Record coastal upwelling in the California Current in 1999

An extremely unusual level of coastal upwelling in the spring and summer of 1999 over much of the California Current system (CCS) is described, based on direct and indirect observations. Wind and ocean anomalies in 1999, a pe riod characterized by an equatorial La Nina, are compared to climate trends for the previous several years, and specifically contrasted with the extre mes associated with the 1997-98 El Nino event. Conditions in the CCS during the spring and summer of 1999) were consistent with extremely high levels of sustained coastal upwelling. The Pacific Fisheries Environmental Laborat ory (PFEL) upwelling indices reached record highs fur a series extending ba ck to 1946. Strong, sustained upwelling-favorable winds were measured at co astal buoys through late 1998 and much of 1999. Coastal sea-surface tempera tures (SSTs) were 3 degrees -4 degreesC below their seasonal mean in spring 1999, and about 10 degrees cooler than the region experienced in late 1997 . Hydrographic surveys of central California suggest upwelling of water by 100 m or more relative to the long-term spring average. Coastal sea-level ( CSL) anomalies ill the northern CCS were the lowest in at least 65 years. G reater than usual southward transport by the California Current is implied. A number of population and ecological changes observed during this period may be linked to the unusual ocean conditions and the striking transition f rom El Nino to La Nina. Physical conditions in the CCS can change swiftly a nd dramatically, and its marine populations appear to respond nearly as rap idly. The large physical and biological changes that occurred in 1999 may s ignify the initiation of a new climate regime for the CCS.