Frequency-wavenumber spectra of shoaling ocean waves

Accurate knowledge of the kinematics and dynamics of ocean waves as they shoal and break in even the simplest morphological situation is a major challenge of current research. The resulting energy flux and radiation stresses drive nearshore turbulence and currents, and these scour up and transport sediments in prodigious amounts during storms. In addition, the high dynamic forces during breaking are a danger to safety of engineering surveying, construction and military operations. This paper describes a new technique for measuring ocean waves, observing these processes and calculating many of the important underlying parameters. A time series of optical images is collected from an aircraft, these are registered to a stationary, geodetic coordinate system on the surface, and 3-D cubes of these data are Fourier transformed to calculate 3-D frequency-wavenumber spectra. These are examined for wave information, including measuring their dispersion, which is interesting in its own right but also used to retrieve the water depth and current field in which the waves are propagating.