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Oceanic Circulation Current = a moving mass of water.

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Presentation on theme: "Oceanic Circulation Current = a moving mass of water."— Presentation transcript:

1 Oceanic Circulation Current = a moving mass of water

2 Oceanic Circulation Surface Currents –horizontally flowing water in the uppermost 400m of the ocean –driven by wind Thermohaline Circulation –slower, deeper circulation –due to the action of gravity on water masses of different densities

3 Surface Currents Wind –primary force responsible for surface currents Friction drags water along Coriolis effect Continents prevent continuous flow and deflect water… Gyre –the circular flow around the periphery of an ocean basin

4 Fig. 8-1, p. 172

5 Fig. 8-4, p. 173

6 Figure 7.4

7 Figure 7.7 Ekman Transport

8 Figure 7.8

9 Geostrophic Gyres Gyres in a balance between the pressure gradient (due to gravity) and the Coriolis Effect


11 Six great surface current North Atlantic Gyre South Atlantic Gyre North Pacific Gyre South Pacific Gyre Indian Ocean Gyre West Wind drift or Antarctic Circumpolar Current

12 Fig. 8-3, p. 173

13 Flow within Gyres Western Boundary Currents (ex: Gulf Stream) –westward intensification - more concentrated due to water piling up due to eastward rotation of earth and the Coriolis Effect –narrow, fast ( 3-10 km per hour or 2-6 miles per hour), deep currents that carry warm water toward poles

14 Figure 7.8

15 Fig. 8-13b, p. 180

16 Flow within Gyres Eastern Boundary Currents (ex: Canary Current) –broad, slow, shallow currents that carry cold water toward equator

17 Table 7.2

18 Flow within Gyres Transverse Currents –Northern or Southern Border currents (ex: North Atlantic Current) –Equatorial currents (ex: North Equatorial current) –currents that flow from east to west or west to east

19 Flow within Gyres Currents affect climate: –North Atlantic current warms England –California current cools San Francisco in the summer

20 Figure 7.9 Sea Surface Temp in August And in February



23 Vertical Circulation Upwelling –upward movement of water Downwelling –downward movement of water

24 Figure 7.12a

25 Vertical Circulation Coastal Upwelling –cold, deeper water upwells to replace the surface water –leads to increased nutrients & productivity and cooler climates

26 Figure 7.10

27 Vertical Circulation Equatorial Upwelling –westward flowing equatorial currents are deflected poleward –deeper water comes up to replace the surface water

28 Figure 7.13- Causes of upwelling

29 Vertical Circulation Downwelling –water driven toward the coast will be forced down –Brings down dissolved gases

30 Figure 7.11

31 ENSO El Nino Southern Oscillation Southern Oscillation = Atmospheric pressure changes in the Pacific every 3 – 8 years –Becomes high in west & low in east –TradeWinds weaken, cease or reverse and blow west to east El Nino = warm water moves east toward North & South America

32 Figure 7.21

33 Fig. 8-19 (a-b), p. 186

34 Fig. 8-19 (c-e), p. 187

35 Figure 7.22 El Nino 1997-98 La Nina 2000

36 ENSO El Nino Southern Oscillation Eastern Pacific (along west coast of South America): –Upwelling ceases –Sea-level rises in eastern Pacific –Water temp increases –Increased precipitation

37 Figure 7.23

38 Deep Circulation Thermohaline Circulation Driven by density differences water masses do not mix easily but flow above or beneath each other

39 Some Water Masses in the Deep Atlantic Antarctic Bottom Water North Atlantic Deep water Mediterranean Intermediate Water Antarctic Intermediate Water



42 Thermohaline Circulation Sinking of water masses is offset by slow, gradual rising across warmer temperate and tropical zones

43 Fig. 8-26, p. 192

44 Thermohaline Circulation Much slower than surface circulation –10-20 km per year or 6-12 miles per year –Would take water a year to move as far as surface water would move in an hour

45 Figure 7.28- The Ocean Conveyor Belt Model

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