Sea level observations are used to estimate the amounts of warm water exchanged during the 1982-1983 El Nino event, indicating an eastward flux of about 40¿106 m3 s-1. At the end of El Nino the equatorial Pacific is depleted of warm water which is lost toward higher latitudes. The duration of a complete El Nino cycle is determined by the time required for the slow accumulation of warm water in the western Pacific. The cycle constitutes an energy relaxation of the ocean-atmosphere system.