1. Major ocean current systems1

2. Generalized picture of equatorial currents

3. ECC EUC NEC SEC 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

6. ECC
NEC
SEC S
EUC 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--> cooler SST
Lower T--> lower atm convection, trade winds switch to normal pattern

10. Review of global wind and current systems (idealized)