| Subinertial Slope-Trapped Waves in the Northeastern Gulf of Mexico |
Jun-2009 |
12 pages |
| Authors:
Z R Hallock; W J Teague; E Jarosz; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
 | Current velocity from moored arrays of acoustic Doppler current profilers (ADCPs) deployed on the outer shelf and slope, south of Mobile Bay in the northeastern Gulf of Mexico, shows evidence of alongslope, generally westward-propagating subinertial baroclinic Kelvin waves with periods of about 16 and 21 days, amplitudes of 5-10 cm/sec, and wavelengths of about 500 km. The observed waves were highly coherent over the slope between about 200 and 500 ... |
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| Acoustic Scattering from Sand Dollars (Dendraster excentricus): Modeling as High Aspect Ratio Oblate Objects and Comparison to Experiment |
Sep-2008 |
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| Authors:
Gregory C Dietzen; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
 | Benthic shells can contribute greatly to the scattering variability of the ocean bottom, particularly at low grazing angles. Among the effects of shell aggregates are increased scattering strength and potential subcritical angle penetration of the seafloor. Sand dollars (Dendraster excentricus) occur commonly in the ocean and have been shown to be significant scatters of sound. In order to understand more fully the scattering mechanisms of these organisms, the scattering from ... |
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| Flow Through the Straits of the Philippine Archipelago Simulated by Global HYCOM and EAS NCOM |
Jan-2008 |
11 pages |
| Authors:
Harley E Hurlburt; E J Metzger; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| We plan to collaborate with other DRI participants to better evaluate and understand the dynamics seen in observations and model results within the Philippine Archipelago, a strategic region with numerous straits. Objectives for our DRI participation are (1) high resolution simulations (with and without tides; with and without data assimilation) which provide a larger scale context for the observations, (2) model data comparisons with the measurements, (3) studies of observational ... |
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| Water Masses in the Monterey Bay during the Summer of 2000 |
19 JAN 2007 |
21 pages |
| Authors:
Alex Warn-Varnas; Avijit Gangopadhyay; J. A. Hawkins; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Water masses in Monterey Bay are determined from the CTD casts of the Monterey Ocean Observing System (MOOS) Upper-water-column Science Experiment (MUSE) August 2000 dataset. It is shown through cluster analysis that the MUSE 2000 CTD dataset contains 5 water masses. These five water masses are bay surface water (BSW), bay warm water (BWW), bay intermediate water (BIW), subarctic upper water (SUW), and North Pacific deep water (NPDW). The BWW ... |
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| Roughness Spectra and Acoustic Response from a Diver-Manipulated Sea Floor |
18 SEP 2006 |
7 pages |
| Authors:
Kevin B. Briggs; Michael D. Richardson; Kevin L. Williams; Anthony P. Lyons; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE
|
| A digital stereo photogrammetric system was designed and implemented to measure seafloor roughness in coastal sands. High-resolution images that achieve more than four pixels/millimeter in either the horizontal or vertical dimension are created by two cameras sealed in watertight housings and actuated simultaneously by a scuba diver. A Digital Elevation Model (DEM) of the photographed sea floor is created from digital autocorrelation of left and right paired images. The DEM ... |
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| Evidence of Multimodal Structure of the Baroclinic Tide in the Strait of Gibraltar |
08 SEP 2006 |
7 pages |
| Authors:
A. Vazquez; N. Stashchuk; V. Vlasenko; M. Bruno; A. Izquierdo; P. C. Gallacher; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| The multimodal structure of the baroclinic tides in the Strait of Gibraltar is studied using observations and numerical simulations. Observational data and model results revealed the presence of two types of tidal internal waves generated over Camarinal Sill (CS). One propagates toward the Mediterranean and disintegrates into a series of nonlinear short internal waves with amplitudes of 50 m and more. The second type, behind the first, propagates slower and ... |
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| Seafloor Roughness, Sediment Grain Size, and Temporal Stability |
JUL 2005 |
9 pages |
| Authors:
Kevin B. Briggs; Anthony P. Lyons; Eric Pouliquen; Larry A. Mayer; Michael D. Richardson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE
|
| Measurement of seafloor microtopography is rapidly approaching the status of a standardized element of geoacoustic characterization of the sea floor. With the advent of underwater stereo cameras and, recently, multiple-megapixel digital cameras adapted for underwater use, more investigators are measuring seafloor roughness at high resolution for applications to high-frequency acoustic modeling. An assessment of the methodologies used to characterize seafloor roughness, the parameterizations of the characterization of seafloor roughness, and ... |
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| The Thermohaline Circulation in Semi-Enclosed Marginal Seas |
2005 |
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| Authors:
Michael A. Spall; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| The principles governing the buoyancy-forced circulation within marginal seas, and their exchange with the open ocean, are addressed using a series of idealized numerical models and theory. It is found that small scale mixing of density and momentum near the boundaries plays a central role in the net down-welling within the marginal sea and, at times, in the basin-scale stratification. Bottom topography is also found to be very important for ... |
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| The Use of Hydroacoustic Phases for the Detection of Oceanic Events: Observations and Numerical Modeling |
JUL 2004 |
63 pages |
| Authors:
Catherine DE Groot-Hedlin; Donna Blackman; John Orcutt; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA
|
| Hydroacoustic monitoring of the Comprehensive Nuclear Test Ban Treaty (CTBT) requires the ability to detect and locate phenomena that give rise to acoustic signals. An improved understanding of the coupling of seismic energy to acoustic energy is necessary to improve location estimates of earthquakes and volcanic eruptions. Using known variations in near-source bathymetry, the authors demonstrated that scattering of seismic to acoustic energy at a rough seafloor yields the approximate ... |
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| Proceedings, ONR Shallow Water Acoustics 2006 Workshop Applied Physics Laboratory, University of Washington 25-26 September 2003 |
APR 2004 |
20 pages |
| Authors:
Dajun Tang; Nick Makris; James Lynch; UNIV OF WASHINGTON SEATTLE APPLIED PHYSICS LAB
|
| The Ocean Acoustics Code, Office of Naval Research, sponsored a two- day workshop on shallow water acoustics. The primary purpose of the workshop was to define and identify key basic research problems to be addressed in a field experiment to be conducted in fiscal year 2006. Seventeen scientists attended the workshop. Several researchers contributed poster presentations as well. The report consists of an 18-page workshop summary, 18 PowerPoint presentations, and ... |
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| Mine Burial Experiments at the Martha's Vineyard Coastal Observatory |
03 FEB 2004 |
8 pages |
| Authors:
Peter Traykovski; Michael D. Richardson; John A. Goff; Larry Mayer; Roy Wilkens; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
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| Several experiments to measure the burial of seafloor mines by scour and fill have been conducted at the Woods Hole Oceanographic Institution Martha's Vineyard Coastal Observatory (MVCO). Two sets of mine scour burial experiments were conducted during the winters of 2001-2002 and 2002-2003 with a single optically instrumented mine in the field of view of a rotary sidescan sonar. Sixteen mines were deployed from October 2003 to April of 2004, ... |
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| NPS ARIES Forward Look Sonar Integration |
01-Jan-2004 |
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| Authors:
A J Healey; D P Horner; NAVAL POSTGRADUATE SCHOOL MONTEREY CA CENTER FOR AUTONOMOUS UNDERWATER VEHICLE RESEARCH
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| This work integrated an experimental Blazed Array Forward Looking Sonar (FLS) developed by the University of Washington, Applied Physics Laboratories into the ARIES autonomous underwater vehicle (AUV). Experiments were conducted and data were gathered using this sonar in a variety of environments. The images generated were analyzed to provide information for use in the further development of forward look obstacle detection and avoidance technologies. The year-end goal of the project ... |
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| A Terrain-Following Crystal Grid Finite Volume Ocean Circulation Model |
2004 |
26 pages |
| Authors:
Peter C. Chu; Chenwu Fan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA NAVAL OCEAN ANALYSIS AND PREDICTION LAB
|
| A three-dimensional hydrostatic finite volume ocean model is developed solving the integral dynamical equations. Since the basic (integral) equations are solved for finite volumes rather than grid points, the flux conservation is easily enforced even on arbitrary meshes. Both upwind and high-order combine compact schemes can be incorporated into the model to increase computational stability and accuracy. For abrupt topography, a terrain-following grid discretization is designed to reduce computational errors ... |
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| The Shelf-Edge Environment in the Central East China Sea and Its Impact on Low Frequency Acoustic Propagation |
OCT 2002 |
29 pages |
| Authors:
Steven R. Ramp; Ching-Sang Chiu; Fred Bahr; James Lynch; Tim Duda; UNIV OF WASHINGTON SEATTLE APPLIED PHYSICS LAB
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| Viewgraphs on presentation of the shelf-edge environment in the Central East China Sea and its impact on low frequency acoustic wave propagation. |
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| Development and Verification of a Comprehensive Community Model for Physical Processes in the Nearshore Ocean |
2002 |
11 pages |
| Authors:
James T. Kirby; John S. Allen; Thomas G. Drake; Steve Elgar; Robert T. Guza; Daniel M. Hanes; Thomas H. Herbers; James M. Kaihatu; George Mellor; H. T. Ozkan-Haller; DELAWARE UNIV NEWARK CENTER FOR APPLIED COASTAL RESEARCH
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| Our goal is to develop a comprehensive, verified community model that predicts nearshore hydrodynamics, sediment transport, and seabed morphology changes given offshore wave conditions and initial bathymetry. The basic scientific objective is to synthesize understanding of physical processes in the nearshore ocean by developing a model for waves and resulting radiation stresses and mass fluxes over evolving coastal bathymetry and currents wave-induced circulation sediment transport and morphological evolution. An additional ... |
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| Evidence from Gravity Anomalies for Interactions of the Marion and Bouvet Hotspots with the Southwest Indian Ridge: Effects of Transform Offsets |
MAR 2001 |
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| Authors:
Jennifer E. Georgen; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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| The ultra-slow spreading Southwest Indian Ridge (SWIR) presents a unique environment to study the interactions between hotspots and ridges with highly segmented geometry. Using recently available satellite free-air gravity and shipboard bathymetry data, we obtain mantle Bouguer (MBA) and residual mantle Bouguer anomalies (RMBA) by removing from free-air gravity the attractions of seafloor topography, sediment thickness variations, a reference crust, and theoretically-predicted effects of lithospheric cooling. The Bouvet hotspot, previously ... |
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| A Fine Resolution Model of the Coastal Eastern Boundary Current Systems off Iberia and Morocco |
MAR 2001 |
109 pages |
| Authors:
Antonio S. Martinho; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| To investigate the role of wind forcing, bottom topography and thermohaline gradients on classical as well as unique features in the northern Canary Current system (NCCS), four experiments are conducted with a sigma coordinate primitive equation model. The first experiment, which investigates the pressure gradient force error, shows that velocity errors inherent in three dimensional sigma coordinate models can be successfully reduced from ^1 m/s to less than 0.5 cm/s ... |
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| Circulation in the Vicinity of Descending Overflows |
22 JAN 2001 |
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| Authors:
Michael A. Spall; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Analytic and numerical models have been used to study the large-scale circulation and exchange between marginal seas and the open ocean resulting from diapycnal mixing near lateral boundaries. The results indicate that mixing near topography can force strong circulations far from the region of mixing, sometimes extending into an adjacent ocean basin. The exchange between marginal seas and the open ocean will be strongly dependent on whether the marginal sea ... |
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| East Asian Marginal Seas Prediction Using a Coastal Atmosphere-Ocean Coupled System (CAOCS) |
2001 |
4 pages |
| Authors:
Peter C. Chu; Shihua Lu; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
|
| The South China Sea (SCS), Yellow/East China Sea (YES), and Japan/East Sea (JES) are major East Asian marginal seas (EAMS). The complex topography includes the broad shallows of the Sunda Shelf in the south/southwest of SCS; the continental shelf of the Asian landmass in the north, extending from the Gulf of Tonkin to the YES; deep, elliptical shaped SCS and JES basins, and numerous reef islands and underwater plateaus scattered ... |
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| Global Ocean Modeling and State Estimation in Support of Climate Research |
OCT 1999 |
24 pages |
| Authors:
D. Stammer; R. Bleck; C. Boning; P. Demey; H. Hurlburt; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
| During the last decade it has become obvious that the ocean circulation shows vigorous variability on a wide range of time and space scales and that the concept of a "sluggish" and slowly varying circulation is rather elusive. Increasing emphasis has to be put, therefore, on observing the rapidly changing ocean state on time scales ranging from weeks to decades and beyond, and on understanding ... |
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| Dynamical Mechanisms for the South China Sea Seasonal Circulation and Thermohaline Variabilities |
APR 1999 |
22 pages |
| Authors:
Peter C. Chu; Nathan L. Edmons; Chenwu Fan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
|
| The seasonal ocean circulation and the seasonal thermal structure in the South China Sea (SCS) were studied numerically using the Princeton Ocean Model (POM) with 20-km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. A 16-month control run was performed using climatological monthly mean wind stresses, restoring-type surface salt and heat, and observational oceanic inflow/outflow at the open boundaries. The seasonally averaged effects of isolated forcing ... |
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| Adriatic Sea Surface Temperature: Satellite and Drifter Observations, May to October, 1995 |
MAR 1999 |
102 pages |
| Authors:
Jason A. Vogt; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
|
| The Adriatic Sea is the northernmost semi-enclosed basin of the Mediterranean Sea and has been the subject of various oceanographic studies since the 19th century. Substantial changes in water properties (such as temperature) and in circulation, both spatially and temporally (seasonal) occur as a result of extreme forcings by the local winds and by the fresh water discharge by rivers. In recent years, extensive measurements have been made, primarily through ... |
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| IOC/IASC/IHO Editorial Board for the International Bathymetric Chart of the Arctic Ocean Report of Meeting: Copenhagen, Denmark; October 19-20 1998 |
JAN 1999 |
50 pages |
| Authors:
Ron Macnab; Arne Nielsen; GEOLOGICAL SURVEY OF CANADA DARTMOUTH (NOVA SCOTIA)
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| Compilation of abstracts and report from the conference/meeting entitled "IOC/IASC/IHO Editorial Board for the International Bathymetric Chart of the Arctic Ocean" held in Copenhagen, Denmark, 19 - 20 October 1998. |
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| Side Scan Sonar Survey of Clinch River and Poplar Creek, Tennessee |
JAN 1999 |
85 pages |
| Authors:
Keith J. Sjostrom; Rodney L. Leist; Thomas S. Harmon Jr.; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
|
| During the 1950s, quantities of chemical materials were released into local waterways in association with nuclear energy research and weapons components production at the Oak Ridge National Laboratory (ORNL). Plans and specifications for studying the distribution and extent of any contamination are presently being prepared by ORNL. The objective of this study is to delineate the characteristics and features of the river bottom topography and sediments along Clinch River and ... |
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| Scattering of High-Frequency Acoustic Energy from Discrete Scatterers on the Seafloor: Glass Spheres and Shells |
1999 |
7 pages |
| Authors:
Michael E. Richardson; Kevin B. Briggs; Kevin L. Williams; Darrell R. Jackson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
|
| Shells and shell debris are common at the water/seafloor interface. Quantifying the scattering from shells is thus important for predicting high frequency backscattering from the seafloor. A backscattering experiment is described in which glass beads (radius equal to 1.75 cm) and shells (largest dimension tip to about 10 cm) were placed near a bottom-mounted sonar and backscattering examined as a function of the number of discrete scatterers Supported by Office ... |
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| Effects of Changing Roughness on Acoustic Scattering: (2) Anthropogenic Changes |
1999 |
9 pages |
| Authors:
Michael E. Richardson; Kevin B. Briggs; Anthony Lyons; Kevin Williams; Darrell Jackson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
|
| Deliberate modification of bottom roughness including smoothing to eliminate centimeter scale natural roughness and raking to induce quasiperiodic roughness was investigated using diver observation, quantification of bottom roughness from Stereo photography, and measurement of acoustic backscattering strength. At 40 kHz. raking perpendicular to the acoustic line-of-sight with a tine spacing equal to one-half wavelength increased scattering by 12-18 dB which decayed to background levels within 24 hours due to biological ... |
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| SeaSoar CTD Observations During the Coastal Mixing and Optics Experiment: R/V Endeavor Cruises from 14 August to 1 September 1996 and 25 April to 15 May 1997 |
OCT 1998 |
502 pages |
| Authors:
R. O'Malley; J. A. Barth; A. Erofeev; J. Fleischbein; P. M. Kosro; OREGON STATE UNIV CORVALLIS COLL OF OCEANIC AND ATMOSPHERIC SCIENCES
|
| Two physical oceanography cruises on the R/V Endeavor were conducted by the co-PIs Jack Barth and Mike Kosro as part of the ONR-sponsored Coastal Mixing and Optics (CMO) Accelerated Research Initiative. The objective was to rapidly survey a region around 40.5N, 70.5W where a set of moorings and a stationary vessel conducting profiling operations were located. The first cruise took place during a period of strong summer stratification (14 August ... |
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| A P-Vector Approach to Absolute Geostrophic Currents in the Adriatic Sea |
MAR 1998 |
89 pages |
| Authors:
Renato L. Pinto; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| With the recent conflict in Bosnia-Herzegovina being in the world news front, the Adriatic Sea has become an important strategic operating area for the North Atlantic Treaty Organization (NATO) and for the U.S. Navy. The NATO Undersea Research Centre located in La Spezia, Italy carried out the Otranto Gap (OGAP) project in 1994 and 1995 to assess the oceanography and bottom geology of the Southern Adriatic. As part of this ... |
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| Structure and Dynamics of the Pacific Upper Mantle |
FEB 1998 |
|
| Authors:
Rafael Katzman; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| A new tomographic technique is employed to investigate the structure and dynamics of the Pacific upper mantle. We invert frequency-dependent travel times residuals of three-component turning and surface waves such as S, SS, SSS, R1 and G1 together with band-center travel times of ScS reverberations for the 2D composite structure in the plane of two Pacific corridors. The model parameters include shear-speed variations throughout the mantle, perturbations to radial shear-wave ... |
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| Pressure/Temperature Logger (PTL) Development and Field Deployment for the Great Bay, NH, Tidal Dynamics Experiment |
JAN 1998 |
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| Authors:
Carl T. Friedrichs; Wayne D. Spencer; David G. Aubrey; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| During 1992 and 1993 experiments were conducted in the shallow east side of Great Bay, New Hampshire. These experiments were conducted to better understand the morphodynamics and evolutionary tendencies of shallow tidal embayments and intertidal flats. Hardware and software used in the collection of data are described. Discussed also are techniques used to collect data. Six pressure temperature loggers (PTL) and one current meter (TCSWG) were ... |
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| High-Frequency Acoustic Imaging of L Lake, Savannah River Site, South Carolina |
SEP 97 |
134 pages |
| Authors:
Keith J. Sjostrom; Rodney L. Leist; Thomas S. Harmon Jr; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
|
| The objective of the seismic reflection and side scan sonar survey is to determine the location, aerial extent, and depth of burial pits situated along the reservoir bottom of L lake, Savannah River Site, SC. The results will be used in the overall characterization of L lake by providing continuous profile line coverage of the boflom and subbottom sediment structure along the entire length of the project area. The results ... |
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| Sixth-Order Difference Scheme for Sigma Coordinate Ocean Models |
SEP 1997 |
9 pages |
| Authors:
Peter C. Chu; Chenwu Fan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
|
| How to reduce the horizontal pressure gradient error is a key issue of using sigma-coordinate ocean models, especially of using primitive equation models for coastal regions. The error is caused by the splitting of the horizontal pressure gradient term into two parts and the subsequent incomplete cancellation of the truncation errors of those parts. Due to the fact that the higher the order of the difference scheme, the less the ... |
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| Dynamic Response of a Semi-Enclosed Sea to Atmospheric and Tidal Forcing |
23 JUL 1997 |
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| Authors:
Julio Candela; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| The internal dynamics of a semi-enclosed sea is influenced by its thermohaline structure, atmospheric forcings, interactions with lateral boundaries, bottom topography and remote interactions transmitted through interconnecting straits. The construction of simple and accurate representations of the dynamical response of a semi-enclosed sea facilitates dynamical interpretation and it is conducive to robust data assimilation models for nowcast and forecast. Our specific objectives are: (1) To develop and exploit practical and ... |
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| Sediment Characteristics of Toroidal Volume Search Sonar (TVSS) Test Sites Off Panama City, Florida |
17 JUL 1997 |
20 pages |
| Authors:
Frederick A. Bowles; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
|
| Acoustic tests were conducted at two sites off Panama City, FL, using the Toroidal Volume Search Sonar (TVSS) which is under development at the Naval Surface Warfare Centers Coastal Systems Station. Inverse modeling of the resultant TVSS acoustic data, using the BOGGART Backscatter model developed by the Applied Research Laboratory at the University of Texas, indicates differences between the sediment physical properties and/or bottom roughness of the sites. Neither seafloor ... |
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| Bistatic Bottom Scattering: Model, Experiments, and Model/Data Comparison |
JUL 1997 |
33 pages |
| Authors:
K. L. Williams; D. R. Jackson; UNIV OF WASHINGTON SEATTLE APPLIED PHYSICS LAB
|
| A model is presented for bistatic scattering from ocean sediments. It treats scattering due to both roughness of the seabed and volume inhomogeneities within the sediment. Accordingly, the scattered intensity is assumed to be a sum of two terms, one proportional to the roughness-scattering cross section and the other proportional to the volume-scattering cross section. The model is tested against data acquired as part of the Coastal Benthic Boundary Layer ... |
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| Nearshore Currents over a Barred Beach |
JUN 97 |
178 pages |
| Authors:
Antonio Fernando Garcez Faria; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The objective of this dissertation is to develop numerical models and compare their predictions with data acquired during the DUCK94 experiment in order to improve our physical understanding of the hydrodynamic processes governing the vertical and cross shore distributions of both longshore and cross shore currents over a barred beach. The vertical structure of the mean longshore current is found to be well described by a logarithmic profile and a ... |
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| Faulting of Gas-Hydrate-Bearing Marine Sediments - Contribution to Permeability |
MAY 1997 |
|
| Authors:
William Dillon; W. S. Holbrook; Rebecca Drury; Joseph Gettrust; Deborah Hutchinson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
|
| Extensive faulting is observed in sediments containing high concentrations of methane hydrate off the southeastern coast of the United States. Faults that break the sea floor show evidence of both extension and shortening; mud diapirs are also present. The zone of recent faulting apparently extends from the ocean floor down to the base of gas-hydrate stability. We infer that the faulting resulted from excess pore pressure in ... |
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| Report of the Office of Naval Research USA-China Conference on Shallow Water Acoustics, December 19-21, 1995 |
JAN 97 |
25 pages |
| Authors:
Ching-Sang Chiu; Warren W. Denner; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
|
| Under the sponsorship of the Office of Naval Research, the first joint USA-China Conference on Shallow-Water Acoustics was held In December 1995 at the Naval Postgraduate School, Monterey, CA. The conference objective was to identify and discuss the outstanding research topics in shallow-water acoustics which are of common interest of both countries and which might form the basis for a collaborative field program in the seas of China. Participants included ... |
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| Morphological and Geophysical Investigation of Western North Atlantic Ocean Crustal Structure: Environmental Work in Support of the Acoustic Reverbation Special Research Program and Morphological and Geophysical Investigation of Western North Atlantic Oce |
JAN 97 |
|
| Authors:
Brian E. Tucholke; Gary E. Jaroslow; W. K. Stewart; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| The Acoustic Reverberation Special Research Program required detailed knowledge of large and small scale seafloor roughness, crustal structure, sediment distribution patterns, and material properties of the ocean floor on the MidAtlantic Ridge in order to advance fundamental research on acoustic wave scattering from the ocean bottom and subbottom at low frequencies and over long propagation paths. To provide this information and to improve our understanding of the fundamental geological processes ... |
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| The Development of an Ice-Ocean Coupled Model for the Northern Hemisphere |
30 DEC 96 |
68 pages |
| Authors:
Abe Cheng; Ruth H. Preller; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS COASTAL AND SEMI- ENCLOSED SEAS SE CTION
|
| The Polar Ice Prediction System (PIPS), based on the Hibler ice model, has been reformulated into spherical coordinates for the Northern Hemisphere. These spherical coordinates help to avoid a numerical singularity at the North Pole and numerical instabilities in high latitudes. Further, a coordinate transformation was chosen so that a new equator coincides with the 170 deg W - 10 deg E great circle, and a new north pole is ... |
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| Ocean Wave Data Analysis Using Hilbert Transform Techniques |
DEC 1996 |
51 pages |
| Authors:
Moises N. Lopez; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A novel technique to determine the phase velocity of long-wavelength shoaling waves is investigated. Operationally, the technique consists of three steps. First, using the Hilbert transform of a time series, the phase of the analytic signal is determined. Second, the correlations of the phases of analytic signals between two points in space are calculated and an average time of travel of the wave fronts is obtained. Third, if directional spectra ... |
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| Ocean Wave Data Analysis Using Hilbert Transform Techniques |
DEC 96 |
52 pages |
| Authors:
Moises N. Lopez; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A novel technique to determine the phase velocity of long-wavelength shoaling waves is investigated. Operationally, the technique consists of three steps. First, using the Hilbert transform of a time series, the phase of the analytic signal is determined. Second, the correlations of the phases of analytic signals between two points in space are calculated and an average time of travel of the wave fronts is obtained. Third, if directional spectra ... |
|
| Investigation of the Arctic Internal Wave Field. Small-Scale Processes in the Arctic Ocean and Sub-Arctic Seas |
13 NOV 96 |
|
| Authors:
Albert J. Plueddemann; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY
|
| The unprecedented subsurface velocity record from the AEDB as it drifted from the Nansen Basin, over the Yermak Plateau, and into the Greenland Sea provided new insights into the high latitude internal wave field. Plueddemann (1992) showed that the wave field over the Yermak Plateau was dominated by near inertial wave groups generated at or near the bottom and propagating upwards. The energy level and spectral slope in the internal ... |
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| Studies of South China Sea Circulation and Thermal Structure Using a Three Dimensional Numerical Model |
SEP 96 |
104 pages |
| Authors:
Nathan L. Edmons; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The seasonal ocean circulation and thermal structure in the South China Sea (SCS) were studied numerically using the Princeton Ocean Model (POM) with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. A sixteen month control run was performed using climatological monthly mean wind stresses and restoring type salt and heat fluxes as surface forcing terms and observational oceanic inflow/outflow at the open boundaries. The ... |
|
| Time Spreading at High Frequency in a Shallow Water Channel |
SEP 96 |
|
| Authors:
Paul C. Hines; Arthur J. Collier; J. S. Hutton; DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA)
|
| Time spreading measurements provide an indirect measure of the acoustic bandwidth that can be supported by the water channel, which is critical to the design of sonar systems. Time spreading measurements were collected in a water channel 100 m deep, off the coast of Nova Scotia. Data were collected at frequencies of 20-22 kHz, 27-29 kHz, and 35-37 kHz using linear FM pulses 25 in duration. The experiments were part ... |
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| Search Methods for an Autonomous Underwater Vehicle Using Scalar Measurements |
18 JUL 96 |
|
| Authors:
Erik A. Burian; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| The continuing development of the autonomous underwater vehicle as an oceanographic research tool has opened up the realm of scientific possibility in the field of deep ocean research. The ability of a vehicle to travel to the ocean floor untethered, collect data for an extended period of time and return to the surface for recovery can make precise oceanographic surveying more economically practical and more efficient. This thesis investigates several ... |
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| Effects of Shallow Water Bottom Interface Roughness and Volume Fluctuations on Broadband Pulse Resolution |
JUN 96 |
68 pages |
| Authors:
Mei-Chun Yuan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Typical acoustic propagation in shallow water environments is dominated by bottom-interacting paths. The effects of rough bottom interfaces and sediment volume fluctuations are investigated using model simulations. A numerical study of low-frequency (approx. 2OO Hz) broadband pulse propagation is presented and several characterizations of bottom factors are examined. In particular, the variations of the interface rms roughness and a volume fluctuation strength constant on the time resolution of the broadband ... |
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| On the World Ocean Circulation. Volume 1. Some Global Features / North Atlantic Circulation |
JUN 96 |
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| Authors:
William J. Schmitz Jr; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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| This is the first volume of a 'final report' that summarizes, often in a speculative vein, what I have learned over the past 35 years or so about large-scale, low-frequency ocean currents, primarily with support from the Office of Naval Research (ONR). I was also fortunate to have been partially supported by the National Science Foundation, and during the preparation of this report, by the Clark Foundation. This report is ... |
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| Infragravity Waves on the Continental Shelf |
JUN 96 |
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| Authors:
Dimitrios A. Evangelidis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| The variability of infragravity frequency (0.004-0.04 Hz) motions on a wide continental shelf was examined with data from a 100km long transect of bottom pressure recorders extending from the beach (6m depth) to the shelf break (87m depth) near Duck, North Carolina. The observed infragravity motions are a mixture of forced waves, phase coupled to local wave groups, and (uncoupled) free waves. Although the contribution of forced waves to the ... |
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| Numerical Modelling of the Continental Shelf Bottom Boundary Layer |
15 MAY 96 |
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| Authors:
Hsiao-ming Hsu; Robert C. Beardsley; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY
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| The primary objective of this project was to examine the nature of wind-driven upwelling and downwelling along a 2-dim shelf with sloping bottom topography. The approach was to use the Semi-spectral Primitive Equation Model (SPEM) developed by D. Haidvogel and coworkers as the basic circulation model, and conduct a series of idealized model runs to investigate the influence of bottom slope, surface windstress and heat flux, and mixing on the ... |
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Reports by Keyword(s)
OCEAN BOTTOM TOPOGRAPHY
