Sandwave migration in Monterey Submarine Canyon, Central California

Repeated high-resolution multibeam bathymetric surveys from 2002 through 2006 at the head of the Monterey Submarine Canyon reveal a sandwave field along the canyon axis between 20 and 250 m water depth. These sandwaves range in wavelength from 20 to 70 m and 1 to 3 m in height. A quantitative measure was devised to determine the direction of sandwave migration based on the asymmetry of their profiles. Despite appreciable spatial variation the sandwaves were found to migrate in a predominantly down-canyon direction, regardless of season and tidal phases. A yearlong ADCP measurement at 250 m water depth showed that intermittent internal tidal oscillations dominated the high-speed canyon currents (50–80 cm/s), which are not correlated with the spring–neap tidal cycle. Observed currents of 50 cm/s or higher were predominantly down-canyon. Applying a simple empirical model, flows of such magnitudes were shown to be able to generate sandwaves of a size similar to the observed ones.