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  • Articles  (6)
  • Estuary  (5)
  • Hudson River Estuary
  • Salt marsh
  • 2020-2023  (3)
  • 2010-2014  (3)
  • 1
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    Turbulent energy production and entrainment at a highly stratified estuarine front (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. 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 109 (2004): C05004, doi:10.1029/2003JC002094.
    Description: Rates of turbulent kinetic energy (TKE) production and buoyancy flux in the region immediately seaward (~1 km) of a highly stratified estuarine front at the mouth of the Fraser River (British Columbia, Canada) are calculated using a control volume approach. The calculations are based on field data obtained from shipboard instrumentation, specifically velocity data from a ship mounted acoustic Doppler current profiler (ADCP), and salinity data from a towed conductivity-temperature-depth (CTD) unit. The results allow for the calculation of vertical velocities in the water column, and the total vertical transport of salt and momentum. The vertical turbulent transport quantities (inline equation, inline equation) can then be estimated as the difference between the total transport and the advective transport. Estimated production is on the order of 10−3 m2 s−3, yielding a value of ɛ(νN2)−1 on the order of 104. This rate of TKE production is at the upper limit of reported values for ocean and coastal environments. Flux Richardson numbers in this highly energetic system generally range from 0.15 to 0.2, with most mixing occurring at gradient Richardson numbers slightly less than inline equation. These values compare favorably with other values in the literature that are associated with turbulence observations from regimes characterized by scales several orders of magnitude smaller than are present in the Fraser River.
    Description: This work was performed as a part of D. MacDonald’s Ph.D. thesis, and was funded by Office of Naval Research grants N000-14-97-10134 and N000-14-97- 10566, National Science Foundation grant OCE-9906787, a National Science Foundation graduate fellowship, and support from the WHOI Academic Programs Office.
    Keywords: Turbulence ; Entrainment ; Estuary
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Using a composite grid approach in a complex coastal domain to estimate estuarine residence time (2010)
    Elsevier B.V.
    Details
    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Computers & Geosciences 36 (2010): 921-935, doi:10.1016/j.cageo.2009.11.008.
    Description: We investigate the processes that influence residence time in a partially mixed estuary using a three-dimensional circulation model. The complex geometry of the study region is not optimal for a structured grid model and so we developed a new method of grid connectivity. This involves a novel approach that allows an unlimited number of individual grids to be combined in an efficient manner to produce a composite grid. We then implemented this new method into the numerical Regional Ocean Modeling System (ROMS) and developed a composite grid of the Hudson River estuary region to investigate the residence time of a passive tracer. Results show that the residence time is a strong function of the time of release (spring vs. neap tide), the along-channel location, and the initial vertical placement. During neap tides there is a maximum in residence time near the bottom of the estuary at the mid-salt intrusion length. During spring tides the residence time is primarily a function of along-channel location and does not exhibit a strong vertical variability. This model study of residence time illustrates the utility of the grid connectivity method for circulation and dispersion studies in regions of complex geometry.
    Description: W.R. Geyer was supported by the Hudson River Foundation Grant 002/07A,H.G.Arango by the Office of Naval Research,and John Warner was supported by the USGS Community Sediment Modeling Project.
    Keywords: Residence time ; Estuary ; Three-dimensional model ; Hudson river estuary ; ROMS ; Composite grid
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  • 3
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    Tidal dispersion in short estuaries (2022)
    Woods Hole Oceanographic Institution
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    Publication Date: 2022-10-21
    Description: The salinity distribution of an estuary depends on the balance between the river outflow, which is seaward, and a dispersive salt flux, which is landward. The dispersive salt flux at a fixed cross-section can be divided into shear dispersion, which is caused by spatial correlations of the cross-sectionally varying velocity and salinity, and the tidal oscillatory salt flux, which results from the tidal correlation between the cross-section averaged, tidally varying components of velocity and salinity. The theoretical moving plane analysis of Dronkers and van de Kreeke (1986) indicates that the oscillatory salt flux is exactly equal to the difference between the “local” shear dispersion at a fixed location and the shear dispersion which occurred elsewhere within a tidal excursion – therefore, they refer to the oscillatory salt flux as “nonlocal” dispersion. We apply their moving plane analysis to a numerical model of a short, tidally dominated estuary and provide the first quantitative confirmation of the theoretical result that the spatiotemporal variability of shear dispersion accounts for the oscillatory salt flux. Shear dispersion is localized in space and time and is most pronounced near regions of flow separation. Notably, we find that dispersive processes near the mouth contribute significantly to the overall salt balance, especially under strong river and tidal forcing. Furthermore, while mechanisms of vertical shear dispersion produce the majority of the dispersive salt flux during neap tide and high river flow, lateral mechanisms associated with flow separation provide the dominant mode of dispersion during spring tide and low flow. Dataset used in support of manuscript "Tidal dispersion in short estuaries". The dataset includes the model output from the idealized estuary for 16 different forcing conditions, corresponding to 4 tidal conditions (weak〈neap〈intm〈spring) and 4 river flow conditions (q01〈q03〈q10〈q30), as well as along-channel salinity measurements in the North River (Marshfield, MA, USA) during a 2017 field campaign.
    Description: This work was funded under NSF Grant OCE-1634490 and NSF Graduate Research Fellowship, Grant No. #1122374
    Keywords: Shear dispersion ; Estuary
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  • 4
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    Using tracer variance decay to quantify variability of salinity mixing in the Hudson River Estuary (2021)
    American Geophysical Union
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    Publication Date: 2022-10-21
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Warner, J. C., Geyer, W. R., Ralston, D. K., & Kalra, T. Using tracer variance decay to quantify variability of salinity mixing in the Hudson River Estuary. Journal of Geophysical Research: Oceans, 125(12), (2020): e2020JC016096, https://doi.org/10.1029/2020JC016096.
    Description: The salinity structure in an estuary is controlled by time‐dependent mixing processes. However, the locations and temporal variability of where significant mixing occurs is not well‐understood. Here we utilize a tracer variance approach to demonstrate the spatial and temporal structure of salinity mixing in the Hudson River Estuary. We run a 4‐month hydrodynamic simulation of the tides, currents, and salinity that captures the spring‐neap tidal variability as well as wind‐driven and freshwater flow events. On a spring‐neap time scale, salinity variance dissipation (mixing) occurs predominantly during the transition from neap to spring tides. On a tidal time scale, 60% of the salinity variance dissipation occurs during ebb tides and 40% during flood tides. Spatially, mixing during ebbs occurs primarily where lateral bottom salinity fronts intersect the bed at the transition from the main channel to adjacent shoals. During ebbs, these lateral fronts form seaward of constrictions located at multiple locations along the estuary. During floods, mixing is generated by a shear layer elevated in the water column at the top of the mixed bottom boundary layer, where variations in the along channel density gradients locally enhance the baroclinic pressure gradient leading to stronger vertical shear and more mixing. For both ebb and flood, the mixing occurs at the location of overlap of strong vertical stratification and eddy diffusivity, not at the maximum of either of those quantities. This understanding lends a new insight to the spatial and time dependence of the estuarine salinity structure.
    Description: This study was funded through the Coastal Model Applications and Field Measurements Project and the Cross‐shore and Inlets Project, US Geological Survey Coastal Marine Hazards and Resources Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.
    Keywords: Hudson River Estuary ; Mixing ; Numerical modeling ; Tracer variance
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  • 5
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    Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baranes, H., Woodruff, J., Geyer, W., Yellen, B., Richardson, J. & Griswold, F. Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh. Journal of Geophysical Research: Earth Surface, 127, (2022): e2021JF006478, https://doi.org/10.1029/2021jf006478.
    Description: he availability and delivery of an external clastic sediment source is a key factor in determining salt marsh resilience to future sea level rise. However, information on sources, mechanisms, and timescales of sediment delivery are lacking, particularly for wave-protected mesotidal estuaries. Here we show that marine sediment mobilized and delivered during coastal storms is a primary source to the North and South Rivers, a mesotidal bar-built estuary in a small river system impacted by frequent, moderate-intensity storms that is typical to New England (United States). On the marsh platform, deposition rates, clastic content, and dilution of fluvially-sourced contaminated sediment by marine material all increase down-estuary toward the inlet, consistent with a predominantly marine-derived sediment source. Marsh clastic deposition rates are also highest in the storm season. We observe that periods of elevated turbidity in channels and over the marsh are concurrent with storm surge and high wave activity offshore, rather than with high river discharge. Flood tide turbidity also exceeds ebb tide turbidity during storm events. Timescales of storm-driven marine sediment delivery range from 2.5 days to 2 weeks, depending on location within the estuary; therefore the phasing of storm surge and waves with the spring-neap cycle determines how effectively post-event suspended sediment is delivered to the marsh platform. This study reveals that sediment supply and the associated resilience of New England mesotidal salt marshes involves the interplay of coastal and estuarine processes, underscoring the importance of looking both up- and downstream to identify key drivers of environmental change.
    Description: The project described in this publication was in part supported by Grant or Cooperative Agreement No. G20AC00071 from the U.S. Geological Survey and a Department of Interior Northeast Climate Adaptation Science Center graduate fellowship awarded to H.E.B (G12AC00001).
    Keywords: Salt marsh ; Sediment ; Estuary ; Tides ; Massachusetts
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  • 6
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    Sediment transport due to extreme events : the Hudson River estuary after tropical storms Irene and Lee (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 5451–5455, doi:10.1002/2013GL057906.
    Description: Tropical Storms Irene and Lee in 2011 produced intense precipitation and flooding in the U.S. Northeast, including the Hudson River watershed. Sediment input to the Hudson River was approximately 2.7 megaton, about 5 times the long-term annual average. Rather than the common assumption that sediment is predominantly trapped in the estuary, observations and model results indicate that approximately two thirds of the new sediment remained trapped in the tidal freshwater river more than 1 month after the storms and only about one fifth of the new sediment reached the saline estuary. High sediment concentrations were observed in the estuary, but the model results suggest that this was predominantly due to remobilization of bed sediment. Spatially localized deposits of new and remobilized sediment were consistent with longer term depositional records. The results indicate that tidal rivers can intercept (at least temporarily) delivery of terrigenous sediment to the marine environment during major flow events.
    Description: This research was supported by grants from the Hudson Research Foundation (002/07A) and the National Science Foundation (1232928).
    Description: 2014-04-18
    Keywords: Sediment transport ; Tidal river ; Estuary ; Sediment trapping
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