Fig. 3: Spectral and coherence analysis of turbulence and inter-layer velocity difference.
Variance-preserving power spectra for (a) estimated turbulent dissipation rate ε in Fig. 2a, b the moored inter-layer along-trough velocity difference ΔU = Ubot − Utop. Utop and Ubot are the moored depth-averaged along-trough velocities for Winter Water (200–280 m) and Circumpolar Deep Water (below 400 m) layers, respectively. Vertical lines represent the inertial period, specific tidal periods, and periods of the first mode of barotropic shelf waves (15.5, 7.8, and 5.2 days, corresponding to wave numbers n = 1, 2, 361). Wavelet analysis for (c) ε and (d) ΔU. Background color indicates the energy levels, which are normalized by standard deviations, and contours are 95% confidence levels based on an autoregressive 1 model with autoregressive coefficients α = 0.65 and 0.6. e Wavelet coherence power spectrum between ΔU and ε. Background colors indicate coherence and black contours denote the 95% confidence level against red noise. Arrows represent the relative phase relationship, with in-phase pointing right and anti-phase pointing left. The cone of influence is shaded in gray in (c–e).
