A tidal-cycle study at Destin Inlet, Northwest Florida, investigated intratidal and residual flow structures for the first time across the inlet. Underway current velocity profiles were combined with hydrographic station profiles at neap tides to document the appearance of tidal fronts, the distribution of tidal currents across two cross-sections, and the residual, or non-tidal, flow structure at the same cross-sections. Intratidal variations of water density and velocity showed the presence of fronts both in 1) late ebb-early flood and 2) late flood-early ebb tidal stages. Late ebb-early flood tidal intrusion fronts brought about depth-independent changes in water density >10kg/m3 in <2h. Their counterparts, late flood-early ebb plume-like fronts, produced similar magnitude of variations in density but were depth-dependent. Diurnal tidal current distributions across the inlet followed a general behavior of a damped wave with strongest currents appearing near the surface and near the deepest part of the cross-sections (thalweg). However, curvature effects seemed to modify this behavior locally by shifting the maximum tidal current away from the thalweg. Frictional and curvature effects on the diurnal flows were confirmed by an analytical solution for tidal currents. The observed density gradients drove residual flows that were vertically sheared, with outflow at the surface and inflow near the bottom. Such residual flow distributions were reproduced by an analytical solution that diagnosed the flow structure as inherent of a dynamically narrow inlet with relatively weak frictional effects.@en

Our understanding of temperature dissipation rate χ within the upper ocean boundary layer, which is critical for climate forecasts, is very limited. Near-surface turbulence also affects dispersion of contaminants and biogeochemical tracers. Using high-resolution optical turbulence measurements, scaling laws for χ are investigated under forcing states where either the daytime heat flux or the wind stress forcing is dominant. We find that χ remains constant over 1.5 times the significant wave height, while over a layer below, χ decays based on the local surface forcing. When the heat flux is dominant, traditional scaling based on the Monin-Obukhov similarity theory remains valid; χ â? z-1. When the wind stress dominates, we observe the emergence of a new scaling, χ â? z-1/2, which is explained by invoking the effect of small-scale coherent structures on vertical heat transport. These results have implications for improved modeling of the ocean's heat and CO2 intake. Key Point We proposed a new χ scaling@en