the ocean general circulation
DESCRIPTION
The Ocean General Circulation. Gulf Stream. Mean Circulation in the Ocean. Gulf Stream. Mean Circulation in the Ocean. California Current. Oceans are filled with energetic eddies!!!. Gulf Stream, Plankton Bloom. Gulf Stream Spiral Eddies. Mediterranean Sea, Shear Wall Spiral Eddies. - PowerPoint PPT PresentationTRANSCRIPT
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The Ocean General Circulation
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Mean Circulation in the Ocean
Gulf Stream
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Mean Circulation in the Ocean
Gulf Stream
California Current
Oceans are filled with energetic eddies!!!
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Gulf Stream, Plankton Bloom
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Gulf Stream Spiral Eddies
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Mediterranean Sea, Shear Wall Spiral Eddies
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Tropical Atlantic, Spiral Eddy
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Greek Island, Spiral Eddies and Wakes
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Strait of Gibralter, Solitons
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Eastern Pacific Internal Waves
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Kelvin Wakes, from Ships
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Coastal DynamicsCalifornia Filamentsand Phytoplankton
Hawaiian Island Wakes
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Key questions:
How does the wind drive surface currents?
What drives oceanic gyres?
What is Ekman transport?
What drives upwelling and downwelling?
Ocean wind driven circulation
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Atmospheric winds
“Hadley” regime
Subtropical high
Intertropical convergence zone (ITCZ)
“Eddy” regimeVariable weatherWesterly wind
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How is the energy of the winds transferred to the ocean?
Ekman Theory …
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How does wind force propagate in the ocean?
surface
balance between friction and rotation
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FWIND
FCoriolis
1) Surface water is pushed by the atmospheric wind2) Coriolis force acting on surface current balances the wind
stress3) Surface current (averaged over tens of meters) points to the
right of the direction of the wind
Ekman transport: Balance between wind and Coriolis force
Ekman transport
Wind direction
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What would happen to the Ekman transport under the cyclonic atmospheric circulation?
L
Wind stressEkman transport
Ekman upwelling under cyclonic circulation
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What would happen to the Ekman transport under the anti-cyclonic atmospheric circulation?
H
Wind stressEkman transport
Ekman pumping under anti-cyclonic circulation
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Ocean temperature structure
Atlantic OceanTemperature structure in the top 1,000mWhat controls this structure?
HH L
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Ekman Theory …and vertical advection in the ocean
COASTAL UPWELLING and DOWNWELLING
OPEN OCEAN EKMAN PUMPING
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Subtropical “ocean gyre” is a geostrophic circulation
1)Atmospheric high pressure Anti-cyclonic wind stress
1)Ekman transport converges toward the middle, raising up the sea surface slightly
2)Pressure force drives the geostrophic gyre circulation
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Fpressure
FCoriolis
1) Particle will have the Coriolis force 90 degrees to the right2) Particles will tend to move along line of constant pressure3) Particles will have the high pressure on their right (same as
Coriolis)
Balance of forces: geostrophic balance
High Pressure
Low Pressure
Applies to the Ocean same as Atmosphere!
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Effects of Ekman Currents
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Ocean general circulation
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Heat transport by the ocean circulation
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Regional circulation: Coastal upwelling
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Equatorial upwelling