Hydrographic profiling across the East China sea shelf edge by an underwater sliding vehicle with CTD sensors

Observation of internal tides in the East China Sea with an underwater sliding vehicle

“…with the second-mode shape are produced at the abrupt topographic change of the shelf break. Previous studies [Maeda, 1983;Misumi et al, 1988;Sato and Shimohira, 1988] reported that temperature and current measurements showed semidiurnal baroclinic signals over the continental shelf of the East China Sea. The high-resolution observa-tions with the USV vividly visualize such internal tide generation occurring at the shelf break.…”

“…These instruments are explained briefly later in this section. In a previous paper [Kuroda et al, 1988], some results of the observations conducted in 1986 (the first year of the series of the observations) during flood tide periods were reported. We have shown that temperature and salinity inversions associated with internal tides occur at the shelf break and lead to strong Copyright 1995 by the American Geophysical Union.…”

“…Such a case is displayed in Figure 11, taken during the 1986 cruise along line B; temperature showed inversions at the shelf break, which was pronounced at the level of the 24øC isotherm. A detailed discussion of this case is given by Kuroda et al [1988] (see their Figure 9). The most probable generation mechanism for these internal bores is that proposed by Baines [1974Baines [ , 1982, in which an intensive internal wave beam forms where the topographic slope and the ray slope (i.e., angle of the characteristic surface) of an internal wave, denoted by (2), coincide with each other.…”

“…The semidiurnal tides are quite strong, and the tidal currents are predominantly in the cross-slope direction, having about 50 cm s-• amplitude during high tides near the shelf break [e.g., Ogura, 1933;Larsen et al, 1985;Odamaki and $ato, 1986]. These conditions are suitable for generating internal tides [Baines, 1982], and in fact temperature and current measurements have indicated their existence [e.g., Maeda, 1983;Misumi et al, 1988; $ato and $himohira, 1988]. The internal tides can cause the exchange of water between the East China Sea and the Kuroshio across the shelf break through internal wave propagation and wave breaking processes, and so they should play important roles in the formation of water masses along the margin of the continental shelf.…”