Ocean Circulation

1
Ocean Circulation

• Currents

2
Currents

• Horizontally
• Vertically

3
The Forces That Drive Currents

• Primary forces
• Starts water movement and determine its velocity
• Stress of wind
• Secondary forces
• Influence the direction and nature of flow
• Coriolis effect
• gravity
• friction
• shape of ocean basins

4
Surface currents

• Wind
• Surface currents
• rapid with well defined boundaries
• slow and diffuse
• horizontal or vertical
• Gyre

5
Bottom Currents

• Driven by the force of gravity - dense water
  sinks and less dense water rises

6
Flow within a Gyre

• North Atlantic gyre
• Four inter connected currents

7

• Eckman spiral
• Eckman transport

8
Geostrophic Gyres

• Geostrophic Gyre
• 5 Geostrophic gyre
• North Atlantic gyre
• South Atlantic gyre
• North Pacific gyre
• South Pacific gyre
• Indian Ocean gyre
• Geostrophic gyres independent of each other in
  each hemisphere
• Geostrophic currents
• 6 current circuits in the world ocean
• 2 in Northern hemisphere 4 in southern hemisphere

9
Currents within Gyres

• Western boundary Currents
• Eastern Boundary Currents
• Transverse currents

10
Western Boundary Currents

• Fastest and deepest
• Found at the western boundaries of the Ocean
  basins
• Narrow
• Move warm water poleward in each gyre

11
Western boundary currents

• Five western boundary currents
• Gulf stream
• Japan or Kuroshio current
• Brazil current
• Agulhas current
• East Australian current
• Sverdrup
• Eddies
• Cold core eddies
• Warm core eddies

12
Eastern Boundary Currents

• The Canary Current
• The Benguela Current
• California Current
• West Australian Current
• The Peru or Humboldt Current

13
Eastern Boundary Currents

• Carry cold water equatorward
• Shallow and broad
• Boundaries not well defined
• Eddies tend not to form

14
Westward Intensification

• The converging flow of the trade winds on either
  side of equator
• The rotation of the earth

15
Transverse Currents

• Currents that flow from east to west
• Linking the eastern and western boundary currents
• Counter Currents
• Under Currents

16
Exceptional Surface Currents

• Monsoon Currents
• High Latitude Currents

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Effects of Surface Currents on Climate

• Distribute tropical heat
• Influences climate and weather

18
Wind-Induced Vertical Circulation

• Upwelling
• Equatorial upwelling
• Coastal upwelling
• Downwelling

19
Langmuir Circulation (page 222 fig 9.16)

• Langmuir Circulation

20
El Nino
21
Thermohaline Circulation

• Density driven

22
Water Masses

• Five common water masses
• Surface water
• Central water
• Intermediate water
• Deep water
• Bottom water

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Formation and downwelling of Deep water

• Antarctic bottom water
• North Atlantic deep water

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Thermohaline Circulation Patterns

• Low and mid latitudes
• Caballing
• Contour currents

25
Studying Currents

• Float method
• Flow method
• Acoustical Tomography