Thus, there are several active generation mechanisms. The first is the usual shelf-break one. Winds may also drive inertial and tidal-frequency motions. Another possible mechanism is barotropic flow over Astoria Canyon. The degree to which the other three mechanisms contribute to non-linearity of plume internal tides is unknown.
River flow provides the buoyancy that supports plume stratification.
Tides have a mixed effect, providing more buoyant outflow and stronger advection of low density water, but also more vertical turbulent mixing. Negative of the windstress is plotted, because of the destruction of stratification by wind-induced mixing. Its temporal structure has little influence on the frequency structure of the stratification, because near-surface fluctuations are much greater. The cross-shore flow is mostly offshore and typically weaker than the alongshore flow. Velocities are much weaker than near the estuary mouth.