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Yiing Jang Yang - One of the best experts on this subject based on the ideXlab platform.
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very large subaqueous sand dunes on the upper Continental Slope in the south china sea generated by episodic shoaling deep water internal solitary waves
Marine Geology, 2011Co-Authors: Benjamin D Reeder, Yiing Jang YangAbstract:Abstract Very large subaqueous sand dunes were discovered on the upper Continental Slope of the northern South China Sea. The dunes were observed along a single 40 km long transect southeast of 21.93°N, 117.53°E on the upper Continental Slope in water depths of 160 m to 600 m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16 m and crest-to-crest wavelengths exceeding 350 m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100 m, and dissipate extremely large amounts of energy via turbulent interaction with the Continental Slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper Continental Slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle).
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very large subaqueous sand dunes on the upper Continental Slope in the south china sea generated by episodic shoaling deep water internal solitary waves
Marine Geology, 2011Co-Authors: Benjamin D Reeder, Yiing Jang YangAbstract:Abstract Very large subaqueous sand dunes were discovered on the upper Continental Slope of the northern South China Sea. The dunes were observed along a single 40 km long transect southeast of 21.93°N, 117.53°E on the upper Continental Slope in water depths of 160 m to 600 m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16 m and crest-to-crest wavelengths exceeding 350 m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100 m, and dissipate extremely large amounts of energy via turbulent interaction with the Continental Slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper Continental Slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle).
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observations of second baroclinic mode internal solitary waves on the Continental Slope of the northern south china sea
Journal of Geophysical Research, 2009Co-Authors: Yiing Jang Yang, Steven R Ramp, Y C Fang, Minghuei Chang, T Y TangAbstract:[1] A temperature and current velocity mooring, located on the upper Continental Slope of the northern South China Sea, recorded a number of second baroclinic mode (mode 2) internal solitary waves (ISWs). These types of waves are seldom observed in nature. The mode 2 ISWs typically showed upward (downward) displacement of isotherms in the upper (lower) water column and three layers of eastward, westward, and eastward current from the uppermost to bottommost portions of a wave. In summer, westward-propagating mode 2 ISWs were observed only occasionally. These waves generally appeared after mode 1 ISWs, a feature that may relate to the diurnal tide with a period of approximately 24 hours. The displacement of isotherms induced by mode 2 ISWs was 20 ± 14 m at 75 m and ―22 ± 15 m at 240 m, and the characteristic time scale was approximately 8.0 ± 4.3 min. In winter, mode 2 ISWs were more active but mode 1 ISWs were rarely observed. Isotherm displacement by mode 2 ISWs in winter was 30 ± 18 m at 75 m and ―26 ± 16 m at 240 m, and the average characteristic time scale was 6.9 ± 4.6 min. The mode 2 ISWs thus had larger amplitudes and smaller time scales in winter than they did in summer. The observed vertical temperature profile also showed notable seasonal change. The thermocline was shallow in summer and deep in winter. In winter, vertical temperature profiles indicated that the main thermocline was located near middepth over the upper Continental Slope near the 350 m isobath. Mode 1 ISWs were more active in summer than in winter, reflecting the larger Ursell numbers for mode 1 ISWs in summer. Among mode 2 ISWs in summer, 90% appeared after mode 1 ISWs. These results suggest that mode 2 ISWs could be related to mode 1 ISWs. In contrast, mode 2 ISWs were more active in winter than in summer, with larger mode 2 Ursell numbers also found in winter. Among winter mode 2 ISWs, 72% appeared without mode 1 ISWs. Mode 2 ISWs in winter could be related to the main thermocline being located near middepth. These seasonal variations of mode 2 ISWs were correlated with the seasonal change of local stratification. Further study on the different generating mechanisms of mode 2 ISWs in summer and winter is needed.
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internal tide and nonlinear internal wave behavior at the Continental Slope in the northern south china sea
IEEE Journal of Oceanic Engineering, 2004Co-Authors: Timothy F Duda, Tswen Yung Tang, Steven R Ramp, James F Lynch, Jim Irish, Robert C Beardsley, Chingsang Chiu, Yiing Jang YangAbstract:A field program to measure acoustic propagation characteristics and physical oceanography was undertaken in April and May 2001 in the northern South China Sea. Fluctuating ocean properties were measured with 21 moorings in water of 350- to 71-m depth near the Continental Slope. The sea floor at the site is gradually Sloped at depths less than 90 m, but the deeper area is steppy, having gradual Slopes over large areas that are near critical for diurnal internal waves and steep steps between those areas that account for much of the depth change. Large-amplitude nonlinear internal gravity waves incident on the site from the east were observed to change amplitude, horizontal length scale, and energy when shoaling. Beginning as relatively narrow solitary waves of depression, these waves continued onto the shelf much broadened in horizontal scale, where they were trailed by numerous waves of elevation (alternatively described as oscillations) that first appeared in the Continental Slope region. Internal gravity waves of both diurnal and semidiurnal tidal frequencies (internal tides) were also observed to propagate into shallow water from deeper water, with the diurnal waves dominating. The internal tides were at times sufficiently nonlinear to break down into bores and groups of high-frequency nonlinear internal waves.
J. D. Nash - One of the best experts on this subject based on the ideXlab platform.
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reflection of linear internal tides from realistic topography the tasman Continental Slope
Journal of Physical Oceanography, 2016Co-Authors: Jody M Klymak, Matthew H Alford, Robert Pinkel, Samuel M. Kelly, Harper L Simmons, Dmitry Braznikov, Jennifer A Mackinnon, J. D. NashAbstract:AbstractThe reflection of a low-mode internal tide on the Tasman Continental Slope is investigated using simulations of realistic and simplified topographies. The Slope is supercritical to the internal tide, which should predict a large fraction of the energy reflected. However, the response to the Slope is complicated by a number of factors: the incoming beam is confined laterally, it impacts the Slope at an angle, there is a roughly cylindrical rise directly offshore of the Slope, and a leaky Slope-mode wave is excited. These effects are isolated in simulations that simplify the topography. To separate the incident from the reflected signal, a response without the reflector is subtracted from the total response to arrive at a reflected signal. The real Slope reflects approximately 65% of the mode-1 internal tide as mode 1, less than two-dimensional linear calculations predict, because of the three-dimensional concavity of the topography. It is also less than recent glider estimates, likely as a result o...
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internal bores and breaking internal tides on the oregon Continental Slope
Journal of Physical Oceanography, 2013Co-Authors: Kim I. Martini, Eric Kunze, Matthew H Alford, Samuel M. Kelly, J. D. NashAbstract:AbstractObservations of breaking internal tides on the Oregon Continental Slope during a 40-day deployment of 5 moorings along 43°12′N are presented. Remotely generated internal tides shoal onto the Slope, steepen, break, and form turbulent bores that propagate upSlope independently of the internal tide. A high-resolution snapshot of a single bore is captured from lowered acoustic Doppler current profilers (LADCP)/CTD profiles in a 25-h time series at 1200 m. The bore is cold, salty, over 100 m tall, and has a turbulent head where instantaneous dissipation rates are enhanced (e > 10−6 W kg−1) and sediment is resuspended. At the two deepest Slope moorings (1452 and 1780 m), similar borelike phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present ( W kg−1 and m s−1) and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, the authors estimate...
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the cascade of tidal energy from low to high modes on a Continental Slope
Journal of Physical Oceanography, 2012Co-Authors: Samuel M. Kelly, Matthew H Alford, J. D. Nash, Kim I. Martini, Eric KunzeAbstract:AbstractThe linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near-critical Continental Slope. A theoretical framework for low-wavenumber energy transfer is derived from “flat bottom” vertical modes and evaluated with observations from the Oregon Continental Slope. To better understand the observations, local tidal dynamics are modeled with a superposition of two idealized numerical simulations, one forced by local surface-tide velocities and the other by an obliquely incident internal tide generated at the Mendocino Escarpment 315 km southwest of the study site. The simulations reproduce many aspects of the observed internal tide and verify the modal-energy balances. Observed transfer of tidal energy into high-mode internal tides is quantitatively consistent with observed turbulent kinetic energy (TKE) dissipation. Locally generated and incident simulated internal tides are superposed with varying phase shifts to mimic the effects of the temporally ...
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Observations of Internal Tides on the Oregon Continental Slope
Journal of Physical Oceanography, 2011Co-Authors: Kim I. Martini, Eric Kunze, Matthew H Alford, Samuel M. Kelly, J. D. NashAbstract:AbstractA complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the Oregon Continental Slope. Presented here are observations from a zonal line of five profiling moorings deployed across the Continental Slope from 500 to 3000 m, a 24-h expendable current profiler (XCP) survey, and five 15–48-h lowered ADCP (LADCP)/CTD stations. The 40-day moored deployment spans three spring and two neap tides, during which the proportions of the locally and remotely forced internal tides vary. Baroclinic signals are strong throughout spring and neap tides, with 4–5-day-long bursts of strong cross-Slope baroclinic semidiurnal velocity and vertical displacement . Energy fluxes exhibit complex spatial and temporal patterns throughout both tidal periods. During spring tides, local barotropic forcing is strongest and energy flux over the Slope is predominantly offshore (westward). During neap tides, shoaling remotely generated internal tides dominate and energy flux is pr...
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hotspots of deep ocean mixing on the oregon Continental Slope
Geophysical Research Letters, 2007Co-Authors: J. D. Nash, Eric Kunze, Matthew H Alford, Kim I. Martini, Samuel M. KellyAbstract:[1] Two deep ocean hotspots of turbulent mixing were found over the Oregon Continental Slope. Thorpe-scale analyses indicate time-averaged turbulent energy dissipation rates of e > 10−7 W/kg and eddy diffusivities of Kρ ∼ 10−2 m2/s at both hotspots. However, the structure of turbulence and its generation mechanism at each site appear to be different. At the 2200-m isobath, sustained >100-m high turbulent overturns occur in stratified fluid several hundred meters above the bottom. Turbulence shows a clear 12.4-h periodicity proposed to be driven by flow over a nearby 100-m tall ridge. At the 1300-m isobath, tidally-modulated turbulence of similar intensity is confined within a stratified bottom boundary layer. Along-Slope topographic roughness at scales not resolved in global bathymetric data sets appears to be responsible for the bulk of the turbulence observed. Such topography is common to most Continental Slopes, providing a mechanism for turbulence generation in regions where barotropic tidal currents are nominally along-isobath.
Shinkuan Chen - One of the best experts on this subject based on the ideXlab platform.
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sulfate reduction and iron sulfide mineral formation in the southern east china sea Continental Slope sediment
Deep Sea Research Part I: Oceanographic Research Papers, 2002Co-Authors: Kuoming Huang, Shinkuan ChenAbstract:Abstract Sulfate reduction rate, organic carbon and sulfide burial rate; organic carbon, carbonate carbon, and reactive iron contents; grain size; and sedimentation rate were determined in sediments of the southern East China Sea Continental Slope. The results show high sulfate reduction and pyrite sulfur burial rates in Slope areas with high organic carbon and sedimentation rates. Unusually high rates of organic carbon deposition enhance sulfate reduction and pyrite sulfide burial in the region. Both sulfate reduction rates and pyrite sulfur burial rates increased linearly with increasing organic carbon burial rate, indicating that deposition of organic carbon on the Slope is the primary controlling factor for pyrite formation. Abundant reactive iron indicated that iron is not limiting pyrite formation. Pyrite is the predominant sulfide mineral; however, acid volatile sulfide constituted up to 50% of total sulfide at some stations. Up to 240 μmol/g of pyrite sulfur and 5 mmol/m 2 /day of sulfate reduction rates were found in the Slope sediment. Sulfate reduction rate and pyrite sulfur did not decrease with increasing overlying water depth. High organic carbon burial rates enhanced the sulfate reduction rate and subsequently the rate of pyrite sulfur burial in the Slope region. As a result, the southern East China Sea Continental Slope environment is an efficient pyrite sulfur burial environment.
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sulfate reduction and iron sulfide mineral formation in the southern east china sea Continental Slope sediment
Deep Sea Research Part I: Oceanographic Research Papers, 2002Co-Authors: Kuoming Huang, Shinkuan ChenAbstract:Abstract Sulfate reduction rate, organic carbon and sulfide burial rate; organic carbon, carbonate carbon, and reactive iron contents; grain size; and sedimentation rate were determined in sediments of the southern East China Sea Continental Slope. The results show high sulfate reduction and pyrite sulfur burial rates in Slope areas with high organic carbon and sedimentation rates. Unusually high rates of organic carbon deposition enhance sulfate reduction and pyrite sulfide burial in the region. Both sulfate reduction rates and pyrite sulfur burial rates increased linearly with increasing organic carbon burial rate, indicating that deposition of organic carbon on the Slope is the primary controlling factor for pyrite formation. Abundant reactive iron indicated that iron is not limiting pyrite formation. Pyrite is the predominant sulfide mineral; however, acid volatile sulfide constituted up to 50% of total sulfide at some stations. Up to 240 μmol/g of pyrite sulfur and 5 mmol/m 2 /day of sulfate reduction rates were found in the Slope sediment. Sulfate reduction rate and pyrite sulfur did not decrease with increasing overlying water depth. High organic carbon burial rates enhanced the sulfate reduction rate and subsequently the rate of pyrite sulfur burial in the Slope region. As a result, the southern East China Sea Continental Slope environment is an efficient pyrite sulfur burial environment.
Benjamin D Reeder - One of the best experts on this subject based on the ideXlab platform.
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very large subaqueous sand dunes on the upper Continental Slope in the south china sea generated by episodic shoaling deep water internal solitary waves
Marine Geology, 2011Co-Authors: Benjamin D Reeder, Yiing Jang YangAbstract:Abstract Very large subaqueous sand dunes were discovered on the upper Continental Slope of the northern South China Sea. The dunes were observed along a single 40 km long transect southeast of 21.93°N, 117.53°E on the upper Continental Slope in water depths of 160 m to 600 m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16 m and crest-to-crest wavelengths exceeding 350 m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100 m, and dissipate extremely large amounts of energy via turbulent interaction with the Continental Slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper Continental Slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle).
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very large subaqueous sand dunes on the upper Continental Slope in the south china sea generated by episodic shoaling deep water internal solitary waves
Marine Geology, 2011Co-Authors: Benjamin D Reeder, Yiing Jang YangAbstract:Abstract Very large subaqueous sand dunes were discovered on the upper Continental Slope of the northern South China Sea. The dunes were observed along a single 40 km long transect southeast of 21.93°N, 117.53°E on the upper Continental Slope in water depths of 160 m to 600 m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16 m and crest-to-crest wavelengths exceeding 350 m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100 m, and dissipate extremely large amounts of energy via turbulent interaction with the Continental Slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper Continental Slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle).
Matthew H Alford - One of the best experts on this subject based on the ideXlab platform.
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reflection of linear internal tides from realistic topography the tasman Continental Slope
Journal of Physical Oceanography, 2016Co-Authors: Jody M Klymak, Matthew H Alford, Robert Pinkel, Samuel M. Kelly, Harper L Simmons, Dmitry Braznikov, Jennifer A Mackinnon, J. D. NashAbstract:AbstractThe reflection of a low-mode internal tide on the Tasman Continental Slope is investigated using simulations of realistic and simplified topographies. The Slope is supercritical to the internal tide, which should predict a large fraction of the energy reflected. However, the response to the Slope is complicated by a number of factors: the incoming beam is confined laterally, it impacts the Slope at an angle, there is a roughly cylindrical rise directly offshore of the Slope, and a leaky Slope-mode wave is excited. These effects are isolated in simulations that simplify the topography. To separate the incident from the reflected signal, a response without the reflector is subtracted from the total response to arrive at a reflected signal. The real Slope reflects approximately 65% of the mode-1 internal tide as mode 1, less than two-dimensional linear calculations predict, because of the three-dimensional concavity of the topography. It is also less than recent glider estimates, likely as a result o...
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internal bores and breaking internal tides on the oregon Continental Slope
Journal of Physical Oceanography, 2013Co-Authors: Kim I. Martini, Eric Kunze, Matthew H Alford, Samuel M. Kelly, J. D. NashAbstract:AbstractObservations of breaking internal tides on the Oregon Continental Slope during a 40-day deployment of 5 moorings along 43°12′N are presented. Remotely generated internal tides shoal onto the Slope, steepen, break, and form turbulent bores that propagate upSlope independently of the internal tide. A high-resolution snapshot of a single bore is captured from lowered acoustic Doppler current profilers (LADCP)/CTD profiles in a 25-h time series at 1200 m. The bore is cold, salty, over 100 m tall, and has a turbulent head where instantaneous dissipation rates are enhanced (e > 10−6 W kg−1) and sediment is resuspended. At the two deepest Slope moorings (1452 and 1780 m), similar borelike phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present ( W kg−1 and m s−1) and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, the authors estimate...
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the cascade of tidal energy from low to high modes on a Continental Slope
Journal of Physical Oceanography, 2012Co-Authors: Samuel M. Kelly, Matthew H Alford, J. D. Nash, Kim I. Martini, Eric KunzeAbstract:AbstractThe linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near-critical Continental Slope. A theoretical framework for low-wavenumber energy transfer is derived from “flat bottom” vertical modes and evaluated with observations from the Oregon Continental Slope. To better understand the observations, local tidal dynamics are modeled with a superposition of two idealized numerical simulations, one forced by local surface-tide velocities and the other by an obliquely incident internal tide generated at the Mendocino Escarpment 315 km southwest of the study site. The simulations reproduce many aspects of the observed internal tide and verify the modal-energy balances. Observed transfer of tidal energy into high-mode internal tides is quantitatively consistent with observed turbulent kinetic energy (TKE) dissipation. Locally generated and incident simulated internal tides are superposed with varying phase shifts to mimic the effects of the temporally ...
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Observations of Internal Tides on the Oregon Continental Slope
Journal of Physical Oceanography, 2011Co-Authors: Kim I. Martini, Eric Kunze, Matthew H Alford, Samuel M. Kelly, J. D. NashAbstract:AbstractA complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the Oregon Continental Slope. Presented here are observations from a zonal line of five profiling moorings deployed across the Continental Slope from 500 to 3000 m, a 24-h expendable current profiler (XCP) survey, and five 15–48-h lowered ADCP (LADCP)/CTD stations. The 40-day moored deployment spans three spring and two neap tides, during which the proportions of the locally and remotely forced internal tides vary. Baroclinic signals are strong throughout spring and neap tides, with 4–5-day-long bursts of strong cross-Slope baroclinic semidiurnal velocity and vertical displacement . Energy fluxes exhibit complex spatial and temporal patterns throughout both tidal periods. During spring tides, local barotropic forcing is strongest and energy flux over the Slope is predominantly offshore (westward). During neap tides, shoaling remotely generated internal tides dominate and energy flux is pr...
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the breaking and scattering of the internal tide on a Continental Slope
Journal of Physical Oceanography, 2011Co-Authors: Jody M Klymak, Matthew H Alford, Robert Pinkel, Renchieh Lien, Yung Jang Yang, Tswen Yung TangAbstract:AbstractA strong internal tide is generated in the Luzon Strait that radiates westward to impact the Continental shelf of the South China Sea. Mooring data in 1500-m depth on the Continental Slope show a fortnightly averaged incoming tidal flux of 12 kW m−1, and a mooring on a broad plateau on the Slope finds a similar flux as an upper bound. Of this, 5.5 kW m−1 is in the diurnal tide and 3.5 kW m−1 is in the semidiurnal tide, with the remainder in higher-frequency motions. Turbulence dissipation may be as high as 3 kW m−1. Local generation is estimated from a linear model to be less than 1 kW m−1. The Continental Slope is supercritical with respect to the diurnal tide, implying that there may be significant back reflection into the basin. Comparing the low-mode energy of a horizontal standing wave at the mooring to the energy flux indicates that perhaps one-third of the incoming diurnal tidal energy is reflected. Conversely, the Slope is subcritical with respect to the semidiurnal tide, and the observed ...