Role of mixed layer turbulence on the generation of internal waves

Turbulence in the ocean mixed layer is a major source of internal gravity waves, yet the efficiency and pathways of this energy transfer remain less understood. We investigate how mixed-layer turbulence excites internal waves and drives the rapid decay of mixed-layer kinetic energy following strong forcing events. Using numerical simulations of a turbulent mixed layer overlying a stratified interior, we explicitly resolve the generation and propagation of internal waves. The non-hydrostatic model shows that surface wave-generated turbulence in the mixed layer radiates high-frequency internal waves near the buoyancy frequency, exporting ~13% of the mixed-layer energy in 20 hours. A hydrostatic model shows that near-inertial baroclinic modes, especially mode 2, redistribute this energy vertically over 2–10 days. These mechanisms provide a fast, localized pathway for upper‑ocean mixing. Normal-mode and spectral analyses link this turbulent radiation to low-baroclinic modes, near-inertial adjustment, and anisotropic wave emission in the presence of a background flow. Together, these results provide compact scaling relations that connect observable mixed-layer properties and turbulence intensity to internal-wave energy fluxes, enabling realistic parameterizations of mixed–layer–to–interior energy transfer in ocean and climate models.