The fall transition off Central California in 2002

Abstract

During the fall of 2002 the physical oceanographic conditions off Central California were monitored by means of CTD casts and VMADCP current measurements during two cruises. The first cruise, included 38 stations and one time series station. The second cruise was sponsored by the Naval Oceanographic Office (NAVOCEANOCEANO) and occupied nine sections along the coast. A total of 86 stations and two time series stations were occupied during the second cruise. CTD calibration and data processing methods are described. The isosteres, current vectors, and salinity distribution from the cruises provide a clear picture of the circulation pattern during the fall 2002. A strong shoreward, anticyclonic meander of the California current was observed. Although the meander itself did not cross the dynamic trough that separated inshore and offshore currents, at the point where the meander was adjacent to the trough, a ridge formed which transported Subarctic waters into the coastal zone. These fresh waters were advected to the north and south along the coast, depending upon the direction of nearshore currents. The observed mesoscale circulation showed the manner in which waters which are upwelled at the coast in summer are replaced by oceanic waters in the fall and winter. Analysis of the geography of the deep sound channel (DSC) during this period showed that the mean pressure of the DSC was at 586 dbar while the mean sound speed minimum was 1480 m/s. The minimum sound speed varied 3 m/s while the pressure of the minimum varied by 330 dbars. The shape of the pycnocline controlled the pressure and depth of the DSC in the region.