ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Estuary  (8)
  • Baroclinic flows  (3)
  • Coastal flows  (2)
  • 1
    facet.materialart.
    Unbekannt
    Estuarine frontogenesis (2015)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2015. 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 45 (2015): 546–561, doi:10.1175/JPO-D-14-0082.1.
    Beschreibung: Model studies and observations in the Hudson River estuary indicate that frontogenesis occurs as a result of topographic forcing. Bottom fronts form just downstream of lateral constrictions, where the width of the estuary increases in the down-estuary (i.e., seaward) direction. The front forms during the last several hours of the ebb, when the combination of adverse pressure gradient in the expansion and baroclinicity cause a stagnation of near-bottom velocity. Frontogenesis is observed in two dynamical regimes: one in which the front develops at a transition from subcritical to supercritical flow and the other in which the flow is everywhere supercritical. The supercritical front formation appears to be associated with lateral flow separation. Both types of fronts are three-dimensional, with strong lateral gradients along the flanks of the channel. During spring tide conditions, the fronts dissipate during the flood, whereas during neap tides the fronts are advected landward during the flood. The zone of enhanced density gradient initiates frontogenesis at multiple constrictions along the estuary as it propagates landward more than 60 km during several days of neap tides. Frontogenesis and frontal propagation may thus be essential elements of the spring-to-neap transition to stratified conditions in partially mixed estuaries.
    Beschreibung: Support for this research was provided by NSF Grant OCE 0926427.
    Beschreibung: 2015-08-01
    Schlagwort(e): Circulation/ Dynamics ; Baroclinic flows ; Coastal flows ; Frontogenesis/frontolysis ; Fronts
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 2
    facet.materialart.
    Unbekannt
    Hydraulics and mixing in a laterally divergent channel of a highly stratified estuary (2017)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2017. 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 122 (2017): 4743–4760, doi:10.1002/2016JC012455.
    Beschreibung: Estuarine mixing is often intensified in regions where topographic forcing leads to hydraulic transitions. Observations in the salt-wedge estuary of the Connecticut River indicate that intense mixing occurs during the ebb tide in regions of supercritical flow that is accelerated by lateral expansion of the channel. The zones of mixing are readily identifiable based on echo-sounding images of large-amplitude shear instabilities. The gradient Richardson number (Ri) averaged across the mixing layer decreases to a value very close to 0.25 during most of the active mixing phase. The along-estuary variation in internal Froude number and interface elevation are roughly consistent with a steady, inviscid, two-layer hydraulic representation, and the fit is improved when a parameterization for interfacial stress is included. The analysis indicates that the mixing results from lateral straining of the shear layer, and that the rapid development of instabilities maintains the overall flow near the mixing threshold value of Ri = 0.25, even with continuous, active mixing. The entrainment coefficient can be estimated from salt conservation within the interfacial layer, based on the finding that the mixing maintains Ri = 0.25. This approach leads to a scaling estimate for the interfacial mixing coefficient based on the lateral spreading rate and the aspect ratio of the flow, yielding estimates of turbulent dissipation within the pycnocline that are consistent with estimates based on turbulence-resolving measurements.
    Beschreibung: NSF Grant Number: OCE 0926427; Devonshire Scholars program
    Beschreibung: 2017-12-12
    Schlagwort(e): Internal hydraulics ; Mixing ; Gradient Richardson number ; Estuary
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 3
    facet.materialart.
    Unbekannt
    Estuarine exchange flow quantified with isohaline coordinates : contrasting long and short estuaries (2012)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2012. 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 42 (2012): 748–763, doi:10.1175/JPO-D-11-086.1.
    Beschreibung: Isohaline coordinate analysis is used to compare the exchange flow in two contrasting estuaries, the long (with respect to tidal excursion) Hudson River and the short Merrimack River, using validated numerical models. The isohaline analysis averages fluxes in salinity space rather than in physical space, yielding the isohaline exchange flow that incorporates both subtidal and tidal fluxes and precisely satisfies the Knudsen relation. The isohaline analysis can be consistently applied to both subtidally and tidally dominated estuaries. In the Hudson, the isohaline exchange flow is similar to results from the Eulerian analysis, and the conventional estuarine theory can be used to quantify the salt transport based on scaling with the baroclinic pressure gradient. In the Merrimack, the isohaline exchange flow is much larger than the Eulerian quantity, indicating the dominance of tidal salt flux. The exchange flow does not scale with the baroclinic pressure gradient but rather with tidal volume flux. This tidal exchange is driven by tidal pumping due to the jet–sink flow at the mouth constriction, leading to a linear dependence of exchange flow on tidal volume flux. Finally, a tidal conversion parameter Qin/Qprism, measuring the fraction of tidal inflow Qprism that is converted into net exchange Qin, is proposed to characterize the exchange processes among different systems. It is found that the length scale ratio between tidal excursion and salinity intrusion provides a characteristic to distinguish estuarine regimes.
    Beschreibung: SNC is supported by a WHOI postdoctoral scholarship, a NSF Grant OCE-0926427, and a Taiwan National Science Council Grant NSC 100- 2199-M-002-028.WRGis supported byNSFGrantOCE- 0926427. JAL is supported by NSF Grant OCE-0452054.
    Beschreibung: 2012-11-01
    Schlagwort(e): Coastal flows
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 4
    facet.materialart.
    Unbekannt
    Turbulent and numerical mixing in a salt wedge estuary : dependence on grid resolution, bottom roughness, and turbulence closure (2017)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2017. 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 122 (2017): 692–712, doi:10.1002/2016JC011738.
    Beschreibung: The Connecticut River is a tidal salt wedge estuary, where advection of sharp salinity gradients through channel constrictions and over steeply sloping bathymetry leads to spatially heterogeneous stratification and mixing. A 3-D unstructured grid finite-volume hydrodynamic model (FVCOM) was evaluated against shipboard and moored observations, and mixing by both the turbulent closure and numerical diffusion were calculated. Excessive numerical mixing in regions with strong velocities, sharp salinity gradients, and steep bathymetry reduced model skill for salinity. Model calibration was improved by optimizing both the bottom roughness (z0), based on comparison with the barotropic tidal propagation, and the mixing threshold in the turbulence closure (steady state Richardson number, Rist), based on comparison with salinity. Whereas a large body of evidence supports a value of Rist ∼ 0.25, model skill for salinity improved with Rist ∼ 0.1. With Rist = 0.25, numerical mixing contributed about 1/2 the total mixing, while with Rist = 0.10 it accounted for ∼2/3, but salinity structure was more accurately reproduced. The combined contributions of numerical and turbulent mixing were quantitatively consistent with high-resolution measurements of turbulent mixing. A coarser grid had increased numerical mixing, requiring further reductions in turbulent mixing and greater bed friction to optimize skill. The optimal Rist for the fine grid case was closer to 0.25 than for the coarse grid, suggesting that additional grid refinement might correspond with Rist approaching the theoretical limit. Numerical mixing is rarely assessed in realistic models, but comparisons with high-resolution observations in this study suggest it is an important factor.
    Beschreibung: NSF Grant Number: OCE 0926427; ONR Grant Number: N00014-08-1-1115
    Beschreibung: 2017-07-28
    Schlagwort(e): Estuary ; Salt wedge ; Numerical mixing ; Turbulence closure ; Numerical model
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 5
    facet.materialart.
    Unbekannt
    Bigger tides, less flooding: Effects of dredging on barotropic dynamics in a highly modified estuary. (2019)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-10-20
    Beschreibung: Author Posting. © American Geophysical Union, 2019. 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 124 (2019): 196-211, doi:10.1029/2018JC014313.
    Beschreibung: Since the late nineteenth century, channel depths have more than doubled in parts of New York Harbor and the tidal Hudson River, wetlands have been reclaimed and navigational channels widened, and river flow has been regulated. To quantify the effects of these modifications, observations and numerical simulations using historical and modern bathymetry are used to analyze changes in the barotropic dynamics. Model results and water level records for Albany (1868 to present) and New York Harbor (1844 to present) recovered from archives show that the tidal amplitude has more than doubled near the head of tides, whereas increases in the lower estuary have been slight (〈10%). Channel deepening has reduced the effective drag in the upper tidal river, shifting the system from hyposynchronous (tide decaying landward) to hypersynchronous (tide amplifying). Similarly, modeling shows that coastal storm effects propagate farther landward, with a 20% increase in amplitude for a major event. In contrast, the decrease in friction with channel deepening has lowered the tidally averaged water level during discharge events, more than compensating for increased surge amplitude. Combined with river regulation that reduced peak discharges, the overall risk of extreme water levels in the upper tidal river decreased after channel construction, reducing the water level for the 10‐year recurrence interval event by almost 3 m. Mean water level decreased sharply with channel modifications around 1930, and subsequent decadal variability has depended both on river discharge and sea level rise. Channel construction has only slightly altered tidal and storm surge amplitudes in the lower estuary.
    Beschreibung: Funding for D. K. R., W. R. G., and C. K. S. was provided by NSF Coastal SEES awards OCE-1325136 and OCE-1325102. Funding for S.T. and H. Z. was provided by the U.S. Army Corps of Engineers (award W1927 N-14-2-0015), and NSF (Career Award 1455350). Data supporting this study are posted to Zenodo (https://doi.org/10.5281/zenodo.1298636).
    Beschreibung: 2019-06-11
    Schlagwort(e): Barotropic tides ; Flood frequency ; Storm surge ; Dredging ; Estuary ; Tidal river
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 6
    facet.materialart.
    Unbekannt
    Shifting sediment dynamics in the Coos Bay Estuary in response to 150 years of modification (2021)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-10-20
    Beschreibung: Author Posting. © American Geophysical Union, 2021. 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 126(1), (2021): e2020JC016771, https://doi.org/10.1029/2020JC016771.
    Beschreibung: Estuaries worldwide have experienced modifications including channel deepening and intertidal reclamation over several centuries, resulting in altered fine sediment routing. Estuaries respond differently based on preexisting geometries, freshwater and sediment supplies, and extents and types of modification. The Coos Bay Estuary in Oregon is a relatively small estuary with complex geometry that has been extensively modified since 1865. A sediment transport model calibrated to modern conditions is used to assess the corresponding changes in sediment dynamics. Over ∼150 years, channel deepening (from ∼6.7 to 11 m), a 12% increase in area, and a 21% increase in volume have led to greater tidal amplitudes, salinity intrusion, and estuarine exchange flow. These changes have reduced current magnitudes, reduced bed stresses, and increased stratification, especially during rainy periods. Historically, fluvially derived sediment was dispersed across broad, deltaic‐style flats and through small tidal channels. Now, river water and sediments are diverted into a dredged navigation channel where an estuarine turbidity maximum (ETM) forms, with modeled concentrations 〉50 mg/L and measured concentrations 〉100 mg/L during discharge events. This “new” ETM supplies sediment to proximal embayments in the middle estuary and the shallow flats. Overall, sediment trapping during winter (and high river discharges) has increased more than two‐fold, owing to increased accommodation space, altered pathways of supply, and altered bed stresses and tidal asymmetries. In contrast to funnel‐shaped estuaries with simpler geometries and river‐channel transitions, these results highlight the importance of channel routing together with dredging in enhancing sediment retention and shifting pathways of sediment delivery.
    Beschreibung: The Science Collaborative is funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center (NAI4NOS4190145).
    Beschreibung: 2021-06-14
    Schlagwort(e): Dredging ; Estuarine turbidity maximum ; Estuary ; Modification ; Sediment
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 7
    facet.materialart.
    Unbekannt
    Sediment transport due to extreme events : the Hudson River estuary after tropical storms Irene and Lee (2014)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: 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.
    Beschreibung: 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.
    Beschreibung: This research was supported by grants from the Hudson Research Foundation (002/07A) and the National Science Foundation (1232928).
    Beschreibung: 2014-04-18
    Schlagwort(e): Sediment transport ; Tidal river ; Estuary ; Sediment trapping
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
    Format: application/msword
    Format: image/tiff
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 8
    facet.materialart.
    Unbekannt
    Sediment transport time scales and trapping efficiency in a tidal river (2018)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2017. 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: Earth Surface 122 (2017): 2042–2063, doi:10.1002/2017JF004337.
    Beschreibung: Observations and a numerical model are used to characterize sediment transport in the tidal Hudson River. A sediment budget over 11 years including major discharge events indicates the tidal fresh region traps about 40% of the sediment input from the watershed. Sediment input scales with the river discharge cubed, while seaward transport in the tidal river scales linearly, so the tidal river accumulates sediment during the highest discharge events. Sediment pulses associated with discharge events dissipate moving seaward and lag the advection speed of the river by a factor of 1.5 to 3. Idealized model simulations with a range of discharge and settling velocity were used to evaluate the trapping efficiency, transport rate, and mean age of sediment input from the watershed. The seaward transport of suspended sediment scales linearly with discharge but lags the river velocity by a factor that is linear with settling velocity. The lag factor is 30–40 times the settling velocity (mm s−1), so transport speeds vary by orders of magnitude from clay (0.01 mm s−1) to coarse silt (1 mm s−1). Deposition along the tidal river depends strongly on settling velocity, and a simple advection-reaction equation represents the loss due to settling on depositional shoals. The long-term discharge record is used to represent statistically the distribution of transport times, and time scales for settling velocities of 0.1 mm s−1 and 1 mm s−1 range from several months to several years for transport through the tidal river and several years to several decades through the estuary.
    Beschreibung: Hudson River Foundation Grant Number: 004/13A; National Science Foundation Grant Number: 1325136
    Beschreibung: 2018-05-02
    Schlagwort(e): Tidal river ; Sediment age ; Trapping efficiency ; Estuary ; Sediment transport
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 9
    facet.materialart.
    Unbekannt
    Salt wedge dynamics lead to enhanced sediment trapping within side embayments in high-energy estuaries (2017)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2017. 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 122 (2017): 2226–2242, doi:10.1002/2016JC012595.
    Beschreibung: Off-river coves and embayments provide accommodation space for sediment accumulation, particularly for sandy estuaries where high energy in the main channel prevents significant long-term storage of fine-grained material. Seasonal sediment inputs to Hamburg Cove in the Connecticut River estuary (USA) were monitored to understand the timing and mechanisms for sediment storage there. Unlike in freshwater tidal coves, sediment was primarily trapped here during periods of low discharge, when the salinity intrusion extended upriver to the cove entrance. During periods of low discharge and high sediment accumulation, deposited sediment displayed geochemical signatures consistent with a marine source. Numerical simulations reveal that low discharge conditions provide several important characteristics that maximize sediment trapping. First, these conditions allow the estuarine turbidity maximum (ETM) to be located in the vicinity of the cove entrance, which increases sediment concentrations during flood tide. Second, the saltier water in the main channel can enter the cove as a density current, enhancing near-bed velocities and resuspending sediment, providing an efficient delivery mechanism. Finally, higher salinity water accumulates in the deep basin of the cove, creating a stratified region that becomes decoupled from ebb currents, promoting retention of sediment in the cove. This process of estuarine-enhanced sediment accumulation in off-river coves will likely extend upriver during future sea level rise.
    Beschreibung: NSF Grant Numbers: EAR-1148244 , OCE-0926427
    Beschreibung: 2017-09-17
    Schlagwort(e): Sediment storage ; Estuary ; Estuarine turbidity maximum
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
  • 10
    facet.materialart.
    Unbekannt
    Reversed lateral circulation in a sharp estuarine bend with weak stratification (2019)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Meteorological Society, 2019. 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 49(6), (2019):1619-1637, doi:10.1175/JPO-D-18-0175.1.
    Beschreibung: Although the hydrodynamics of river meanders are well studied, the influence of curvature on flow in estuaries, with alternating tidal flow and varying water levels and salinity gradients, is less well understood. This paper describes a field study on curvature effects in a narrow salt-marsh creek with sharp bends. The key observations, obtained during times of negligible stratification, are 1) distinct differences between secondary flow during ebb and flood, with helical circulation as in rivers during ebb and a reversed circulation during flood, and 2) maximum (ebb and flood) streamwise velocities near the inside of the bend, unlike typical river bend flow. The streamwise velocity structure is explained by the lack of a distinct point bar and the relatively deep cross section in the estuary, which means that curvature-induced inward momentum redistribution is not overcome by outward redistribution by frictional and topographic effects. Through differential advection of the along-estuary salinity gradient, the laterally sheared streamwise velocity generates lateral salinity differences, with the saltiest water near the inside during flood. The resulting lateral baroclinic pressure gradient force enhances the standard helical circulation during ebb but counteracts it during flood. This first leads to a reversed secondary circulation during flood in the outer part of the cross section, which triggers a positive feedback mechanism by bringing slower-moving water from the outside inward along the surface. This leads to a reversal of the vertical shear in the streamwise flow, and therefore in the centrifugal force, which further enhances the reversed secondary circulation.
    Beschreibung: This project was funded by NSF Grant OCE-1634490. During this work W.M. Kranenburg was supported as USGS Postdoctoral Scholar at Woods Hole Oceanographic Institution. A.M.P. Garcia was supported by the Michael J. Kowalski Fellowship in Ocean Science and Engineering (AMPG), and the Diversity Fellowship of the MIT Office of the Dean of Graduate Education (AMPG). The authors thank Jay Sisson for the technical support and Peter Traykovski for providing the bathymetric data. Also, the suggestions for improvement by Dr. K. Blanckaert and an anonymous reviewer are thankfully acknowledged.
    Schlagwort(e): Estuaries ; Advection ; Baroclinic flows ; Barotropic flows
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    ARTIKEL (OA)
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...