Observations of Breaking Wave Dissipation and Their Relationship to Atmosphere-Ocean Energy Transfer

Abstract

Energy is transferred from the atmosphere to the ocean primarily through ocean surface waves, and the majority is dissipated locally in the near-surface ocean. Observations of turbulent kinetic energy (TKE) in the upper ocean have shown dissipation rates exceeding law-of-the-wall theory by an order of magnitude. The excess near-surface ocean TKE dissipation rate is thought to be driven primarily by wave breaking, which limits wave growth and transfers energy from the surface wave field to the wave-affected layer of the ocean. Here, the statistical properties of breaking wave dynamics in a coastal area are extracted from visible imagery and used to estimate TKE dissipation rates due to breaking waves. The statistical properties of whitecap dynamics are quantified with Λ(c), a distribution of total whitecap crest length per unit area as a function of crest speed, and used to compute energy dissipation by breaking waves, S_ds. S_ds approximately balances elevated subsurface dissipation in young seas but accounts for only a fraction of subsurface dissipation in older seas. The wind energy input is estimated from wave spectra from polarimetric imagery and laser altimetry. S_ds balances the wind energy input except under high winds. Λ(c)-derived estimates of TKE dissipation rates by breaking waves compare well with the atmospheric deficit in TKE dissipation, a measure of energy input to the wave field (Cifuentes-Lorenzen et al., 2024). These results tie the observed atmospheric dissipation deficit and enhancement in subsurface TKE dissipation to wave driven energy transport, constraining the TKE dissipation budget near the air-sea interface.