Download Strong Tidal Currents Observed near the Bottom in the

Journal of Oceanography
Vol. 49, pp. 683 to 696. 1993
Strong Tidal Currents Observed near the Bottom
in the Suruga Trough, Central Japan
MASAJI MATSUYAMA1, SUGURU OHTA2 , TOSHIYUKI HIBIYA 3 and HARUYA YAMADA1*
2Ocean
1Tokyo University of Fisheries, Konan 4-5-7, Minato-ku, Tokyo 108, Japan
Research Institute, University of Tokyo, Minamidai 1-16-4, Nakano-ku, Tokyo 164, Japan
3Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo 060, Japan
(Received 9 April 1993; in revised form 15 June 1993; accepted 16 June 1993)
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 semidiurnal 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.
1. Introduction
Suruga Bay is a representative deep bay in Japan, with the depth reaching the maximum of
about 2,500 m at the bay mouth and being more than 1,000 m even near the head of the bay where
the Suruga Trough is deeply incised (Fig. 1). On the basis of the photographic observations of
the highly disturbed bottom features and disharmonious features of the megabenthos in the
Suruga Trough (i.e., the predominance of highly mobile organisms and opportunistic species),
Ohta (1983) suggested rather strong bottom current and frequent occurrence of turbidity current.
Vertical slice of the bottom sediment cores and submersible observations substantiated the
occurrence of episodic turbidity current probably induced by earthquake and/or by flooding of
large rivers around the bay in response to typhoon during summer and early fall.
In order to confirm such strong currents near the sea bottom, we carried out current
measurements at 4 m above the sea bed in the Suruga Trough during three weeks in the early fall
of 1985. Although the water depth is about 1,370 m, a significant tidal current was observed
throughout the observation period, but no turbidity current was recorded. A semidiurnal
component, especially M2 tidal current was found to be dominant during most of the time, with
*Present address: Japan Sea National Fisheries Research Institute, Suido-chou 1-5939-22, Niigata 951, Japan.
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M. Matsuyama et al.
Fig. 1. Bathymetric chart of Suruga Bay (depth in meters). Location of mooring sites are also shown.
Station U indicates the location of the Uchiura tidal station.
the amplitude being more than 10 cm s–1. Such strong tidal currents are also observed near the
bottom in submarine canyons on the east coast of USA, such as Hudson Canyon (Hotchkiss and
Wunsch, 1982) and Baltimore Canyon (Hunkins, 1988).
The numerical experiments for surface tides indicate that the amplitude of the surface tidal
current is less than 1 cm s–1 at every tidal constituent in the deep waters along the Suruga Trough
(Ohwaki et al., 1991). Thus, the remarked tidal currents are possible to be related to internal tides.
The internal tides in Suruga Bay have often been observed through current and temperature
measurements carried out in surface layers shallower than 100 m (Inaba, 1981, 1984; Matsuyama
and Teramoto, 1985; Matsuyama, 1985a), and diurnal components are found to be dominant
except in Uchiura Bay, located at the head of Suruga Bay (Fig. 1), where semidiurnal internal
tides are amplified through the resonant coupling to the longitudinal internal seiche under the
stratification during summer and early fall (Matsuyama, 1985b, 1991). The internal tides
observed in surface layers in Suruga Bay are shown to be originated from a steep slope of the
northern part of the Izu-Ogasawara Ridge in the numerical experiments by Matsuyama (1985b)
and Ohwaki et al. (1991). The internal tide is possible to exist in the deep water in the Suruga
Trough, because the internal tide energy can be incident in deep water under continuous
stratification (e.g., LeBlond and Mysak, 1978). In order to examine the vertical distributions of
the current energy at each tidal period in deep waters in the Suruga Trough, the current
measurements were carried out at three or four depths at two stations along the main axis of the
Suruga Trough (Stns. NB and SB, see Fig. 1) during August to October 1988.
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
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2. Strong Tidal Currents on the Sea Floor Observed in Early Fall of 1985
The Suruga Trough, the representative deep submarine canyon in Japan, has sharp sidewalls as shown in Fig. 1. The contours for the depths more than 1,000 m run nearly north to south.
The water depth inside the trough is 2,500 m near the bay mouth, and still about 1,000 m near
the bay head which is only 9 km away from the coast. The current measurement was carried out
at Stn. OB located at the northern edge of the Suruga Trough (see Fig. 1). The current-meter
(Aanderaa RCM-4) was installed 4 m above the sea bottom (water depth of about 1,370 m). The
current and temperature measurements were made for about three weeks, from 18 September to
9 October 1985, with an interval of 5 minutes.
Figure 2 shows the time series of temperature and east- and north-components of current
velocity. The semidiurnal tidal fluctuations are evident in the current velocity where the north
component (the velocity in the direction of the main axis of the Suruga Trough) is found to be
dominant with the total amplitude reaching 50 cm s–1. The tidal period fluctuations are evident
in the temperature records as well, though the total range is limited to being, at most, 0.5°C.
To obtain the amplitudes and phases of four major tidal constituents, the harmonic constants
are calculated for the current and temperature (Table 1). The M2 tidal constituent is largest among
the four major tidal constituents and the length of major axis for the M2 tidal ellipse is about 14.9
cm s–1 which is about five times that for the K1 tidal ellipse. The orientation of the major axis for
the M2 tidal ellipse is 18°T, namely, approximately coincident with that of the main axis of the
Suruga Trough, though the ratio of the minor to major axes is 0.45, so that a particle trajectory
Fig. 2. Time series of temperature, east and north components of current velocity at 4 m above the sea
bottom at Stn. OB during the period from September 19 to October 9, 1985.
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Table 1. Harmonic constants of tidal currents at Stn. OB and sea level at Uchiura tidal station.
Currents
Length of major axis (cm s –1)
Orientation (degrees)
Phase (degrees)
Length of minor axis (cm s –1)
Temperature
Amplitude (°C × 10 –2)
Phase (degrees)
Sea level
Amplitude (cm)
Phase (degrees)
K1
O1
M2
S2
3.0
16
65
0.7
2.6
–2
104
0.5
14.9
18
169
3.4
1.9
2
44
0.1
0.7
272
1.0
188
4.4
293
0.6
250
21.0
180
15.5
161
41.0
167
18.9
192
Observation period (September 18 to October 9, 1985).
Sea level: Uchiura tidal station (after Tide Table prepared by JODC).
forms somewhat roundish ellipse.
The temperature fluctuations at each tidal period are considered to be closely related to the
vertical isotherm displacements, so that we can obtain the time series of vertical isotherm
displacements from the time series of temperature and vertical temperature distribution. Since
the temperature varies so little with depth in deep waters, however, the estimated values might
include unexpectedly large error. For this reason, the temperature amplitudes in Table 1 are only
used to examine the relative magnitudes of vertical isotherm displacements for four major tidal
constituents. The amplitude of the M2 tidal constituent is seen to be more than four times those
of any other constituents.
The strong tidal currents on the sea bottom in the trough are considered to be internal modes
from the following two reasons. First, the velocities of surface tidal current are numerically
estimated to be less than 1 cm s–1 in the Suruga Trough, where the water depth is more than 1,000
m (Ohwaki et al., 1991). The observed tidal currents on the sea bottom are, therefore, too strong
to be explained as the surface tidal currents. Another reason is found in the phase relation between
the current velocity and sea level at each tidal constituent. The surface tide in Suruga Bay shows
that the phase of the current velocity lead that of the sea level by 90 degrees (Ohwaki et al., 1991).
The harmonic constants of sea level at Uchiura tidal station (for the geographical location, see
Fig. 1) are also shown in Table 1. The phase of the current velocity with M2 tidal period (the most
dominant constituent), is seen fairly coincident with that of the sea level with M2 tidal period,
suggesting that those are not surface modes.
The current measurements near the sea bottom at the northern edge of the Suruga Trough
thus clearly show the existence of marked semidiurnal tidal currents, which cannot be explained
as surface modes. To examine whether or not such bottom intensified tidal currents exist all the
way along the main axis of the Suruga Trough, we carried out current measurements at three or
four depths at two stations along the main axis of the Suruga Trough for about 70 days from
August to October 1988.
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
687
3. Current Measurements in 1988
3.1 Measurements
Locations of the current measurement sites, Stns. NB and SB, are almost on the main axis
of the Suruga Trough as shown in Fig. 1. Location of Stn. NB (water depth of 1,360 m) is selected
such that it is very close to Stn. OB, whereas the location of Stn. SB (water depth of 1,585 m) is
about 13 km to the south from that of Stn. OB. The instruments were installed 4 m, 200 m and
500 m above the sea bottom at both stations and an additional current meter was installed 800
m above the sea bottom at Stn. SB. For convenience, each record is referred to by the name of
the station and instrument depth, such as SB1085. The current measurements were carried out
for about 70 days, from August to October 1988. The details of the current measurements are
summarized in Table 2. The length of the two records are shorter than those of the other four
because of the trouble of the current meters.
Table 2. The details of the current measurements carried out from August to October 1988.
Site
Depth
Location
Start date
Length of record
(days)
NB860
NB1160
NB1356
860 m
1160 m
1356 m
35°00.5′ N
138°39.5′ E
Aug. 18, 1988
16
65
65
SB785
SB1085
SB1385
SB1581
785 m
1085 m
1385 m
1581 m
34°53.0′ N
138°39.5′ E
Aug. 18, 1988
2
55
65
65
Fig. 3. Vertical profile of buoyancy frequency near Stn. SB obtained on October 30, 1988.
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M. Matsuyama et al.
Figure 3 shows the vertical distribution of the buoyancy frequency near the observation sites
on 30 October 1988. We can see the presence of a surface mixed layer with a thickness of about
30 m and a sharp seasonal pycnocline beneath it. Reflecting this vertical stratification, the
buoyancy frequency is maximum at the depth of about 70 m and gradually decreases downwards
beneath the seasonal pycnocline. The buoyancy frequencies at the depths of six current meters
are considered to be fairly constant with time, because the seasonal variations of the density
structure mainly occur in shallower waters, namely, from the sea surface down to the depth of
about 150 m (Nakamura, 1982). The values of the buoyancy frequency at the depths of the current
meters are in the range of 1.5 × 10–3 to 2.5 × 10–3 s–1.
3.2 General features of current velocity fluctuations
Figures 4 and 5 show the time series of the north and east components of the current velocity
at the depths of six current meters, respectively. Since we are interested in the variability of
current velocity in the tidal frequency band, fluctuations with a period less than 3 hours and
greater than 30 hours were filtered out from each raw record. The amplitude of current velocity
fluctuations at the northern station (Stn. NB) is seen to increase toward the sea bottom; the total
range of the fluctuations reaches 50 cm s–1 at NB1356, whereas it is, at most, 20 cm s–1 at NB860.
Although the difference in the amplitude of current velocity fluctuations is less evident between
the upper two depths at the southern station (SB1085 and SB1385), the range of the fluctuations
is seen to be largest in the deepest record (SB1581).
Figure 6 shows the bandpassed records of temperature at the depths of six current meter
respectively. The amplitudes of the tidal fluctuations are found to be larger at Stn. NB compared
to those at Stn. SB at nearly the same depth indicating that the vertical isothermal motions at Stn.
NB are more energetic than those at Stn. SB.
3.3 Power density
In order to discuss the characteristic features of tidal currents in the Suruga Trough more
definitely, we obtain the total spectra of the current velocity, defined by a sum of rotary
components (Gonella, 1972) as shown in Fig. 7. Significant spectral peaks are found at diurnal
and semidiurnal tidal periods together with smaller ones at 1/3 and 1/4 day periods. Table 3 shows
the spectral peak values at each period estimated from Fig. 7 excluding NB860, the record length
of which is limited to 16 days. It should be noted that, possibly because of the doppler effect (e.g.,
LeBlond and Mysak, 1978), the spectral peaks are not so sharp but rather broad even at
semidiurnal and diurnal tidal periods, and that they are not separated into M2 and S2 constituents,
and K1 and O1 constituents, respectively. The orientation of the major axis of the current ellipse
and the power density of the temperature fluctuations are also examined for each period.
At Stn. NB, the spectral values at semidiurnal tidal period is seen to be much larger than those
at diurnal tidal period. Furthermore, semidiurnal tidal currents are significantly amplified near
the sea bottom as seen in Table 3, where the spectral value at NB1356 becomes more than twice
that at NB1160. At Stn. SB, semidiurnal tidal currents are less energetic, and diurnal tidal currents
are more energetic compared to those at Stn. NB so that, at SB1085, for example, the spectral
values at these two periods become comparable. As the sea bottom is approached, however,
semidiurnal components are significantly amplified while such amplification does not take place
for diurnal components, so that semidiurnal tidal currents become dominant over the diurnal tidal
currents near the sea bottom. The major axes of the current ellipses for semidiurnal and diurnal
components near the sea bottom are both roughly coincident with the orientation of the main axis
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
689
Fig. 4. Bandpassed records of the north component of current velocity during the period from August 20
to October 24, 1988.
of the Suruga Trough.
The biharmonic components with 1/3 and 1/4 day periods, possibly caused by nonlinear
interaction between the diurnal and semidiurnal tides (e.g., LeBlond and Mysak, 1978), are also
seen to be significantly amplified near the sea bottom at both Stns. NB and SB, though the spectral
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M. Matsuyama et al.
Fig. 5. As in Fig. 4 but for the east component of the current velocity.
values are much less than those at semidiurnal period. In contrast to the case for semidiurnal and
diurnal components, the major axes of the current ellipses for these components near the sea
bottom are roughly in the east-west direction, i.e., almost perpendicular to the orientation of the
major axis of the Suruga Trough.
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
691
Fig. 6. As in Fig. 4 but for the temperature fluctuations.
The power spectra of the temperature fluctuations indicate that the semidiurnal component
is dominant over the diurnal component at Stn. NB, whereas both components become
comparable at Stn. SB, consistent with the results from the total spectra of current velocity.
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Fig. 7. Total spectra of current velocities. Side bar shows 95% confident limit.
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
693
Table 3. Total spectra of current velocity and orientation of major axis of current ellipse and spectra of
temperature for each tidal component.
Period
Diurnal
Semi-diu.
1/3-day.
1/4-day.
NB1160
E.L.
Ori.
Temp.
1.7
0
1.48
8.3
348
2.25
1.4
7
0.18
0.5
296
0.23
NB1356
E.L.
Ori.
Temp.
2.5
346
1.23
18.6
19
3.05
2.0
39
0.12
1.2
260
0.12
SB1085
E.L.
Ori.
Temp.
4.4
11
0.86
3.8
1
0.37
0.2
20
0.15
0.5
281
0.07
SB1385
E.L.
Ori.
Temp.
3.9
22
0.26
7.0
358
0.46
0.6
310
0.08
0.3
11
0.08
SB1581
E.L.
Ori.
Temp.
4.3
355
0.11
9.7
27
0.10
2.6
271
0.02
3.5
275
0.03
E.L.: Total spectra of horizontal velocity (×102 (cm s–1)2/cph).
Ori.: Orientation of major axis of current ellipse (degrees).
Temp.: Spectra of temperature (×10–2 (°C2/cph)).
4. Summary and Discussions
The current measurements carried out at the depth of 4 m above the sea bottom near the
northern edge (Stn. OB) of the Suruga Trough in the fall of 1985 have indicated the existence of
strong tidal currents near the sea bottom. These tidal currents are considered to be associated with
internal tides because the amplitude is too large to be explained as surface tides. Semidiurnal tidal
components are shown to be dominant over diurnal tidal components.
From the observations carried out at three or four depths at two stations (Stns. NB and SB)
along the main axis of the Suruga Trough during August to October 1988, we have 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 Suruga Trough; (2) the semidiurnal internal
tide is dominant over the diurnal internal tide at 4 m above the sea bottom at both stations; (3)
the semidiurnal internal tide at Stn. NB is dominant over the diurnal internal tide, whereas they
are nearly equal at Stn. SB except at 4 m above the sea bottom; (4) the biharmonic internal tides
with 1/3 day and 1/4 day periods, are also found near the sea bottom at both stations and the major
axis of the tidal ellipse is in the east-west direction, nearly perpendicular to the orientation of the
main axis of the Suruga Trough.
The bottom intensified tidal currents are also observed at 100 m above the sea bottom near
the mouth of Suruga Bay (the water depth of about 2,170 m) at 34°40′ N, 138°38′ E by Yasuda
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M. Matsuyama et al.
Fig. 8. Distribution of the sediments on the sea bottom in Suruga Bay (after Ohta (1983)).
Strong Tidal Currents Observed near the Bottom in the Suruga Trough, Central Japan
695
et al. (1992), and near the sea bottom at central region of the bay (the water depth of about 2,000
m) at 34°43′ N, 138°35′ E by Midorikawa et al. (1988), though the observation period was only
two days. The strong tidal currents were actually experienced in the axial floor of Suruga Bay
during submersible dives (Otsuka and Niitsuma, 1985; Midorikawa et al., 1988).
Taira and Teramoto (1985) carried out long-term current measurements near the sea bottom
south of the Suruga Trough for about one year. The current meters were set at 7 m above the sea
bottom at Stn. SR1 (34°20′ N, 138°25′ E, water depth of 1,520 m), and at 7 m and 27 m above
the sea bottom at Stn. SR2 (34°10′ N, 138°31′ N, water depth of 3,632 m). The time series of the
current velocity at 7 m and 27 m above the sea bottom at Stn. SR2 showed the existence of marked
tidal currents. The variance between 10 and 30 hours periods, occupied mainly by tidal current
energy, are shown to be 42–82% of the total variance. Although no detailed analysis associated
with the tidal periods have been made by Taira and Teramoto (1985), the strong tidal currents are
likely to exist even near the sea bottom south of the Suruga Trough.
According to the existing theory (Wunsch, 1969; Hotchkiss and Wunsch, 1982), submarine
canyons with a V shaped cross section, such as the Suruga Trough, can focus the energy of
internal waves of frequency ω greater than the critical frequency given by
ω c2 =
f 2 + S2 N 2
S2 + 1
where N is buoyancy frequency, f the Coriolis parameter and S an average slope of the sidewalls
of the canyon. In the case of the Suruga Trough, S ⯝ 0.2, f = 8.34 × 10–5 s–1 and N ranges from
1.5 × 10–3 to 5.0 × 10–3 s–1 for the depths 400 to 1450 m (see Fig. 3), so that the critical frequency
ωc is estimated to be 0.51 to 0.75 cph. It follows that the internal waves of semidiurnal tidal period
possibly originated from the upper continental slope should focus toward the canyon floor while
reflecting at the steep canyon walls. Furthermore, since the canyon narrows toward the floor, the
amplitude of the motions increases as waves propagate downward thus qualitatively accounting
for the bottom amplification of kinetic energy at semidiurnal tidal period.
The strong tidal currents on the sea bottom are considered to have strong influence on the
distribution of the benthos and bottom sediments in the Suruga Trough. Figure 8 shows the
distribution of the sediments on the sea bottom in Suruga Bay (Ohta, 1983), where the lower part
of the continental slope along the trough axis is seen to be mostly occupied by the sedimentary
rock covered with thin silt. In addition, long sediment cores taken along the main axis of the
trough reveal a gravel bed below a level of 0.5 to 4.0 m from the bottom surface (Sato, 1962;
Otsuka, 1980; Nakamura and Okusa, 1981). Therefore, the distribution of the sediments in the
Suruga Trough suggests the existence of strong currents in deep waters from the northern edge
to the mouth of Suruga Bay along the trough axis (Ohta, 1983; Okada and Ohta, 1993).
We are planning to carry out detailed numerical experiments taking account of all the
topographic features in Suruga Bay to clarify the mechanism for the bottom intensified baroclinic
tidal currents observed along the main axis of the Suruga Trough.
Acknowledgements
We are grateful to the captain and crew of R/V Hakuho-Maru for assisting the work at sea.
A part of this study was supported by a Scientific Research Grant from the Ministry of Education,
Science and Culture in 1989 (Grant No. 01540337).
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M. Matsuyama et al.
References
Gonella, J. (1972): A rotary-component method for analyzing meteorological and oceanographic vector time series.
Deep-Sea Res., 19, 833–846.
Hotchkiss, F. S. and C. Wunsch (1982): Internal waves in Hudson Canyon with possible geological implications.
Deep-Sea Res., 29, 415–442.
Hunkins, K. (1988): Mean and tidal currents in Baltimore Canyon. J. Geophys. Res., 93, C6, 6917–6929.
Inaba, H. (1981): Circulation pattern and current variations with respect to tidal frequency in the sea near the head
of Suruga Bay. J. Oceanogr. Soc. Japan, 37, 149–159.
Inaba, H. (1984): Current variations in the sea near the mouth of Suruga Bay. J. Oceanogr. Soc. Japan, 40, 193–198.
LeBlond, P. H. and L. A. Mysak (1978): Waves in the Ocean. Elsevier Scientific, 602 pp.
Matsuyama, M. (1985a): Internal tides in Uchiura Bay—Subsurface temperature observations near the bay head. J.
Oceanogr. Soc. Japan, 41, 135–144.
Matsuyama, M. (1985b): Numerical experiments of internal tides in Suruga Bay. J. Oceanogr. Soc. Japan, 41, 145–
156.
Matsuyama, M. (1991): Internal tides in Uchiura Bay. p. 489–503. In Tidal Hydrodynamics, ed. by B. Parker, Wiley
& Sons Ins.
Matsuyama, M. and T. Teramoto (1985): Observations of internal tides in Uchiura Bay. J. Oceanogr. Soc. Japan,
41, 39–48.
Midorikawa, K., H. Monma, K. Mitsuzawa and H. Hotta (1988): Measurement of the deep-sea current near the
bottom in the Suruga Trough. Jamstectr Deepsea Research (1988), 101–109 (in Japanese with English abstract).
Nakamura, Y. (1982): Oceanographic feature of Suruga Bay from view point of fisheries oceanography. Bull. Shizuoka
Pref. Fish. Exp. Stn., 17 (Spec. No.), 1–153 (in Japanese with English abstract).
Nakamura, T. and S. Okusa (1981): Geotechnical properties of surface sediments in Suruga Bay. J. Fac. Mar. Sci.
Technol. Tokai Univ., 235–246 (in Japanese with English abstract).
Ohta, S. (1983): Photographic census large-sized benthic organisms in the bathyal zone of Suruga Bay, central Japan.
Bull. Ocean Res. Ins., Univ. Tokyo, No. 15, 244 pp.
Ohwaki, A., M. Matsuyama and S. Iwata (1991): Evidence for predominance of internal tidal currents in Sagami and
Suruga Bays. J. Oceanogr. Soc. Japan, 47, 194–206.
Okada, H. and S. Ohta (1993): Photographic evidence of variable bottom-current activity in the Suruga and Sagami
Bays, central Japan. Sediment. Geology, 82, 221–237.
Otsuka, K. (1980): Results of piston-core sampling in Suruga Bay, central Japan during the research cruises KT-777 and KT-78-19 of R/V Tansei-Maru. Geosci. Rep. Shizuoka Univ., 5, 23–30 (in Japanese with English abstract).
Otsuka, K. and N. Niitsuma (1985): Sedimentary geology and tectonic features of Suruga Trough, off Matsuzaki—
The results of dive 86 by the submersible “SHINKAI 2000”. Jamstectr Deepsea Research (1985), 45–57 (in
Japanese with English abstract).
Sato, T. (1962): Sand and gravel bed cored from the bottom of the Suruga Bay. J. Geol., 8, 609–617 (in Japanese
with English abstract).
Taira, K. and T. Teramoto (1985): Bottom currents in Nankai Trough and Sagami Trough. J. Oceanogr. Soc. Japan,
41, 388–398.
Wunsch, C. (1969): Progressive internal waves on slopes. J. Fluid Mech., 35, 131–144.
Yasuda, K., H. Inaba, K. Kawabata, H. Moriya and M. Mitsui (1992): The deep tidal current in Suruga Trough. Bull.
Inst. Oceanic Res. Develop., Tokai Univ., 13, 17–31 (in Japanese with English abstract).