Turning depths of internal tides in the South China Sea inferred from profile data

Near‐Inertial Wave Propagation in the Deep Canadian Basin: Turning Depths and the Homogeneous Deep Layer

“…Our results of N 2 bin and σ N 2 are comparable to previous observations of N 2 in weakly stratified waters. For example, using the method of King et al (2012), squared buoyancy frequencies lower than the diurnal tidal frequency were found in the South China Sea (Liu et al, 2022) with N 2 bin ≈ 5.317 × 10 9 s 2 . This is comparable to the average N 2 bin below 3,000 m of ∼3.1 × 10 9 s 2 ± 2.1 × 10 9 s 2 .…”

“…For example, using the method of King et al. (2012), squared buoyancy frequencies lower than the diurnal tidal frequency were found in the South China Sea (Liu et al., 2022) with $${N}_{\mathit{bin}}^{2}\approx 5.317\times 1{0}^{-9}$$ s −2 . This is comparable to the average $${N}_{\mathit{bin}}^{2}$$ below 3,000 m of ∼3.1 × 10 −9 s −2 ± 2.1 × 10 −9 s −2 .…”

“…Turning depths for the semidiurnal tide, with N(z)≤ ω M 2 ≈ 1.405 × 10 4 s 1 (N 2 (z) ≤ 1.974 × 10 8 s 2 ), are ubiquitous in the entire Ocean (King et al, 2012). In the South China Sea, turning depths were also found for the diurnal tide ω K 1 ≈ 7.292 × 10 5 s 1 (ω 2 K 1 ≈ 0.5317 × 10 8 s 2 ) (Liu et al, 2022). For NIWs, the buoyancy frequency must be in the order of N(z) ≤ ω ≈ 1.4 × 10 4 s 1 (N 2 (z) ≤ 1.959 × 10 8 s 2 ), which corresponds to the average Coriolis frequency in the Arctic Ocean (>70°N).…”