Publications

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2015
Fiedler, JW, Brodie KL, McNinch JE, Guza RT.  2015.  Observations of runup and energy flux on a low-slope beach with high-energy, long-period ocean swell. Geophysical Research Letters. 42:9933-9941.   10.1002/2015gl066124   AbstractWebsite

The transformation of surface gravity waves from 11 m depth to runup was observed on the low-sloped (1/80) Agate Beach, Oregon, with a cross-shore transect of current meters, pressure sensors, and a scanning lidar. Offshore wave heights H-0 ranged from calm (0.5 m) to energetic (> 7 m). Runup, measured with pressure sensors and a scanning lidar, increases linearly with (H0L0)(1/2), with L-0 the deep-water wavelength of the spectral peak. Runup saturation, in which runup oscillations plateau despite further increases in (H0L0)(1/2), is not observed. Infragravity wave shoaling and nonlinear energy exchanges with short waves are included in an infragravity wave energy balance. This balance closes for high-infragravity frequencies (0.025-0.04 Hz) but not lower frequencies (0.003-0.025 Hz), possibly owing to unmodeled infragravity energy losses of wave breaking and/or bottom friction. Dissipative processes limit, but do not entirely damp, increases in runup excursions in response to increased incident wave forcing.

2006
Thomson, J, Elgar S, Raubenheimer B, Herbers THC, Guza RT.  2006.  Tidal modulation of infragravity waves via nonlinear energy losses in the surfzone. Geophysical Research Letters. 33   10.1029/2005gl025514   AbstractWebsite

The strong tidal modulation of infragravity (200 to 20 s period) waves observed on the southern California shelf is shown to be the result of nonlinear transfers of energy from these low-frequency long waves to higher-frequency motions. The energy loss occurs in the surfzone, and is stronger as waves propagate over the convex low-tide beach profile than over the concave high-tide profile, resulting in a tidal modulation of seaward-radiated infragravity energy. Although previous studies have attributed infragravity energy losses in the surfzone to bottom drag and turbulence, theoretical estimates using both observations and numerical simulations suggest nonlinear transfers dominate. The observed beach profiles and energy transfers are similar along several km of the southern California coast, providing a mechanism for the tidal modulation of infragravity waves observed in bottom-pressure and seismic records on the continental shelf and in the deep ocean.

Henderson, SM, Guza RT, Elgar S, Herbers THC, Bowen AJ.  2006.  Nonlinear generation and loss of infragravity wave energy. Journal of Geophysical Research-Oceans. 111   10.1029/2006jc003539   AbstractWebsite

[1] Nonlinear energy transfers with sea and swell (frequencies 0.05-0.40 Hz) were responsible for much of the generation and loss of infragravity wave energy (frequencies 0.005-0.050 Hz) observed under moderate- and low-energy conditions on a natural beach. Cases with energetic shear waves were excluded, and mean currents, a likely shear wave energy source, were neglected. Within 150 m of the shore, estimated nonlinear energy transfers to ( or from) the infragravity band roughly balanced the divergence (or convergence) of the infragravity energy flux, consistent with a conservative energy equation. Addition of significant dissipation (requiring a bottom drag coefficient exceeding about 10(-2)) degraded the energy balance.