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  • 1
    Publication Date: 2017-01-04
    Description: Data collected during multiple surveys of hydrography, velocity, and biological quantities are presented from a 9-day cruise aboard the R/V Oceanus near the island of St. Thomas, USVI and a subsequent transit to Bermuda during December, 2008. This cruise (OC449-09) was undertaken primarily to field test a newly acquired towed-undulating body, the Scanfish. The Scanfish and a second towed body, the Video Plankton Recorder (VPR), were used to survey hydrographic, optical, and biological properties north and south of St. Thomas. Conductivity-Temperature-Depth (CTD) casts and plankton net-tows were made at locations along the survey transects for inter-comparison. The VPR was also used to profile conditions between St. Thomas and Bermuda during transit. An overview of the cruise is given along with descriptions of the data collection methods, processing steps taken, and data products available for distribution.
    Description: Funding for this research was provided by the King Abdullah University of Science and Technology (KAUST) under a cooperative research agreement with Woods Hole Oceanographic Institution.
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: application/pdf
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  • 2
    Publication Date: 2017-01-05
    Description: Author Posting. © American Meteorological Society, 2011. 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 Atmospheric and Oceanic Technology 28 (2011): 1539–1553, doi:10.1175/JTECH-D-11-00001.1.
    Description: Turbulent Reynolds stresses are now routinely estimated from acoustic Doppler current profiler (ADCP) measurements in estuaries and tidal channels using the variance method, yet biases due to surface gravity waves limit its use in the coastal ocean. Recent modifications to this method, including spatially filtering velocities to isolate the turbulence from wave velocities and fitting a cospectral model to the below-wave band cospectra, have been used to remove this bias. Individually, each modification performed well for the published test datasets, but a comparative analysis over the range of conditions in the coastal ocean has not yet been performed. This work uses ADCP velocity measurements from five previously published coastal ocean and estuarine datasets, which span a range of wave and current conditions as well as instrument configurations, to directly compare methods for estimating stresses in the presence of waves. The computed stresses from each were compared to bottom stress estimates from a quadratic drag law and, where available, estimates of wind stress. These comparisons, along with an analysis of the cospectra, indicated that spectral fitting performs well when the wave climate is wide-banded and/or multidirectional as well as when instrument noise is high. In contrast, spatial filtering performs better when waves are narrow-banded, low frequency, and when wave orbital velocities are strong relative to currents. However, as spatial filtering uses vertically separated velocity bins to remove the wave bias, spectral fitting is able to resolve stresses over a larger fraction of the water column.
    Description: J. Rosman acknowledges funding from the National Science Foundation (OCE-1061108).
    Keywords: Coastal flows ; Momentum ; Ocean circulation ; Waves, oceanic ; In situ observations ; Instrumentation/sensors
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2017-02-19
    Description: Author Posting. © American Meteorological Society, 2016. 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 46 (2016): 2645-2662, doi:10.1175/JPO-D-15-0191.1.
    Description: The occurrence, drivers, and implications of small-scale O(2–5) km diameter coherent vortices, referred to as submesoscale eddies, over the inner shelf south of Martha’s Vineyard, Massachusetts, are examined using high-frequency (HF), radar-based, high-resolution (400 m) observations of surface currents. Within the 300 km2 study area, eddies occurred at rates of 1 and 4 day−1 in winter and summer, respectively. Most were less than 5 h in duration, smaller than 4 km in diameter, and rotated less than once over their lifespan; 60% of the eddies formed along the eastern edge of study area, adjacent to Wasque Shoal, and moved westward into the interior, often with relative vorticity greater than f. Eddy generation was linked to vortex stretching on the ebb and flood tide as well as the interaction of the spatially variable tide and the wind-driven currents; however, these features had complex patterns of surface divergence and stretching. Eddies located away from Wasque Shoal were related to the movement of wind-driven surface currents, as wind direction controlled where eddies formed as well as density effects. Using an analysis of particles advected within the radar-based surface currents, the observed eddies were found to be generally leaky, losing 60%–80% of particles over their lifespan, but still more retentive than the background flow. As a result, the combined translation and rotational effects of the observed eddies were an important source of lateral exchange for surface waters over the inner shelf.
    Description: The HF radar data utilized here were obtained using internal funding from the Woods Hole Oceanographic Institution. The analysis was supported by NSF OCE Grant 1332646.
    Description: 2017-02-19
    Keywords: Geographic location/entity ; Continental shelf/slope ; Circulation/ Dynamics ; Currents ; Eddies ; Observational techniques and algorithms ; Radars/Radar observations
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Woods Hole Oceanographic Institution, Department of Physical Oceanography
    Publication Date: 2018-01-25
    Description: This data was collected by Kirincich and Lentz as part of the Inner Shelf Lateral Exchange Study focused on examining the spatial variability of the mechanisms and process that lead to the exchange of water masses across the inner part of the continental shelf. The ISLE study area spanned a 15 km by 25 km domain south of the Island of Martha’s Vineyard Massachusetts. See published works by Kirincich (2016, JOAT) or Kirincich and Lentz (2017, JGR) for details on the study area. The two zip files contain three types of files: HF radar surface currents, station/mooring velocity data, and station/mooring hydrography data. See the text files for additional information. Converted to netCDF via MATLAB by A. Kirincich.
    Description: HF radar surface currents data was collected by Kirincich as part of ongoing studies examining the spatial variability of the mechanisms and process that lead to the exchange of water masses across the inner part of the continental shelf. The data consists of estimates of the near-surface horizontal (East and North) ocean currents made via High Frequency (HF) radar-based remote sensing of the ocean backscatter spectrum. The dataset spans an 18-month period from February 2011 to August 2012. The effective measurement depth of the WHOI HF radars is 0.5 m below the ocean surface.
    Description: Station/mooring velocity and hydrography data was collected by Kirincich and Lentz as part of the Inner Shelf Lateral Exchange Study focused on examining the spatial variability of the mechanisms and process that lead to the exchange of water masses across the inner part of the continental shelf. The data consists of estimates of Water Temperature and Salinity using SBE 37 Microcats, and horizontal (East and North) ocean currents made via ADCPs with transmit frequencies of 600 or 120 kHz. The dataset spans the 6—8 month period of June 9th 2014 to January 15, 2017.
    Description: The observations used in this study were supported by NSF OCE Grant #1332626 and internal funding from the Woods Hole Oceanographic Institution.
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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  • 5
    Publication Date: 2018-02-11
    Description: Author Posting. © American Meteorological Society, 2017. 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 Atmospheric and Oceanic Technology 34 (2017): 1679-1691, doi:10.1175/JTECH-D-16-0162.1.
    Description: For direction-finding high-frequency (HF) radar systems, the correct separation of backscattered spectral energy due to Bragg resonant waves from that due to more complex double-scattering represents a critical first step toward attaining accurate estimates of surface currents from the range-dependent radar backscatter. Existing methods to identify this “first order” region of the spectra, generally sufficient for lower-frequency radars and low-velocity or low-surface gravity wave conditions, are more likely to fail in higher-frequency systems or locations with more variable current, wave, or noise regimes, leading to elevated velocity errors. An alternative methodology is presented that uses a single and globally relevant smoothing length scale, careful pretreatment of the spectra, and marker-controlled watershed segmentation, an image processing technique, to separate areas of spectral energy due to surface currents from areas of spectral energy due to more complex scattering by the wave field or background noise present. Applied to a number of HF radar datasets with a range of operating frequencies and characteristic issues, the new methodology attains a higher percentage of successful first-order identification, particularly during complex current and wave conditions. As operational radar systems continue to expand to more systematically cover areas of high marine traffic, close approaches to ports and harbors, or offshore energy installations, use of this type of updated methodology will become increasingly important to attain accurate current estimates that serve both research and operational interests.
    Description: This analysis was supported by internal funds from the Woods Hole Oceanographic Institution.
    Description: 2018-02-11
    Keywords: Ocean circulation ; Waves, oceanic ; Data processing ; Radars/Radar observations ; Remote sensing ; Pattern detection
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2016-11-01
    Description: The WHOI HF radar system, as operated during the 2011-2012 time period, consisted of 3 individual HF radars located along the south coast of the island of Martha's Vineyard, MA at infrastructure of the Martha's Vineyard Coastal Observatory (MVCO). The system had the technical goal of measuring currents at scales approaching 400 m within a 20 km by 20 km domain south of Martha's Vineyard. The system is composed of three closely spaced sites with SeaSonde-type DF instruments running at operating frequencies near 25 MHz. Two of the three sites are located on land, with one placed at the MVCO Shore Meteorological Station (METS) and the second approximately 10 km to the west at the Long Point Wildlife Refuge (LPWR). The third site is located on the MVCO Air-Sea Interaction Tower (ASIT), approximately 4 km offshore and south of the island. To achieve the highest possible radial resolution (420 m) given the 350 kHz of bandwidth available at 25 MHz, all sites run at common frequencies using GPS- based timing to separate the transmissions from each site. Given the small spatial domain that can be adequately sampled at low geometric error with this configuration, as well as potential for interactions between the instruments at the land and tower sites, all sites transmit at low power (1-2 W, less than 3% of typical systems). The MVCO HFRs were configured to maximize the spatial and temporal independence of the observations. Spectral estimates of the observed Doppler-shifted velocities are collected in bursts of 1028 non-overlapping frequency sweeps with a sweep rate of 2 Hz for finer-resolution Doppler velocities than is typical for 25-MHz systems without interpolation. A maximum of three, but normally two, successive spectral estimates are averaged to create the necessary ensemble estimate every 15 min. Direction finding and azimuthal averaging into 5deg bands is performed on each ensemble and, for data processed using the standard software suite, successive radial velocity estimates are time averaged into 60-min averages every 30 min. No interpolation is used to smooth the fields or fill in radial gaps, but, as in previous works, outliers are removed before computing vector velocities. Given the dense spacing of the radial grid points, the vector averaging is performed using a 400-m grid with grid points starting approximately 600 m offshore and an averaging radius equal to the grid width. These alternative methods were used to achieve finer-resolution velocity estimates having greater spatial independence at the potential expense of increased noise. For the datasets used here, a number of steps were taken to ensure that the radial velocity estimates were of the highest quality possible. The first-order region limits utilized for the analysis were optimized for the conditions present south of Martha's Vineyard. Measured antenna patterns were obtained for each site and utilized in the DF algorithm to estimate radial currents over water. Finally, the spatial structure of the M2 tidal ellipses for the entire domain, estimated from the vector velocity time series at each grid point using T_Tide (Pawlowicz et al. 2002), were analyzed for patterns of unrealistic ellipse inclination (orientation) emanating from a particular site, which serve as an indication of potential bearing-related errors. The measured beam patterns were adjusted by smoothing and/or interpolation, similar to that described by Cosoli et al. (2010) and de Paolo and Terrill (2007), to minimize errors identified. The spatial extent of the vector velocities was limited by theoretical Geometrical Dilution of Precision (GDOP) values less than 1.75. An error estimate for the East, North, and total (norm) of the vector velocity components is given. Converted to netCDF via MATLAB by A. Kirincich
    Description: This data was collected by Kirincich as part of ongoing studies examining the spatial variability of the mechanisms and process that lead to the exchange of water masses across the inner part of the continental shelf. The data consists of estimates of the near-surface horizontal (East and North) ocean currents made via High Frequency (HF) radar-based remote sensing of the ocean backscatter spectrum. The dataset spans an 18-month period from February 2011 to August 2012. The effective measurement depth of the WHOI HF radars is 0.5 m below the ocean surface.
    Description: The observations used in this study were supported by NSF OCE Grant #1332626 and internal funding from the Woods Hole Oceanographic Institution.
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
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  • 7
    Publication Date: 2017-01-04
    Description: Author Posting. © American Meteorological Society, 2009. 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 39 (2009): 2942-2956, doi:10.1175/2009JPO4041.1.
    Description: Recent work by S. Lentz et al. documents offshore transport in the inner shelf due to a wave-driven return flow associated with the Hasselmann wave stress (the Stokes–Coriolis force). This analysis is extended using observations from the central Oregon coast to identify the wave-driven return flow present and quantify the potential bias of wind-driven across-shelf exchange by unresolved wave-driven circulation. Using acoustic Doppler current profiler (ADCP) measurements at six stations, each in water depths of 13–15 m, observed depth-averaged, across-shelf velocities were generally correlated with theoretical estimates of the proposed return flow. During times of minimal wind forcing, across-shelf velocity profiles were vertically sheared, with stronger velocities near the top of the measured portion of the water column, and increased in magnitude with increasing significant wave height, consistent with circulation due to the Hasselmann wave stress. Yet velocity magnitudes and vertical shears were stronger than that predicted by linear wave theory, and more similar to the stratified “summer” velocity profiles described by S. Lentz et al. Additionally, substantial temporal and spatial variability of the wave-driven return flow was found, potentially due to changing wind and wave conditions as well as local bathymetric variability. Despite the wave-driven circulation found, subtracting estimates of the return flow from the observed across-shelf velocity had no significant effect on estimates of the across-shelf exchange due to along-shelf wind forcing at these water depths along the Oregon coast during summer.
    Description: This work was performed with the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO), funded primarily by the Gordon and Betty Moore Foundation and David and Lucile Packard Foundation. SL acknowledges support from NSF Ocean Science Grant #OCE-0548961. AK acknowledges support from the WHOI Coastal Ocean Institute Fellowship.
    Keywords: Waves, oceanic ; Ekman pumping/transport ; Coastlines ; Ocean circulation ; Gravity waves
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    Publication Date: 2017-01-04
    Description: Author Posting. © American Meteorological Society, 2013. 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 43 (2013): 2752–2771, doi:10.1175/JPO-D-12-0153.1.
    Description: In situ observations of turbulent momentum flux, or Reynolds stresses, were estimated from a 10-yr acoustic Doppler current profiler (ADCP) record of inner-shelf velocities at the Martha’s Vineyard Coastal Observatory (MVCO) using recently developed analysis techniques that account for wave-induced biases. These observations were used to examine the vertical structure of stress and turbulent mixing in the coastal ocean during tidal-, wave-, and wind-driven circulation by conditionally averaging the dataset by the level of forcing or stratification present. Bottom-intensified stresses were found during tidally driven flow, having estimated eddy viscosities as high as 1 × 10−2 m−2 s−1 during slack water. An assessment of the mean, low-wave, low-wind stress results quantified the magnitude of an unmeasured body force responsible for the mean circulation present in the absence of wind and wave forcing. During weak stratification and isolated wind forcing, downwind stresses matched the observed wind stress near the surface and generally decreased with depth linearly for both along- and across-shelf wind forcing. While consistent with simple models of circulation during across-shelf wind forcing, the linear slope of the stress profile present during along-shelf wind forcing requires the existence of an along-shelf pressure gradient that scales with the wind forcing. At increased levels of stratification, the observed downwind stresses generally weakened and shifted to the across-wind direction during across-shelf and mixed-direction (i.e., onshore and along shelf) wind forcing consistent with Ekman spiral modification, but were more variable during along-shelf wind forcing. No measurable stresses were found due to wave-forced conditions, confirming previous theoretical results.
    Description: The analysis was funded by the National Science Foundation under Grant OCE#1129348.
    Description: 2014-06-01
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
    Publication Date: 2016-05-26
    Description: Moored hydrographic and velocity observations along with vessel surveys of the Outer Cape Coastal Current off Nauset, MA.
    Description: This data was used in the preparation of a manuscript "Drivers of Spring and Summer Variability in the Coastal Ocean Offshore of Cape Cod, MA." submitted for publication to the Journal of Geophysical Research. The work describes the drivers of spring and summer variability within the coastal ocean east of Cape Cod, Massachusetts, a critical link between the Gulf of Maine and Mid-Atlantic Bight, are investigated using two years of shipboard and moored hydrographic and velocity observations from 2010 and 2011. Converted to netCDF via MATLAB by A. Kirincich
    Description: The observations used in this study were supported by NOAA SeaGrant #NA10OAR4170083 and internal funding from the Woods Hole Oceanographic Institution. Analysis was supported via internal funding from the Woods Hole Oceanographic Institution
    Keywords: Tioga (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Dataset
    Format: application/nc
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  • 10
    Publication Date: 2017-11-27
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 1789–1805, doi:10.1002/2015JC011252.
    Description: The drivers of spring and summer variability within the coastal ocean east of Cape Cod, Massachusetts, a critical link between the Gulf of Maine and Mid-Atlantic Bight, are investigated using 2 years of shipboard and moored hydrographic and velocity observations from 2010 and 2011. The observations reveal sharp differences in the spring transition and along-shelf circulation due to variable freshwater and meteorological forcing, along with along-shelf pressure gradients. The role of the along-shelf pressure gradient is inferred using in situ observations of turbulent momentum flux, or Reynolds stresses, estimated from the ADCP-based velocities using recently developed methods and an inversion of the along-shelf momentum balance. During spring, the locally relevant along-shelf pressure gradient contains a sizable component that is not coupled to the along-shelf winds and often opposes the regional sea level gradient. Together with the winds, local pressure gradients dominate along-shelf transport variability during spring, while density-driven geostrophic flows appear to match the contribution of the local winds during summer. These results suggest that local effects along the Outer Cape have the potential to cause significant changes in exchange between the basins.
    Description: NOAA. Grant Number: NA10OAR4170083; Woods Hole Oceanographic Institution
    Description: 2016-09-19
    Keywords: Coastal circulation ; Reynolds stresses ; Pressure gradients ; Along shelf transport ; Inter-annual variability
    Repository Name: Woods Hole Open Access Server
    Type: Article
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