Ocean Circulation Flashcards
Two types of Ocean Currents:
- Surface Circulation, Wind driven
- Thermohaline Circulation, Gravity or Density Driven
- Surface Current
- Deep Water Current
Surface Currents move water ____ and occur in ocean’s surface waters within and above the ____ to a depth of ~1km (make up 10% of ocean)
Horizontally, Pycnocline
Surface currents closely follow _____. Trade winds at 0-30 degree latitude blow surface currents to the ____ while prevailing westerlies at 30-60 degree latitude blow currents to the ____.
Global wind belt pattern, east, west
Surface Currents generally mirror average planetary ______.
Atmospheric Circulation Patterns
_____ develop from friction between the ocean and the wind that blows across its surface. Only ___ of the wind’s energy is transferred to the ocean surface. They are driven by wind and also distribution of continents on earth.
Surface Currents, 2%
Equatorial currents travel westward along the equator and form the equatorial boundary current of _____. Each Gyre is composed of 4 main currents:
Subtropical Gyres:
- Equatorial Currents
- Western Boundary Currents
- Northern and Southern Boundary Currents
- Eastern Boundary Currents
6 Great Current Circuits in the World Ocean:
- North Atlantic Gyre
- North Pacific Gyre
- South Atlantic Gyre
- South Pacific Gyre
- Indian Ocean Gyre
- West Wind Drift or Antarctic Circumpolar Current
A current of any fluid forming on the side of a main current; usually moves in a circular path; develops where currents encounter obstacles or flow past one another. Swirling.
Eddy
More apparent in Pacific because of dome of equatorial water that becomes trapped in the island-filled embayment between Australia and Asia; western basin 2m higher than eastern basin
Equatorial Countercurrents
Driven in a westerly direction by polar easterlies, smaller and fewer, best developed in Atlantic Ocean between Greenland and Europe, and Weddell Sea
Subpolar Gyres
Other Factors affecting ocean surface circulation:
- Ekman Spiral and Ekman Transport
- Geostrophic Current
- Western Intensification of Subtropical Gyres
Surface currents move at angle to wind. Describes speed and direction of seawater flow at different depths. Each successive layer moves increasingly to right (N hemisphere)
Ekman Spiral
All the layers combine however create a net water movement that is 90deg from the direction of the wind. In shallow coastal waters, _____ may be very near the same direction as the wind.
Ekman Transport
Net transport of water as an effect of steady blowing wind; theoretically 90 degrees to the right of wind direction in the Northern Hemisphere and 90 degrees to the left of wind direction in the Southern Hemisphere
Ekman Transport
The process by which deep, cold, nutrient-laden water is brought to the surface, usually by diverging equatorial currents or coastal currents that pull water away from the coast
Upwelling
Ekman transport piles up water within subtropical gyres. Surface water flows downhill (gravity) and
Also to the right (Coriolis effect). Balance of downhill and to the right causes ____ around the “hill”.
Geostrophic Flow
Top of hill formed within rotating gyre is closer to western boundary than the center. Western boundary currents of gyre is faster, narrower and deeper than eastern boundary current counterparts.
Western Intensification of Subtropical Gyres
Current convergence occurs when surface waters pile up. When currents converge, no place to go but downwards.
Converging Surface Seawater
A cellular circulation set up by winds that blow consistently in one direction with speeds in excess of 12 km/hr. Helical spirals (convection cells) running parallel to the wind direction are alternately clockwise and counterclockwise.
Langmuir Circulation
Previously warm,
salty water, transported
to low S. latitudes, cooled
and downwelled at the
Antarctic Convergence.
Thermohaline Circulation
For every ___of deep water formed, ___ liter of deep water must upwell
One
Combination deep ocean currents and surface currents
Conveyor-Belt Circulation
Youngest Circulation and Oldest Current Circulation found in what areas respectively?
Atlantic Ocean and Pacific Ocean
Masses of air that move across earth’s surface from subtropical high-pressure belts toward equatorial low-pressure belt
Trade Winds
Move from NE to SW, curve to the right due to Coriolis
NE Trade Winds
Move the SE to NW, curve to the left due to Coriolis
SE Trade Winds
Some of air that descends in subtropical regions moves to higher latitudes as the _____? (blow from SW to NE in N Hem, and from NW to SE in S Hem)
Prevailing Westerly Wind Belts
Coriolis effect maximized at high latitudes
Polar Easterly Wind Belts
Trade winds which blow from the SE in the S Hem and from the NE in the N Hem set in motion water masses between the tropics resulting in ________. They travel westward along the equator and form the equatorial boundary current of the gyres.
Equatorial Currents
- Fastest and deepest geostrophic currents found on the western boundaries of ocean basins
- Narrow, fast, deep currents move warm water poleward in each of the gyres
- Gulf Stream (N Atlantic), Kuroshio (N Pacific), Brazil (S Atlantic), Agulhas (Indian), East Australian (S Pacific)
Western Boundary Currents
- Opposite of western boundary currents
- Carry cold water equatorward
- Shallow and broad
- Canary (N Atlantic), California (N Pacific), Benguela (S Atlantic)
Eastern Boundary Currents
The____, named in honour of the pioneering oceanographerHarald Sverdrup, is aunit of measureofvolumetransport.
Sverdrup
- When currents converge, no place to go but downwards called ______.
- Low biological productivity
Downwelling
