Major ocean current systems 1
Generalized picture of equatorial currents
ECC EUC NEC SEC ECC and EUC: geostrophic currents; ECC: runs along doldrums w/ little wind opposition
Surface water transport from E to W wind W E Mixed surface layer (EUC: flows below wind driven layer) thermocline
Current velocity (cm/s) of EC
ECC NEC SEC S EUC N
Trade winds
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 (29C, 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
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
Review of global wind and current systems (idealized)