On the Momentum, Vorticity and Mass Balance on the Oregon Shelf

Abstract Velocity measurements from the continental shelf off Oregon taken during the Coastal Upwelling Experiment CUE-2 in the summer of 1973 are utilized to investigate momentum, vorticity and mass balance relationships for subinertial frequency (ω < 0.6 cpd) current fluctuations. Measurements from stations in water of depths of 54, 100 and 200 m are utilized. By a comparison of the magnitude of terms involving horizontal velocities in the linear momentum and in the nonlinear, depth-integrated momentum equations, support is found for the linear geostrophic balance of the alongshore velocity in the onshore-offshore momentum equation and, in the depth range 100 m ≤ H ≤ 200 m, for a linear ageostrophic balance in the alongshore momentum equation. Evidence is also found to support the validity of a linear depth-integrated vorticity balance, again for depths 100 m ≤ H ≤ 200 m. In this balance, which is similar to that in the theory for continental shelf waves, the interaction of the onshore velocity with the...