Papers by Brian Sanderson
Coasts and Ports 2005 : Coastal Living - Living Coast; Australasian Conference; Proceedings, 2005
The NSW Waverider buoy network was developed in response to a series of destructive storms in 197... more The NSW Waverider buoy network was developed in response to a series of destructive storms in 1974. The resulting wave database now has four stations with over 25 years of records and one site at Sydney with over 12 years of directional data. A summary of the ...
The Lagrangian autocorrelation coefficient, of velocities with the local mean current extracted, ... more The Lagrangian autocorrelation coefficient, of velocities with the local mean current extracted, has e-folding time scales of 15 and 22 hours for the x and y components of motion respectively. Periodicities that might be attributed to either semidiurnal tides or inertial oscillations are evident, as are diurnal periodicities. Local vorticity is typically 5 times greater than local divergence and, apart from the coastal boundary layer, has a magnitude less than 1/5 the Coriolis parameter. This is consistent with quasigeostrophic motion. The variance and covariance of residual velocities vary from one grid to the next. Thus both the mean and residual velocity fields are inhomogeneous. An advection-diffusion model developed by 0kubo et al, (1983) can be used to calculate the uncertainty of iceberg trajectories from velocity gradients and eddy-diffusivities. This gives a good estimate of the uncertainty for periods much greater than the integral time scale.
Cold Regions Science and Technology, Jul 1, 1990
Abstract The objective of this work is to devise strategies for optimum deployment of Tiros satel... more Abstract The objective of this work is to devise strategies for optimum deployment of Tiros satellite-tracked Ocean Drifters (TOD) in order to derive measurements of ocean currents for iceberg drift forecasting off the Canadian east coast. The mean velocity field and its standard deviation are determined from several data sources. The velocity field and its variability are used by a trajectory model to determine the probable movement of a TOD released in the study area. A desirability index is defined to quantify the need for TOD measuremennts at a site in terms of: the amount and type of human activity; the variability and knowledge of ocean currents; and the iceberg population density, and other considerations. This enables us to develop a method for arriving at a TOD deployment agenda. Based on data from oil drilling operations off Labrador and Newfoundland, typical residence times for TOD's is about 2.5 months. For the area off Labrador, TOD releases should be within the Labrador current (between the 200 m and 1000 m isobaths) as far north as pack ice allows. Peak release rates off Newfoundland should be in May to July in order to coincide with peak iceberg numbers. A prohibitive number (1000) of TOD's would be required to resolve eddy structure in the areas considered. However, a more reasonable number (20–100) of TOD's would adequately resolve much of the wind-induced current variability.
Our research project addresses a fundamental problem in turbulence theory, the relation between L... more Our research project addresses a fundamental problem in turbulence theory, the relation between Lagrangian and Eulerian.-statistics, by carrying out, analyzing, and interpreting a set of field experiments in the coastal waters off the south shore of Long Island. The study will not only provide information on the relation between the Lagrangian and Eulerian autocorrelations but also between the various experimental methods for quantitatively estimating turbulent diffusion. Two experiments, one in summer and one in winter, consisting of simultaneous measurements of dye diffusion, drogue dispersion, and Eulerian current velocities in a typical coastal locale were planned. In order to ensure a match between the Lagrangian (drogues, dye) scales of motion and the Eulerian (current meters) scales, however, a preliminary experiment, consisting of a 6 mooring current meter array and a short (~ 3 hours) drogue experiment, was conducted during March 1980. Results of this preliminary experiment and their implications to our experimental program are discussed in this progress reporl. The principal rc!;ults \•Jere: 1) An improved design of our current meter array, and 2) A wider variety of drogue experiments, i.e., multilevel, multi-scale, and continuous source simulation. Details of our redesigned summer experiment, scheduled for 14-29 July 1980, are given.
Canadian Acoustics, Aug 27, 2015
Current interests in harnessing tidal energy from Minas Passage, a high flow (up to 6 m/s) channe... more Current interests in harnessing tidal energy from Minas Passage, a high flow (up to 6 m/s) channel in the upper Bay of Fundy, require examination of potential effects of tidal turbines on the environment, including impacts on commonly occurring harbour porpoise, Phocoena phocoena (Linnaeus, 1758). To collect baseline data on porpoise presence in the FORCE turbine test site in Minas Passage, two Passive Acoustic Monitoring (PAM) technologies were used: the C-POD (porpoise click logger, Chelonia Ltd) and the icListenHF (digital hydrophone, Ocean Sonics). Prior multi-year PAM studies in the Minas Passage involved C-POD hydrophones housed within streamlined SUB buoys suspended 3m above the seafloor. During high flows, these SUB buoys experienced high variability in tilt. In addition, high-flow induced noise in the Minas Passage exceeded the C-POD’s maximum recordable clicks per minute and thus under-detected harbour porpoise click trains, an effect referred to as lost time. To increase detection efficiency, changes to mooring design and the use of acoustic shrouds were tested. The housing of hydrophones (two icListenHFs and two C-PODs) in a stationary bottom moored platform (i.e. minimal instrument tilt) was shown to reduce the detection of non-target noise and thus reduce time lost. To minimize pseudonoise, various shroud setups were tested before deployment and the best performing shroud (20 ppi, 1.27cm thick acoustic foam) selected for field deployment. The shroud did not significantly reduce pseudonoise within the bandwidth of harbour porpoise clicks (120 kHz to 140 kHz). The icListenHF raw audio data were used to validate C-POD harbour porpoise clicks. A comparison of the performance of both technologies showed that the icListenHF recorded five times the number of C-POD Detection Positive Minutes. We recommend that bottom mounted platforms fitted with cabled digital HF hydrophones be used for monitoring harbour porpoise in and near the FORCE test site.
Boundary-Layer Meteorology, Jun 1, 2004
Non-stationary turbulence can invalidate eddy flux calculations. Two-hour long records of wind ve... more Non-stationary turbulence can invalidate eddy flux calculations. Two-hour long records of wind velocity, temperature and humidity are classified as stationary or non-stationary based on the behaviour of the flux as a function of Reynolds averaging period; a number of indicators of stationarity are investigated. The two-hour Maritime Continent Thunderstorm Experiment wind datasets are not completely stationary, as indicated by the lack of a spectral gap, but can be classified as approximately stationary, when the mean wind speed is greater than 3.8 m s −1 , or the standard deviation of true wind direction is ≤ 10 • , or the ratio of horizontal wind variance to wind speed is < 0.25. In the stationary case the calculated friction velocity exhibits a 7% decrease on average when the Reynolds averaging period is doubled, while data classified as non-stationary exhibit an increase of 32%. There is little non-stationary behaviour in the kinematic heat fluxes, and is independent of the non-stationarity of the friction velocity. The kinematic heat fluxes show small decreases (around 3%) when the Reynolds averaging period is doubled.
Journal of Atmospheric and Oceanic Technology, 2005
A method for removing ship motion from wind measurements using a simple and inexpensive strap-dow... more A method for removing ship motion from wind measurements using a simple and inexpensive strap-down system of accelerometers is described and analyzed. In slight seas, error analysis indicates that mean root-mean-square uncertainties associated with the motion correction are 0.03 and 0.006 m s Ϫ1 for the horizontal and vertical wind, respectively, for all runs analyzed. The mean uncertainty in the wind stress due to motion correction is 8 ϫ 10 Ϫ4 N m Ϫ2. In a shallow coastal sea setting, ship motion appears to almost always be successfully detected and removed from the vertical component of the observed wind. The horizontal wind components appear to be successfully corrected in 86% of the runs analyzed. Motion correction is shown to have a significant influence on the covariance-calculated wind stress. In approximately half of the runs analyzed the wind stress changes by more than 15%. Motion correction has a smaller effect on the heat fluxes.
Canadian Journal of Fisheries and Aquatic Sciences, Dec 1, 2016
Winter presence and temperature-related diel vertical migration of Striped Bass (Morone saxatilis... more Winter presence and temperature-related diel vertical migration of Striped Bass (Morone saxatilis) in an extreme high flow passage in the inner Bay of Fundy
Animal Biotelemetry, Mar 14, 2022
The anadromous alewife is a commercially fished clupeid in Atlantic Canada, whose oceanic migrati... more The anadromous alewife is a commercially fished clupeid in Atlantic Canada, whose oceanic migration is poorly understood. Migration of alewives is presently investigated from the lower reaches of Gaspereau River into Minas Basin, Bay of Fundy. Seventy-five post-spawning adults were tagged on their downstream migration; within two days of being tagged, most alewives had left Gaspereau River and 57 entered into the Southern Bight of Minas Basin. Thirty-one alewives were detected in Minas Passage and their average time from tagging to final detection was 28 days with standard deviation of 11 days. None of the alewives were detected in Minas Passage until day 20 after the start of tagging. After day 20, the residence timescale in Minas Basin was only 8.8 days with 95% CI of 8.4-9.3 days. Fast tidal currents prevail in much of the study area, and alewives travelled many large tidal excursions in Minas Basin and Minas Passage. Separation distances between pairs of alewives increased greatly after day 20, indicating tidal mixing over large distances within the study area. Offshore movement was associated with seasonal warming, with alewives moving down the spatial temperature gradient and into deeper waters. Offshore, larger tidal displacements widely dispersed tagged alewives through Minas Basin and to Minas Passage. During transit of Gaspereau River, 18 ± 2 alewives were lost with corroborating evidence of mortality for 4 of these. By day 20, the apparent mortality within Minas Basin was ≤ 10 alewives. Individual alewives were observed to make many transits through Minas Passage during their migration, where they may become exposed to in-stream tidal turbines.
Journal of Marine Science and Engineering, Aug 14, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
An ocean flow that has all its scales resolved on a model grid can be more efficiently calculated... more An ocean flow that has all its scales resolved on a model grid can be more efficiently calculated to within a required accuracy by using high-order numerics than by grid refinement with low-order numerics. The differencing order must be at least as great as the space‐time dimensionality D of the model to ensure that grid refinement reduces truncation error at least as quickly as computational cost increases. Ocean flows often have variability on a wide range of scales that cannot all be resolved on any practical grid. In such circumstances the distribution of variability among the scales determines whether grid refinement or increased order results in the greatest accuracy per unit computational cost. A model that simulates the 25/3 power law of the inertial subrange of three-dimensional turbulence would most efficiently exploit low-order numerics for all terms. The spectra of different terms in the equations of motion can be different and can therefore require different orders of accuracy for efficient computation. Modeling geophysical turbulence with a power law of23 would require high-order numerics for the advective terms but low-order numerics would be sufficient for other terms. Output from several ocean models are observed to have spectra that are sufficiently red to justify using high-order numerics for all terms. In the case of one relatively simple ocean modeling problem the author demonstrates that leading-order terms dominate the truncation error.
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 seconds were usually detected by the receiver array even in fast currents during spring tides but pulse position modulation tags were inadequate. Sometimes very few high residency tag signals were detected when fast tidal currents swept a drifter through the receiver array, so increasing the transmission interval degrades performance at the tidal energy development area. High residency tags suspended close to the sea surface were slightly less likely to be detected if they passed by during calm conditions. Previously measured detection efficiencies were found to slightly overestimate the chances of a high residency tag carried by a drifter being detected as it passed by a receiver. This works elucidates the effectiveness with which acoustically tagged fish are detected in fast, highly turbulent tidal currents and informs the application of detection efficiency measurements to calculate the probability that fish encounter a marine hydrokinetic turbine.
This report provides details of the field studies, experimental results, and an analysis and disc... more This report provides details of the field studies, experimental results, and an analysis and discussion of both dye patch and plume experiments. The time rate of change of variance relative to the centroid for the dye patches and the time rate of change of variance, both relative and absolute, for the dye plumes are presented. For each drogue experiment, results are provided in terms of the time rate of change of the drogue cluster centroid, of the cluster variance and covariance and variance relative to the cluster principal axis, of the cluster rotation and elongation, of diffusivities, of velocity gradients and velocity gradient parameters, i.e., divergence, shear, vorticity, etc., and of the cluster areas both measured and predicted. Rotational invariants (rotary auto spectra and cross spectra) of the current meter records are presented as are mean values of the alongshore and on/offshore components of the current and horizontal and vertical velocity gradients.
Ocean Modelling, 2011
Abstract Many ocean models are primarily concerned with calculating currents of slowly propagatin... more Abstract Many ocean models are primarily concerned with calculating currents of slowly propagating modes that are dynamically associated with buoyancy, Coriolis, field accelerations, and slowly-varying forcing. Calculating such slow modes involves adjustments by the very much faster barotropic mode. In order to minimize the computational cost, two approaches are commonly used. The split-explicit method solves for both fast and slow modes explicitly but with different time steps. The semi-implicit method uses the same time step for fast and slow modes but treats the fast barotropic waves implicitly and the slow modes explicitly. The present work demonstrates a refinement to the semi-implicit method. Weighted Jacobi iterations are used to low-pass filter the fast barotropic mode so that long wavelengths can be treated explicitly. The short-wave part of the fast barotopic mode is still treated implicitly. Damping of the fast barotropic modes is less severe than for the corresponding implicit calculation. Importantly, tests show that a slow internal wave is accurately modelled and the solution is stable, even with the addition of barotropic noise. The method is demonstrated using a three-dimensional model of a lagoon system.
Coastal research library, 2017
The objectives of this chapter are to (1) document lessons learned from the design, implementatio... more The objectives of this chapter are to (1) document lessons learned from the design, implementation and monitoring of a salt marsh restoration in the upper Bay of Fundy, Canada, and (2) consider how the lessons can be applied to future restoration projects. The Fort Beausejour salt marsh restoration sites are exposed to very large tides (up to 14 m), waves, and snow and ice in winter. This project involved a managed re-alignment, with two restoration cells and two reference sites. Before breaching, design criteria were established (e.g., the restoration cells must fully flood at high tide and drain slowly) and a hydrodynamic model was used to test breaching options. Pre-restoration monitoring was completed in 2009–2010, the old dike was breached in October 2010, and post-breach monitoring commenced thereafter. Measurements of water level, velocities, and discharge at one breach, compared very well to model predictions. Likewise, patterns of sediment deposition were as predicted, and sedimentation rates were as expected based on empirical studies done in the area. The bioengineering species saltwater cordgrass (Spartina alterniflora) took 2 years to colonize the cells; it initially spread vegetatively and then by seeds. Plant cover became extensive in year 5 post-breach. Invertebrate and salt pool biological communities are lagging behind. Lessons learned include: (1) plan for future conditions and provide adequate accommodation space for development of a new marsh; (2) multi-level partnerships are critical to the success of such projects; (3) monitoring with a research focus ensures observation and quantification of unexpected phenomena; and (4) the design process used, including the hydrodynamic model, was successful and can be used again for similar situations.
OCEANS '87, 1987
The Lagrangian autocorrelation coefficient, of velocities with the local mean current extracted, ... more The Lagrangian autocorrelation coefficient, of velocities with the local mean current extracted, has e-folding time scales of 15 and 22 hours for the x and y components of motion respectively. Periodicities that might be attributed to either semidiurnal tides or inertial oscillations are evident, as are diurnal periodicities. Local vorticity is typically 5 times greater than local divergence and, apart from the coastal boundary layer, has a magnitude less than 1/5 the Coriolis parameter. This is consistent with quasigeostrophic motion. The variance and covariance of residual velocities vary from one grid to the next. Thus both the mean and residual velocity fields are inhomogeneous. An advection-diffusion model developed by 0kubo et al, (1983) can be used to calculate the uncertainty of iceberg trajectories from velocity gradients and eddy-diffusivities. This gives a good estimate of the uncertainty for periods much greater than the integral time scale.
Semidiurnal tidal currents can exceed 5 ms−1 in Minas Passage, Bay of Fundy, where a tidal energy... more Semidiurnal tidal currents can exceed 5 ms−1 in Minas Passage, Bay of Fundy, where a tidal energy demonstration area has been designated to generate electricity using marine hydrokinetic turbines. The risk of harmful fish-turbine interaction cannot be dismissed for either migratory or local fish populations. Individuals belonging to several fish populations have been acoustically-tagged and monitored by using acoustic receivers moored within Minas Passage. Detection efficiency ρ is required as the first step to estimate probability of fish-turbine encounter. Moored Innovasea HR2 receivers and high residency (HR) tags were used to obtain detection efficiency ρ as a function of range and current speed, for near-seafloor signal paths within the tidal energy development area. Strong tidal currents moved moorings so HR tag signals, and their reflections from the sea surface, were used to measure ranges from tags to receivers. HR2 self-signals that reflected off the sea surface showed whi...
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Papers by Brian Sanderson