The Effects of Ice and Currents on Wave-driven Turbulence at the Ocean Surface

In the open ocean, wind driven wave breaking imparts turbulent kinetic energy (TKE) to the ocean surface, which then diffuses downward. Despite the process being wave driven, the flux of TKE is often successfully parameterized from wind measurements by invoking wind-wave equilibrium. In more complex environments, the pathways for mechanical energy and momentum between the atmosphere, waves, and ocean are less direct. We present measurements of wave spectra and near surface turbulent dissipation rates measured from SWIFT drifters at two field sites, one influenced by ice, the other by currents. In partial ice cover, atmospheric momentum is partitioned between ice and ocean, and feedback between waves and ice damps wave breaking, muting exchanges through the air-ocean interface. Measurements from the Beaufort Sea show that surface roughness (as wave mean squared slope) is well correlated with near surface turbulence (as TKE dissipation rate), and both are reduced by two orders of magnitude in partial ice cover. This implies a smaller partition of atmospheric momentum directly to the ocean surface than previously thought. At river inlets, shallow depths and opposing currents enhance wave breaking, increasing the exchange of momentum and energy from the waves to the ocean. Measurements from the mouth of the Columbia River show increased breaking rates at the plume front, where horizontal gradients in currents are large, and over the bar, where waves are shoaling. These breaking locations exhibit increased surface TKE dissipation rates, which are well scaled vertically by wave parameters.