Hydrographic variability in an upwelling area off northern Baja California in June 1976

Abstract

Hydrographic, wind and current observations we re made near Punta Colonet, Baja California at the peak of the upwelling season in June 197 6. The mean hydrographic fields were typical of the seasonal mean upwelling over the continental sh elf and the poleward undercurrent confined to a narrow zone (<20 km) over the slope. The density field exhibited a response to variation of the alongshore component of wind velocity. Stronger winds were followed by upwarping of the shallow isosurfaces over the inner shelf and comple te vertical mixing within about 7 km of shore. The effect of the prominent cape of Punta Colonet, evident at the surface as a tongue-like structure of colder water oriented down-stream and offshore o f the point, was not discernible at 20 m depth. One day of current profiles indicated strong equato rward flow in the upper layer decreasing uniformly with depth. The cross-shelf flow was vari able and weak in the mean. The hydrographic data over the continental slope suggested the wi dth of the undercurrent and presumably its strength varied greatly over periods of days.