共查询到20条相似文献，搜索用时 47 毫秒
1.
The transformation of internal waves over the oceanic shelf of variable depth is studied analytically within a linear theory
of a two-layer flow. It is shown that, at a specific character of depth variation, the internal wave propagates without reflection
from the slope even if it is sufficiently steep. The properties of such progressive waves are studied—their form and the current
structure in the upper and lower layers. The transformation of the wave propagating from the open ocean, where the depth is
assumed to be constant, is considered. It is shown that the wave is transformed at the shelf edge and does not change its
form in the course of time during its further propagation over the shelf. The height and form of the internal wave are calculated
at the interface of the transition of the two-layer flow into the one-layer flow. Applications of the developed analytical
theory to the estimation of internal wave transformation over a real shelf are discussed. 相似文献
2.
V. A. Dubinina A. A. Kurkin E. N. Pelinovsky O. E. Poloukhina 《Izvestiya Atmospheric and Oceanic Physics》2006,42(2):254-261
Nonlinear three-wave interactions of Stokes edge waves propagating both in one direction and in opposite directions along a uniformly sloping shelf are considered. In the cases when only the lowest four modes participate in interaction, the synchronism conditions are determined and interaction coefficients are calculated. It is shown that the interaction coefficients of unidirectional edge-wave modes can vanish for certain triads. The spatiotemporal dynamics of a triad of edge waves is investigated. In addition, expressions are given for the resonance interaction coefficients of edge waves over the bottom of an arbitrary profile. 相似文献
3.
海南岛东部陆架海底地貌 总被引：4，自引：0，他引：4
林美华 《海洋地质与第四纪地质》1995,15(4):37-46
通过二十多条测线的测深、旁测声纳和浅地层连续测量的调查以及底质等资料，概述了海南岛东部陆架海底堆积平原地貌及其上的地貌类型，其中海底沟，坎、岗阜等地貌类型的线性排列和古海岸线的位置相应。 相似文献
4.
Within the framework of the linear theory of long waves, we perform the numerical investigation of transformations of a barotropic
diurnal tide in the process of its motion from the deepwater region of the sea into the region of continental slope and shelf
zone at any angle to the coast line. For a linear profile of the bottom of the continental slope and shelf, we establish dependences
of the amplitudes and velocities of waves on the direction of propagation of the tidal wave and the latitude of the place.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
5.
The directivity of energy radiation of the tsunami generated in the vicinity of a continental shelf 总被引：1，自引：0，他引：1
Kinjiro Kajiura 《Journal of Oceanography》1972,28(6):260-277
The radiation pattern of the tsunami generated by a broad crustal deformation on or near the continental shelf is examined analytically in the framework of a linear long-wave approximation. Detailed discussion, however, is made only for a model of step-type bottom topography.The proportion of the energy trapped on the shelf as edge wave modes relative to that radiated into deep water increases with the decrease of the long-shore dimension of the source. The nearer is the source to the coastline, the greater is the rate of total edge wave generation. However, the proportion of higher modes increases for the source near the shelf edge.The proportion of the wave energy radiated in deep water, normal to the coastline, increases with the increase of the long-shore dimension of the source and/or the decrease of the depth difference between the shelf and deep water. Furthermore, this proportion increases with the increased distance of the source location from the coastline and approaches the value for the case without a shelf. For a source of the square shape, the directive difference of energy radiation in deep water is mainly caused by the refractive effect of the shelf edge. For larger long-shore dimension of the source, however, the geometric shape effect of the source is more important to cause the directive difference. 相似文献
6.
Yoshifumi Kuroda Toshiaki Hara Atsunobu Misumi Gentaro Kai Jun Suwa 《Progress in Oceanography》1988,21(3-4)
Temperature, salinity and density structures were observed on Sept. 23 and 24, 1986 at one vertical section across the East China Sea shelf edge by an advanced type of towed vehicle with CTD sensors which was developed by the Japan Marine Science and Technology Center. The vehicle was towed at a speed of 2.5 m s−1 down to 150 m depth and at intervals of 170–500 m width. The observed profile was 50 km long on Sept. 23 and 70 km long on Sept. 24 along the cross-shelf section. An on-ship acoustic Doppler current profiler was simultaneously used to measure current velocities at depths of 20, 50 and 100 m.Interesting features were noticed. Firstly, there was a vertical displacement of pycnoclines at the lower edge of the surface mixed layer accompanied by vertical inversion of the salinity and temperature in the vicinity of the shelf edge. Pycnoclines were displaced upward by 12 m toward the outer edge on Sept. 23 and by 20 m on Sept. 24. On Sept. 23, the salinity inversion took place in a layer 20 m thick and 8 km wide, whereas the temperature inversion took place in a layer 8 m thick and 1.5 km wide. These vertical inversions were probably generated by vertical shear of tidal currents which was observed by the Doppler current profiler. These results throw light on understanding the vertical mixing process of stratified water on the continental shelf edge. Secondly, an intrusion of the shelf water into the Kuroshio water was observed along pycnoclines below the surface mixed layer 60 to 70 m deep in the Kuroshio region outer break. The measurement was successful in showing a horizontal mixing process of the shelf water and the Kuroshio water which could not be found out by standard CTD observations. 相似文献
7.
Based on the full water-wave equation,a second-order analytic solution for nonlinear interaction of short edge waves on a plane sloping bottom is presented in this paper.For special case of slope angle β=π/2,this solution can reduced to the same order solution of deep water gravity surface waves traveling along parallel coastline.Interactions between two edge waves including progressive,standing and partially reflected standing waves are also discussed.The unified analytic expressions with transfer functions for kinematic-dynamic elements of edge waves are also given.The random model of the unified wave motion processes for linear and nonlinear irregular edge waves is formulated,and the corresponding theoretical autocorrelation and spectral density functions of the first and the second orders are derived.The boundary conditions for the determination of the parameters of short edge wave are suggested,that may be seen as one special simple edge wave excitation mechanism and an extension to the sea wave refraction theory.Finally some computation results are demonstrated. 相似文献
8.
Based on the full water-wave equation, a second-order analytic solution for nonlinear interaction of short edge waves on a constant plane sloping bottom is presented in this paper. For special case of slope angle b=p/2, this solution can be reduced to the same order solution of deep water gravity surface waves traveling along parallel coastline. Interactions between two edge waves including progressive, standing and partially reflected standing waves were also discussed. The unified analytic expressions with transfer functions for kinematic-dynamic elements of edge waves were also discussed. The random model of the unified wave motion processes for linear and nonlinear irregular edge waves is formulated, and the corresponding theoretical autocorrelation and spectral density functions of the first and second orders are derived. The boundary conditions for the determining determination of the parameters of short edge wave are suggested, that may be seen as one special simple edge wave excitation mechanism and an extension to the sea wave refraction theory. Finally some computation results are demonstrated. 相似文献
9.
John M. Huthnance 《Progress in Oceanography》1995,35(4)
The coastal ocean meets the deep sea at the continental shelf edge. Questions of global change entail elucidation of the processes that determine the quantities, transformation and fate of materials transported between the shelf and ocean, the measurement and definition of exchange processes, and the development of prognostic models of exchanges.Physical processes control the large-scale movement and irreversible small-scale mixing of water and its constituents. At the shelf edge, steep bathymetry may inhibit ocean-shelf exchange, but in combination with stratification gives rise to special processes and modelling challenges.A preliminary assessment is made of coastal-trapped waves; along-slope currents, instability and meanders; eddies; upwelling, fronts and filaments; downwelling, cascading; tides, surges; internal tides and waves as potentially influential processes in ocean-shelf exchange, water-mass structure and general circulation, according to their scales and context. For this purpose, theory and previous measurements are interpreted.Future studies needed to improve this assessment are discussed. 相似文献
10.
We present four new high-resolution multibeam bathymetry datasets from the shelf edge of the northern Great Barrier Reef (GBR). Analysis of these data, combined with Chirp sub-bottom profiles and existing submersible observation data provides a fresh insight into the detailed morphology and spatial distribution of submerged reefs and terraces at the shelf edge. An extensive and persistent line of drowned shelf edge reefs exist on the GBR margin in about 40 to 70 m. They appear as barrier reefs up to 200 m wide and comprising twin parallel ridges of rounded pinnacles. Subtle yet consistent terrace and step features lie between 78 and 114 m seaward of the shelf edge reefs in the southern study area. Submersible observations confirm that the drowned reefs now provide a favorable hard substrate for live soft corals and algae. They form a consistent and extensive seabed habitat that extends for possibly 900 km along the GBR shelf edge. The submerged reef and terraces features may reflect a complex history of growth and erosion during lower sea-levels, and are now capped by last deglaciation reef material. 相似文献
11.
Tetsuo Yanagi Satoru Takahashi Akira Hoshika Terumi Tanimoto 《Journal of Oceanography》1996,52(5):539-552
Seasonal variation in the transport of suspended matter across the East China Sea is investigated with the use of results of field observations and diagnostic numerical experiments. Suspended matter is transported from the shelf edge to the inner shelf in summer and from the inner shelf to the shelf edge in autumn and winter due to the vertical circulation mainly induced by the monsoon wind. The maximum transport of suspended matter from the inner shelf to the shelf edge occurs in autumn. 相似文献
12.
V. G. Bondur Yu. V. Grebenyuk S. I. Muyakshin K. D. Sabinin 《Izvestiya Atmospheric and Oceanic Physics》2011,47(2):233-240
This paper analyzes the results of investigations into extremely large releases of current velocities registered by an acoustic
Doppler profiler during experiments performed on the Hawaii shelf. An integral analysis of the variability of current fields
relies on the profile data of current velocities, temperature, and acoustic-scattering layers. Based on these investigations,
we proposed a hypothesis stating that the small-scale variability of currents in profiler data is conditioned by the passage
of fine vortices emerging in the outflow and rise of freshened waters from a subsurface sink near the shelf edge. To confirm
this hypothesis on the emergence mechanism of the observed releases of current velocities, we conducted a mathematical simulation
of the response that the Doppler meter has to the passage of fine vortex, which revealed a good agreement between model calculations
and experimental data. Similar phenomena were also found in the Gelendzhik Bay of the Black Sea. 相似文献
13.
Southwestward volume transport (referred to 1,500 db) out of the Gulf of Alaska seaward of the continental shelf in May 1972 was 12.5 Sv, and nearly 3/4 of this flow occurred within 50 km of the shelf edge. Mean geostrophic velocities of about 50 cm s–1 occurred in a band 20 km wide, which extended 500 km along the shelf edge; a maximum velocity of 98 cm s–1 (nearly 2 knots) was obtained. Bottom flow along the inshore part of the shelf as determined by seabed drifters was generally onshore at 0.5 cm s–1. Evidence is presented of a large cyclonic gyre on the shelf encompassing the Portlock and Albatross Banks, perturbations in surface flow along the shelf edge, and relations between coastal tidal heights and fluctuations in geopotential topography at the shelf edge. 相似文献
14.
The data accumulated by a measuring complex equipped with a gradient-distributed temperature sensor in the course of towing in the shelf zone near the South Coast of the Crimea and in the region where the flow of the Rim Current crosses the shelf edge are used to analyze the energy and space characteristics of internal waves formed when the flow runs through the shelf edge and to study the process of their propagation both to the coast and to the open part of the sea. 相似文献
15.
Mediterranean shelf-edge muddy contourites: examples from the Gela and South Adriatic basins 总被引：1，自引：1，他引：1
We present new evidence of shallow-water muddy contourite drifts at two distinct locations in the central Mediterranean characterized
by a relatively deep shelf edge (between 170 and 300 m below sea level): the south-eastern Adriatic margin and the north-western
Sicily Channel. The growth of these shelf-edge contourite drifts is ascribed to the long-term impact of the Mediterranean
themohaline circulation. The Levantine Intermediate Water flows continuously, with annual or inter-annual variations, and
affects the shelf edge and the upper slope in both study areas. In addition, the SW Adriatic margin is impinged by the seasonally
modulated off-shelf cascading of North Adriatic Dense Water. This water mass has formed ever since the large Adriatic continental
shelf was drowned by the post-glacial sea-level rise. It energetically sweeps the entire slope from the shelf edge to the
deep basin. These bottom currents flow parallel or oblique to the depth contours, and are laterally constricted along markedly
erosional moats aligned parallel to the shelf edge where they increase in flow velocity. The internal geometry and growth
patterns of the shelf-edge contourites reflect changes in oceanographic setting affecting the whole Mediterranean Sea. In
particular, seismic correlation with published sediment cores documents that these deposits are actively growing and migrating
during the present interglacial, implying an enhancement in bottom-water formation during intervals of relative sea-level
rise and highstand. Regardless of the specific mechanisms of formation, sediment drifts in both study areas have been affected
by widespread thin-skinned mass-wasting events during post-glacial times. Repeated mass-transport processes have affected
in particular the downslope flank of the shelf-edge contourite drifts, indicating that these muddy deposits are prone to failure
during, or soon after, their deposition. 相似文献
16.
The applicability of three different wave-propagation models in nonlinear dispersive wave fields has been investigated. The numerical models tested here are based on three different wave theories: a fully nonlinear potential theory, a Stokes second-order theory, and a Boussinesq-type theory with an improved dispersion relation. Physical experiments and computations were conducted for wave evolutions during passage over a submerged shelf under various wave conditions. As expected, the fully nonlinear solutions agree better with the measurements than do the other solutions. Although the second-order solution has sufficient accuracy for smaller-amplitude wave cases, the truncation after the third harmonics causes significant discrepancies in wave form for larger waves. In addition, the second-order model markedly overestimates the first- and second-harmonic amplitudes in transmitted waves. The Boussinesq model provides excellent predictions of wave profile over the shelf even in larger wave cases. However, this model also overestimates the magnitudes of several higher harmonics in transmitted waves. These facts may indicate that energy transfer from bound components into free waves in these higher harmonics cannot be accurately evaluated by the Boussinesq-type equations. 相似文献
17.
陆架波的性质如频散关系、形成机制等受地形影响。研究地形对陆架波的性质影响具有重要意义。基于陆架拦截波理论,数值计算了分段线性地形下不同宽度陆架上陆架拦截波的频散关系、长波假设下波动的相速度、阻尼情况下的波动耗散率以及强迫波的外力影响因子。分析了陆架宽度及坡度对自由及强迫陆架拦截波性质的影响。陆架宽度影响陆架拦截波的频散关系。陆架变宽,使得长波频散曲线的斜率增大。陆架宽度的增加使第一模态陆架拦截波有明显的性质变化:相速度增大,波动受辐散影响的程度变大,摩擦衰减距离增大,且风应力旋度在波动的生成机制中起到的作用渐强。在宽的陆架上,研究陆架拦截波的生成及强迫波的振幅时,应充分考虑风应力旋度的作用。第二、三模态波动的相速度受陆架坡度的影响较大,但摩擦衰减距离基本都在200km左右,几乎不随陆架宽度改变,属于局地波。 相似文献
18.
《Ocean Engineering》2004,31(3-4):305-341
The paper seeks to examine hydrodynamic coefficients of a rectangular structure in shallow water and to establish analytical formulae for fast computations. A two-dimensional rectangular profile is considered with the under-bottom clearance assumed to be small compared with structure dimensions and the water depth. Following the method of matched asymptotic expansions, the radiation problem is solved under assumptions of the linear wave theory, by matching two ‘outer’ flows with the ‘inner’ flow near the structure edge. Closed asymptotic formulae are obtained for all hydrodynamic coefficients for heave, sway and roll motions. The zero and infinite frequency values of the added mass are examined and formulae are derived intended for quick engineering estimations. Numerical results compare well with those published in literature, and the approach is shown to be consistent with known fundamental relations in the body–wave interaction theory. 相似文献
19.
20.
Data from a high-resolution mooring array deployed across the Alaskan Beaufort shelfbreak and slope, together with an idealized numerical model, are used to investigate the dynamics of wind-driven upwelling and the magnitude of the resulting shelf–basin exchange. The analysis focuses on a single storm event in November 2002 when the sea-ice concentration was 50–70%. The normally eastward-flowing shelfbreak jet was reversed to the west, and the secondary circulation near the shelfbreak was characterized by offshore flow in the upper layer and a nearly equal amount of onshore flow at depth. Ekman theory accurately predicts the strength of the secondary circulation when one takes into account the ice–ocean stress. The depth-integrated alongstream momentum balance reveals that, near the shelf edge, the reversed jet is driven by a combination of the surface stress and divergence of cross-stream momentum flux. The reversed jet is primarily spun-down – before the winds subside – by the alongstream pressure gradient that likely results from the variation in sea surface height. The shelf–basin fluxes of heat, freshwater, and nitrate resulting from the storm are substantial. Much of the yearly supply of heat to the Beaufort shelf from the inflowing Pacific water through Bering Strait was fluxed offshore, and the amount of freshwater transported into the basin represents a substantial fraction of the year-to-year variation in the freshwater inventory of the Beaufort Gyre. The on-shelf flux of nitrate from 4 to 5 such storms could account for most of the net annual primary production that occurs on the Beaufort shelf. 相似文献