Upper‐ocean mixing due to surface gravity waves

Abstract

Surface gravity waves play an important role in the lower layer of the atmosphere and the upper layer of the ocean. Surface waves effect upper‐ocean mixing mainly through four processes: wave breaking, Stokes drift interaction with the Coriolis force, Langmuir circulation, and stirring by nonbreaking waves. We introduce the impact of these four processes into a 1‐D k−ϵ ocean turbulence model. The parameterizations used are based mainly on existing investigations. Comparison of simulation results and measurements demonstrates that considering all the effects of waves, rather than just one effect, significantly improves model performance. The nonbreaking‐wave‐induced mixing and Langmuir turbulence are the most important terms when considering the impact of waves on upper‐ocean mixing. Under high‐wave conditions, the turbulent mixing induced by nonbreaking waves can be of the same order of magnitude as the viscosity induced by other terms at the surface. Nonbreaking waves contribute very little to shear production and their impact is negligible in the models. Sensitivity experiments demonstrate that the vertical profile of the Stokes drift calculated from the 2‐D wave spectrum improves model performance significantly compared with other methods of introducing wave effects.

Modeling the Effect of Waves on the Diurnal Temperature Stratification of a Shallow Lake

“…For α this set up is in agreement with most of the studies, where it also is treated as 1.0 [11,14,25]. The empirical constant β ranges between 0.15 and 1.5 by fitting Eq.…”

“…If the wave spectrum is narrow enough bulk parameters can indeed characterize the effect of the irregular wave motion with sufficient accuracy, as opposed to deriving turbulent mixing and shear production from the spectrum [19]. In the absence of a wave spectrum (modeled or measured), many researchers successfully applied mixing parametrizations based on bulk characteristic [14,23] but it has to be underlined that several studies reported that model results improve significantly by using a 2D spectral wave model since wave mixing can be overestimated by bulk parametrizations [25,26].…”

A comparative study of wave‐current interactions over the eastern Canadian shelf under severe weather conditions using a coupled wave‐circulation model

“…It should be noted that Langmuir cells (with a length scale of ∼5–100 m) cannot be resolved with this horizontal resolution. Incorporating the impact of Langmuir cells on the ocean mixing requires an additional parameterization [ Wu et al ., ], which is a topic of future studies. There are 40 sigma levels in the vertical which are concentrated near the surface and bottom, and are equally distributed in the interior.…”

“…[] also showed that mesoscale eddies can be detected from the synthetic aperture radar images via the influence of eddy currents on the surface wave fields. In the ocean upper layer, the Coriolis‐Stokes force, Langmuir circulation, breaking, and nonbreaking wave‐induced mixing all contribute to the upper ocean mixing [ Wu et al ., ]. For example, Zhang et al .…”

Impact of wave breaking on upper-ocean turbulence

“…The experimental settings of the control experiment Exp_NW are same as those of the Exp‐1 in Wu et al . [], except that the vertical resolution is set to 0.2 m in this study. For details of the parameters for experiments Exp_NW and Exp_1, refer to Wu et al .…”