis effect.

12. Ocean Currents Key Points:
I can describe how the Coriolis effect influences surface winds.
I can explain the difference between factors affecting surface circulation vs. deep ocean circulation.
I can describe oceanic gyres & their rotations.

13. Idealized winds generated by pressure gradient and Coriolis Force.
Horse Latitudes Around 30°N we see a region of subsiding (sinking) air.  Sinking air is typically dry and free of substantial precipitation. Many of the major desert regions of the northern hemisphere are found near 30° latitude.  E.g., Sahara, Middle East, SW United States.
Doldrums Located near the equator, the doldrums are where the trade winds meet and where the pressure gradient decreases creating very little winds.  That's why sailors find it difficult to cross the equator and why weather systems in the one hemisphere rarely cross into the other hemisphere.  The doldrums are also called the intertropical convergence zone (ITCZ).
Idealized winds generated by pressure gradient and Coriolis Force. 
Actual wind patterns owing to land mass distribution..

14. Ocean Currents Surface Currents
The upper 400 meters of the ocean (10%).
Deep Water Currents
Thermal currents (90%)

15. Surface Currents
Forces
Solar Heating (temp, density)
Winds
Coriolis

16. Wind-driven surface currents

17. Current Gyres Gyres are large circular-moving loops of water
Five main gyres (one in each ocean basin):
North Pacific
South Pacific
North Atlantic
South Atlantic
Indian
Generally 4 currents in each gyre
Centered about 30o north or south latitude

18. Geostrophic flow- caused by Coriolis deflection and Ekman transport

19. Surface and Deep-Sea Current Interactions
Unifying concept: “Global Ocean Conveyor Belt”

20. Heat Transport by Currents
Surface currents transport heat energy from equator towards the poles
Currents also involved with gas exchanges, especially O2 and CO2
Nutrient exchanges important within surface waters (including outflow from continents) and deeper waters (upwelling and downwelling)
Pollution dispersal
Impact on fisheries and other resources

21. Thermohaline Circulation
Global ocean circulation that is driven by differences in the density of the sea water which is controlled by temperature and salinity.

22. Thermohaline Circulation
                                                                                                                                                        
The global ocean circulation system, often called the Ocean Conveyor, transports heat throughout the planet. White sections represent warm surface currents. Purple sections represent deep cold currents. (Illustration by Jayne Doucette, WHOI Graphic Services).
White sections represent warm surface currents.
Purple sections represent deep cold currents

23. Thermohaline Circulation
Wind and the rotation of the Earth are important in determining the flow of surface currents and local areas of upwelling and downwelling, but the true driving force of deep water movement is thermohaline circulation. 
Sometimes called the ocean conveyer belt, this mechanism is responsible for bringing the oxygen that sustains life to the deepest reaches of the sea, and in moving warmer waters from the tropics towards the poles. Movement of this conveyer belt depends on sinking of cold water in certain polar regions, thereby triggering the global thermohaline circulation. 

24. Ocean Currents Recap the Key Points:
I can describe how the Coriolis effect influences surface winds.
I can explain the difference between factors affecting surface circulation vs. deep ocean circulation.
I can describe oceanic gyres & their rotations.

25. Ocean Currents
Key Points:

26. Upwelling and downwelling
Vertical movement of water ()
Upwelling = movement of deep water to surface
Hoists cold, nutrient-rich water to surface
Produces high productivities and abundant marine life
Downwelling = movement of surface water down
Moves warm, nutrient-depleted surface water down
Not associated with high productivities or abundant marine life

27. upwelling
downwelling

28. Satellite Observations
TOPEX/Poseidon, Jason 1, and other satellites have observed patterns of change over the past few years
Animation of seasonal and climatically-influence shifts available at

29. El Niño-Southern Oscillation (ENSO)
El Niño = warm surface current in equatorial eastern Pacific that occurs periodically around Christmastime
Southern Oscillation = change in atmospheric pressure over Pacific Ocean accompanying El Niño
ENSO describes a combined oceanic-atmospheric disturbance

30. Oceanic and atmospheric phenomenon in the Pacific Ocean
El Niño
Oceanic and atmospheric phenomenon in the Pacific Ocean
Occurs during December
2 to 7 year cycle
Sea Surface Temperature
Atmospheric Winds
Upwelling

31. Normal conditions in the Pacific Ocean

32. El Niño conditions (ENSO warm phase)

33. La Niña conditions (ENSO cool phase; opposite of El Niño)

34. Non El Niño
El Niño
1997

35. Non El Niño
upwelling
El Niño
thermocline

36. El Niño events over the last 55 years
El Niño warmings (red) and La Niña coolings (blue) since Source: NOAA Climate Diagnostics Center

37. World Wide Effects of El Niño Weather patterns Marine Life
Economic resources
Floods
El Niño Sea-Level Rise Wreaks Havoc in California's San Francisco Bay Region (31-Jan-2000)
1998 California Floods (11-Mar-1998)
The Spring Runoff Pulse from the Sierra Nevada (14-Jan-1998)
Effects of El Niño on Streamflow, Lake Level, and Landslide Potential (16-Dec-1997)
Climate and Floods in the Southwestern U.S. (10-Jul-1997)
Real-time flows on rivers and streams
More USGS information on Floods
Landslides
Recent landslide events--News and Information (updates regularly)
Landslide publications and reports (14-Oct-2003)
USGS Circular 1244 (26-Sep-2003) "National Landslide Hazards Mitigation Strategy—A Framework for Loss Reduction"
USGS Landslide Hazards web site
More USGS information on Landslides
Information on Landslides during the El Niño:
Map Showing Locations of Damaging Landslides in Alameda County, California, Resulting From El Niño Rainstorms (10-Jan-2000)
El Niño and 1998 California Landslides (20-Mar-1998)
Geologic mapping and El Niño: Landslide and debris-flow susceptibility maps, including southern California, Mojave Desert, and San Francisco Bay Area (02-Feb-1998)
Landslide Recognition and Safety Guidelines (29-Jan-1998)
USGS Producing Landslide Hazard Maps for Emergency Services in San Francisco Bay Area (16-Dec-1997)
Potential San Francisco Bay Landslides During El Niño (16-Dec-1997)
El Niño and the National Landslide Hazard Outlook for (16-Dec-1997)
Coastal hazards
El Niño Sea-Level Rise Wreaks Havoc (31-Jan-2000) in California's San Francisco Bay Region
Coastal Erosion Along the U.S. West Coast During El Niño (12-August-99)
Coastal Erosion From El Niño Winter Storms (31-Aug-1998) with before and after air photos from Southern Washington, Northern Oregon, Central California, and Southern California
El Niño Coastal Erosion, San Mateo County, California (6-May-1998)
El Niño Coastal Monitoring Program (31-Mar-1998) with before and after photos of Santa Cruz County, California beach erosion.
Hydroclimatology of San Francisco Bay Freshwater Inflows and Salinity, with weather and salinity movies (14-Jan-1998)
El Niño Effects on Sea-Level Near San Francisco Bay (16-Dec-1997)
Coastal Impacts of an El Niño Season (3-Nov-1997)
More USGS information on Coastal hazards
Climate
Long-term climate variation in the Mojave Desert (15-Jan-1998)
Effects of El Niño on Streamflow, Lake Level, and Landslide Potential (revised 16-Dec-1997)
El Nino Animation

38. Effects of severe El Niños

39. Inquiry What is a convection cell?
Which direction do currents get deflected in the Southern Hemisphere?
What depth should the water be for an Ekman spiral to occur?
How are surface currents created?
What is a gyre?
How can an El Nino impact upwelling?
Coriolis Effect is strongest near the _____?