Role of wave breaking in the air–sea interaction - Breaking and Dissipation of Ocean Surface Waves - page 382

Figure 9.9 Scheme of momentum fluxes and mixing processes which couple waves and currents.
Processes are indicated for horizontally uniform conditions, and possible profiles of eddy viscosity
K Z and drift velocity U are shown. Figure is reproduced from Ardhuin et al. ( 2005 ) by permission
of American Geophysical Union

in a in

τ = τ 0 , direct flux to the mean flow τ − τ = T r , and the flux from the waves to

dis
which goes into wave growth (or wave decay for that matter, if the wave-breaking stress is
greater than the input stress, see (9.27) below).
More details of the wave influence are shown below the surface. Here, the wave-breaking
sublayer is highlighted where the momentum fluxes are dominated by the direct wave-
breaking action. Its vertical scale is of the order of significant wave height H s . Other
vertical scales indicated are the characteristic depth of penetration of Stokes drift and
MLD. Near the bottom at depth h , two other vertical scales can be mentioned which
correspond to the wave bottom-boundary layer

dis in

the mean flow τ = τ c . Net stress to the waves is also demonstrated as τ w = τ − τ

δ 1 (provided that the ocean is shallow
enough to still experience the wave action at the bottom) and to the thicker current-bottom
boundary layer

δ 2 . Vertical solid lines demonstrate profiles of eddy viscosity K Z and drift

velocity U .