Headland Rip Very Low Frequency Fluctuations and Surfzone Eddies During High-Energy Wave Events

Abstract A wave-group-resolving model is used to investigate the driving mechanisms and spatiotemporal variability of very low frequency (VLF) fluctuations a headland deflection rip, measured during 4-m oblique wave event. Surfzone eddies (SZE) occurring in presence strongly sheared longshore current V at longshore-uniform beach are first modeled. The spectral signature SZE displayed compared with literature. then explore dynamics vorticity surf zone against under energetic conditions. resulting weakly found host large-scale propagating toward speed decreasing seaward. Vorticity animations diagrams indicate that VLF rip driven by upstream SZE. In line measurements, periods from 40 min 1 h dominate spectrum hundreds meters tide. At high tide, spectra much narrower than zone, suggesting enforces merging This mechanism further analyzed using idealized simulations varying lengths, aiming extending traditional patterns scale. Finally, we discuss existence continuum mechanisms, going fully wave-group-driven both wave-group- shear-instability-driven for , respectively. suggests importance groups produce