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gfdl's home page > gfdl on-line bibliography > 1980: Journal of Geophysical Research, 85(C2), 1123-1136
The generation of equatorial currents
| Philander, S. G. H., and R. C. Pacanowski, 1980: The generation of equatorial currents. Journal of Geophysical Research, 85(C2), 1123-1136. |
| Abstract: In response to the sudden onset of zonal winds the surface layers of the ocean accelerate in the direction of the wind. Motion is most intense near the equator where a jet forms within a week. The next stage in the evolution of equilibrium conditions is associated with wave fronts, excited initially at the coasts, that propagate across the ocean basin and establish zonal density gradients. Wave modes trapped in and above the strong shallow tropical thermocline because of internal reflection there are responsible for the adjustment of the upper ocean in low latitudes. These thermocline-trapped modes extend over a depth greater than that of the wind-driven surface currents and hence give rise to an undercurrent in the thermocline. This undercurrent is zonal and particularly intense near the equator, where it appears in the wake of an eastward traveling Kelvin or westward traveling Rossby wave after about 1 month. In the case of eastward winds, nonlinearities intensify the eastward equatorial surface jet and weaken the westward undercurrent. In the case of westward winds a different nonlinear mechanism intensidies the eastward Equatorial Undercurrent and weakens the westward surface flow. In a 5000-km winde basin, equilibrium equatorial currents are established about 150 days after the onset of the winds. The response time of the ocean below a depth of a few hundred meters is much longer. Winds with no spatial and a simple temporal structure generate currents with a complex vertical structure in the deep ocean. Closed current systems are possible in a confined forced region of an unbounded ocean; meridional coasts are not essential for their maintenance. The intensity of equatorial current is sensitive to dissipation parameters. |