Sellers Cynthia J.

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Cynthia J.

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  • Other
    Brazil Basin Tracer Release Experiment
    (Woods Hole Oceanographic Institution, 2021-04) Ledwell, James R. ; Donoghue, Terence ; Guest, Brian J. ; Lemmond, Peter ; Sellers, Cynthia J. ; Cortes, Norbert
    The purpose of the Brazil Basin Tracer Release Experiment is to measure diapycnal (across isopycnal) mixing and epipycnal (along-isopycnal) mixing and stirring in the deep ocean. This cruise is the fourth in the overall experiment. In the first cruise in early 1996, 110 kg of sulfur hexafluoride (SF6) were released on an isopycnal surface near 4000 meters depth in the eastern part of the basin on the flanks of the Mid-Atlantic Ridge (MAR). The location of the release was near 21.7 S, 18.4 W. The release site was over a zonal valley that leads to the MAR and is about 5000 m deep. The isopycnal surface of the release was defined as the surface on which the potential density anomaly, referenced to 4000 dbar pressure, was 45.9408 kg/m3. The release streaks and results of initial sampling in 1996 are described in Polzin et al. [1997].
  • Technical Report
    Microscale, finescale, and mesoscale measurements made during the 2004 Structured Mixing Project (Micro-Tow 04) Cruise
    (Woods Hole Oceanographic Institution, 2016-04) Duda, Timothy F. ; Sellers, Cynthia J.
    A physical oceanographic sampling voyage was made with RV Endeavor during August 2004 to evaluate diapycnal mixing processes on the continental shelf south of Massachusetts and Rhode Island, USA. The goal of the project was to look for a relationship between intensity of microstructure (thermal variance dissipation rate) and finestructure (background temperature gradient), in so-called doubly-stable water, which would be indicative of a density gradientdependent diapycnal heat flux. To satisfy the requirement that a large amount of data be collected to constrain the statistically estimated result, a microstructure sensor was towed on a platform behind the ship, providing continuous sampling at the depths of interest. To obtain the necessary finestructure quantities the platform measured temperature, conductivity and depth with a standard pumped Seabird 9plus CTD. Attitude and speed of the platform were recorded to assure proper data quality. This report shows temperature, salinity, density, and sound speed in twenty-five tow-yo transects obtained using the towed unit. Only statistics and results from microscale data are shown. In waters with stable salt stratification and stable temperature stratification, a previously obtained empirical result of reduced flux at increased density gradient is supported by the data. The 2004 Cruise Report is included (Appendix).
  • Article
    Resonance classification of mixed assemblages of fish with swimbladders using a modified commercial broadband acoustic echosounder at 1–6 kHz
    (NRC Research Press, 2012-04-19) Stanton, Timothy K. ; Sellers, Cynthia J. ; Jech, J. Michael
    Recently developed broadband acoustic methods were used to study mixed assemblages of fish spanning a wide range of lengths and species. Through a combination of resonance classification and pulse-compression signal processing, which provides for high-range resolution, a modified commercial broadband echosounder was demonstrated to provide quantitative information on the spatial distribution of the individual size classes within an assemblage. In essence, this system spectrally resolves the different size classes of fish that are otherwise not resolved spatially. This method reveals new insights into biological processes, such as predator–prey interactions, that are not obtainable through the use of a conventional narrowband high-frequency echosounder or previous broadband systems. A recent study at sea with this system revealed aggregations containing bladdered fish 15–30 cm in length (Atlantic herring (Clupea harengus) and silver hake (Merluccius bilinearis)) and a variety of species of smaller fish 2–5 cm in length. These observations infer that the smaller 2–5 cm fish can be colocated in the same aggregations as their predator, the larger silver hake, as well as pre-spawning herring. While this technological advancement provides more information, there remain challenges in interpreting the echo spectra in terms of meaningful biological quantities such as size distribution and species composition.
  • Technical Report
    Acoustic and oceanographic observations and configuration information for the WHOI moorings from the SW06 experiment
    (Woods Hole Oceanographic Institution, 2007-05) Newhall, Arthur E. ; Duda, Timothy F. ; von der Heydt, Keith ; Irish, James D. ; Kemp, John N. ; Lerner, Steven A. ; Liberatore, Stephen P. ; Lin, Ying-Tsong ; Lynch, James F. ; Maffei, Andrew R. ; Morozov, Andrey K. ; Shmelev, Alexey A. ; Sellers, Cynthia J. ; Witzell, Warren E.
    This document describes data, sensors, and other useful information pertaining to the moorings that were deployed from the R/V Knorr from July 24th to August 4th, 2006 in support of the SW06 experiment. The SW06 experiment was a large, multi-disciplinary effort performed 100 miles east of the New Jersey coast. A total of 62 acoustic and oceanographic moorings were deployed and recovered. The moorings were deployed in a “T” geometry to create an along-shelf path along the 80 meter isobath and an across-shelf path starting at 600 meters depth and going shoreward to a depth of 60 meters. A cluster of moorings was placed at the intersection of the two paths to create a dense sensor-populated area to measure a 3-dimensional physical oceanography. Environmental moorings were deployed along both along-shelf and across-shelf paths to measure the physical oceanography along those paths. Moorings with acoustic sources were placed at the outer ends of the “T” to propagate various signals along these paths. Five single hydrophone receivers were positioned on the across shelf path and a vertical and horizontal hydrophone array was positioned at the intersection of the “T” to get receptions from all the acoustics assets that were used during SW06.
  • Article
    Navigational infrastructure at the East Pacific Rise 9°50′N area following the 2005–2006 eruption : seafloor benchmarks and near-bottom multibeam surveys
    (American Geophysical Union, 2008-11-06) Soule, Samuel A. ; Ferrini, Vicki L. ; Kinsey, James C. ; Fornari, Daniel J. ; Sellers, Cynthia J. ; White, Scott M. ; Von Damm, Karen L. ; Carbotte, Suzanne M.
    Four seafloor benchmarks were deployed with ROV Jason2 at frequently visited areas along the northern East Pacific Rise (NEPR) ridge crest near 9°50′N, within the Ridge2000 EPR integrated study site (ISS) bull's eye. When used in concert with established deep-ocean acoustic positioning techniques, these benchmarks provide navigational infrastructure to facilitate the integration of near-bottom data at this site by allowing efficient and quantitative coregistration of data and observations collected on multiple dives and over multiple cruises. High-resolution, near-bottom multibeam bathymetric surveys also were conducted along and across the ridge crest to provide a morphological and geological context for the benchmark areas. We describe the navigation and data processing techniques used to constrain the benchmark positions and outline operational details to effectively use benchmarks at this and other deep-ocean sites where multidisciplinary time series studies are conducted. The well-constrained positions of the benchmarks provide a consistent geospatial framework that can be used to limit navigational uncertainties during seafloor sampling and mapping programs and enable accurate spatial coregistration and integration of observations. These data are important to test a range of multidisciplinary hypotheses that seek to link geological, chemical, and biological processes associated with crustal accretion and energy transfer from the mantle to the hydrosphere at mid-ocean ridges.
  • Article
    Evaluation of an acoustic remote sensing method for frontal-zone studies using double-diffusive instability microstructure data and density interface data from intrusions
    (Elsevier, 2016-10-19) Duda, Timothy F. ; Lavery, Andone C. ; Sellers, Cynthia J.
    Understanding intrusive exchange at oceanic water mass fronts may depend on building data-constrained models of the processes, but obtaining the needed representative and comprehensive data is challenging. Acoustic imaging (remote sensing) is an attractive method for mapping the three-dimensional intrusion geometry to enable the required focused in situ sampling of the mixing processes in intrusions. The method depends on backscatter of sound from sharp interfaces and from microstructure resulting from double-diffusive instability (DDI), a probable occurrence at intrusions. The potential of the method is evaluated using data collected using established methods in a field of intrusions south of New England. Above and beneath warm and salty intrusions may lie diffusive–convective DDI microstructure and salt-fingering microstructure, respectively, marking the intrusion boundaries, providing the backscattering features. The data show that both types of microstructure can occur in close proximity within intrusions, but the question of whether this is common or not is unanswered by the modest amount of data, as are questions about continuity of DDI-microstructure in intrusions (to facilitate intrusion acoustic imaging) and variability of DDI-driven heat, salt and buoyancy fluxes. Analysis here shows that detectable backscatter from DDI-microstructure will occur, and can be easily measured when plankton scattering is low enough. Interface scattering is also likely to be detectable. The DDI-linked microstructure data used here are inherently interesting in their own right and are presented in some detail.