Strong tidal currents observed near the bottom in the Suruga Trough, central Japan

Abstract

Current measurements carried out at the depth of 4 m above the sea bottom near the northern edge of the Suruga Trough in the early fall of 1985 indicated the existence of strong semidinrnal tidal currents, which were considered to be associated with internal tides. In order to examine the spatial structure of the bottom intensified tidal flow, more detailed current observations were carried out at three or four depths at two stations along the main axis of the Suruga Trough during about 70 days from August to October 1988. We obtained the following results: (1) the variations of the current velocity caused by the semidiurnal and diurnal internal tides are evident in all of the records, and the orientation of the major axis of each tidal ellipse nearly coincides with that of the main axis of the trough; (2) the'semidiurnal internal tide is dominant over the diurnal internal tide at 4 m above the sea bottom at both stations; (3) at the northern station the semidiurnal internal tide is dominant over the diurnal internal tide, whereas they are nearly equal at the southern station except at 4 m above the sea bottom; (4) the biharmonic internal tides with 1/3 day and 1/4 day periods, are found near the sea bottom and the major axis of the tidal ellipse is perpendicular to the orientation of the main axis of the Suruga Trough.

Observed Variations in Turbulent Mixing Efficiency in the Deep Ocean

“…During the cruises in October 2012 and October 2013, three casts were made in the deep troughs of Suruga Bay and Sagami Bay (Fig. 1a), where large-amplitude internal tides had been observed (Ohwaki et al 1991;Matsuyama et al 1993;Kitade and Matsuyama 1997).…”

Phylogeography of the intertidal goby Chaenogobius annularis associated with paleoenvironmental changes around the Japanese Archipelago

“…To the east and west of the Izu Peninsula are 2 deep bays, Suruga and Sagami, whose respective depths are approximately 2500 and 1500 m (Coastal Oceanography Research Committee 1985). Their deep troughs run into closed-off sections, with narrow continental shelves that are very small in area and drop off suddenly, leaving little suitable habitat for this goby (Coastal Oceanography Research Committee 1985, Matsuyama et al 1993, Katayama et al 2008. Therefore, the shallow coastal areas which were suitable for C. annularis likely disappeared from the above 2 bays due to the sea level fall in the Pleistocene glacial periods, resulting in vicariant separation.…”

Measuring currents in submarine canyons: Technological and scientific progress in the past 30 years

“…These long time-series data that have sampling rates of a few minutes allow a wide variety of techniques to be used to describe, analyze, and interpret the observations. For example, the spatially and temporally high resolution data matrix of current velocity and temperature and salinity are essential in computing the variations of isotherm displacement as well as density and velocity structures, all of which are key ingredients for characterizing the amplitudes and frequencies of internal (baroclinic) tides (Hotchkiss and Wunsch, 1982;Matsuyama et al, 1993;Petruncio et al, 1998;Rosenfeld et al, 1999;Palanques et al, 2005;Wang et al, 2008). Translation of computer programs into a common, user-friendly computing language such as MATLAB has made the processing and analyzing these data sets much easier (Pawlowicz et al, 2002).…”