“…e f e f e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f If we hypothetically extrapolate further and use previous estimates (Armi, 1978(Armi, , 1979Garrett, 1990Garrett, , 1991 , which is the value needed to maintain the overall density stratification (Munk and Wunsch, 1998). This value supports earlier conjectures (e.g., Munk, 1966;Armi, 1978;Garrett, 1990) at a variety of (tidally) noncritical slopes (e.g., Klymak and Moum, 2003;Hosegood et al, 2004;Bonnin et al, 2006;Nash et al, 2007). temporal) resolution of internal waveturbulence motions toward understanding their intrinsic properties.…”
Section: Box 2 | Mixing Measurements Using Moored Sensorssupporting
confidence: 78%
“…Such a bore dominates sediment resuspension (Hosegood et al, 2004;Bonnin et al, 2006), which resembles an atmospheric dust storm.…”
Section: Box 1 | Temper Ature As a Tr Acer For Densit Y Variationsmentioning
“…e f e f e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f If we hypothetically extrapolate further and use previous estimates (Armi, 1978(Armi, , 1979Garrett, 1990Garrett, , 1991 , which is the value needed to maintain the overall density stratification (Munk and Wunsch, 1998). This value supports earlier conjectures (e.g., Munk, 1966;Armi, 1978;Garrett, 1990) at a variety of (tidally) noncritical slopes (e.g., Klymak and Moum, 2003;Hosegood et al, 2004;Bonnin et al, 2006;Nash et al, 2007). temporal) resolution of internal waveturbulence motions toward understanding their intrinsic properties.…”
Section: Box 2 | Mixing Measurements Using Moored Sensorssupporting
confidence: 78%
“…Such a bore dominates sediment resuspension (Hosegood et al, 2004;Bonnin et al, 2006), which resembles an atmospheric dust storm.…”
Section: Box 1 | Temper Ature As a Tr Acer For Densit Y Variationsmentioning
“…Median grain sizes were observed between 150-400 μm, with a spectral sub-peak at 1,000 μm (Bonnin et al 2006). These values are lower than the expected resonance scale of several millimetres for a 300 kHz ADCP, but uncertainty exists in the precise 'size' for acoustic reflection when particles are in suspension in a stratified turbulent environment.…”
Relative 'echo intensity' data (dI) from a bottommounted four-beam 300 kHz acoustic Doppler current profiler (ADCP) are used to infer propagation of vigorous processes above a continental slope. The 3-to 60-m horizontal beam spread and the 2-Hz sampling allow the distinction of different arrival times t i , i=1,..., 4, at different distances in the acoustic beams from sharp changes in dI-content associated with frontal non-linear and turbulent bores or 'waves'. The changes in dI are partially due to variations in amounts of resuspended material carried by the near-bottom turbulence and partially due to the fast variations in density stratification ('stratified turbulence'), as inferred from 1-Hz sampled thermistor string data above the ADCP. Such bores are observed to pass the mooring up to 80 m above the bottom, having typical propagation speeds c=0.15-0.5 m s −1 , as determined from dI(t i ). Particle speeds in the immediate environment of a bore amount to |u| env =c±0.05 m s −1 , the equality being a necessary condition for kinematic instability, whilst the maximum particle speeds amount |u| max =1.2-2c. The dI-determined directions of up-, down-and alongslope processes are all to within ±10°of the ADCP's beam-spread averaged current (particle velocity) data.
“…They reported 0.5 m vertical excursions with a 10 s period during deployment, and this and tilt could have affected their results. Bonnin et al (2002Bonnin et al ( , 2006 deployed cylindrical traps with a concentrating cone at the bottom near the seafloor and found no increase in trapping rates as a function of Reynolds number over the same range of trap Reynolds numbers. These varying results may in part derive from the different trap designs, but also from differences in the full mooring configurations, deployment conditions, and the characteristics of ambient particles.…”
Section: B Progress In Understanding the Origin And Scope Of Hydrodymentioning
This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton "swimmers," and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short-term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods.
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