FY 1986

Sea level and near surface temperature variability at the Galapagos Islands, 1979–83

Hayes, S.P.

In El Niño in the Galapagos Islands: The 1982–83 Event, G. Robinson and E.M. del Pino (eds.), Charles Darwin Foundation for the Galapagos Islands, Quito, Ecuador (1985)

An array of near surface temperature and pressure gauges on the Galápagos Islands was used to describe changes in the thermal field and sea level which occurred during the 1982-83 El Niño event. These changes are contrasted with the variability observed during the three year period (July 1979 to July 1982) prior to the event. The location of gauges on the western side of the archipelago permitted monitoring of the strength of the Galápagos Front. In non El Niño times the cross front temperature gradient had a strong annual variation; it was largest in October. A station usually north of the front had pronounced semiannual variability while south of the front the annual component was dominant. The superposition of these two signals led to the observed annual change in frontal strength. During the El Niño event the front disappeared from the islands in October 1982 and did not reappear until July 1983. During the redevelopment, cold water occurred first at the southern stations; its occurrence north of the front was delayed by about 1 month. By October 1983 the cross frontal temperature gradient in the islands was near normal. El Niño related sea level variations at the Galápagos reflected the large scale changes throughout the tropical Pacific. Maxima were observed in December 1982 and May 1983. The onset of rising sea level in early August 1982 followed by about one month the sea level rise in the central Pacific. This initial signal had properties consistent with equatorial Kelvin wave dynamics. The subsequent development was not so easily described.