scholarly journals Freshwater Composition and Connectivity of the Connecticut River Plume During Ambient Flood Tides

2021 ◽  
Vol 8 ◽  
Author(s):  
Michael M. Whitney ◽  
Yan Jia ◽  
Kelly L. Cole ◽  
Daniel G. MacDonald ◽  
Kimberly D. Huguenard
Keyword(s):  
Mixing Time ◽  
Growth Period ◽  
Tidal Currents ◽  
Surface Flow ◽  
River Plume ◽  
Tidal River ◽  
Initial Growth ◽  
Connecticut River ◽  
Tidal Period ◽  
Source Waters

The Connecticut River plume interacts with the strong tidal currents of the ambient receiving waters in eastern Long Island Sound. The plume formed during ambient flood tides is studied as an example of tidal river plumes entering into energetic ambient tidal environments in estuaries or continental shelves. Conservative passive freshwater tracers within a high-resolution nested hydrodynamic model are applied to determine how source waters from different parts of the tidal cycle contribute to plume composition and interact with bounding plume fronts. The connection to source waters can be cut off only under low-discharge conditions, when tides reverse surface flow through the mouth after max ambient flood. Upstream plume extent is limited because ambient tidal currents arrest the opposing plume propagation, as the tidal internal Froude number exceeds one. The downstream extent of the tidal plume always is within 20 km from the mouth, which is less than twice the ambient tidal excursion. Freshwaters in the river during the preceding ambient ebb are the oldest found in the new flood plume. Connectivity with source waters and plume fronts exhibits a strong upstream-to-downstream asymmetry. The arrested upstream front has high connectivity, as all freshwaters exiting the mouth immediately interact with this boundary. The downstream plume front has the lowest overall connectivity, as interaction is limited to the oldest waters since younger interior waters do not overtake this front. The offshore front and inshore boundary exhibit a downstream progression from younger to older waters and decreasing overall connectivity with source waters. Plume-averaged freshwater tracer concentrations and variances both exhibit an initial growth period followed by a longer decay period for the remainder of the tidal period. The plume-averaged tracer variance is increased by mouth inputs, decreased by entrainment, and destroyed by internal mixing. Peak entrainment velocities for younger waters are higher than values for older waters, indicating stronger entrainment closer to the mouth. Entrainment and mixing time scales (1–4 h at max ambient flood) are both shorter than half a tidal period, indicating entrainment and mixing are vigorous enough to rapidly diminish tracer variance within the plume.

scholarly journals Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries

2017 ◽  
Vol 5 (4) ◽  
pp. 731-756 ◽  
Author(s):  
Maarten G. Kleinhans ◽  
Maarten van der Vegt ◽  
Jasper Leuven ◽  
Lisanne Braat ◽  
Henk Markies ◽  
...  
Keyword(s):  
Sea Level ◽  
Tidal Currents ◽  
Surface Flow ◽  
Water Levels ◽  
Tidal Range ◽  
Level Fluctuation ◽  
Tidal Period ◽  
Sea Level Fluctuations ◽  
Sediment Mobility ◽  
Sea Level Fluctuation

Abstract. Analogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Our recently discovered method to drive tidal currents by periodically tilting the entire flume leads to intense sediment transport in both the ebb and flood phase, causing dynamic channel and shoal patterns. However, it remains unclear whether tilting produces periodic flows with characteristic tidal properties that are sufficiently similar to those in nature for the purpose of landscape experiments. Moreover, it is not well understood why the flows driven by periodic sea level fluctuation, as in nature, are not sufficient for morphodynamic experiments. Here we compare for the first time the tidal currents driven by sea level fluctuations and by tilting. Experiments were run in a 20  ×  3 m straight flume, the Metronome, for a range of tilting periods and with one or two boundaries open at constant head with free inflow and outflow. Also, experiments were run with flow driven by periodic sea level fluctuations. We recorded surface flow velocity along the flume with particle imaging velocimetry and measured water levels along the flume. We compared the results to a one-dimensional model with shallow flow equations for a rough bed, which was tested on the experiments and applied to a range of length scales bridging small experiments and large estuaries. We found that the Reynolds method results in negligible flows along the flume except for the first few metres, whereas flume tilting results in nearly uniform reversing flow velocities along the entire flume that are strong enough to move sand. Furthermore, tidal excursion length relative to basin length and the dominance of friction over inertia is similar in tidal experiments and reality. The sediment mobility converges between the Reynolds method and tilting for flumes hundreds of metres long, which is impractical. Smaller flumes of a few metres in length, on the other hand, are much more dominated by friction than natural systems, meaning that sediment suspension would be impossible in the resulting laminar flow on tidal flats. Where the Reynolds method is limited by small sediment mobility and high tidal range relative to water depth, the tilting method allows for independent control over the variables flow depth, velocity, sediment mobility, tidal period and excursion length, and tidal asymmetry. A periodically tilting flume thus opens up the possibility of systematic biogeomorphological experimentation with self-formed estuaries.

scholarly journals Non-Linear Processes in the Gironde River Plume (North-East Atlantic): Instabilities and Mixing

2021 ◽  
Vol 8 ◽  
Author(s):  
Adam Ayouche ◽  
Guillaume Charria ◽  
Xavier Carton ◽  
Nadia Ayoub ◽  
Sébastien Theetten
Keyword(s):  
River Discharge ◽  
Ocean Surface ◽  
Tidal Currents ◽  
River Plume ◽  
Frontal Region ◽  
Small Scale ◽  
Coastal Current ◽  
East Atlantic ◽  
North East ◽  
Wind Bursts

Instability and mixing are ubiquitous processes in river plumes but their small spatial and temporal scales often limit their observation and analysis. We investigate flow instability and mixing processes in the Gironde river plume (Bay of Biscay, North-East Atlantic ocean) in response to air-sea fluxes, tidal currents, and winds. High-resolution numerical simulations are conducted in March (average river discharge) and in August (low discharge) to explore such processes. Two areas of the Gironde river plume (the bulge and the coastal current) experience different instabilities: barotropic, baroclinic, symmetric, and/or vertical shear instabilities. Energy conversion terms reveal the coexistence of barotropic and baroclinic instabilities in the bulge and in the coastal current during both months. These instabilities are intensified over the whole domain in August and over the inner-shelf in March. The Hoskins criterion indicates that symmetric instability exists in most parts of the plume during both periods. The evolution of the Gironde plume with the summer stratification, tidal currents and winds favors its development. During both seasons, ageostrophic flow and large Rossby numbers characterize rapidly-growing and small-scale frontal baroclinic and symmetric instabilities. The transition between these instabilities is investigated with an EKE decomposition on the modes of instability. In the frontal region of the plume, during both months, symmetric instabilities grow first followed by baroclinic and mixed ones, during wind bursts and/or high discharge events. In contrast, when the wind is weak or relaxing, baroclinic instabilities grow first followed by symmetric and then mixed ones. Their growth periods range from a few hours to a few days. Mixing at the ocean surface is analyzed via Potential Vorticity (PV) fluxes. The net injection of PV at the ocean surface occurs at submesoscale buoyant fronts of the Gironde plume during both months. Vertical mixing at these fronts has similar magnitude as the wind-driven and surface buoyancy fluxes. During both months, the frontal region of the plume is restratified during wind relaxation events and/or high river discharge events through frontogenetic processes. Conversely, wind bursts destratify the frontal plume interior through non-conservative PV fluxes.

scholarly journals Turning the tide: comparison of tidal flow by periodic sealevel fluctuation and by periodic bed tilting in the Metronome tidal facility

2017 ◽  
Author(s):  
Maarten G. Kleinhans ◽  
Maarten van der Vegt ◽  
Jasper Leuven ◽  
Lisanne Braat ◽  
Henk Markies ◽  
...  
Keyword(s):  
Tidal Flow ◽  
Tidal Currents ◽  
Surface Flow ◽  
Water Levels ◽  
Flow Equations ◽  
Tidal Basins ◽  
Analogue Models ◽  
Rough Bed ◽  
Constant Head ◽  
Particle Imaging

Abstract. Analogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Since Osborne Reynolds' experiments over a century ago, experimental tidal flow has been driven by periodic sealevel fluctuations. Recently we discovered a novel method to drive periodic tidal currents: periodically tilting the entire flume. This leads to sediment transport in both the ebb and flood phase which in tidal systems with dynamic channel and shoal patterns. Here we compare the tidal currents driven by sealevel fluctuations with those driven by tilting. We use a bespoke flume of 20 m by 3 m with rough bed: the Metronome. Experiments were run in a straight flume with different tilting periods and with either one or both boundaries open at constant head with free inflow and outflow. Also experiments were run with flow driven by periodic sealevel fluctuations. We recorded surface flow velocity along the flume with Particle Imaging Velocimetry and water levels along the flume. Furthermore we compared the results to a one-dimensional model with shallow flow equations for a rough bed. We found that Reynolds’ method results in negligible flows along the flume except for the first few meters, whereas flume tilting results in nearly uniform, reversing flow velocities along the entire flume that are strong enough to move sand. A periodically tilting flume therefore has the potential to simulate estuaries as observed in a pilot experiment and opens up the possibility of systematic biomorphological experimentation with self-formed estuaries.

scholarly journals Localization and phenotype of cycling and post-cycling murine thymocytes studied by simultaneous detection of bromodeoxyuridine and surface antigens.

1988 ◽  
Vol 36 (5) ◽  
pp. 473-478 ◽  
Author(s):  
C Penit
Keyword(s):  
T Cell ◽  
Interleukin 2 ◽  
Simultaneous Detection ◽  
Growth Period ◽  
Surface Antigens ◽  
Cell Receptor ◽  
Initial Growth ◽  
Outer Cortex

Bromodeoxyuridine (BrdUrd) was incorporated in vivo or in vitro into the DNA of proliferating murine thymocytes. Surface antigens Thy1, Lyt2 (CD8), L3T4 (CD4), interleukin-2 receptor (IL2-R), and the V beta 8 chain of the T-cell receptor were detected using specific monoclonal antibodies with the biotin-avidin system, and cells were then treated for DNA denaturation. Simultaneous detection of BrdUrd and surface markers was performed on cell smears and frozen sections by double-color immunofluorescence. The phenotype of cycling cells, determined in fetal thymus and in the thymus of mice from birth to one year of age, showed relative stability after the initial growth period, despite severe involution of the gland. Phenotypic evolution of cycling cells and their progeny was also studied in colchicine-treated animals and was shown to reproduce sequential events of T-cell differentiation. On sections, the highest frequency of cycling cells was observed in the outer cortex in normal thymus, but the first cells to start proliferation during regeneration were mostly located in the deep cortex and corticomedullary junction. These results show the high potential of this method, as compared to autoradiography of radiolabeled cells.

scholarly journals Influence of temperature and nitrogen on growth, photosynthesis and accumulation of non-structural carbohydrate in a tropical grass, Panicum maximum var. trichoglum.

1975 ◽  
Vol 23 (1) ◽  
pp. 48-61 ◽  
Author(s):  
J.R. Wilson
Keyword(s):  
Leaf Area ◽  
Dark Respiration ◽  
Growth Period ◽  
Panicum Maximum ◽  
Initial Growth ◽  
Hoagland Solution ◽  
Influence Of Temperature ◽  
Unit Leaf ◽  
Influence Of Temperature On ◽  
Half Strength

After an initial growth period on half-strength Hoagland solution at 25 deg C, plants of P. maximum var. trichoglume were transferred to N-free nutrient solution and an equal number were kept on half-strength Hoagland solution. Plants from both N treatments were grown under constant temperatures of 15, 20, 25, 30 or 35 deg . Leaf net photosynthetic rate, RGR and NAR/unit leaf area were affected to a similar relative extent with change in temperature or N, thereby precluding accumulation of very high percentages of total non-structural carbohydrates (% TNC). At low temperature and low N, changes in % TNC were inversely related to relative leaf area growth rate and also to some extent with dark respiration rate. In high-N plants, reduction in % TNC at higher temperatures was probably accentuated by the use of constant day/night temperatures. The influence of temperature on % TNC in low-N plants was slight. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Temperature Effects on Growth of Impatiens Plug Seedlings in Controlled Environments

1992 ◽  
Vol 117 (2) ◽  
pp. 209-215 ◽  
Author(s):  
David R. Dreesen ◽  
Robert W. Langhans
Keyword(s):  
Leaf Area ◽  
Growth Period ◽  
Dry Weight ◽  
Photon Flux ◽  
Initial Growth ◽  
Growth Responses ◽  
Shoot Height ◽  
Seedling Age ◽  
Shoot Dry Weight ◽  
Air Temperatures

The objective of this study was to determine the dry weight, height, and leaf area growth responses of impatiens (Impatiens walerana Hook. f.) plug seedlings to air temperatures ranging from 18 to 29C. The conditions maintained in the controlled-environment growth rooms (CEGR) were ambient C02 levels, 24-h lighting, and photosynthetic photon flux (PPF) ranging from ≈215; to 335 μmol·m-2·s-1. Mean daily temperatures of the plug medium ranged from 19.6 to 27.7C. At the higher PPF level, shoot dry weight decreased at plug medium temperatures (PMT) > 25C; at lower PPF levels (<300 μmol·m-2·s-1), shoot dry weight continued to increase with PMT > 25C. The mean relative growth rate (MRGR) of shoot dry weight was positively correlated with PMT during the initial growth period (up to 14 days from sowing) and was negatively correlated thereafter. The maximum MRGR was predicted to occur at 11.7 days from sowing for a PMT of 19.6C, at 10.8 days for a PMT of 21.6C, and at 9.7 days for a PMT of 23.6C. Linear regression coefficients of shoot height as a function of PMT were substantially higher for seedlings grown at lower PPF than those for seedlings from the highest PPF level. Seedling leaf area consistently increased with increasing temperature. Net assimilation rate (NAR) decreased with increasing seedling age NAR increased with increasing PPF. A decrease in NAR was apparent at 29C relative to values at the lower temperatures. Leaf area ratio (LAR) declined with increasing seedling age and PPF; a quadratic relationship of LAR as a function of PMT indicates a minimum LAR at 22.5C. The seedlings grown at 29C were excessively tall, had thin succulent leaves, and were judged unacceptable for shipping and transplanting. Maximum quality indices (i.e., dry weight per height) were found at PMT of 24.3 to 25.OC for 10- to 14-day-old seedlings and at PMT of 23.0 to 24.OC for 16- to 20-day-old seedlings.

Early Radio Listening as Modernist Practice: Ambient Radio and the Aesthetic of Distraction

2015 ◽  
Vol 10 (1) ◽  
pp. 6-25 ◽  
Author(s):  
Shawn VanCour
Keyword(s):  
Growth Period ◽  
The United States ◽  
Domestic Space ◽  
Urban Life ◽  
Initial Growth ◽  
Department Stores ◽  
The Aesthetic ◽  
Public Recreation ◽  
Trade Shows ◽  
Privileged Site

Moving beyond radio's textual affinities with neighboring forms of modernist art, this essay explores the listening practices and modes of aural experience associated with the medium during its initial growth period in the United States from 1920 to 1930. Challenging emphases on private domestic space as the privileged site of radio reception, it argues that encounters with radio in public spaces outside the home were equally important for shaping popular experiences of broadcasting and linked the medium to a modern aesthetic of distraction. Public listening on city streets, in department stores, and at early trade shows positioned radio as an aural attraction that invited short bursts of attention and encouraged practices of acoustic flanerie. Listening in spaces of public recreation, by contrast, invited more sustained engagement but positioned radio as a background medium and object of secondary attention. These twin regimes of ambient radio and their associated modes of distracted listening echoed parallel tendencies observed by scholars of visual modernity, while indexing much broader structural and experiential shifts in early twentieth century urban life.

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