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  • 1
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    Internal waves, finestructure, mocrostructure, and mixing in the ocean (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Also published as: Reviews of geophysics and space physics (1979) 17: 1524-1548
    Description: Progress in measuring, interpreting, and understanding oceanic internal gravity waves and fine and microstructure is reviewed; we emphasize the quadrennium 1975-1978. The context is how these subjects contribute to oceanic mixing. The overlap between the areas is examined, as is the relevance of the subjects to other aspects of Present trends and suggestions for future work are included, and we offer some speculation on possible progress during the next quadrennium, which may be substantial especially for finestructure understanding.
    Description: Prepared for the Office of Naval Research under Contracts N00014-76-C-0197; NR 083-004 and N00014-75-C-0502 (to the University of Washington) and for the National Science Foundation under Grant OCE 77-25803.
    Keywords: Internal waves ; Fine-structure constant ; Microstructure
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 2
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    Critical layers and the Garrett-Munk spectrum (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Also published as: Journal of Marine Research 38 (1980): 135~145
    Description: The effects of critical level absorption of oceanic internal waves by a mean flow are estimated using the Garrett and Munk (1975) model spectrum. The horizontal currents of the wave field are found to be more intense perpendicular to the mean flow than parallel to it. The cause of this anisotropy is preferential absorption of waves travelling with the mean flow. However, the current anisotropy is only half as large as would be necessary to explain Frankignoul's (1974) observations. The wave momentum flux lost to critical level absorption is found to be nearly proportional to the mean velocity. When the momentum flux is deposited throughout a 400 m thick shear zone, typical of the main thermocline in the North-west Atlantic, the observed stress-shear relationship would correspond to a wave-induced eddy viscosity of -200 cm2 s-1. The effect of the absorbed momentum on the mean flow is to cause a slow (5 m/day) downward phase propagation and slow broadening of the shear profile.
    Description: Prepared for the Office of Naval Research under Contract N00014-76-C-0197; NR 083~400.
    Keywords: Internal waves
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  • 3
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    Bispectra of internal waves (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Derived from the equations of motion, the bispectrum of power indicates the rate of energy transfer among components of the internal wave field . This, or any other bispectrum, can be evaluated from weak resonant interaction theory given the wave spectrum. Using the Garrett and Munk model of the deep open ocean internal wave spectrum, the bispectrum of power and the closely related auto-bispectrum of vertical displacements are evaluated numerically with the intention of providing an observational test of the weak interaction theory and its predictions. The resulting levels of the bispectra for typical deep ocean internal waves are generally too low to be observed with any statistical confidence in an experiment of reasonable length and cost.
    Description: Prepared for the National Science Foundation under Grant OCE76-23532 and in part by Grants OCE77-25803 and OCE76-14739.
    Keywords: Internal waves ; Energy transfer
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  • 4
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    On the internal wave variability during the Internal Wave Experiment (IWEX) (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Also published as: Journal of Geophysical Research 84 (1979): 769-776.
    Description: The relation between internal wave variability and larger and smaller scales of motion is investigated, using the IWEX data set. To investigate the role of internal waves in the vertical diffusion of large scale momentum, the time variability of the vertical flux of horizontal internal wave momentum (estimated from temperature and current data) is compared to that of the mean vertical shear. It is found that internal waves cannot cause a vertical viscosity as large as proposed by Müller (1976), but that the data are too noisy to detect a possible wave‐induced viscosity in absolute value of the order of 10−2 m2 s−1 or less. Similarities in the time behavior of the total internal wave energy and that of the square mean vertical shear suggest that some kind of dynamical coupling exists between internal waves and larger scale flows. There is some evidence that the level of temperature finestructure activity also varies in a related way. An analysis of CTD station data taken during Mode demonstrates the mappability of the finestructure activity, and again suggests a relation with the geostrophic eddy flow.
    Description: Prepared for the Office of Naval Research under Contracts N00014-74-C-0262; NR 083- 004 , N00014-76-C-0197: NR 083-400 and for the National Science Foundation under Grant OCE 74-19782 .
    Keywords: Internal waves
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  • 5
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    A four-dimensional primitive equation model for coupled coastal - deep ocean studies (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: A prototype four-dimensional (x,y,z,t) continental shelf/deep ocean model is described. In its present form, the model incorporates the effects of finite-amplitude topography, advective nonlinearities, and variable stratification and rotation. The model can be forced either directly by imposed atmospheric windstress and surface pressure distributions, and energetic mean currents imposed by the exterior oceanic circulation; or indirectly by initial distributions of shoreward propagating mesoscale waves and eddies. To avoid concerns over the appropriate specification of "open" boundary conditions on the cross-shelf and seaward model boundaries, a periodic channel geometry (oriented along-coast) is used. The model employs a traditional finite-difference expansion in the cross-shelf direction, and a Fourier (periodic) representation in the long-shelf coordinate. A modified sigma coordinate system, and a Chebyshev-tau approximation scheme, are used to incorporate the vertical dependence. The model has been validated against a variety of propagating topographic wave problems. Representative run times and error estimates are given.
    Description: Prepared for the National Aeronautics and Space Administration under Grant NAG 5-8.
    Keywords: Ocean waves ; Internal waves
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  • 6
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    Vertical coherence of the internal wave field from towed sensors (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Also published as: Journal of Physical Oceanography 9 (1979): 518-530
    Description: Constant depth and isopycnal‐following tows are used to estimate the, towed vertical coherence of the internal wave field, at vertical separations of 8.5, 18, 28 and 70 m. The depths of the tows are ∼750 m at the maximum of the buoyancy frequency in the main thermocline of the Sargasso Sea, and near 350 m in the buoyancy frequency minimum between the main and seasonal thermoclines. The towed spectra and towed vertical coherence are compared with three model spectra (GM75, GM76 and IWEX): at 750 m the agreement between data and models is very good, with IWEX being slightly better. At 350 m several of the measured towed vertical coherence spectra are more complex than the spectra from the deeper tows, there are anomalously high coherences in a band from 0.7 to 2 cycles per kilometer that are not predictable by the models. We suggest this coherence bump may be evidence of Eckart resonance, i.e., modes tunneling between the two thermoclines into the region of low buoyancy frequency.
    Description: Prepared for the Office of Naval Research under Contract N00014-74-C-0262; NR 083-004 and for the National Science Foundation under Grant OCE 74-19608.
    Keywords: Internal waves
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  • 7
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    Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic (2018)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: Also published as: Journal of Physical Oceanography 9 (1979): 489-517
    Description: A total of four moorings from POLYMODE array I and II were analyzed in an investigation of the interaction of wavefields and mean flow. In particular, evidence for internal wave-mean flow interaction was sought by searching for time correlations between the vertically acting Reynolds stress of the wavefield (estimated using the temperature and velocity records), and the mean shear. No significant stress-shear correlations were found at the less energetic moorings (u¯≲10 cm s−1), indicating that the magnitude of the eddy viscosity was under 200 cm2 s−1, with the sign of the energy transfer uncertain. This is considerably below the O(4500 cm2 s−1) predicted by Müller (1976). An extensive error analysis indicates that the large wave stress predicted by the theory should have been observable clearly under the conditions of measurement. At moorings typified by a higher mean velocity (u¯≈25 cm s−1), statistically significant stress-shear correlations were found, and the wavefield energy level was observed to modulate with the strength of the mean shear. The observations were consistent with generation of short (∼1 km horizontal wavelength) internal waves by the mean shear near the thermocline, resulting in an effective eddy viscosity of ∼100 cm2 s−1. Theoretical computations indicate that the wavefield “basic state” may not be independent of the mean flow as assumed by Müller (1976) but can actually be modified by large-scale vertical shear and still remain in equilibrium. In that case, the wavefield does not exchange momentum with a large-scale vertical shear flow and, excepting critical-layer effects, a small vertical eddy viscosity is to be expected. Using the Garrett-Munk (1975) model internal wave spectrum, estimates were made of the maximum momentum flux (stress) expected to be lost to critical-layer absorption. This stress was found to increase almost linearly with the velocity difference across the shear zone, corresponding to a vertical eddy viscosity of −100 cm2 s−1. Stresses indicative of this effect were not observed in the data.
    Description: Prepared for the Office of Naval Research under Contract N00014-76-C-0197; NR 083-400.
    Keywords: Internal waves ; Ocean currents
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  • 8
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    Passive time reversal acoustic communications through shallow-water internal waves (2011)
    IEEE
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © IEEE, 2010. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 35 (2010): 756-765, doi:10.1109/JOE.2010.2060530.
    Description: During a 12-h period in the 2006 Shallow Water Experiment (SW06), binary phase shift keying (BPSK) signals at the carrier frequencies of 813 and 1627 Hz were propagated over a 19.8-km source–receiver range when a packet of strong internal waves passed through the acoustic track. The communication data are analyzed by time reversal processing followed by a single-channel decision feedback equalizer. Two types of internal wave effects are investigated in the context of acoustic communications. One is the rapid channel fluctuation within 90-s data packets. It can be characterized as decreased channel coherence, which was the result of fast sound-speed perturbations during the internal wave passage. We show its effect on the time reversal receiver performance and apply channel tracking in the receiver to counteract such fluctuation. The other one is the long-term (in the scale of hours) performance degradation in the depressed waveguide when the internal waves passed through the acoustic track. Even with channel tracking, the time reversal receiver experiences average 3–4-dB decrease in the output signal-to-noise ratio (SNR). Such long-term performance degradation is explained by the ray approximation in the depressed waveguide.
    Description: This work was supported by the U.S. Office of Naval Research (ONR) Code 322OA under Grants N00014-07-1-0546 and N00014-06-1019.
    Keywords: Acoustic communications ; Decision feedback equalizers ; Internal waves ; Time reversal processing
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Modeling weak fluctuations of undersea telemetry signals (2007)
    IEEE
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 1991. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 16 (1991): 3-11, doi:10.1109/48.64880.
    Description: Numerical calculation of acoustic field perturbation expressions can be used to predict fluctuations after propagation through ocean sound-speed structures, but before the onset of multipath. The general form of the expressions for signal spectra or correlation functions allow numerical evaluation for an unlimited quantity of vector wave-number spectral models of refractive index. In order to help define the bounds of applicability of the theory, log-intensity fluctuation variances have been calculated for three major situations: ocean internal waves, ocean turbulence, and continuous strong large-scale turbulence. Propagation through ocean thermocline internal waves, realistically weak thermocline turbulence, and unrealistically strong turbulence show that scintillations of intensity can be predicted and understood to first order up to ranges of tens of kilometers, given the proper transmission geometry. Internal wave effects dominate over any effects from expected microstructure. Nonhorizontal transmission yields small fluctuations, but eventually refractive effects of the sound channel will contribute some additional spatial variability and multipath, complicating the use of the theory. Multipath due to the sound channel can exist at ranges where the random small-scale structures would contribute only small perturbations (no multipath from small structures)
    Description: This work was supported by the Office of Naval Research, Ocean Acoustics Program.
    Keywords: Wave propagation ; Forward scattering ; Internal waves ; Microstructure
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  • 10
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    Tides of Massachusetts and Cape Cod Bays (2006)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: The Massachusetts Bays Program made bottom pressure and water velocity observations in Massachusetts and Cape Cod Bays during 1990 and 1991. In the Bays, the sea surface elevation appeared to rise and fall in phase with equal amplitudes at each diurnal or semidiurnal tidal frequency. There is some amplification in Boston and Provincetown harbors. The semidiurnal tides (particularly the M2 constituent) dominate. Massachusetts and Cape Cod Bays are part of the Gulf of Maine/Bay of Fundy system which is resonant near the semidiurnal frequency. This resonance amplifies the importance of the semidiurnal tides so that diurnal and higher harmonic tides become negligible. The sea level tides force currents which move with the same frequencies, but whose amplitudes are affected by the bathymetry. The strongest currents exist in the channel between Race Point and Stellwagen Bank where tidal currents exceed 1 knot. Analysis of current records for their tidal signal is complicated by internal tides which contaminate the records. These internal waves at tidal frequency exist on the stratification in the water column, and disappear during winter well-mixed times. At other times they must be considered as a signifcant source of energy for mixing and resuspension of sediments.
    Keywords: Tides ; Currents ; Internal waves
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 11
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    Internal tide and nonlinear internal wave behavior at the continental slope in the northern south China Sea (2006)
    IEEE
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1105-1130, doi:10.1109/JOE.2004.836998.
    Description: 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.
    Description: This work was supported in part by grants from the U.S. Office of Naval Research, Physical Oceanography and Ocean Acoustics Programs, and by the National Science Council of Taiwan.
    Keywords: Baroclinic tides ; Internal waves ; Nonlinear waves
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  • 12
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    South China Sea internal tide/internal waves-impact on the temporal variability of horizontal array gain at 276 Hz (2006)
    IEEE
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1292-1307, doi:10.1109/JOE.2004.836794.
    Description: The temporal variability of the spatial coherence of an acoustic signal received on a bottomed horizontal array has been calculated for 276-Hz narrow-band signals. A conventional plane wave beamformer was applied to the received signals. The temporal variability of the array's omnipower, beam power, and array gain are related to variability in the sound-speed field. The spectral characteristics of array omnipower are nonstationary and changed as the spectral characteristics of the temperature field varied. The array omnipower and beam-power variability tracked each other in time and varied by as much as 15 dB over time intervals as short as 7 min. Array gain varied up to 5 dB and usually tracked the omnipower variability. A contiguous 24-h section of data is discussed in detail. This data section is from a time period during which the high-frequency fluid dynamic perturbation of the sound-speed field was of smaller amplitude than other sections of the 16-d data set. Consequently, this section of data sets an upper bound for the realizable array gain. The temporal variability of array gain and spatial coherence at times appears to be correlated with environmental perturbation of the sound-speed field, but are also correlated with changes in the signal-to-noise ratio. The data was acquired during the Office of Naval Research's South China Sea Asian Seas International Acoustics Experiment. The 465-m 32-channel horizontal array was placed on the bottom in 120 m of water at the South China Sea shelf break. The acoustic source was moored in 114 m of water /spl sim/19 km from the receiving array.
    Description: This work was supported by the Office of Naval Research.
    Keywords: Array signal gain ; Coherence ; Internal waves ; Narrow-band conventional beamforming ; Shallow-water arrays
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  • 13
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    Shelf-edge frontal structure in the central East China Sea and its impact on low-frequency acoustic propagation (2006)
    IEEE
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1011-1031, doi:10.1109/JOE.2004.840842.
    Description: Two field programs, both parts of the Asian Seas International Acoustics Experiment (ASIAEX), were carried out in the central East China Sea (28 to 30 N, 126 30 to 128 E) during April 2000 and June 2001. The goal of these programs was to study the interactions between the shelf edge environment and acoustic propagation at a wide range of frequencies and spatial scales. The low-frequency across-slope propagation was studied using a synthesis of data collected during both years including conductivity- temperature-depth (CTD) and mooring data from 2000, and XBT, thermistor chain, and wide-band source data from 2001. The water column variability during both years was dominated by the Kuroshio Current flowing from southwest to northeast over the continental slope. The barotropic tide was a mixed diurnal/semidiurnal tide with moderate amplitude compared to other parts of the Yellow and East China Sea. A large amplitude semidiurnal internal tide was also a prominent feature of the data during both years. Bursts of high-frequency internal waves were often observed, but these took the form of internal solitons only once, when a rapid off-shelf excursion of the Kuroshio coincided with the ebbing tide. Two case studies in the acoustic transmission loss (TL) over the continental shelf and slope were performed. First, anchor station data obtained during 2000 were used to study how a Kuroshio warm filament on the shelf induced variance in the transmission loss (TL) along the seafloor in the NW quadrant of the study region. The corresponding modeled single-frequency TL structure explained the significant fine-scale variability in time primarily by the changes in the multipath/multimode interference pattern. The interference was quite sensitive to small changes in the phase differences between individual paths/modes induced by the evolution of the warm filament. Second, the across-slope sound speed sections from 2001 were used to explain the observed phenomenon of abrupt signal attenuation as the transmission range lengthened seaward across the continental shelf and slope. This abrupt signal degradation was caused by the Kuroshio frontal gradients that produced an increasingly downward-refracting sound-speed field seaward from the shelf break. This abrupt signal dropout was explained using normal mode theory and was predictable and source depth dependent. For a source located above the turning depth of the highest-order shelf-trapped mode, none of the propagating modes on the shelf were excited, causing total signal extinction on the shelf.
    Keywords: Environmental acoustics ; Internal waves ; Kuroshio Current ; Shelf circulation
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  • 14
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    Research highlights from the Asian Seas International Acoustics Experiment in the South China Sea (2006)
    IEEE
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 1067-1074, doi:10.1109/JOE.2005.843162.
    Description: The Asian Seas International Acoustics Experiment (ASIAEX) included two major field programs, one in the South China Sea (SCS) and the other in the East China Sea (ECS). This paper summarizes results from the work conducted during April and May 2000 and 2001 over the continental shelf and slope in the northeastern South China Sea, just east of Dongsha Island (Pratis Reef). The primary emphasis of the field program was on water-column variability and its impact on acoustic propagation loss. The reader is steered to the appropriate paper within this Special Issue when more information on a specific topic is desired.
    Description: The planning, execution, and analysis of this work was funded by the U.S. Office of Naval Research Ocean Acoustics and Physical Oceanography Programs. Significant support was also made by the National Science Council of Taiwan.
    Keywords: Acoustic propagation ; Asian Seas International Acoustics Experiment (ASIAEX) ; Internal waves ; Ocean currents ; South China Sea
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  • 15
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    The 1998 WHOI/IOS/ONR internal solitary wave workshop : contributed papers (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: A workshop entitled "Internal Solitary Waves in the Ocean: Their Physics and Implications for Acoustics, Biology, and Geology" was held during October, 1998 in Sydney, British Columbia, Canada. It was jointly organized by the Woods Hole Oceanographic Institution (MA, USA), the Institute of Ocean Sciences, (Sydney, BC, Canada), and the U. S. Office of Naval Research. More than 60 scientists from seven countries attended. Participants contributed papers prior to the meeting which were published on the internet at the Woods Hole web site. Those papers are reproduced here.
    Description: Funding was provided by the Office of Naval Research under Contract Nos. N00014-95-1-0633 and N00014-99-1-0126.
    Keywords: Solitary waves ; Internal waves ; Wave workshop
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  • 16
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    2004 program of study : tides (2005)
    Woods Hole Oceanographic Institution
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    Publication Date: 2022-05-25
    Description: The summer of 2004 saw the GFD program tackle “Tides”. Myrl Hendershott (Scripps Institution of Oceanography) gave a fabulous introduction to the subject in the first week of the course, laying the foundations from astronomy and classical geophysical fluid dynamics. In the second week, Chris Garrett (University of Victoria) admirably followed up with recent developments on the subject, including the recent observations from satellite altimetry, their implications to mixing and circulation, and even a memorable lecture on the noble theme of how we might solve the world's energy crisis. The principal lectures proved unusually popular this summer, and the seminar room at Walsh often overflowed in the first two weeks. Following on from the lectures, the seminar schedule of the summer covered in greater detail the oceanographic issues with which researchers are actively grappling. We also heard about related problems regarding atmospheric, planetary and stellar tides, together with the usual mix of topics on GFD in general. The summer once again featured a lecture for the general public in the Woods Hole area. Carl Wunsch delivered a very well received lecture entitled “Climate Change Stories”, in which he gave an impression of how scientists generally believe our climate is currently changing, whilst simultaneously urging caution against some of the more outrageous and exaggerated claims. The lecture was held at Lilly Auditorium, thanks to the hospitality of the Marine Biology Laboratory. The reception following the lecture was enjoyed by all. Neil Balmforth and Stefan Llewellyn Smith acted as Co-Directors for the summer. Janet Fields, Jeanne Fleming and Penny Foster provided the administrative backbone to the Program, both during the summer and throughout the year beforehand. As always, we were grateful to the Woods Hole Oceanographic Institution for the use of Walsh Cottage, and Keith Bradley's solid service could not be overlooked. Shilpa Ghadge and Shreyas Mandre are to be thanked for their part in comforting the fellows, developing the summer's proceedings volume (available on the GFD web site) and for running the computer network.
    Description: Funding was provided by the Office of Naval Research under Contract No. N00014-04-1-0157 and the National Science Foundation under Grant No. OCE-0325296.
    Keywords: Tides ; Internal waves ; Ocean tides
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Acoustic mode coupling by nonlinear internal wave packets in a shelfbreak front area (2005)
    IEEE
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © IEEE, 2004. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 29 (2004): 118-125, doi:10.1109/JOE.2003.822975.
    Description: A computational case study of coupled-mode 400-Hz acoustic propagation over the distance 27 km on the continental shelf is presented. The mode coupling reported here is caused by lateral gradients of sound-speed within packets of nonlinear internal waves, often referred to as solitary wave packets. In a waveguide having unequal attenuation of modes, directional exchange of energy between low- and high-loss modes, via mode coupling, can become time dependent by the movement of waves and can cause temporally variable loss of acoustic energy into the bottom. Here, that bottom interaction effect is shown to be sensitive to stratification conditions, which determine waveguide properties and, in turn, determine modal attenuation coefficients. In particular, time-dependent energy loss due to the presence of moving internal wave packets is compared for waveguides with and without a frontal feature similar to that found at the shelfbreak south of New England. The mean and variability of acoustic energy level 27 km distant from a source are shown to be altered in a first order way by the presence of the frontal feature. The effects of the front are also shown to be functions of source depth.
    Description: This work was supported by the Office of Naval Research Grants N00014-99-1-2074 and N00014-01-1-0772.
    Keywords: Continental shelf ; Internal waves ; Mode coupling ; Shallow water ; Shelfbreak front ; Solitary waves ; Sound propagation
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