Drivers of the Continuous Oceanic Energy Spectrum at High Frequencies: A realistic modeling approach

The dynamic processes that generate a continuous oceanic energy spectrum remain poorly understood. We investigate the relative roles of tides, mesoscale eddies, high-frequency winds, and nonlinear interactions using a submesoscale-resolving ICON simulation of the South Atlantic, which captures substantially more ocean variability than conventional eddy-resolving models. Model realism is demonstrated by comparing simulated energy spectra with observations from a dedicated field campaign and satellite data. Sensitivity experiments isolate individual processes, including simulations without tidal forcing to suppress tidal waves, without high-frequency winds to suppress near-inertial waves and without mesoscale eddies to reduce wave–mean-flow interactions. Frequency–wavenumber spectra are used to distinguish random variability from wave-driven variability by identifying elevated energy along the first modes of the dispersion relation. We find that tides and high resolution are essential to reproduce realistic energy levels in the internal wave band. Suppressing near-inertial waves reduces energy between tidal peaks while enhancing energy at the peaks, highlighting the importance of wave–wave interactions in sustaining a continuous spectrum. In contrast, suppressing mesoscale eddies has a weaker effect, suggesting that wave–mean-flow interactions play a less significant role.