Longshore Current Generation by Internal Waves in the Strait of Georgia

1975 ◽  
Vol 12 (3) ◽  
pp. 472-488 ◽  
Author(s):  
Richard E. Thomson
Keyword(s):  
Internal Waves ◽  
Maximum Speed ◽  
Longshore Current ◽  
Delta Area ◽  
Strait Of Georgia ◽  
Wave Characteristics ◽  
Fraser River Delta ◽  
Vertical Eddy ◽  
Measured Water ◽  
A Current

Presented in this paper is a derivation of the longshore current generated by breaking lowest mode internal waves in a two layer fluid of slowly shallowing depth, with emphasis on the nearshore region of the Fraser River delta in the Strait of Georgia. It is proposed that such a current, having a maximum speed of order 104/μv cm3/s2 (equal to 102 cm/s for reasonable vertical eddy viscosities, μv, of 102 cm2/s) and a width of order kilometers based on measured water properties and internal wave characteristics in the Strait, is responsible for the persistent northward flow observed to be associated with the delta in summer. Accordingly, it is suggested that the longshore current would have important implications to sedimentation rates and pollutant dispersal in the delta area, with greatest effects possibly occurring in summer and fall when the stratification in the Strait of Georgia is most pronounced.

Postglacial deltaic sediments, southern Fraser River delta, British Columbia

1991 ◽  
Vol 28 (9) ◽  
pp. 1386-1393 ◽  
Author(s):  
John J. Clague ◽  
J. L. Luternauer ◽  
S. E. Pullan ◽  
J. A. Hunter
Keyword(s):  
Seismic Reflection ◽  
Drill Hole ◽  
Main Channel ◽  
River Delta ◽  
Fraser River ◽  
The South ◽  
The West ◽  
Radiocarbon Dates ◽  
Strait Of Georgia ◽  
Fraser River Delta

The Fraser River delta, the largest delta on the west coast of Canada, has been built into the Strait of Georgia during the Holocene. Drill-hole and seismic reflection records reveal a succession of sedimentary units deposited during early Holocene progradation of the delta. These overlie an irregular surface developed on Pleistocene drift. Mud and silt, similar to sediments presently accumulating off the mouth of Fraser River in the southern Strait of Georgia, are conformably overlain by a thick unit of sandy foreset beds, dipping gently to the south-southwest into Boundary Bay and deposited in a foreslope environment. The foreset unit is sharply overlain by a much thinner topset sequence comprising silt and sand deposited in intertidal, fluvial-channel, and overbank environments, and peat deposited in swamps and bogs. Fifteen accelerator mass spectrometry radiocarbon dates on shell and wood indicate that most of the deltaic sediments south of the Main Channel of Fraser River were deposited between ca. 7500 and 5000 BP. By 5000 BP the locus of sedimentation had shifted from the south, into Boundary Bay, to the west and southwest, into the Strait of Georgia proper.

Substrates of the Strait of Georgia, British Columbia

1983 ◽  
Vol 40 (7) ◽  
pp. 1026-1032 ◽  
Author(s):  
J. L. Luternauer ◽  
J. J. Clague ◽  
C. H. Pharo
Keyword(s):  
British Columbia ◽  
Sea Level ◽  
Intertidal Zone ◽  
Fraser River ◽  
Pleistocene Glaciation ◽  
Delta Front ◽  
Strait Of Georgia ◽  
Local Wave ◽  
Fraser River Delta ◽  
Sand And Gravel

The subtidal floor of the Strait of Georgia west of the Fraser River Delta and north to Texada Island is blanketed mainly by silt and clay derived from the Fraser River and from failed deposits at the delta front. On the western part of the Strait south of the delta to the San Juan and Orcas islands, sediments are mainly lag sand and gravel eroded from Pleistocene deposits by strong tidal currents. East of this area in a more sheltered embayed part of the Strait the seafloor is covered by silt and clay derived from local mainland streams and possibly from the Fraser River. North of southern Texada Island, influence of the Fraser River also has been minimal. Although bottoms of basins in this part of the Strait are blanketed by mud, coarser sediments are dominant elsewhere. Substrate materials in the northern Strait are products of wave and current reworking of Pleistocene deposits and deposition from local streams and rivers. The shoreline of the Strait is mainly rocky but includes sand and/or gravel beaches and deltaic tidal flats. Development of the intertidal zone has been controlled by Pleistocene glaciation, postglacial changes in sea level, local wave and current regimes, and sediment availability.

FLUCTUATIONS OF THE MODAL ARRIVAL TIMES DUE TO LINEAR INTERNAL WAVES: APPLICATION TO INVERSION

2006 ◽  
Vol 14 (04) ◽  
pp. 469-487 ◽  
Author(s):  
GERALDINE BOUCHAGE ◽  
MICHAEL I. TAROUDAKIS
Keyword(s):  
Travel Time ◽  
Internal Waves ◽  
Acoustic Field ◽  
Sound Speed ◽  
Inversion Method ◽  
Perturbation Approach ◽  
Arrival Times ◽  
Inversion Procedure ◽  
Time Information ◽  
A Current

It is well known that internal waves in the ocean are an important source of environmental variability which has serious effects in the structure of an acoustic field due to a known source. When measurements of the acoustic field form the input data for an inversion procedure aiming at the recovery of the environmental parameters, the information they carry on includes the internal wave effects. It is therefore natural to assume that neglecting the effects of the internal waves in an inversion procedure based on acoustic field measurements, errors are induced in the inversion. The paper deals with this problem and addresses the case of inversion schemes using travel time information of an acoustic signal. Using a statistical 2D model of the internal waves, based on the Garrett and Munk spectrum, the spatial and temporal evolution of the internal waves field as well as the fluctuations of the sound speed profile is estimated for a characteristic shallow-water environment. Considering a sound speed anomaly in the water column as the oceanographic feature to be recovered, the paper studies the influence of the internal waves field on the modal travel time information obtained through the propagation of a tomographic signal through this environment. The sound speed anomaly denoted as "current" is described by a suitable Gaussian function. Using an analytical expression based on a perturbation approach, the difference in the modal arrival times calculated for a background environment and a perturbed one (considering that the sound speed perturbations are due either to a current or to the summation of a current and of the internal waves field) was calculated for each propagating mode of the waveguide. These calculations led to the conclusion that the internal waves have a non-negligible impact on the arrival times and that the maximum amplitude of a current can be under- or overestimated of several meters per second when these waves are not taken into account in the inversion method, whereas they are present in the oceanic medium.

scholarly journals Studies of Internal Waves in the Strait of Georgia Based on Remote Sensing Images

2019 ◽  
Vol 11 (1) ◽  
pp. 96 ◽  
Author(s):  
Caixia Wang ◽  
Xin Wang ◽  
Jose C. B. Da Silva
Keyword(s):  
Remote Sensing ◽  
Internal Waves ◽  
River Mouth ◽  
Temporal Distribution ◽  
Tidal Currents ◽  
River Plume ◽  
Remote Sensing Images ◽  
Strait Of Georgia ◽  
Narrow Channels ◽  
Propagating Waves

This paper analyzes over 500 sets of internal waves in the Strait of Georgia (British Columbia, Canada) based on a large number of satellite remote sensing images. The spatial and temporal distribution of internal waves in the central region of the strait are discussed via statistical analysis. Possible generation origins of the observed internal waves are divided into three categories based on their different propagation directions and geographical locations: (1) the interaction between the narrow channels to the south of the Strait and the tidal currents, leading to the formation of mainly eastward and northward propagating waves; (2) the interaction between the tidal currents and the topography near Point Roberts, resulting in mainly westward propagating waves; (3) excitation by river plume, mainly near Fraser River mouth, leading to the formation of mainly westward waves along the direction of the river plume. The relation between the occurrence of internal waves in remote sensing images and wind or tide level is also discussed. It is found that most of the observed internal waves occur at low tides. However, due to the influence of the river, the eastward propagating internal waves near the river mouth seldom occur at the lowest tide. Also, internal waves are captured more easily by remote sensing images in summer due to the lower wind speed than winter and therefore the seasonal distribution of internal waves in remote sensing images may not be able to completely represent the real situation in the study area. Finally, combining the in situ measured data and model output data, the Benjamin-Ono equation is found to satisfyingly simulate the characteristic parameters of the studied internal waves.

Ocean currents measured concurrently on and off the Sydney area continental shelf

1974 ◽  
Vol 25 (3) ◽  
pp. 427 ◽  
Author(s):  
GR Cresswell
Keyword(s):  
Internal Waves ◽  
Current Speed ◽  
East Australian Current ◽  
Surface Currents ◽  
M Current ◽  
Variable Surface ◽  
Oscillatory Velocity ◽  
Counter Current ◽  
A Current ◽  
Experiment Duration

Recording current meters, a GEK, and XBT'S were used to study on and off-shelf currents for a 10 day period. Oscillatory currents with frequencies 3-8 cph were observed quite frequently at a mid-shelf mooring (depth 140 m). They were perhaps due to internal waves and were often associated with sudden increases or decreases in current speed. On two occasions the speed increases occurred when meteorological fronts passed over. The horizontal oscillatory velocity components of two of the best wave examples showed clear evidence for clockwise polarization. At the edge of the shelf (180 m), current meters 10 and 50 m above the bottom, while not showing internal waves, showed a current somewhat variable in speed (mean: 20 cm/sec; maximum 50 cm/sec), but reasonably constant in direction (northward) for the experiment duration. At this time the main southward flowing core of the East Australian Current was 120 km out from the edge of the shelf, while the region out to 50 km from the shelf contained variable surface currents. The current in the deeper water at the edge of the shelf was tentatively labelled a counter current.

scholarly journals Vertical transport of momentum by internal waves in a shift current

2019 ◽  
Vol 55 (6) ◽  
pp. 194-200
Author(s):  
A. A. Slepyshev ◽  
N. V. Laktionova
Keyword(s):  
Wave Propagation ◽  
Internal Waves ◽  
Boussinesq Approximation ◽  
Stokes Drift ◽  
Drift Speed ◽  
Two Layer Model ◽  
Rotation Of The Earth ◽  
Wave Flux ◽  
Parallel Current ◽  
A Current

In Boussinesq approximation free internal waves are considered at the account of rotation of the Earth and a plane-parallel current, perpendicular to a direction to wave propagation. For homogeneous stratification and at constant shift of speed of a current the boundary-value problem for amplitude of vertical velocity analytically solved and the dispersive parity is defined. Vertical wave fluxes of momentum and two components of Stokes drift speed are defined. Stokes drift speed, cross-section to a direction a wave propagation, is distinct from zero in the presence of the specified shift current. Similar calculations are executed for two-layer model. The vertical wave flux of momentum can exceed a corresponding turbulent flux.

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