The source of interannual changes in the ocean climate of the Gulf of California, indicated by sea level and shore temperature anomalies, is determined by comparison with large-scale circulation in the Pacific Ocean and atmosphere. Independent modes of variability in the large-scale circulation are defined by empirical orthogonal function analysis of eight time series representing the principle ocean currents and surface wind systems. Interannual ocean climate in the Gulf of California is related only to the equatorial mode of variability commonly known as the El Niño/Southern Oscillation. There is no discernible relationship between the Gulf and independent modes of variability in the North Pacific gyre. Interannual variability in the Gulf is associated with the cyclonic north equatorial circulation composed of the North Equatorial Countercurrent, the North Equatorial Current and the Costa Rica Current.