Seasonal variation of semidiurnal internal tides in the East/Japan Sea

Abstract

The seasonal variation of semidiurnal internal tides in the East/Japan Sea was investigated using 25 month long output from a real-time ocean forecasting system. The z coordinate eddy-resolving high-resolution numerical model, called the RIAM ocean model, incorporates data assimilation that nudges temperature and salinity fields together with volume transport through the Korea Strait to produce realistic oceanic currents and stratification. In addition to atmospheric forcing, it includes tidal forcing of 16 major components along open boundaries. The model generates energetic semidiurnal internal tides around the northern entrance of the Korea Strait. Energy conversion from barotropic to baroclinic (internal) tides varies seasonally with maxima in September (ranging 0.48-0.52 GW) and minima in March (ranging 0.11-0.16 GW). This seasonal variation is induced by the seasonality in stratification near the southwestern East/Japan Sea. The propagation distance of the internal tides is associated with generation intensity and wavelength. From late summer to early winter, the semidiurnal internal tides travel relatively far from the generation region due to stratification changes; its energy dissipates less as a result of longer wavelengths. Our results suggest that spatiotemporal variation of internal-tide-induced mixing due to the seasonality in the generation, propagation, and dissipation of internal tides should be considered for a more realistic simulation of water masses and circulation in models of the East/Japan Sea.

Effect of the North Equatorial Counter Current on the generation and propagation of internal solitary waves off the Amazon shelf (SAR observations)

“…Conversion rates (C) and energy fluxes (F E ) are particularly useful parameters in numerical models accounting for ITs and have been found to be good indicators in global circulation models and in several other independent studies (see e.g. Gerkema et al, 2004;Shriver et al, 2012;Jeon et al, 2014;Kang and Fringer, 2012). Despite detailed numerical simulations being beyond the scope of the present study, we note that preliminary results (following from Buijsman et al, 2016) proved very useful in identifying IT sources and their spatial distributions.…”

Seasonal and Spatial Variations of the M2 Internal Tide in the Yellow Sea

“…However, the seasonal modulation of barotropic tides cannot sufficiently explain the dramatic seasonal variation in internal tides (the BKE varies by a factor of 2 or 3). Seasonal stratification has important implications for the entire life cycle of internal tides, which includes their generation, propagation, and dissipation, and could be responsible for the significant seasonal variability of internal tides (Jeon et al, ). Thus, the formation mechanism of seasonal stratification in the YS is discussed.…”

Temporal and Spatial Variability of Near‐Inertial Waves in the East/Japan Sea From a High‐Resolution Wind‐Forced Ocean Model

“…The external model data that are daily mean values and do not include high‐frequency signals are linearly interpolated in time and space for each model grid and time step for the data assimilation (More details are provided at https://dreams-c.riam.kyushu-u.ac.jp/vwp/). Using outputs from data‐assimilative models utilizing almost identical procedure, Jeon et al () and Varlamov et al () successfully simulated the behaviors of internal tides affected by stratification and background currents.…”

“…Time‐mean depth‐integrated horizontal kinetic energy of NIWs in the mixed and deep layers is calculated by where t is time, z is a vertical Cartesian coordinate positive upward, ρ is the water density, T (= 30 days) is an averaged period, and u ′ and v ′ are baroclinic zonal and meridional velocities filtered in near‐inertial frequency (Jeon et al, ; Park et al, ; Zhao et al, ). The depths A and B are set to be MLD and 0 for the mixed layer, and 1,000 and 400 m for the deep layer, respectively.…”