In the equatorial Pacific, wind stress changes can alter local sea surface height; as the Earth rotates, this causes a pulse of water to propagate eastward. This pulse, called a Kelvin wave, hits the South American continental margin, and deflects according to Coriolis forces. Recognizing this, Ramos et al. (2006) sought to more fully understand oscillations observed in the Peru-Chile Undercurrent off the coast of South America. Through studies of ocean cruise data between 1981 and 1998, they found that the main thermocline (the underwater surface that represents the point at which temperature changes the most dramatically) oscillates annually according to changes in local wind stresses and secondarily to an annual equatorial Kelvin wave. In contrast, the semiannual component observed in hydrographic data off Peru and Chile is due mainly to Kelvin waves and their products. One such product, called Rossby waves, spin off from Kelvin waves as the latter hit the shore, causing westward (seaward) propagation. These Rossby waves may modulate the thermocline depth several hundreds of kilometers offshore; since biological activity decreases significantly below the thermocline, this can influence local carbon budgets.
Published: 11 May 2006
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Citation: (2006), Seasonal variability of the permanent thermocline off northern Chile, Geophys. Res. Lett., 33, L09608, doi:10.1029/2006GL025882.
Copyright 2006 by the American Geophysical Union.