HR: 0800h
AN: OS11A-0492    [Abstracts]
TI: Energy Flux Balance of Surfzone Infragravity Waves
AU: * Sheremet, A
EM: ashere1@lsu.edu
AF: Coastal Studies Institute and Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803 United States
AU: Guza, R T
EM: rtg@coast.ucsd.edu
AF: Integrative Oceanography Division,Scripps Institution of Oceanography,, University of California at San Diego, La Jolla, CA 92093-0209 United States
AU: Herbers, T H
EM: thherber@nps.edu
AF: Department of Oceanography, Naval Postgraduate School, Monterey, CA 93943 United States
AU: Elgar, S
EM: elgar@whoi.edu
AF: Woods Hole Oceanographic Institution, MS #11, Woods Hole, MA 02513 United States
AB: Infragravity waves, with periods (between roughly 20-200 s) longer than sea-swell (between about 2-20 s), are ubiquitous on ocean shorelines. Generation by groups of sea and swell, dissipation, shoreline reflection, and refractive trapping have been suggested to contribute significantly to the infragravity energy balance in shallow, nearshore waters. Methods used previously to analyze infragravity wave data either have assumed unidirectionality or have neglected dissipation (i.e. associated all trapped energy with edge waves). Here, spectra of cross-shore infragravity energy fluxes in alongshore wavenumber - frequency space are estimated from pressure and cross-shore velocity measured on alongshore-oriented transects using a new method based on the WKB approximation. The energy fluxes of infragravity waves are studied using field observations from five alongshore arrays deployed for 4 months across the shoaling and surf zones (between 1- and 5-m water depth) of a gently sloping sandy beach. Estimates of cross- and alongshore infragravity energy flux allow calculation of the distribution of the flux reflection coefficient in the alongshore wavenumber - frequency space, as well as bulk (frequency-integrated) reflection coefficients for trapped and leaky waves. Results suggest dissipation occurs over a broad range of infragravity frequencies, and at oblique angles with alongshore wavenumber within the range of theoretically trapped waves. Supported by ONR and NSF.
DE: 4546 Nearshore processes
DE: 4560 Surface waves and tides (1255)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting