Major ocean current systems

1
Major ocean current systems
2
Generalized picture of equatorial currents
3
NEC
SEC
ECC
EUC
ECC and EUC geostrophic currents ECC runs
along doldrums w/ little wind opposition
4
Surface water transport from E to W
wind
W
E
Mixed surface layer
(EUC flows below wind driven layer)
thermocline
5
Current velocity (cm/s) of EC
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ECC
NEC
SEC
EUC
S
N
7
Trade winds
8
El Niño sets in

• Decrease in trade winds in central, W Pacific
• Accompanying decrease in horizontal pressure
  gradient
• thermocline sinks from 20 to 100 m, upwelling
  continues, but upwelled water is warm (29?C, not
  16-18? C)
• Change propagates W to E in 2-3 months
• SST increases, region of ascending moist air over
  W Pacific expands E

9
End of El Niño

• Begins in W Pacific N, S of Equator, thermocline
  rises, cooler water to surface--gt cooler SST
• Lower T--gt lower atm convection, trade winds
  switch to normal pattern

10
Review of global wind and current systems
(idealized)