Propagated temperature changes during onset and recovery of the 1982–83 El Niño

Abstract

El Niño is the appearance of anomalously warm sea surface temperatures along the coast of Peru. El Niño is also associated with changes of sea level and thermocline depth which are linked to a large-scale interaction of the global atmosphere and tropical ocean1–4. Linear wind driven theory suggests that Kelvin waves are responsible for the El Niño thermocline displacements³, but in model systems it is difficult to relate thermocline changes induced by Kelvin waves to the observed changes in sea surface temperature⁵. We have now examined daily sea surface temperatures along the coast of Peru and subsurface temperature records from the Galapagos and 10° S and 79° W (Fig. 1) made during onset and recovery of the 1982–83 El Niño⁶. Our data show that the onset of the anomalous warming in this region propagated at speeds slower than Kelvin wave speeds. The speed of travel calculated from changes in temperature from the Galapagos to the coast of South America and then poleward along the coast is extremely coherent, and during onset appears to be related to advective processes. The rapid decrease in sea surface temperature associated with recovery from the 1982–83 El Niño was propagated at much higher speeds, very suggestive of Kelvin wave dynamics.