|Title||The suppression of surfzone cross-shore mixing by alongshore currents|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||dispersion; eddy diffusivity; equations; generation; mean longshore-current; nearshore; shear instabilities; southern-ocean; transport; waves|
Mixing by horizontal surfzone eddies is important to the cross-shore exchange of material through the surfzone. Surfzone cross-shore mixing for normally and obliquely incident waves, with very similar incident significant wave heights and directional spreads, is quantified using Boussinesq modeled drifter trajectories. For t < 100 s, surfzone cross-shore diffusivities K(t) are independent of incident wave angle <(theta)over bar> owing to similar eddy velocities nu approximate to 0.1 m s(-1). For 600 < t < 10, 000 s, K(t) is maximum for normally incident waves and decreases with incident wave angle. Thus, the mixing parameterization K proportional to nu L-E is not completely applicable to the surfzone, because. and LE do not change for these experiments. Reduced mixing for obliquely incident waves results from large eddies (wavelengths > 200 m) propagating at a velocity C different than the mean current velocity V(x)-the same mechanism that reduces mixing for mesoscale eddies.