- Shore-based video remote sensing is used to observe and continually monitor nonlinear internal waves
propagating across the inner shelf. Month-long measurements of velocity from bottom-mounted acoustic
Doppler current profilers and temperature from thermistor chains at the 10- and 20-m isobaths are combined
with sea surface imagery from a suite of cameras (Argus) to provide a kinematic description of 11 borelike
internal waves as they propagate across the central Oregon inner shelf. The surface expression of these waves,
commonly seen by eye as alternating rough and smooth bands, are identified by increased pixel intensity in
Argus imagery (average width 39 ± 6 m), caused by the convergence of internal wave-driven surface currents.
These features are tracked through time and space using 2-min time exposure images and then compared to
wave propagation speed and direction from in situ measurements. Internal waves are refracted by bathymetry,
and the measured wave speed (~0.15 m s⁻¹) is higher than predicted by linear theory (< 0.1 m s⁻¹).
Propagating internal waves are also visible in subsampled Argus pixel time series (hourly collections of 17 min
worth of 2-Hz pixel intensity from a subset of locations), thus extending the observational record to times
without an in situ presence. Results from this 5-month record show that the preferred sea state for successful
video observations occurs for wind speeds of 2–5 m s⁻¹. Continued video measurements and analysis of extensive
existing Argus data will allow a statistical estimate of internal wave occurrence at a variety of inner-shelf