Altimeter-derived variability of surface velocities in the California Current System: 2. Seasonal circulation and eddy statistics

Abstract

Satellite surface height and temperature fields are used to examine the seasonal surface circulation in the California Current System. In spring and summer, an equatorward jet develops next to the coast, with an initial latitudinal structure that responds to the latitudinal distribution of equatorward alongshore winds. This jet moves offshore from spring to fall and develops meanders and closed eddies that contribute eddy kinetic energy and water mass properties to the nearby deep ocean. Higher EKE appears first in spring near the coast and moves offshore with the seasonal jet. Along altimeter tracks parallel to the coastline 200 and 400 km offshore, the greatest EKE is found in summer and fall, respectively, with wavelengths of approximately 300 km. These are the wavelengths of the largest meanders and the distance between the largest eddies visible in altimeter “snapshots” of the jet. At 600–800 km offshore, the wavelengths are generally smaller (100–150 km), similar to eddy sizes reported by others for the quiescent northeast Pacific. Some energy with longer wavelengths arrives at the track 600 km offshore in winter and 800 km offshore in spring, which we interpret as the most offshore extension of the EKE generated by the jet and eddy system closer to the coast in the previous spring and summer. A sequence of snapshots from October 1992 to October 1993 shows details of the evolution of the jet and eddy system over one complete annual cycle.