[1] In the ocean, interaction among the mean current, the surface waves, and turbulence is a major mechanism for energy transfer from surface waves to the turbulence field. This process is associated with attenuation of surface waves. This paper deals with waveturbulence interaction and its induced mixing using field observations and a onedimensional, level 2.5 turbulence closure model. The results show that both the turbulence kinetic energy dissipation rate and the vertical mixing induced by wave-turbulence interaction are a function of u s0 u * 2 and wave parameters, where u s0 is the Stokes drift at the sea surface and u * is the friction velocity in water. The former decays with the depth away from the surface in the form of e 2kz , while the latter decays as e 3kz (k is the wave number). We also analyze the wave decay induced by wave-turbulence interaction. The decay time scale is in proportion to cL/u * 2 , while in inverse proportion to ffiffi ffi p , where c is a phase speed, L is a wavelength, and d is a wave steepness. A series of numerical experiments are performed to evaluate the effects of wave-turbulence interaction. The results from the cases with effects of wave-turbulence interaction show significant improvement in simulation of turbulence characteristics compared to the cases in the absence of surface waves. This implies that wave-turbulence interaction is a significant mechanism for generation of turbulence kinetic energy in the upper ocean and plays an important role in regulating vertical mixing and surface wave decay.

[1] The Mellor-Yamada turbulence closure scheme, used in many ocean circulation models, is often blamed for overly high simulated surface temperature and overly low simulated subsurface temperature in summer due to insufficient vertical mixing. Surface waves can enhance turbulence kinetic energy and mixing of the upper ocean via wave breaking and nonbreaking-wave-turbulence interaction. The influences of wave breaking and wave-turbulence interaction on the Mellor-Yamada scheme and upper ocean thermal structure are examined and compared with each other using one-dimensional and threedimensional ocean circulation models. Model results show that the wave-turbulence interaction can effectively amend the problem of insufficient mixing in the classic MellorYamada scheme. The behaviors of the Mellor-Yamada scheme, as well as the simulated upper ocean thermal structure, are significantly improved by adding a turbulence kinetic energy production term associated with wave-turbulence interaction. In contrast, mixing associated with wave breaking alone seems insufficient to improve significantly the simulations as its effect is limited to the very near-surface layers. Therefore, the effects of wave-turbulence interaction on the upper ocean are much more important than those of wave breaking.

[1] The critical role of oceanic surface waves in climate system is attracting more and more attention. We set up an Earth System Model, which is named as the First Institute of Oceanography-Earth System Model (FIO-ESM), composed of a coupled physical climate model and a coupled carbon cycle model. A surface wave model is introduced through including the nonbreaking wave-induced vertical mixing, which can improve the performance of climate model especially in the simulation of upper ocean mixed layer depth in the southern ocean, into the ocean general circulation model. The FIO-ESM is employed to conduct Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments. The historical simulation of FIO-ESM's physical climate model for shows that the simulated patterns of surface air temperature (SAT), rainfall, and El Niño-Southern Oscillation (ENSO) match those of the observations. Future projections under the four scenarios of RCP2.6, RCP4.5, RCP6.0, and RCP8.5 are also conducted and the global averaged SAT in 2100 would be À0.007 C, 1.10 C, 1.85 C, and 3.92 C higher than that in 2005, respectively. The historical simulation and future projection under RCP8.5 with global carbon cycle show the SAT and atmospheric CO 2 concentration are well reproduced in the historical period and the global averaged SAT would increase by 3.90 C in 2100, which is quite similar to the physical climate model's result. Further analysis shows surface wave makes projected SAT in RCP2.6 about 2 C cooler in the Arctic area and 2 C warmer in the southern ocean.

The ability of CMIP5 models in simulating surface mixed layer depth (MLD) during summer is assessed using 45 climate models. Their ocean models differ greatly in terms of vertical mixing parameterizations and model configurations. In some models, effects of surface waves, Langmuir circulations, submesoscale eddies, as well as additional wind mixing are included to improve upper-ocean simulation. Similar to findings by previous studies, the summer MLDs are significantly underestimated in most of the models. Compared with the observation, only five of these models have deeper summer MLDs in the Southern Ocean, eight models have deeper summer MLDs in the central North Atlantic Ocean, and nine models have deeper summer MLDs in the central North Pacific Ocean. This underestimation of MLD is not caused by sea surface forcing, because most of the models tend to overestimate the surface wind stress, while they underestimate the net surface heat flux. Therefore, insufficient vertical mixing in the upper ocean may still be one of the potential reasons for this systematic underestimation of MLD in the climate models.