Field observations of shear waves in the surf zone
Noyes, T. James
Guza, R. T.
Herbers, T. H. C.
MetadataShow full item record
Alongshore propagating meanders of the mean alongshore current in the surf zone called shear waves have periods of a few minutes and wavelengths of a few hundred meters. Here shear wave properties are estimated with arrays of current meters deployed for 4 months within 300 m of the shoreline of a sandy beach. Shear wave velocity fluctuations are approximately horizontally isotropic, with root mean square values between 10 and 40% of the mean (3-hour-averaged) alongshore current V. Cross-shore variations of the time-averaged shear wave momentum flux are consistent with shear wave energy generation close to shore where the breaking wave-driven mean alongshore current V and current shear Vx are strong and with shear wave energy dissipation and transfer back to the mean flow farther offshore where V and Vx are weak. In case studies where V is a narrow jet near the shoreline the observed strong decay of shear wave energy levels seaward of the jet, and the cross-shore and alongshore structure of shear waves within the jet, are similar to predictions based on the linearly unstable modes of the observed V. Shear wave energy levels also are high in a marginally unstable case with a strong, but weakly sheared, V.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C01031, doi:10.1029/2002JC001761.
Showing items related by title, author, creator and subject.
Duda, Timothy F. (2005-10-03)Four drifting floats were used to measure the magnitude of the vertical derivative of horizontal velocity in waters above the rough bathymetry of the Mid Atlantic Ridge. This derivative is typically the dominant component ...
Rakow, Kelly C.; Graham, William M. (2006)Individual Aurelia sp. medusae were distributed around regions of current shear associated with vertical density discontinuities during three vertically towed camera profiles in the northern Gulf of Mexico. Along shear ...
Ralston, David K.; Stacey, Mark T. (Sears Foundation for Marine Research, 2006-01)In intertidal regions with subtidal channels, effects of bathymetry on overlying flow vary greatly with tidal stage. Around low water when mudflats and marsh are exposed, flow is constrained to channels, but when water ...