1. Chapter 8: Ocean Circulation
Fig. 8-26

2. Ocean currents move large
amounts of water and heat
 Wind-driven
surface ocean
circulation
 Density-driven
deep-ocean
circulation
 Both redistribute
heat from warmer
regions to cooler
Fig. 8-16

3. Measuring ocean currents
 Direct measurement
 Floating objects/instruments
 Fixed instruments
 Indirect measurement
 Distribution of density
 Satellite data
 Doppler flow meter
 Chemical tracers
 Distinctive water masses

7. Surface currents
 Frictional drag due to winds
 Surface currents similar to global winds
 Continents affect surface current
patterns
 Other factors:

Gravity

Friction

Coriolis Effect

9. Subtropical gyres
 Large circular flow
 Clockwise in northern oceans,
e.g., North Atlantic
 Counterclockwise in southern
oceans, e.g., South Atlantic
 4 main currents in each gyre

11. Ekman spiral and Ekman
transport  Ekman transport
moves surface
seawater about
90o
to the right of
the wind in the
Northern
Hemisphere
 90o
left in
Southern
Hemisphere
Fig. 8-6a

13. Western intensification
 “Hill” of seawater is steeper on western side
 Western currents are fast, narrow, deep

14. Subtropical gyres
 Ekman transport
piles up “hill” of
seawater at about
30o
N and S
 Water flows downhill
under gravity and
veers right (Northern
hemisphere) due to
Coriolis Effect
 Circular flow Fig. 8-7

15. Upwelling
 Ekman transport
moves seawater
offshore
 Ekman transport
moves seawater
away from
another water
mass
Fig. 8-11a

16.  Cooler, nutrient-
rich water rises
vertically toward
sea surface
 High biologic
productivity
 Downwelling
opposite
Fig. 8-11b

18. Surface currents
 Pattern similar in major ocean
basins
 Northern ocean gyre moves
clockwise
 Southern ocean gyre moves
counter-clockwise

19. Antarctic circulation
 Antarctic Circumpolar Current (or
West Wind Drift)
 Greatest volume
 Connects main oceans
 East Wind Drift
 Antarctic Divergence (upwelling)

20. North Atlantic Circulation
 North Equatorial Current
 Gulf Stream
 North Atlantic Current
 Gulf Stream and North Atlantic
Currents warm Europe
 Canary Current

21. North Equatorial Current

22. Gulf Stream

23. North Atlantic Current

24. Canary Current

25. South Atlantic Ocean
 South Equatorial Current
 Brazil Current
 Antarctic Circumpolar Current
 Greatest volume
 Connects three main oceans
 Benguela Current

26. South Equatorial current

27. Brazil Current

28. Benguela Current

29. North Pacific Ocean
 North Equatorial Current
 Kuroshio Current
 North Pacific Current
 California Current
 Strong Equatorial Counter Current

30. South Pacific Ocean
 South Equatorial Current
 East Australian Current
 Antarctic Circumpolar Current
 Peru Current
 Strong Equatorial Counter Current

31. ENSO El Niño-Southern
Oscillation
 Irregular shift in ocean and
atmosphere characteristics every 2-
10 years
 Affects global climate
 Harmful and beneficial
consequences

32. El Niño ENSO Warm Phase
 Most obvious in Equatorial Pacific
 Pacific Warm Pool moves eastward across
Equatorial Pacific
 Changes in pattern of upwelling/downwelling
in eastern Pacific Ocean
Fig. 8-2

33. ENSO warm phase effects
 Warmer seawater higher sea level
 Warmer seawater less upwelling in
eastern Pacific
 Lower biologic productivity
 Warmer seawater kills some marine life
 Shift in atmosphere pressure
 Shift in areas of precipitation

37. La Niña ENSO Cool Phase
 Stronger tradewinds
 Warm pool stays in western Pacific
 Increased upwelling in eastern Pacific
 Shift in precipitation patterns
 Shift in atmospheric pressure

38. ENSO data collection
 TOGA Tropical Ocean Global
Atmosphere
 TAO Tropical Atmosphere Ocean
 Monitor ocean and atmosphere
 Data indicate what phase ENSO
 Pacific Decadal Oscillation
 Decades-long cycles of warming
and cooling in Pacific Ocean

39. Indian Ocean Circulation
 North and South Equatorial Currents
 Equatorial Counter Current
 Agulhas Current
 Antarctic Circumpolar Current
 West Australian
 Seasonal shifts (monsoons) of winds
and currents

42. Thermohaline circulation
 90% of world ocean
 Below pycnocline
 Large volumes of
seawater
 Extremely slow
speed
 Each ocean basin is
similar in deep-
ocean circulation

43. Sources of deep water
 Densest seawater is cold
 Most deep water masses from
polar oceans
 Sink to density level and move
horizontally

44. Antarctic Bottom Water
 Densest deep water
(coldest)
 Sinks around
Antarctica
 Most widespread
deep-water mass
 Found as far as
40o
N
 Carries O2 into deep
ocean Fig. 8-25

45. North Atlantic Deep Water
 Complex mixture
of cold seawater
from Norwegian
sea mixing with
 Gulf Stream
 Mediterranean
Intermediate
Water
 Other NA water
masses
 Extends from
North Atlantic to
about 40o
south

46. Intermediate Water Masses
 Antarctic Intermediate Water
 Sinks at Antarctic Convergence
 Cold
 Salinity less than average
 Mediterranean Intermediate Water
 Warm
 Very salty

47. Conveyor Belt Circulation
 Mixture of surface
ocean circulation
and deep-ocean
circulation
 Mixes surface
and deep
 Mixes waters in
different oceans Fig. 8-26

48. Langmuir Circulation
 Alternately converging and diverging
convection cells
 Wind blowing over calm ocean
 Alternate rows of upwelling and downwelling

49. End of Chapter 8: Ocean
Circulation