This work sits among studies of infragravity wave generation in the surf zone, alongside topics such as inflation, the cosmic microwave background, and baryon acoustic oscillations. Neighboring works examine waves frozen at a moving source, gravitational waves from charged fields, internal ocean waves, and primordial black holes. This paper stands out by considering the finite extent and evolution of the breaking zone rather than an idealized breaking point, which allows separating the contributions of breaking and bound waves within the same wave field.
The authors derive a local decomposition of the forcing into breaking and bound-wave contributions from the energy balance equation for short waves. They then describe the breaking forcing field as a finite, evolving source via its integral strength, centroid, cross-shore width, and shape. Using a Green's function, they obtain the radiated response and analyze the roles of breaking depth, finite-source interference, and forcing-region migration. Numerical experiments with a wave-resolving model are conducted for nine beach slopes ranging from 1:10 to 1:50.
The finite source width creates spatial interference: phase differences among contributions from different points attenuate the high-frequency part of the infragravity response, and this attenuation shifts to lower frequencies as the source widens. Source migration induces a directional Doppler shift: shoreward motion compresses arrivals at a shore-based observer and stretches them at a sea-based observer. The breaking depth controls both the conversion of forcing into surface elevation and the speeds that determine travel-time effects. Numerical experiments reproduce the predicted signatures: wider source footprints enhance attenuation of the upper band on both branches. The diagnosed migration history, with the strongest breaking during shoreward motion, partially compensates this attenuation near the shore and enhances it offshore.
This work differs from neighboring studies by providing an exact local separation of infragravity wave generation mechanisms applicable in irregular wave fields. Unlike idealized models with a moving point of breaking, it accounts for the finite width of the breaking zone, leading to new filtering and Doppler shift effects. This allows direct diagnosis of the breaking contribution in wave-resolving models and better interpretation of field measurements.
The topic could advance by testing the mechanisms in phase-resolving models, laboratory experiments, and field observations. One could also investigate the influence of wave height, period, and spectral width on source properties. It is important to account for the surface roller, which delays and distributes the effective forcing, as well as nonlinear effects near the shore.
The results will affect modeling of coastal flooding and sediment transport, as well as the design of harbor structures susceptible to resonance.
Next steps include validating the predictions in phase-resolving simulations and laboratory wave flumes, and analyzing field data from reefs and beaches.
In nearshore hydrodynamics, the exact contribution of different generation mechanisms to infragravity waves under real conditions remains unresolved. This work offers a method to separate the contributions of breaking and bound waves, bringing us closer to solving this problem. However, the role of nonlinear interactions and reflection from the shore remains an open question.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The authors separate the contribution of wave breaking and bound waves to infragravity wave generation by treating the surf zone as a finite moving source. They show that the source width causes spatial interference that suppresses high frequencies, while source migration produces a Doppler shift. Numerical experiments on beaches with different slopes confirm the predictions.
Where its strength is
A precise local separation of infragravity wave generation mechanisms, applicable in irregular wave fields, accounting for the finite width of the surf zone, which yields new filtering and Doppler shift effects.
Where it could go next
Worth trying
Why this may matter
Accounting for the finite width of the surf zone could improve the interpretation of field measurements of infragravity waves and refine energy transfer models in the coastal zone, which is important for predicting wave impact on shores.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.50, against a usual 0.64. It looks like few have drilled nearby.
Infragravity waves have periods from 20 to 250 seconds, comparable to the time it takes for a person to take several breaths. These waves can cause water level oscillations in harbors, leading to resonance that rocks moored vessels.