The physical, chemical and biological effects related to onset of the 1992 El Ni¿o in central California are described. Oceanic Kelvin waves link atmospheric events in the western equatorial Pacific and onset of temperature and primary productivity anomalies. The perturbations observed off California, with a deeper thermocline and nutricline reducing the supply of nutrients and regulating productivity, are similar to those observed along the coast of Peru during El Ni¿o. ¿ American Geophysical Union 1996