The 1982–1983 El Niño signal off northern California

Abstract

The major El Niño event of 1982–1983 affected the entire California Current system. The anomalous conditions along the west coast of North America were related to the equatorial anomalies and also to the anomalous atmospheric circulation in the northeast Pacific, where the Aleutian Low was east of its usual position and the associated 700‐mbar height reached its lowest value on record in February–March 1983. Positive temperature and negative salinity anomalies in the upper ocean, extending from the coast to at least 200 km offshore, were reported from San Diego to Vancouver Island. In data acquired in domains centered approximately 180 km off northern California by the Ocean Prediction Through Observation, Modeling and Analysis Program, anomalies in both temperature and salinity were most pronounced subsurface. Spatially and monthly averaged temperatures were about 3°C warmer than normal at 80 to 100 m in April and again in December 1983. At 100 to 120 m, salinity was about 0.4 parts per thousand lower than normal in July 1983 and July 1984, several months later than the temperature anomaly maxima. The temperature anomalies may be related to the poleward propagation of the equatorial El Niño perturbation by coastally trapped waves, with offshore propagation by planetary Rossby waves possibly playing some role in the relaxation of the perturbed eastern boundary current circulation. Anomalous onshore advection associated with the perturbed atmospheric circulation, deeper than normal mixed layers, or depression of the thermocline and halocline by the passage of Rossby waves could each account for coincident positive temperature and negative salinity anomalies.