The flow of the undercurrent over the continental borderland off southern California

Complex bathymetric features offshore of southern California have a pronounced effect upon the flow of the California Undercurrent Geostrophic dynamics and water mass characteristics are used to reveal the various paths of flow and spread of undercurrent waters for a July 1985 survey. Undercurrent waters are identified by relatively high spiciness and low dissolved oxygen at densities between σt = 26.4 and 26.9 (∼200 to 400 m). A jetlike core of flow follows the continental slope within the California Bight and exits the bight through a gap in the Santa Rosa‐Cortes Ridge. Mixtures that include undercurrent waters exit the bight through other gaps in the bathymetric ridge and about the southern end of the ridge. As evidenced by patterns in the fields of geostrophic currents and water mass characteristics, baroclinic instabilities develop about the ridge which result in the diversion of undercurrent waters offshore beneath the California Current and into the offshore mesoscale eddy field. The offshore subsurface diversion of undercurrent waters and their inclusion in the offshore mesoscale eddy field are also found in the long‐term mean distributions for July.