Structure of a coastal upwelling event observed off Oregon during July 1973

Abstract

A few coastal upwelling events occur during summer off the Oregon coast. During one such event in July 1973 the southward wind stress (maximum t′'_o ≈ 5dynes cm⁻² occured between periods of northward stress. Vertical velocities from hydrographic observations decreased exponentially with distance offshore, producing a zonal scale about 15 km. The time scale for the onset of the mesoscale waas 1 to 3 days. At the surface the wind-generated surface drift was about 50 cm⁻¹, 45°cum sole to the direction of the wind stress. The wind-drift layer was about 15 m thick and the eddyviscosity coefficient of the turbulent motions within it was about 55 cm²s⁻¹. During the event the Ekman transport computed from wind observations was nearly equal to the measured offshore transport. Several of the observations were compared with recent hypothesis of the dominant processes controlling the dynamics of coastal upwelling.