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  • 1
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    Measurements of Momentum and Heat Transfer across the Air–Sea Interface (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-05-01
    Description: This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict mean vertical gradients beneath the ocean’s wavy surface. Observations were made at 20 Hz at nominal depths of 2.2 and 1.7 m in ∼16 m of water. A new method is developed to estimate the fluxes and the length scales of dominant flux-carrying eddies from cospectra at frequencies below the wave band. The results are compared to independent estimates of those quantities, with good agreement between the two sets of estimates. The observed temperature gradients were smaller than predicted by standard rigid-boundary closure models, consistent with the suggestion that wave breaking and Langmuir circulation increase turbulent diffusivity in the upper ocean. Similarly, the Monin–Obukhov stability function ϕh was smaller in the authors’ measurements than the stability functions used in rigid-boundary applications of the Monin–Obukhov similarity theory. The dominant horizontal length scales of flux-carrying turbulent eddies were found to be consistent with observations in the bottom boundary layer of the atmosphere and from laboratory experiments in three ways: 1) in statically unstable conditions, the eddy sizes scaled linearly with distance to the boundary; 2) in statically stable conditions, length scales decreased with increasing downward buoyancy flux; and 3) downwind length scales were larger than crosswind length scales.
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Published by American Meteorological Society
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  • 2
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    Observations of near-bottom flow in a wave-dominated nearshore environment (2006)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: To provide observational data for analysis of near-bottom, wave-induced flows, a downward-looking laser Doppler velocimeter (LDV) was deployed to profile the near-bed velocity structure of a six meter water column at a site just outside the surfzone off the coast of North Carolina. 90 second "snap-shots" of the velocity at six elevations below 20 cm above bottom were measured at 25 Hz, while pressure was concurrently measured at 126 cm above bottom. The near-bottom data were supplemented with a benthic acoustic stress sensor (BASS) at approximately 20 cm above bottom which concurrently measured velocity components at 10 Hz. The purposes of this report are to document the collection, processing and archival of these data and to present the profiles for evaluation.
    Description: Funding was provided by the Coastal Sciences Program of the Office of Naval Research under Grant N00014-92-J-12300.
    Keywords: Near-bed velocity ; Wave-induced flow ; Bass/LDV measurements ; Larc (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 5748092 bytes
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  • 3
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    Observations and a model of undertow over the inner continental shelf (2010)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 2341-2357, doi:10.1175/2008JPO3986.1.
    Description: Onshore volume transport (Stokes drift) due to surface gravity waves propagating toward the beach can result in a compensating Eulerian offshore flow in the surf zone referred to as undertow. Observed offshore flows indicate that wave-driven undertow extends well offshore of the surf zone, over the inner shelves of Martha’s Vineyard, Massachusetts, and North Carolina. Theoretical estimates of the wave-driven offshore transport from linear wave theory and observed wave characteristics account for 50% or more of the observed offshore transport variance in water depths between 5 and 12 m, and reproduce the observed dependence on wave height and water depth. During weak winds, wave-driven cross-shelf velocity profiles over the inner shelf have maximum offshore flow (1–6 cm s−1) and vertical shear near the surface and weak flow and shear in the lower half of the water column. The observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the surf zone. Instead, the vertical structure is similar to the Stokes drift velocity profile but with the opposite direction. This vertical structure is consistent with a dynamical balance between the Coriolis force associated with the offshore flow and an along-shelf “Hasselmann wave stress” due to the influence of the earth’s rotation on surface gravity waves. The close agreement between the observed and modeled profiles provides compelling evidence for the importance of the Hasselmann wave stress in forcing oceanic flows. Summer profiles are more vertically sheared than either winter profiles or model profiles, for reasons that remain unclear.
    Description: This research was funded by the Ocean Sciences Division of the National Science Foundation under Grants OCE-0241292 and OCE-0548961.
    Keywords: Continental shelf ; Transport ; Shear structure/flows ; Coastal flows ; Gravity waves
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Turbulence in the coastal environment during HYCODE (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: A tall tripod equipped with two acoustic Doppler velocimeters (ADVs) was deployed at a water depth of 15 m off the coast of New Jersey near the LEO-15 site. Sensors were co-located near the bottom to provide good estimates of Reynolds stress. Thermistors were located within several centimeters of the velocity sample volume to provide simultaneously sampled estimates of turbulent temperature variance and vertical temperature flux. One of the ADVs was equipped with a pressure and a temperature sensor. A wave/tide gauge was placed at 4 meters above bottom. The instruments were deployed late July through early December of 2000 and late June through early August of 2001. For the 2001 deployment, a single beam acoustic Doppler velocity sensor (DopBeam) was added to measure high frequency vertical velocity variance and echo intensity within the bottom boundary layer. A second tripod was deployed nearby and was equipped with an array of LISST sensors and an MSCAT. The purpose of this report is to document the instrumentation and deployment of the tripods and to document the tall tripod data by providing a description of the processing and data formats, time-series summaries of the burst averaged data along with preliminary analyses.
    Description: Funding was provided by the Office of Naval Research under Contract No. N00014-99-1-0213.
    Keywords: Turbulence ; Stress ; HYCODE ; Endeavor (Ship: 1976-) Cruise EN342 ; Endeavor (Ship: 1976-) Cruise EN344 ; Endeavor (Ship: 1976-) Cruise EN347 ; Endeavor (Ship: 1976-) Cruise EN356 ; Endeavor (Ship: 1976-) Cruise EN358
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 5
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    Stress, salt flux, and dynamics of a partially mixed estuary (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: A field study was performed in the lower Hudson River, a partially mixed estuary with a relatively simple geometry (Figure 1), between August and October of 1995. The objectives of the study were (1) to quantify and characterize the turbulent transport of momentum and salt, and (2) to relate the turbulent transport processes to the local and estuary-wide dynamics. The measurement program consisted of fixed and shipboard components. At a central site, a moored array of temperature-conductivity sensors and optical backscatter sensors (OBS), a bottom-mounted acoustic Doppler current profiler (ADCP), and a bottom-mounted array of acoustic travel-time current sensors (BASS), temperature-conductivity sensors, and OBS sensors resolved the vertical structure of velocity, salinity and turbidity and the near-bottom turbulence structure. Moored and bottom-mounted velocity, temperature, conductivity and pressure sensors at five secondary sites quantified the spatial and temporal variabilty of velocity, salinity and bottom pressure. Shipboard measurements with an ADCP and a conductivity-temperature-depth (CTD) profiler, accompanied by an OBS sensor, resolved the spatial structure and tidal variability of velocity, salinity and turbidity along several cross-channel and along-channel transects. This report describes the measurements in detail. Section II describes the instrumentation, Section III describes the deployment and sampling schemes, Section IV describes the data processing, and Section V is a summary of plots of selected data. Section VI documents the data files and Sections VII and VII give acknowledgments and references.
    Description: Funding was provided by the National Science Foundation under Grant OCE-94-15617 and The Hudson River Foundation.
    Keywords: Stress ; Salt flux ; Mixed estuary
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 6
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    Measurements of momentum and heat transfer across the air–sea interface (2010)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1054–1072, doi:10.1175/2007JPO3739.1.
    Description: This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict mean vertical gradients beneath the ocean’s wavy surface. Observations were made at 20 Hz at nominal depths of 2.2 and 1.7 m in 16 m of water. A new method is developed to estimate the fluxes and the length scales of dominant flux-carrying eddies from cospectra at frequencies below the wave band. The results are compared to independent estimates of those quantities, with good agreement between the two sets of estimates. The observed temperature gradients were smaller than predicted by standard rigid-boundary closure models, consistent with the suggestion that wave breaking and Langmuir circulation increase turbulent diffusivity in the upper ocean. Similarly, the Monin–Obukhov stability function ϕh was smaller in the authors’ measurements than the stability functions used in rigid-boundary applications of the Monin–Obukhov similarity theory. The dominant horizontal length scales of flux-carrying turbulent eddies were found to be consistent with observations in the bottom boundary layer of the atmosphere and from laboratory experiments in three ways: 1) in statically unstable conditions, the eddy sizes scaled linearly with distance to the boundary; 2) in statically stable conditions, length scales decreased with increasing downward buoyancy flux; and 3) downwind length scales were larger than crosswind length scales.
    Description: We are grateful to the Office of Naval Research for funding this work as a part of CBLAST-Low.
    Keywords: Momentum ; Heating ; Air–sea interaction
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Observations of cross-shelf flow driven by cross-shelf winds on the inner continental shelf (2010)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 2358-2378, doi:10.1175/2008JPO3990.1.
    Description: Six-yr-long time series of winds, waves, and water velocity from a cabled coastal observatory in 12 m of water reveal the separate dependence of the cross-shelf velocity profile on cross-shelf and along-shelf winds, waves, and tides. During small waves, cross-shelf wind is the dominant mechanism driving the cross-shelf circulation after tides and tidal residual motions are removed. The along-shelf wind does not drive a substantial cross-shelf circulation. During offshore winds, the cross-shelf circulation is offshore in the upper water column and onshore in the lower water column, with roughly equal and opposite volume transports in the surface and bottom layers. During onshore winds, the circulation is nearly the reverse. The observed profiles and cross-shelf transport in the surface layer during winter agree with a simple two-dimensional unstratified model of cross-shelf wind stress forcing. The cross-shelf velocity profile is more vertically sheared and the surface layer transport is stronger in summer than in winter for a given offshore wind stress. During large waves, the cross-shelf circulation is no longer roughly symmetric in the wind direction. For onshore winds, the cross-shelf velocity profile is nearly vertically uniform, because the wind- and wave-driven shears cancel; for offshore winds, the profile is strongly vertically sheared because the wind- and wave-driven shears have the same sign. The Lagrangian velocity profile in winter is similar to the part of the Eulerian velocity profile due to cross-shelf wind stress alone, because the contribution of Stokes drift to the Lagrangian velocity approximately cancels the contribution of waves to the Eulerian velocity.
    Description: This research was funded by the Ocean Sciences Division of the National Science Foundation under Grants OCE-0241292 and OCE-0548961 and by National Aeronautics and Space Administration Headquarters under Grant NNG04GL03G and the Earth System Science Fellowship Grant NNG04GQ14H. MVCO is partly funded by the Woods Hole Oceanographic Institution and the Jewett/EDUC/Harrison Foundation.
    Keywords: Continental shelf ; Wind
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Vorticity measurements within the bottom boundary layer in the Strait of Juan De Fuca (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: Electromagnetic fluctuations and turbulent vorticity fluctuations were measured over a nine month period in the strong tidal flows of the Strait of Juan De Fuca off the coast of the Olympic Peninsula of Washington. A collaborative experiment was designed to test the hypothesis that electromagnetic fluctuations at the sea floor are forced by turbulent vorticity fluctuations in the bottom boundary layer. This report describes the measurement of turbulent vorticity fluctuations and the associated analysis which focuses on testing existing theoretical predictions for the inertial subrange and on characterizing spectra at frequencies below the inertial subrange.
    Description: Funding was provided by the Office of Naval Research through Grant No. N00014-94-I-0436.
    Keywords: Vorticity ; Electromagnetic fluctuations ; Bottom boundary layer ; Turbulent fluctuation ; Thomas G. Thompson (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 2333148 bytes
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  • 9
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    Fluid mechanical measurements within the boundary layer over the northern California Continental Shelf during STRESS (2006)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: In studying the processes controlling particle distrbution of fine sediments over the continental shelf, the height, structure and dynamics of the bottom boundary layer must be better understood. The Sediment Transport Events on Shelves and Slopes (STRESS) program provides a comprehensive set of data over the bottom half of the water column at the 90m and the 130m isobaths along the northern California continental shelf during the winters of 1988-89 and 1990-91. This report presents the STRESS salinity, temperature, velocity, wave characteristics and attenuation data. The report describes the processing, provides plots and tables of the data and corresponding statistics for evaluation of the data, and documents the data fies. The combined set of moored and tripod mounted instrument measurements provides integrated, hourly-averaged profiles of the lower half of the water column at the four sites which can be used for analysis and modeling purposes.
    Description: Funding provided by the Office of Naval Research under contracts N00014-89-J-1067, N00014-89-J-1058 and N00014-89-J-1074.
    Keywords: Bottom boundary layer ; Sediment transport ; Continental shelf ; Integrated profies
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 3705240 bytes
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  • 10
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    Fluid mechanical measurements within the bottom boundary layer during coastal mixing and optics (2005)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: To quantify and understand the role of vertical mixing processes in determining mid-shelf vertical structure of hydrographic and optical properties and particulate matter, the Office of Naval Research (ONR) funded a program called Coastal Mixing and Optics (CMO), which was conducted at a mid-shelf location in the Mid-Atlantic Bight, south of Martha's Vineyard, Massachusetts. As part of the CMO program, a tall tripod, called 'SuperBASS,' was equipped to collect a year-long, near-bottom time-series of velocity, temperature, salinity and pressure. The BASS sensors were modified to measure absolute as well as differential acoustic travel time, to provide sound speed (a surrogate for temperature) and velocity in a single sample volume. Seven BASS velocity and time travel sensors were placed between 0.4 and 7 meters above bottom. Three acoustic Doppler velocity (ADV) meters were mounted near the bottom-most BASS sensors at 0.3 meters above bottom. The sensors were used to obtain high-quality time-series measurements of velocity and temperature throughout a large fraction of the bottom bondary layer on the New England shelf. The measurements provide vertical structure of the Reynolds-averaged velocity and temperature fields, direct covariance estimates of turbulent Reynolds stress and turbulent heat flux, and indirect inertial range estimates of dissipation rate for turbulent kinetic energy and temperature variance. The purpose of this report is to describe the SuperBASS instrumentation and deployments, to provide summaries of the data collected, and to document the processing, preliminary analysis and archival of data collected for this component of the program.
    Description: Funding was provided by the Office of Naval Research under contract number N00014-95-1-0373.
    Keywords: Bottom boundary layer ; Stress ; Dissipation ; Oceanus (Ship : 1975-) Cruise ; Endeavor (Ship: 1976-) Cruise ; Seward Johnson (Ship) Cruise ; Coastal Mixing and Optics (CMO) Experiment
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 5482992 bytes
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