Currents and water masses at the entrance to the Gulf of California, spring 1970

Graduation date: 1975Hydrographic data and drogue observations were used to describe\ud the circulation and water masses in the upper 500 meters of\ud the region of the entrance to the Gulf of California in the early spring\ud of 1970.\ud The thermohaline structure of the water and the general circulation\ud in the vicinity of the entrance to the Gulf of California indicated\ud that four water masses were present. California Current water on\ud the western side of the entrance, Subtropical Surface water in the\ud middle part and Gulf water on the eastern side. Underlying these\ud three waters, Subtropical Subsurface water was found from about\ud 150 to 500 meters.\ud The geostrophic calculations indicate that a broad region of\ud outflow from the Gulf existed on the eastern side associated with a\ud marked upward displacement of isopycnals towards the east.\ud Speeds were near 30 cm/sec at the surface and decreased to less\ud than 3 cm/sec at 300 meters. Outflow also occurred on the western\ud side, near the Baja California coast, at lower speeds. Inflow to the\ud Gulf was observed near the middle part of the entrance at speeds of\ud 30 to 40 cm/sec at the surface, decreasing to less than 6 cm/sec at\ud 300 meters.\ud The drogue observations were in agreement with the general\ud circulation pattern inferred from geostrophic currents. Drogue and\ud geostrophic velocities showed agreement better than 70% at 10 and 50\ud meters.\ud The decrease of geostrophic velocity with depth indicates that\ud a baroclinic condition existed. Comparison of these velocities with\ud the drogue measurements indicates that the baroclinic circulation\ud was predominant in the upper 100 meters.\ud In the upper 150 meters the low salinity water from the California Current was flowing into the Gulf. The high salinity Gulf water\ud was found in the regions of outflow as to be expected to avoid accumulation\ud of salt inside the Gulf by strong evaporation