Large‐scale, realistic laboratory modeling of M₂ internal tide generation at the Luzon Strait

Abstract

The complex double‐ridge system in the Luzon Strait in the South China Sea (SCS) is one of the strongest sources of internal tides in the oceans, associated with which are some of the largest amplitude internal solitary waves on record. An issue of debate, however, has been the specific nature of their generation mechanism. To provide insight, we present the results of a large‐scale laboratory experiment performed at the Coriolis platform. The experiment was carefully designed so that the relevant dimensionless parameters, which include the excursion parameter, criticality, Rossby, and Froude numbers, closely matched the ocean scenario. The results advocate that a broad and coherent weakly nonlinear, three‐dimensional, M2 internal tide that is shaped by the overall geometry of the double‐ridge system is radiated into the South China Sea and subsequently steepens, as opposed to being generated by a particular feature or localized region within the ridge system.

Estimation of internal wave velocity in the shallow South China Sea using single and multiple satellite images

“…HYCOM data include the temperature and salinity with the 1/12°equatorial resolution, and data at each resolution grid consist of 32 vertical layers. It is known that most of the IWs in this area are generated from the Luzon Strait (St. Laurent et al 2011;Mercier et al 2013), and therefore, the mean phase velocity of IWs in group 2 is expected to be larger than that in group 1 due to energy dissipation as they propagate towards shallower waters. Table 1 lists the mean velocities of IWs measured by the MTI and TPI methods.…”

Tidal energy redistribution among vertical modes in a fluid with a mid-depth pycnocline

“…In our configurations, there is only one tidal frequency but tidal harmonics can be generated. Moreover, non-linearity can induce the emerging of additional characteristic frequencies on the frequency spectra (Mercier et al 16 , Dossmann et al 17 ). The amplitude of the spectrum at the fundamental frequency (f 0 = 1/T = 0.0625 s -1 ) is considered as the amplitude of the vertical mode:…”

Tidally-forced flow in a rotating, stratified, shoaling basin

“…Here f and N are the local inertial and buoyancy frequencies respectively. Previous studies have focused on internal tides generated at isolated topographic features within basins such as ridge systems like the Hawaiian Ridge (Merrifield and Holloway, 2002;Merrifield et al, 2001;Rudnick et al, 2003) and the Luzon Strait (Li and Farmer, 2011;Mercier et al, 2013;Zhao, 2014) or at continental slope-shelf breaks where the topographic slope transitions from super-to subcritical values with respect to the inclination angle of energy propagation for internal tides (Gerkema et al, 2004;Huthnance, 1989;Pingree and New, 1992). Near ridges the interest is mostly in energetic, low-vertical-mode internal tides that evolve as they propagate away to the far field, e.g.…”