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Jim Thomson

Principal Oceanographer

Associate Professor, Civil and Environmental Engineering





Research Interests

Environmental Fluid Mechanics, Ocean Surface Waves, Marine Renewable Energy (tidal and wave), Coastal and Nearshore Processes, Ocean Instrumentation


Dr. Thomson studies waves, currents, and turbulence by combining field observations and remote sensing techniques


B.A. Physics, Middlebury College, 2000

Ph.D. Physical Oceanography, MIT/WHOI, 2006


Inner Shelf Dynamics

The inner shelf region begins just offshore of the surf zone, where breaking by surface gravity waves dominate, and extends inshore of the mid-shelf, where theoretical Ekman transport is fully realized. Our main goal is to provide provide improved understanding and prediction of this difficult environment. This will involve efforts to assess the influence of the different boundaries — surf zone, mid and outer shelf, air-water interface, and bed — on the flow, mixing and stratification of the inner shelf. We will also gain information and predictive understanding of remotely sensed surface processes and their connection to processes in the underlying water column.

15 Dec 2015

Measuring Vessel Wakes in Rich Passage, Puget Sound

APL-UW is using wave buoys to measure the wakes of Washington State DOT car ferries as they transit through Rich Passage. The objective is to assess the effectiveness of the speed reduction protocol through the passage, which is intended to minimize the vessel wake and minimize any subsequent changes to the shoreline.

22 Oct 2014

Tidal Flats

Under an ONR-sponsored Department Research Initiative researchers are studying thermal signatures of inter-tidal sediments. The goal is to understand how sediment properties feedback on morphology and circulation, and the extent to which such properties
can be sensed remotely.


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Marine Renewable Energy: Kvichak River Project

At a renewable energy site in the village of Igiugig, Alaska, an APL-UW and UW Mechanical Engineering team measured the flow around an electricity-generating turbine installed in the Kvichak River. They used modified SWIFT buoys and new technologies to measure the natural river turbulence as well as that produced by the turbine itself. The turbine has the capacity to generate a sizable share of the village's power needs.

25 Sep 2014

Ferry-Based Monitoring of Puget Sound Currents

Acoustic Doppler Current Profilers are installed on two Washington State Department of Transportation ferries to measure current velocities in a continuous transect along their routes. WSDOT ferries occupy strategic cross-sections where circulation and exchange of Puget Sound and Pacific Ocean waters occurs. A long and continuous time series will provide unprecedented measurements of water mass movement and transport between the basins.

9 May 2014

DARLA: Data Assimilation and Remote Sensing for Littoral Applications

Investigators completed a series of experiments in April 2013 at the mouth of the Columbia River, where they collected data using drifting and airborne platforms. DARLA's remote sensing data will be used to drive representations of the wave, circulation, and bathymetry fields in complex near-shore environments.

5 Dec 2013

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Marginal Ice Zone (MIZ) Program

An integrated program of observations and numerical simulations will focus on understanding ice–ocean–atmosphere dynamics in and around the MIZ, with particular emphasis on quantifying changes associated with decreasing ice cover. The MIZ measurement program will employ a novel mix of autonomous technologies (ice-based instrumentation, floats, drifters, and gliders) to characterize the processes that govern Beaufort Sea MIZ evolution from initial breakup and MIZ formation though the course of the summertime sea ice retreat.

22 Mar 2013

Turbulence Generated by Tides in the Canal de Chacao, Chile

At a proposed tidal energy conversion site in southern Chile, APL-UW researchers are measuring the magnitude and scales of turbulence, both to aid in the design of turbines for the site and to understand the fundamental dynamics of flows through the channel.

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7 Mar 2013

Principal Investigator Jim Thomson chronicled all phases of the Chilean experiment through posts to the New York Times 'Scientist at Work' blog.

Sea State and Boundary Layer Physics of the Emerging Arctic Ocean

This ONR Departmental Research Initiative is in response to the observed decline in Arctic sea ice extent. The U.S. Navy has a renewed interest in understanding and predicting the environment in this region, including a desire to forecast the presence or absence of sea ice at a variety of lead times.

7 Mar 2013

Storm Chasing in the North Pacific

A research cruise was conducted in October 2012 to find stormy conditions and heavy seas far out in the Pacific Ocean. The objectives were to measure, with remote sensing technologies, the intense winds, large waves, and the turbulence generated by wave breaking. Understanding the balance of energy going into and breaking out of waves will be used to improve open ocean wave forecasts.

2 Nov 2012

Sound Sounds: Listening to the Undersea Noise in Puget Sound

Doctoral student researcher Chris Bassett is analyzing a long time series of ambient noise data from Puget Sound. Vessel traffic is the most significant noise source, but breaking waves, precipitation, biology, and sediment moving on the seabed are other common underwater noise sources. The research is being pursued in conjunction with a program to assess the environmental impacts from a tidal energy conversion system placed on the seafloor.

13 Mar 2012

SWIFT: Surface Wave Instrument Float with Tracking

The Surface Wave Instrumentation Float with Tracking is a free drifting system to measure turbulence and noise at the ocean surface.

23 Jan 2012

Wave Breaking in Mixed Seas

Waves are generated by wind blowing across the ocean and dissipated by breaking, either as whitecaps or surf. This research aims to understand the breaking process and the resulting turbulence, especially in wave fields that are a mix of wind waves and swell. Measurements from APL-UW SWIFT instruments quantify the turbulence and the wave motions. Additional video measurements quantify the size distribution of the breakers. Applications include improved wave forecasting and parameterization of gas exchange.

12 Apr 2011

Tidal Power from the Seafloor

Researchers are conducting an extensive survey of the oceanographic properties of a proposed tidal energy site in Puget Sound to inform the safety and effectiveness of power-generating turbines.

1 Nov 2010


2000-present and while at APL-UW

Dissipation of wind waves by pancake and frazil ice in the autumn Beaufort Sea

Rogers, W.E., J. Thomson, H.H. Shen, M.J. Doble, P. Wadhams, and S. Cheng, "Dissipation of wind waves by pancake and frazil ice in the autumn Beaufort Sea," J. Geophys. Res., EOR, doi:10.1002/2016JC012251, 2016.

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13 Oct 2016

A model for wind-generated surface gravity waves, WAVEWATCH III®, is used to analyze and interpret buoy measurements of wave spectra. The model is applied to a hindcast of a wave event in sea ice in the western Arctic, October 11–14 2015, for which extensive buoy and ship-borne measurements were made during a research cruise. The model, which uses a viscoelastic parameterization to represent the impact of sea ice on the waves, is found to have good skill — after calibration of the effective viscosity — for prediction of total energy, but over-predicts dissipation of high frequency energy by the sea ice. This shortcoming motivates detailed analysis of the apparent dissipation rate. A new inversion method is applied to yield, for each buoy spectrum, the inferred dissipation rate as a function of wave frequency. For 102 of the measured wave spectra, visual observations of the sea ice were available from buoy-mounted cameras, and ice categories (primarily for varying forms of pancake and frazil ice) are assigned to each based on the photographs. When comparing the inversion-derived dissipation profiles against the independently derived ice categories, there is remarkable correspondence, with clear sorting of dissipation profiles into groups of similar ice type. These profiles are largely monotonic: they do not exhibit the "roll-over" that has been found at high frequencies in some previous observational studies. This article is protected by copyright. All rights reserved.

Stratified Ocean Dynamics in the Arctic: Science and Experiment Plan

Lee, C.M., et al., "Stratified Ocean Dynamics in the Arctic: Science and Experiment Plan," APL-UW TR 1601, Technical Report, Applied Physics Laboratory, University of Washington, Seattle, September 2016, 46pp.

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15 Sep 2016

Vertical and lateral water properties and density structure within the Arctic Ocean are intimately related to the ocean circulation, and have profound consequences for sea ice growth and retreat as well as for propagation of acoustic energy at all scales. Our current understanding of the dynamics governing arctic upper ocean stratification and circulation derives largely from a period when extensive ice cover modulated the oceanic response to atmospheric forcing. Recently, however, there has been significant arctic warming, accompanied by changes in the extent, thickness distribution, and properties of the arctic sea ice cover. The need to understand these changes and their impact on arctic stratification and circulation, sea ice evolution, and the acoustic environment motivate the Office of Naval Research (ONR) Stratified Ocean Dynamics of the Arctic Departmental Research Initiative.

Emerging trends in the sea state of the Beaufort and Chukchi seas

Thomson, J., et al., "Emerging trends in the sea state of the Beaufort and Chukchi seas," Ocean Model., 105, doi:10.1016/j.ocemod.2016.02.009, 2016.

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1 Sep 2016

The sea state of the Beaufort and Chukchi seas is controlled by the wind forcing and the amount of ice-free water available to generate surface waves. Clear trends in the annual duration of the open water season and in the extent of the seasonal sea ice minimum suggest that the sea state should be increasing, independent of changes in the wind forcing. Wave model hindcasts from four selected years spanning recent conditions are consistent with this expectation. In particular, larger waves are more common in years with less summer sea ice and/or a longer open water season, and peak wave periods are generally longer. The increase in wave energy may affect both the coastal zones and the remaining summer ice pack, as well as delay the autumn ice-edge advance. However, trends in the amount of wave energy impinging on the ice-edge are inconclusive, and the associated processes, especially in the autumn period of new ice formation, have yet to be well-described by in situ observations. There is an implicit trend and evidence for increasing wave energy along the coast of northern Alaska, and this coastal signal is corroborated by satellite altimeter estimates of wave energy.

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Spatial characteristics of ocean surface waves

Gemmrich, J., J. Thomson, W.E. Rogers, A. Pleskachevsky, and S. Lehner, "Spatial characteristics of ocean surface waves," Ocean Dyn., 66, 1025-1035, doi:10.1007/s10236-016-0967-6, 2016.

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1 Aug 2016

The spatial variability of open ocean wave fields on scales of O (10 km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III® model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.

On the modeling of wave-enhanced turbulence nearshore

Moghimi, S., J. Thomson, T. Özkan-Haller, L. Umlauf, and S. Zippel, "On the modeling of wave-enhanced turbulence nearshore," Ocean Model., 103, 118-132, doi:10.1016/j.ocemod.2015.11.004, 2016.

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1 Jul 2016

A high resolution k – ω two-equation turbulence closure model, including surface wave forcing was employed to fully resolve turbulence dissipation rate profiles close to the ocean surface. Model results were compared with observations from Surface Wave Instrument Floats with Tracking (SWIFTs) in the nearshore region at New River Inlet, North Carolina USA, in June 2012. A sensitivity analysis for different physical parameters and wave and turbulence formulations was performed. The flux of turbulent kinetic energy (TKE) prescribed by wave dissipation from a numerical wave model was compared with the conventional prescription using the wind friction velocity. A surface roughness length of 0.6 times the significant wave height was proposed, and the flux of TKE was applied at a distance below the mean sea surface that is half of this roughness length. The wave enhanced layer had a total depth that is almost three times the significant wave height. In this layer the non-dimensionalized Terray scaling with power of –1.8 (instead of –2) was applicable.

Wave breaking turbulence in the ocean surface layer

Thomson, J., M.S. Schwendeman, S.F. Zippel, S. Moghimi, J. Gemmrich, and W.E. Rogers, "Wave breaking turbulence in the ocean surface layer," J. Phys. Oceanogr., 46, 1857-1870, doi:10.1175/JPO-D-15-0130.1, 2016.

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1 Jun 2016

Observations of winds, waves, and turbulence at the ocean surface are compared with several analytic formulations and a numerical model for the input of turbulent kinetic energy by wave breaking and the subsequent dissipation. The observations are generally consistent with all of the formulations, although some differences are notable at winds greater than 15 m/s. The depth dependence of the turbulent dissipation rate beneath the waves is fit to a decay scale, which is sensitive to the choice of vertical reference frame. In the surface following reference frame, the strongest turbulence is isolated within a shallow region of depths much less than one significant wave height. In a fixed reference frame, the strong turbulence penetrates to depths that are at least half of the significant wave height. This occurs because the turbulence of individual breakers persists longer that the dominant period of the waves, and thus the strong surface turbulence is carried from crest to trough with the wave orbital motion.

Scaling observations of surface waves in the Beaufort Sea

Smith, M., and J. Thomson, "Scaling observations of surface waves in the Beaufort Sea," Elem. Sci. Anth., 4, 000097, doi:10.12952/journal.elementa.000097, 2016.

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14 Apr 2016

The rapidly changing Arctic sea ice cover affects surface wave growth across all scales. Here, in situ measurements of waves, observed from freely-drifting buoys during the 2014 open water season, are interpreted using open water distances determined from satellite ice products and wind forcing time series measured in situ with the buoys. A significant portion of the wave observations were found to be limited by open water distance (fetch) when the wind duration was sufficient for the conditions to be considered stationary. The scaling of wave energy and frequency with open water distance demonstrated the indirect effects of ice cover on regional wave evolution. Waves in partial ice cover could be similarly categorized as distance-limited by applying the same open water scaling to determine an ‘effective fetch’. The process of local wave generation in ice appeared to be a strong function of the ice concentration, wherein the ice cover severely reduces the effective fetch. The wave field in the Beaufort Sea is thus a function of the sea ice both locally, where wave growth primarily occurs in the open water between floes, and regionally, where the ice edge may provide a more classic fetch limitation. Observations of waves in recent years may be indicative of an emerging trend in the Arctic Ocean, where we will observe increasing wave energy with decreasing sea ice extent.

Air–sea interactions in the marginal ice zone

Zippel, S., and J. Thomson, "Air–sea interactions in the marginal ice zone," Elem. Sci. Anth., 4, 000095, doi:10.12952/journal.elementa.000095, 2016.

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31 Mar 2016

The importance of waves in the Arctic Ocean has increased with the significant retreat of the seasonal sea-ice extent. Here, we use wind, wave, turbulence, and ice measurements to evaluate the response of the ocean surface to a given wind stress within the marginal ice zone, with a focus on the local wind input to waves and subsequent ocean surface turbulence. Observations are from the Beaufort Sea in the summer and early fall of 2014, with fractional ice cover of up to 50%. Observations showed strong damping and scattering of short waves, which, in turn, decreased the wind energy input to waves. Near-surface turbulent dissipation rates were also greatly reduced in partial ice cover. The reductions in waves and turbulence were balanced, suggesting that a wind-wave equilibrium is maintained in the marginal ice zone, though at levels much less than in open water. These results suggest that air-sea interactions are suppressed in the marginal ice zone relative to open ocean conditions at a given wind forcing, and this suppression may act as a feedback mechanism in expanding a persistent marginal ice zone throughout the Arctic.

Wind and wave influences on sea ice floe size and leads in the Beaufort and Chukchi seas during the summer-fall transition 2014

Wang, Y., B. Holt, W.E. Rogers, J. Thomson, and H.H. Shen, "Wind and wave influences on sea ice floe size and leads in the Beaufort and Chukchi seas during the summer-fall transition 2014," J. Geophys. Res., 121, 1502-1525, doi:10.1002/2015JC011349, 2016.

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20 Feb 2016

Sea ice floe size distribution and lead properties in the Beaufort and Chukchi Seas are studied in the summer-fall transition 2014 to examine the impact on the sea ice cover from storms and surface waves. Floe size distributions are analyzed from MEDEA, Landsat8, and RADARSAT-2 imagery, with a resolution span of 1–100 m. Landsat8 imagery is also used to identify the orientation and spacing of leads. The study period centers around three large wave events during August–September 2014 identified by SWIFT buoys and WAVEWATCH III model data. The range of floe sizes from different resolutions provides the overall distribution across a wide range of ice properties and estimated thickness. All cumulative floe size distribution curves show a gradual bending toward shallower slopes for smaller floe sizes. The overall slopes in the cumulative floe size distribution curves from Landsat8 images are lower than, while those from RADARSAT-2 are similar to, previously reported results in the same region and seasonal period. The MEDEA floe size distributions appeared to be sensitive to the passage of storms. Lead orientations, regardless of length, correlate slightly better with the peak wave direction than with the mean wave direction. Their correlation with the geostrophic wind is stronger than with the surface wind. The spacing between shorter leads correlates well with the local incoming surface wavelengths, obtained from the model peak wave frequency. The information derived shows promise for a coordinated multisensor study of storm effects in the Arctic marginal ice zone.

Observations of whitecap coverage and the relation to wind stress, wave slope, and turbulent dissipation

M. Schwendeman, and J. Thomson, "Observations of whitecap coverage and the relation to wind stress, wave slope, and turbulent dissipation," J. Geophys. Res., 120, 8346-8363, doi:10.1002/2015JC011196, 2015.

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28 Dec 2015

Shipboard measurements of whitecap coverage are presented from two cruises in the North Pacific, and compared with in situ measurements of wind speed and friction velocity, average wave steepness, and near-surface turbulent dissipation. A threshold power law fit is proposed for all variables, which incorporates the flexibility of a power law with the threshold behavior commonly seen in whitecapping. The fit of whitecap coverage to wind speed, U10, closely matches similar relations from three recent studies, particularly in the range of 6–14 m/s. At higher wind speeds, the whitecap coverage data level off relative to the fits, and an analysis of the residuals shows some evidence of reduced whitecapping in rapidly developing waves. Wave slope variables are examined for potential improvement over wind speed parameterizations. Of these variables, the mean square slope of the equilibrium range waves has the best statistics, which are further improved after normalizing by the directional spread and frequency bandwidth. Finally, the whitecap coverage is compared to measurements of turbulent dissipation. Though still statistically significant, the correlation is worse than the wind or wave relations, and residuals show a strong negative trend with wave age. This may be due to an increased influence of microbreaking in older wind seas.

Observations of whitecap coverage and the relation to wind stress, wave slope, and turbulent dissipation

Schwendeman, M., and J. Thomson, "Observations of whitecap coverage and the relation to wind stress, wave slope, and turbulent dissipation," J. Geophys. Res., 120, 8346-8363, doi:10.1002/2015JC011196, 2015.

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28 Dec 2015

Shipboard measurements of whitecap coverage are presented from two cruises in the North Pacific, and compared with in situ measurements of wind speed and friction velocity, average wave steepness, and near-surface turbulent dissipation. A threshold power law fit is proposed for all variables, which incorporates the flexibility of a power law with the threshold behavior commonly seen in whitecapping. The fit of whitecap coverage to wind speed, U10, closely matches similar relations from three recent studies, particularly in the range of 6–14 m/s. At higher wind speeds, the whitecap coverage data level off relative to the fits, and an analysis of the residuals shows some evidence of reduced whitecapping in rapidly developing waves. Wave slope variables are examined for potential improvement over wind speed parameterizations. Of these variables, the mean square slope of the equilibrium range waves has the best statistics, which are further improved after normalizing by the directional spread and frequency bandwidth. Finally, the whitecap coverage is compared to measurements of turbulent dissipation. Though still statistically significant, the correlation is worse than the wind or wave relations, and residuals show a strong negative trend with wave age. This may be due to an increased influence of microbreaking in older wind seas.

Biofouling effects on the response of a wave measurement buoy in deep water

Thomson, J., J. Talbert, A. de Klerk, A. Brown, M. Schwendeman, J. Goldsmith, J. Thomas, C. Olfe, G. Cameron, and C. Meinig, "Biofouling effects on the response of a wave measurement buoy in deep water," J. Atmos. Ocean. Technol., 32, 1281-1286, doi:10.1175/JTECH-D-15-0029.1, 2015.

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1 Jun 2015

The effects of biofouling on a wave measurement buoy are examined using concurrent data collected with two Datawell Waveriders at Ocean Station P: one heavily biofouled at the end of a 26-month deployment, the other newly deployed and clean. The effects are limited to the high-frequency response of the buoy and are correctly diagnosed with the spectral "check factors" that compare horizontal and vertical displacements. A simple prediction for the progressive change in frequency response during biofouling reproduces the check factors over time. The bulk statistical parameters of significant wave height, peak period, average period, and peak direction are only slightly affected by the biofouling because the contaminated frequencies have very low energy throughout the comparison dataset.

Estimating wave energy dissipation in the surf zone using thermal infrared imagery

Carini, R.J. C.C. Chickadel, A.T. Jessup, and J. Thomson, "Estimating wave energy dissipation in the surf zone using thermal infrared imagery," J. Geophys. Res., 120, 3937-3957, doi:10.1002/2014JC010561, 2015.

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1 Jun 2015

Thermal infrared (IR) imagery is used to quantify the high spatial and temporal variability of dissipation due to wave breaking in the surf zone. The foam produced in an actively breaking crest, or wave roller, has a distinct signature in IR imagery. A retrieval algorithm is developed to detect breaking waves and extract wave roller length using measurements taken during the Surf Zone Optics 2010 experiment at Duck, NC. The remotely derived roller length and an in situ estimate of wave slope are used to estimate dissipation due to wave breaking by means of the wave-resolving model by Duncan (1981). The wave energy dissipation rate estimates show a pattern of increased breaking during low tide over a sand bar, consistent with in situ turbulent kinetic energy dissipation rate estimates from fixed and drifting instruments over the bar. When integrated over the surf zone width, these dissipation rate estimates account for 40–69% of the incoming wave energy flux. The Duncan (1981) estimates agree with those from a dissipation parameterization by Janssen and Battjes (2007), a wave energy dissipation model commonly applied within nearshore circulation models.

Characterization of turbulence anisotropy, coherence, and intermittency at a prospective tidal energy site: Observational data analysis

McCaffrey, K., B. Fox-Kemper, P.E. Hamlington, and J. Thomson, "Characterization of turbulence anisotropy, coherence, and intermittency at a prospective tidal energy site: Observational data analysis," Renewable Energy, 76, 441-453, doi:10.1016/j.renene.2014.11.063, 2015.

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1 Apr 2015

As interest in marine renewable energy increases, observations are crucial for understanding the environments that prospective turbines will encounter. Data from an acoustic Doppler velocimeter in Puget Sound, WA are used to perform a detailed characterization of the turbulent flow encountered by a turbine in a tidal strait. Metrics such as turbulence intensity, structure functions, probability density functions, intermittency, coherent turbulence kinetic energy, anisotropy invariants, and a new scalar measure of anisotropy are used to characterize the turbulence. The results indicate that the scalar anisotropy magnitude can be used to identify and parameterize coherent, turbulent events in the flow. An analysis of the anisotropy characteristics leads to a physical description of turbulent stresses as being primarily one- or two-dimensional, in contrast to isotropic, three-dimensional turbulence. A new measure of the anisotropy magnitude is introduced to quantify the level of anisotropic, coherent turbulence in a coordinate-independent way. These diagnostics and results will be useful for improved realism in modeling the performance and loading of turbines in realistic ocean environments.

Turbulence measurements from moving platforms

Thomson, J., J. Talbert, A. de Klerk, S. Zippel, M. Guerra, and L. Kilcher, "Turbulence measurements from moving platforms," Proc. 11th IEEE/OES Current, Waves and Turbulence Measurement (CWTM) Workshop, 2-6 March, St. Petersburg, FL, doi:10.1109/CWTM.2015.7098107 (IEEE, 2015).

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2 Mar 2015

Two recent methods for making high-fidelity turbulence measurements from moving platforms are described and demonstrated. The first is a method for measuring profiles of near-surface turbulence from a wave-following 'SWIFT' buoy. The second is a method for measuring time series of turbulence from a submerged compliant mooring. Both approaches use coherent Doppler instruments and inertial motion units (IMUs). In the buoy method, wave motions (e.g., pitch, roll, and heave) are quantified via GPS and IMU measurements. These wave motions are not present in the turbulence observations, because buoy follows the wave orbital motion, and thus the turbulent velocities are processed in the wave-following reference frame. In the mooring method, IMU measurements track the mooring motions (e.g., strum and kiting) and these motions are removed in post-processing to obtain turbulent velocities in the fixed earth reference frame. These approaches successfully quantify turbulence in regions previously unavailable or limited by the noise and spatial aliasing of sampling from bottom-mounted platforms.

Wave breaking and turbulence at a tidal inlet

Zippel, S., and J. Thomson, "Wave breaking and turbulence at a tidal inlet," J. Geophys. Res., 120, 1016-1031, doi:10.1002/2014JC010025, 2015.

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1 Feb 2015

Field measurements collected with surface drifters at New River Inlet (NC, USA) are used to characterize wave breaking and turbulence in the presence of currents. Shoreward wave evolution is affected by currents, and breaking is observed in deeper water with opposing currents (ebb tides) relative to the following currents (flood tides). Wave dissipation models are evaluated with observed cross-shore gradients in wave energy flux. Wave dissipation models that include the effects of currents are better correlated with the observations than the depth-only models. Turbulent dissipation rates measured in the breaking regions are used to evaluate two existing scaling models for the vertical structure and magnitude of turbulent dissipation relative to wave dissipation. Although both describe the rapid decay of turbulence beneath the surface, exponential vertical scaling by water depth is superior to power law vertical scaling by wave height.

A horizon-tracking method for shipboard video stabilization and rectification

Schwendeman, M., and J. Thomson, "A horizon-tracking method for shipboard video stabilization and rectification," J. Atmos. Ocean. Technol., 32, 164-176, doi:10.1175/JTECH-D-14-00047.1, 2015.

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1 Jan 2015

An algorithm is presented for the stabilization and rectification of digital video from floating platforms. The method relies on a horizon-tracking technique that was tested under a variety of lighting and sea-state conditions for 48 h of video data over 12 days during a research cruise in the North Pacific Ocean. In this dataset, the horizon was correctly labeled in 92% of the frames in which it was present. The idealized camera model assumes pure pitch-and-roll motion, a flat sea surface, and an unobstructed horizon line. Pitch and roll are defined along the camera look direction rather than in traditional ship coordinates, such that the method can be used for any heading relative to the ship. The uncertainty in pitch and roll is estimated from the uncertainties of the horizon-finding method. These errors are found to be of the order 0.6° in roll and 0.3° in pitch. Errors in rectification are shown to be dominated by the uncertainty in camera height, which may change with the heave motion of a floating platform. The propagation of these errors is demonstrated for the breaking-wave distribution Λ(c). A toolbox for implementation of this method in MATLAB is shared via the MATLAB File Exchange.

Wave breaking turbulence at the offshore front of the Columbia River Plume

Thomson, J., A.R. Horner-Devine, S. Zippel, C. Rusch, and W. Geyer, "Wave breaking turbulence at the offshore front of the Columbia River Plume," Geophys. Res. Lett., 41, 8987-8993, doi:10.1002/2014GL062274, 2014.

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28 Dec 2014

Observations at the Columbia River plume show that wave breaking is an important source of turbulence at the offshore front, which may contribute to plume mixing. The lateral gradient of current associated with the plume front is sufficient to block (and break) shorter waves. The intense whitecapping that then occurs at the front is a significant source of turbulence, which diffuses downward from the surface according to a scaling determined by the wave height and the gradient of wave energy flux. This process is distinct from the shear-driven mixing that occurs at the interface of river water and ocean water. Observations with and without short waves are examined, especially in two cases in which the background conditions (i.e., tidal flows and river discharge) are otherwise identical.

Historical Wave and Wind Observations at Ocean Station P

Belka, D.J., M. Schwendeman, J. Thomson, and M.F. Cronin, "Historical Wave and Wind Observations at Ocean Station P," Technical Report, APL-UW TR 1407, Applied Physics Laboratory, University of Washington, Seattle, August 2014, 15 pp.

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1 Aug 2014

An historical data set with 30 years of wave and wind observations from Ocean Weather Station P (50°N, 145°W) is described and validated against modern measurements. Observation biases are discussed and corrections are made where appropriate. Climate trends are explored, including a negative correlation between waves and the Pacific Decadal Oscillation. The validated historical data are deposited in a public archive with online access.

Video recognition of breaking waves

Rusch, C., J. Thomson, S. Zippel, and M. Schwendeman, "Video recognition of breaking waves," Proc., OCEANS'14, 14-19 September, St. John's, Newfoundland (MTS/IEEE, 2014).

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15 Jul 2014

An algorithm is presented to automate the identification of breaking waves in images collected with a camera on a drifting buoy. Each image is given a score from four separate analysis techniques: brightness detection, pixel histogram, entropy (texture) analysis, and glare identification. By combining these in a composite score, potential breaking wave images are detected and the number of images requiring manual review is a small fraction of the original set. Most of the images with false breaking wave signals due to sun glare are identified and removed. The final output is the wave-breaking rate over the length of the video capture.

Noise correction of turbulent spectra obtained from acoustic Doppler velocimeters

Durgesh, V., J. Thomson, M. Richmond, and B. Polagye, "Noise correction of turbulent spectra obtained from acoustic Doppler velocimeters," Flow Meas. Instrum., 37, 29-41, doi:10.1016/j.flowmeasinst.2014.03.001, 2014.

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1 Jun 2014

Velocity spectra are essential in characterizing turbulent flows. The Acoustic Doppler Velocimeter (ADV) provides three-dimensional time series data at a single point in space which are used for calculating velocity spectra. However, ADV data are susceptible to contamination from various sources, including instrument noise, which is the intrinsic limit to the accuracy of acoustic Doppler processing. This contamination results in a flattening of the velocity spectra at high frequencies (O(10)Hz).

This paper demonstrates two elementary methods for attenuating instrument noise and improving velocity spectra. First, a "Noise Auto-Correlation" (NAC) approach utilizes the correlation and spectral properties of instrument noise to identify and attenuate the noise in the spectra. Second, a Proper Orthogonal Decomposition (POD) approach utilizes a modal decomposition of the data and attenuates the instrument noise by neglecting the higher-order modes in a time-series reconstruction. The methods are applied to ADV data collected in a tidal channel with maximum horizontal mean currents up to 2 m/s. The spectra estimated using both approaches exhibit an f-5/3 slope, consistent with a turbulent inertial sub-range, over a wider frequency range than the raw spectra. In contrast, a Gaussian filter approach yields spectra with a sharp decrease at high frequencies.

In an example application, the extended inertial sub-range from the NAC method increased the confidence in estimating the turbulent dissipation rate, which requires fitting the amplitude of the f-5/3 region. The resulting dissipation rates have smaller uncertainties and are more consistent with an assumed local balance to shear production, especially for mean horizontal currents less than 0.8 m/s.

Swell and sea in the emerging Arctic Ocean

Thomson, J., and W.E. Rogers, "Swell and sea in the emerging Arctic Ocean," Geophys. Res. Lett., 41, 3136-3140, doi:10.1002/2014GL059983, 2014.

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16 May 2014

Ocean surface waves (sea and swell) are generated by winds blowing over a distance (fetch) for a duration of time. In the Arctic Ocean, fetch varies seasonally from essentially zero in winter to hundreds of kilometers in recent summers. Using in situ observations of waves in the central Beaufort Sea, combined with a numerical wave model and satellite sea ice observations, we show that wave energy scales with fetch throughout the seasonal ice cycle. Furthermore, we show that the increased open water of 2012 allowed waves to develop beyond pure wind seas and evolve into swells. The swells remain tied to the available fetch, however, because fetch is a proxy for the basin size in which the wave evolution occurs. Thus, both sea and swell depend on the open water fetch in the Arctic, because the swell is regionally driven. This suggests that further reductions in seasonal ice cover in the future will result in larger waves, which in turn provide a mechanism to break up sea ice and accelerate ice retreat.

Observations and modeling of heat fluxes on tidal flats

Rinehimer, J.P., and J. Thomson, "Observations and modeling of heat fluxes on tidal flats," J. Geophys. Res.,119, 133-146, doi:10.1002/2013JC009225, 2014.

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1 Jan 2014

A cross-shore model of tidal flat heat and mass fluxes is developed to understand the heat exchange between the sediment bed and the water column. A convective heat-transfer coefficient is used to model sediment-water heat fluxes which are as great as 20% of the incoming solar shortwave radiation. The model results match well with observations and are used to assess processes accross tidal to seasonal timescales. During the summer, tidal flat sediments store incoming shortwave radiation during exposure and act effectively as a net source of heat to the water column. This pattern changes in the winter, when the flats cool during exposure and act effectively as a net sink of heat. Additionally, during the summer water temperatures at the edge of the flooding front are elevated 5°C above the surface sediment temperatures. Model results replicate this process only when water column light extinction coefficients are high, consistent with visual observations of high turbidity (and thus high light absorption) at the leading edge of the flooding front.

Quantifying upper ocean turbulence driven by surface waves

D'Asaro, E.A., J. Thomson, A.Y. Shcherbina, R.R. Harcourt, M.F. Cronin, M.A. Hemer, and B. Fox-Kemper, "Quantifying upper ocean turbulence driven by surface waves," Geophys. Res. Lett, 41, 102-107, doi:10.1002/1013GL058193, 2014.

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1 Jan 2014

Nearly all operational ocean models use air-sea fluxes and the ocean shear and stratification to estimate upper ocean boundary layer mixing rates. This approach implicitly parameterizes surface wave effects in terms of these inputs. Here, we test this assumption using parallel experiments in a lake with small waves and in the open ocean with much bigger waves. Under the same wind stress and adjusting for buoyancy flux, we find the mixed layer average turbulent vertical kinetic energy in the open ocean typically twice that in the lake. The increase is consistent with models of Langmuir turbulence, in which the wave Stokes drift, and not wave breaking, is the dominant mechanism by which waves energize turbulence in the mixed layer. Applying these same theories globally, we find enhanced mixing and deeper mixed layers resulting from the inclusion of Langmuir turbulence in the boundary layer parameterization, especially in the Southern Ocean.

Wave breaking dissipation in a young wind sea

Schwendeman, M., J. Thomson, and J. Gemmrich, "Wave breaking dissipation in a young wind sea," J. Phys. Oceanogr., 44, 104-127, doi: 10.1175/JPO-D-12-0237.1, 2014.

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1 Jan 2014

Coupled in situ and remote sensing measurements of young, strongly forced wind waves are applied to assess the role of breaking in an evolving wave field. In situ measurements of turbulent energy dissipation from wave-following Surface Wave Instrument Float with Tracking (SWIFT) drifters and a tethered acoustic Doppler sonar system are consistent with wave evolution and wind input (as estimated using the radiative transfer equation).

The Phillips breaking crest distribution Λ(c) is calculated using stabilized shipboard video recordings and the Fourier-based method of Thomson and Jessup, with minor modifications. The resulting Λ(c) are unimodal distributions centered around half of the phase speed of the dominant waves, consistent with several recent studies. Breaking rates from Λ(c) increase with slope, similar to in situ dissipation. However, comparison of the breaking rate estimates from the shipboard video recordings with the SWIFT video recordings show that the breaking rate is likely underestimated in the shipboard video when wave conditions are calmer and breaking crests are small. The breaking strength parameter b is calculated by comparison of the fifth moment of Λ(c) with the measured dissipation rates. Neglecting recordings with inconsistent breaking rates, the resulting b data do not display any clear trends and are in the range of other reported values. The Λ(c) distributions are compared with the Phillips equilibrium range prediction and previous laboratory and field studies, leading to the identification of several inconsistencies.

Inference of turbulence parameters from a ROMS simulation using the k–ε closure scheme

Thyng, K.M., J.J. Riley, and J. Thomson, "Inference of turbulence parameters from a ROMS simulation using the k–ε closure scheme," Ocean Model., 72, 104-118, doi:10.1016/j.ocemod.2013.08.008, 2013.

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1 Dec 2013

Comparisons between high resolution turbulence data from Admiralty Inlet, WA (USA), and a 65-meter horizontal grid resolution simulation using the hydrostatic ocean modelling code, Regional Ocean Modeling System (ROMS), show that the model's k–ε turbulence closure scheme performs reasonably well. Turbulent dissipation rates and Reynolds stresses agree within a factor of two, on average. Turbulent kinetic energy (TKE) also agrees within a factor of two, but only for motions within the observed inertial sub-range of frequencies (i.e., classic approximately isotropic turbulence). TKE spectra from the observations indicate that there is significant energy at lower frequencies than the inertial sub-range; these scales are not captured by the model closure scheme nor the model grid resolution. To account for scales not present in the model, the inertial sub-range is extrapolated to lower frequencies and then integrated to obtain an inferred, diagnostic total TKE, with improved agreement with the observed total TKE. The realistic behavior of the dissipation rate and Reynolds stress, combined with the adjusted total TKE, imply that ROMS simulations can be used to understand and predict spatial and temporal variations in turbulence. The results are suggested for application to siting tidal current turbines.

Method for identification of Doppler noise levels in turbulent flow measurements dedicated to tidal energy

Richard, J-.B., J. Thomson, B. Polagye, and J. Bard, "Method for identification of Doppler noise levels in turbulent flow measurements dedicated to tidal energy," Int. J. Mar. Energy, 3-4, 52-64, doi:10.1016/j.ijome.2013.11.005, 2013.

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1 Dec 2013

Acoustic Doppler sensors used for flow measurements at energetic tidal sites present an inherent "Doppler noise" in the measured signal, varying with hardware configuration and flow conditions. At scales comparable to the sensors' sampling frequencies, the corresponding perturbations notably contaminate the signal, and cannot be corrected in the time series.

At such scales, dynamic phenomena are of particular interest in the process of increasing reliability and effectiveness of tidal turbines, and are mostly addressed in terms of statistics. In the case of inflow speed variations, the bias due to Doppler noise should be taken into account, and can be assessed via manufacturer specifications.

Here, a method is presented that enables a direct estimation of the Doppler noise strength from the measured signal itself. Inspired from polynomial least square regression, it is based on a spectral analysis of the measured signal respect to turbulence theory, under the hypothesis of a white Doppler noise contamination. The subsequent limitations are discussed and illustrated by practical cases.

The values found are generally higher than suggested by manufacturers, but still in the same order of magnitude. The use of the highest sampling frequency available is recommended.

Waves and the equilibrium range at Ocean Weather Station P

Thomson, J., E.A. D'Asaro, M.F. Cronin, W.E. Rogers, R.R. Harcourt, and A. Shcherbina, "Waves and the equilibrium range at Ocean Weather Station P," J. Geophys. Res., 118, 5951-5962, doi:10.1002/2013JC008837, 2013.

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1 Nov 2013

Wave and wind measurements at Ocean Weather Station P (OWS-P, 50°N 145°W) are used to evaluate the equilibrium range of surface wave energy spectra. Observations are consistent with a local balance between wind input and breaking dissipation, as described by Philips (1985). The measurements include direct covariance wind stress estimates and wave breaking dissipation rate estimates during a 3 week research cruise to OWS-P. The analysis is extended to a wider range of conditions using observations of wave energy spectra and wind speed during a 2 year mooring deployment at OWS-P. At moderate wind speeds (5–15 m/s), mooring wave spectra are in agreement, within 5% uncertainty, with the forcing implied by standard drag laws and mooring wind measurements. At high wind speeds (>15 m/s), mooring wave spectra are biased low, by 13%, relative to the forcing implied by standard drag laws and mooring wind measurements. Deviations from equilibrium are associated with directionality and variations at the swell frequencies. A spectral wave hindcast accurately reproduces the mooring observations, and is used to examine the wind input.

Sea State and Boundary Layer Physics of the Emerging Arctic Ocean: Science Plan

Thomson, J., et al., "Sea State and Boundary Layer Physics of the Emerging Arctic Ocean: Science Plan," Technical Report, APL-UW TR1306, Applied Physics Laboratory, University of Washington, Seattle, September 2013, 59 pp.

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16 Sep 2013

The Office of Naval Research initiated a Department Research Initiative (DRI) titled Sea State and Boundary Layer Physics of the Emerging Arctic Ocean. The central hypothesis of the "Sea State" DRI is that surface waves now have a much greater role in the contemporary Arctic Ocean. Indeed, the entire Arctic Ocean in summer may soon resemble a marginal ice zone (MIZ), where waves propagate through the ice pack and affect the evolution of sea ice over large scales.

The Sea State DRI will use a combination of modeling, in situ observations, and remote sensing to address the following science objectives:

  - Develop a sea state climatology for the Arctic Ocean
  - Improve wave forecasting in the presence of sea ice
  - Improve theory of wave attenuation/scattering in the sea ice cover
  - Apply wave–ice interactions directly in integrated arctic system models
  - Understand heat and mass fluxes in the air–sea–ice system

The DRI will focus on arctic conditions during the late summer and early autumn, especially the freeze-up of the Beaufort and Chukchi seas, to capture the strongest storms and maximum open water. This focus also complements the Marginal Ice Zone DRI (MIZ-DRI) that is studying the summer breakup and ice retreat. Field observations will be collected primarily during a cruise in the fall of 2015, supplemented by long-term moorings and autonomous platforms.

This Science Plan presents the overall goals and approach of the Sea State DRI. Individual contributions are noted, but the focus is on an integrated vision of the science. Although many of the details will necessarily evolve during the five-year program (2013–2017), it is expected that the priorities defined herein will continue to guide the science that is carried out.

An Evaluation of the U.S. Department of Energy's Marine and Hydrokinetic Resource Assessments

Marine and Hydrokinetic Energy Technology Assessment Committee (including J. Thomson); Board on Energy and Environmental Systems; Division on Engineering and Physical Sciences; Ocean Studies Board; Division on Earth and Life Sciences; National Research Council, "An Evaluation of the U.S. Department of Energy's Marine and Hydrokinetic Resource Assessments," Washington, D.C.: The National Academies Press, 2013, 154 pp.

1 Sep 2013

Resource mapping at tidal energy sites

Palodichuk, M., B. Polagye, and J. Thomson, "Resource mapping at tidal energy sites," IEEE J. Ocean. Eng., 38, 433-446, doi:10.1109/JOE.2012.2227578, 2013.

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1 Jul 2013

Station keeping, a vessel-based spatial surveying method for resolving details of the hydrokinetic resource, is presented in the context of the general methodology and also for the specific case of a survey conducted in northern Admiralty Inlet, Puget Sound, WA, in June 2011. The acoustic Doppler current profiler (ADCP) measurements collected during the June 2011 survey were part of a broader effort to characterize the resource at this location before tidal turbine installation. Autonomous bottom-lander (bottom-mounted) ADCP measurements are used to evaluate the accuracy with which data collected from this vessel-based survey reflect stationary measurements and also to analyze the potential for cycle-to-cycle variations in the conclusions drawn. Results indicate good agreement between shipboard and bottom-mounted observations in capturing spatial resource differences. Repeated surveys over several tidal cycles are required to obtain results consistent with long-term observations. Station-keeping surveys help to optimize bottom-mounted ADCP deployments that are then used to estimate turbine power generation potential and make final siting decisions.

Thermal observations of drainage from a mud flat

Rinehimer, J. P., J. Thomson, and C.C. Chickadel, "Thermal observations of drainage from a mud flat," Cont. Shelf. Res., 60, S125-S135, doi:10.1016/j.csr.2012.11.001, 2013.

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15 Jun 2013

Incised channels on tidal flats create a complex flow network conveying water on and off the flat during the tidal cycle. In situ and remotely sensed field observations of water drainage and temperature in a secondary channel on a muddy tidal flat in Willapa Bay, Washington (USA) are presented and a novel technique, employing infrared imagery, is used to estimate surface velocities when the water depth in the channel becomes too shallow for ADCP measurements, i.e., less than 10 cm. Two distinct dynamic regimes are apparent in the resulting observations: ebb-tidal flow and the post-ebb discharge period. Ebb tide velocities result from the surface slope associated with the receding tidal elevation whereas the post-ebb discharge continues throughout the low tide period and obeys uniform open-channel flow dynamics. Volume transport calculations and a model of post-ebb runoff temperatures support the hypothesis that remnant water on the flats is the source of the post-ebb discharge.

Sediment-generated noise and bed stress in a tidal channel

Bassett, C., J. Thomson, and B. Polagye, "Sediment-generated noise and bed stress in a tidal channel," J. Geophys. Res., 118, 2249-2265, doi:10.1002/jgrc.20169, 2013.

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30 Apr 2013

Tidally driven currents and bed stresses can result in noise generated by moving sediments. At a site in Admiralty Inlet, Puget Sound, Washington State (USA), peak bed stresses exceed 20 Pa. Significant increases in noise levels are attributed to mobilized sediments at frequencies from 4–30 kHz with more modest increases noted from 1–4 kHz. Sediment-generated noise during strong currents masks background noise from other sources, including vessel traffic. Inversions of the acoustic spectra for equivalent grain sizes are consistent with qualitative data of the seabed composition. Bed stress calculations using log layer, Reynolds stress, and inertial dissipation techniques generally agree well and are used to estimate the shear stresses at which noise levels increase for different grain sizes. Regressions of the acoustic intensity versus near-bed hydrodynamic power demonstrate that noise levels are highly predictable above a critical threshold despite the scatter introduced by the localized nature of mobilization events.

Implications of tidal phasing for power generation at a tidal energy site

Polagye, B., and J. Thomson, "Implications of tidal phasing for power generation at a tidal energy site," in Proc., 1st Marine Energy Technology Symposium, MET13, 10-11 April, Washington, D.C., 2013.

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10 Apr 2013

Spatial resource gradients have been observed at a number of proposed tidal energy sites. However, these gradients are typically quantified using the first or second moments (i.e., mean or standard deviation) of time series which obscures information about the co%u2010temporal amplitude and phase variation. These co%u2010temporal variations have a number of interesting implications for power production from arrays of tidal turbines. Here, co%u2010temporal time series data from several locations in northern Admiralty Inlet, Puget Sound, Washington (USA) are used to investigate phase variations in kinetic power density over length scales of less than 5 km. Results demonstrate that large phase variations in kinetic power density are routinely produced by phase variations in the harmonic and aharmonic currents. However, exploiting these phase variations in a way that reduces power generation intermittency requires that locations which are out of phase have similar mean kinetic power density and intermittency. Further investigation of local phasing at tidal energy sites of commercial interest is recommended.

Low-cost ultility-scale wave energy enabled by magnetostriction

Nair, B., R. Shendure, J. Nachlas, A. Gill, Z. Murphree, J. Campbell, V. Challa, J. Thomson, J. Talbert, A. De Klerk, and C. Rusch, "Low-cost ultility-scale wave energy enabled by magnetostriction," Proc., 1st Marine Energy Technology Symposium, METS13, 10-11 April, Washington, D.C., 2013.

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10 Apr 2013

Oscilla Power, Inc. (OPI) is developing a patented magnetostrictive wave energy harvester (MWEH) that could enable the disruptively low-cost production of grid-scale electricity from ocean waves, a large-scale resource that is more predictable and more proximal to demand growth than solar or wind. Designed to operate cost-effectively across a wide range of wave conditions, the MWEH will be the first use of reverse magnetostriction for large-scale energy production.

Tidal turbulence spectra from a compliant mooring

Thomson, J., L. Kilcher, M. Richmond, J. Talbert, A. deKlerk, B. Polagye, M. Guerra, and R. Cienfuegos, "Tidal turbulence spectra from a compliant mooring," Proc., 1st Marine Energy Technology Symposium, METS2013, 10-11 April, Washington, D.C., 2013.

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10 Apr 2013

A compliant mooring to collect high frequency turbulence data at a tidal energy site is evaluated in a series of short demonstration deployments. The Tidal Turbulence Mooring (TTM) improves upon recent bottom-mounted approaches by suspending Acoustic Doppler Velocimeters (ADVs) at mid-water depths (which are more relevant to tidal turbines). The ADV turbulence data are superior to Acoustic Doppler Current Profiler (ADCP) data, but are subject to motion contamination when suspended on a mooring in strong currents. In this demonstration, passive stabilization is shown to be sufficient for acquiring bulk statistics of the turbulence, without motion correction. With motion correction (post-processing), data quality is further improved. Results from two field sites are compared, and the differences are attributed to the generation of large eddies by headlands and sills.

A vessel noise budget for Admiralty Inlet, Puget Sound, Washington (USA)

Bassett, C., B. Polagye, M. Holt, and J. Thomson, "A vessel noise budget for Admiralty Inlet, Puget Sound, Washington (USA)," J. Acoust. Soc. Am., 132, 3706-3719, doi:10.1121/1.4763548, 2012.

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1 Dec 2012

One calendar year of Automatic Identification System (AIS) ship-traffic data was paired with hydrophone recordings to assess ambient noise in northern Admiralty Inlet, Puget Sound, WA (USA) and to quantify the contribution of vessel traffic. The study region included inland waters of the Salish Sea within a 20 km radius of the hydrophone deployment site. Spectra and hourly, daily, and monthly ambient noise statistics for unweighted broadband (0.02–30 kHz) and marine mammal, or M-weighted, sound pressure levels showed variability driven largely by vessel traffic. Over the calendar year, 1363 unique AIS transmitting vessels were recorded, with at least one AIS transmitting vessel present in the study area 90% of the time. A vessel noise budget was calculated for all vessels equipped with AIS transponders. Cargo ships were the largest contributor to the vessel noise budget, followed by tugs and passenger vessels. A simple model to predict received levels at the site based on an incoherent summation of noise from different vessels resulted in a cumulative probability density function of broadband sound pressure levels that shows good agreement with 85% of the temporal data.

Wave breaking dissipation observed by SWIFT drifters

Thomson, J., "Wave breaking dissipation observed by SWIFT drifters," J. Atmos. Ocean. Technol., 29, 1866-1882, doi:10.1175/JTECH-D-12-00018.1, 2012.

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1 Dec 2012

Energy dissipation rates during ocean wave breaking are estimated from high-resolution profiles of turbulent velocities collected within 1 m of the surface.The velocity profiles are obtained from a pulse-coherent acoustic Doppler sonar on a wave-following platform, termed a Surface Wave Instrument Float with Tracking, or "SWIFT", and the dissipation rates are estimated from the structure function of the velocity profiles. The purpose of the SWIFT is to maintain a constant range to the time-varying surface and thereby observe the turbulence in breaking crests (i.e., above the mean still water level). The Lagrangian quality is also useful to pre-filter wave orbital motions and mean currents from the velocity measurements, which are limited in magnitude by phase-wrapping in the coherent Doppler processing. Field testing and examples from both offshore whitecaps and nearshore surf breaking are presented. Dissipation is elevated (up to 10-3 m2 s-3) during strong breaking conditions, which are confirmed using surface videos recorded onboard the SWIFT. Although some velocity contamination is present from platform tilting and heaving, the structure of the velocity profiles is dominated by a turbulent cascade of eddies (i.e., the inertial sub-range). The noise, or uncertainty, in the dissipation estimates is shown to be normally distributed and uncorrelated with platform motion. Aggregated SWIFT measurements are shown to be useful in mapping wave breaking dissipation in space and time.

Marginal Ice Zone (MIZ) Program: Science and Experiment Plan

Lee, C.M., et al., "Marginal Ice Zone (MIZ) Program: Science and Experiment Plan," APL-UW TR 1201, Technical Report, Applied Physics Laboratory, University of Washington, Seattle, October 2012, 48 pp.

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9 Oct 2012

The Marginal Ice Zone (MIZ) intensive field program will employ an array of cutting-edge autonomous platforms to characterize the processes that govern Beaufort Sea MIZ evolution from initial breakup and MIZ formation though the course of the summertime sea ice retreat. Instruments will be deployed on and under the ice prior to initial formation of the MIZ along the Alaska coast, and will continue sampling from open water, across the MIZ, and into full ice cover, as the ice edge retreats northward through the summer. The flexible nature of ice-mounted and mobile, autonomous oceanographic platforms (e.g., gliders and floats) facilitates access to regions of both full ice cover and riskier MIZ regions. This approach exploits the extended endurance of modern autonomous platforms to maintain a persistent presence throughout the entire northward retreat. It also takes advantage of the inherent scalability of these instruments to sample over a broad range of spatial and temporal scales.

Measurements of turbulence at two tidal energy sites in Puget Sound, WA

Thomson, J., B. Polagye, V. Durgesh, M.C. Richmond, "Measurements of turbulence at two tidal energy sites in Puget Sound, WA," IEEE J. Ocean. Eng., 37, 363-374, doi:10.1109/JOE.2012.2191656, 2012.

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15 May 2012

Field measurements of turbulence are presented from two sites in Puget Sound, WA, that are proposed for electrical power generation using tidal current turbines. Time series data from multiple acoustic Doppler instruments are analyzed to obtain statistical measures of fluctuations in both the magnitude and direction of the tidal currents. The resulting turbulence intensities (i.e., the turbulent velocity fluctuations normalized by the deterministic tidal currents) are typically 10% at the hub heights (i.e., the relevant depth) of the proposed turbines. Length and time scales of the turbulence are also analyzed. Large-scale, anisotropic eddies dominate the turbulent kinetic energy (TKE) spectra, which may be the result of proximity to headlands at each site. At small scales, an isotropic turbulent cascade is observed and used to estimate the dissipation rate of TKE, which is shown to balance with shear production. Data quality and sampling parameters are discussed, with an emphasis on the removal of Doppler noise from turbulence statistics. The results are relevant to estimating the performance and fatigue of tidal turbines.

Underwater noise measurements of a 1/7th scale wave energy converter

Bassett, C., J. Thomson, B. Polagye, and K. Rhinefrank, "Underwater noise measurements of a 1/7th scale wave energy converter," In Proceedings, MTS/IEEE OCEANS 2011, Waikoloa, 19-22 September, doi:110.1109/OCEANS.2010.5664380 (MTS/IEEE, 2011).

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22 Sep 2011

Field measurements of the underwater acoustic signature of Columbia Power Technologies (Columbia Power) SeaRay wave energy converter (WEC) prototype are presented. The device was deployed in the vicinity of West Point (Puget Sound, Washington State) at a depth of approximately 20 meters. The 1/7th scale SeaRay prototype is a heave and surge, point absorber secured to the seabed with a three-point mooring. Acoustic measurements were made in order to satisfy permit requirements and assure that marine life is not adversely affected. A series of one-minute hydrophone recordings were collected on March 30, 2011 for approximately 4 hours. During these recordings, significant wave height varied from 0.4 to 0.7 m, peak wave periods varied from 2.9 to 3.2 seconds, and southerly winds varied from 5 to 10 m s-1. These are approximately twice the amplitude of typical operating conditions for the SeaRay in Puget Sound. Shipping vessel and ferry traffic levels also were typical. Received sound pressure levels during the experiment vary from 116 to 132 dB re 1 µPa in the integrated bands from 20 Hz to 20 kHz. At times, ship traffic dominates the signal, as determined from spectral characteristics and vessel proximity. Received sound pressure levels attributed to the WEC cycle from 116 to 126 dB re 1 µPa in the integrated bands from 60 Hz to 20 kHz at distances from 10 to 1500 m from the SeaRay. The cycling is well correlated with the peak wave period, including peaks and harmonics in the pressure spectral densities. Masking by ship noise prevents rigorous extrapolation to estimate the WEC source level at the conventional 1 m reference.

Characterizing underwater noise at a proposed tidal energy site in Puget Sound

Bassett, C., J. Thomson, and B. Polagye, "Characterizing underwater noise at a proposed tidal energy site in Puget Sound," In Proceedings, MTS/IEEE Oceans 2010, 20-23 September, doi:10.1109/OCEANS.2010.5664380 (MTS/IEEE, 2010).

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20 Sep 2010

Ambient underwater acoustics data are presented for one year at a potential tidal energy site in Admiralty Inlet, WA (USA) with maximum currents exceeding 3 m/s. The site, at a depth of approximately 60 meters, is located near shipping lanes, a local ferry route, and a transit area for many cetacean species. A key finding is that the statistical distribution of total sound pressure levels are dependent on tidal currents at the site. Pseudosound, cobbles shifting on the sea bed, and vibrations induced by forces on the equipment are possible explanations. Non-propagating turbulent pressure fluctuations, termed pseudosound, can mask ambient noise, especially in highly energetic environments suitable for tidal energy development.

A statistical method identifies periods during which changes in the mean and standard deviation of the one-third octave band sound pressure levels are statistically significant and thus suggestive of pseudosound contamination. For each deployment, recordings with depth averaged tidal currents greater than 1 m/s are found to be contaminated, and only recordings with currents below this threshold are used in the subsequent ambient noise analysis. Mean total sound pressure levels (0.156 - 30 kHz) over all recordings are 117 dB re 1 micoPa. Total sound pressure levels exceed 100 dB re 1 microPa 99% of the time and exceed 135 dB re 1 microPa 4% of the time. Commercial shipping and ferry traffic are found to be the most significant contributors to ambient noise levels at the site, with secondary contributions from rain, wind, and marine mammal vocalizations. Post-processed data from an AIS (Automatic Identification System) receiver is used to determine the location of ships during each recording.

Limits to the predictability of tidal current power

Polagye, B., J. Epler, and J. Thomson, "Limits to the predictability of tidal current power," In Proceedings, MTS/IEEE Oceans 2010, Seattle, 20-23 September doi:10.1109/OCEANS.2010.5664588 (MTS/IEEE, 2010).

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20 Sep 2010

The predictability of tidal currents in the context of hydrokinetic power generation are assessed using current data from a series of surveys in Admiralty Inlet, Puget Sound, Washington, USA. Both current speed and kinetic power density are shown to be well-described by harmonic analysis. Three challenges to predictability are identified. First, non-sinusoidal fluctuations over time scales on the order of hours are observed but cannot be replicated by conventional harmonic analysis. Second, turbulent fluctuations over time scales on the order of seconds are relatively large and inherently unpredictable. Third, for this site, predictions may not be extrapolated more than 100 m from the location of measurement. While none of these issues are insurmountable, they contribute to a degree of unpredictability for tidal hydrokinetic power.

Quantifying turbulence for tidal power applications

Thomson, J., M. Richmond, B. Polagye, and V. Durgesh, "Quantifying turbulence for tidal power applications," In Proceedings, MTS/IEEE OCEANS 2010, Seattle, 20-23 September, doi:10.1109/OCEANS.2010.5664600 (MTS/IEEE, 2010).

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20 Sep 2010

Using newly collected data from a tidal power site in Puget Sound, WA, metrics for turbulence quantification are assessed and discussed. Of particular interest is the robustness of the "turbulent intensity," defined as the ratio of velocity standard deviation to velocity mean. Simultaneously, the quality of raw ping Acoustic Doppler Current Profiler (ADCP) data for turbulence studies is evaluated against Acoustic Doppler Velocimeter (ADV) data at a point. Removal of Doppler noise from the raw ping data is shown to be a crucial step in turbulence quantification. Excluding periods of slack tide, the corrected turbulent intensity estimates at a height of 4.6 m above the seabed are 10% and 11% from the ADCP and ADV, respectively. Estimates of the turbulent dissipation rate are more variable, from 10-3 to 10-1 W/m3. An example analysis of coherent Turbulent Kinetic Energy (TKE) is presented.

Shipboard acoustic Doppler current profiler surveys to assess tidal current resources

Epler, J. B. Polagye, and J. Thomson, "Shipboard acoustic Doppler current profiler surveys to assess tidal current resources," In Proceedings, MTS/IEEE Oceans 2010, Seattle, 20-23 September, doi:10.1109/OCEANS.2010.5664387 (MTS/IEEE, 2010).

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20 Sep 2010

A compelling aspect of power generation from tidal currents is the predictability of the resource, which is generated by the gravitational pull of the sun and moon on the earth's oceans. For technical feasibility studies, it is presupposed that once the currents at a site have been well characterized it is possible to make accurate predictions of the electricity that would be generated by an array of turbines. These data are generally collected by Acoustic Doppler Current Profilers (ADCP), which use active acoustics to measure currents throughout the water column.

Stationary ADCP deployments in Admiralty Inlet, WA, indicate operationally important variability over length scales less than 100 m and use of shipboard ADCP surveys aims to identify regions of peak currents without deploying a high resolution grid of stationary ADCPs. Shipboard surveys involve multiple laps during a tidal cycle around a short "racetrack". Data are aggregated within bins such that multiple laps produce time series at 100 m spatial resolution along the track. The time series is then fitted with a half sine wave assuming that each tidal cycle can be represented as such due to the periodic nature of tidal currents. The amplitude and timing of the peak currents along the survey track are estimated from the fit. Multiple ebb current surveys indicate that relative amplitude trends are consistent between cycles of differing strength and time of the year. Therefore, by overlapping surveys, greater spatial coverage can be achieved from multiple cycles without changing the survey characteristics.

Results obtained to date suggest a noise floor of approximately plus/minus 15 minutes for phase. This method could be applied to other tidal energy sites as a lower cost alternative to siting studies using arrays of stationary ADCPs.

Observations of thermal diffusivity and a relation to the porosity of tidal flat sediments

Thomson, J., "Observations of thermal diffusivity and a relation to the porosity of tidal flat sediments," J. Geophys. Res., 115, doi:10.1029/2009JC005968, 2010.

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19 May 2010

Time series observations of vertical profiles of sediment temperature are presented for several locations at two distinct tidal flats. Surface sediment temperatures are shown to be strongly dependent on solar insolation during low-tide exposure, and that signal is communicated to the subsurface sediment temperatures. A vertical diffusion balance explains the observations well (up to 97% of the observed variance at some locations and 76% on average), and an estimate of thermal diffusivity is obtained for each location. A theoretical model relating sediment porosity to thermal diffusivity is presented and shown to agree with independent estimates of porosity. In addition, thermal diffusivity is shown to correlate with direct observations of sediment composition (percent sand) and surface strength. Results are suggested for application to remote classification of sediments using infrared time series images.

Site characterization for tidal power

Gooch, S., J. Thomson, B. Polagye, and D. Meggitt, "Site characterization for tidal power," In Proceedings, MTS/IEEE Oceans 2009, Biloxi, MS, 26-29 October (MTS/IEEE, 2009).

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26 Oct 2009

Tidal In-Stream Energy Conversion (TISEC) is a promising source of clean, renewable and predictable energy. One of the preliminary steps in developing the technology is establishing a standardized and repeatable methodology for the characterization of potential deployment sites. Stationary Acoustic Doppler Profiler (ADCP) velocity data collected at four sites near Marrowstone Island, Puget Sound are used to test the applicability of metrics characterizing maximum and mean velocity, eddy intensity, rate of turbulent kinetic energy dissipation, vertical shear, directionality, ebb and flood asymmetry, vertical profile and other aspects of the flow regime deemed relevant to TISEC.

Based on these analyses, the flow at three sites clustered along the east bank of Marrowstone Island (referred to as the "D" sites) are found to be mainly bidirectional and have similar ebb and flood velocities and relatively low levels of turbulent activity. The site near the north point of Marrowstone Island (the "C" site) has higher maximum and mean ebb velocities, but is more asymmetrical and has higher levels of turbulent activity. In addition, methods are applied to data from another Puget Sound site (Admiralty Inlet), and results are compared. A two-dimensional "velocity map" is developed for the more promising "D" sites, showing the spatial variation of velocities throughout the area. This map is based on data collected using a vessel-mounted ADCP in linear transects running roughly perpendicular to the flow at the site. Interpolation between these transects along isobaths yields a rough grid of velocities, from which the velocity map can be determined using a two-dimensional interpolation scheme. Results are promising, although this method may not work well at sites with different bathymetry and geographic characteristics. The methods and conclusions are device-neutral, however device specific considerations will be important prior to developing TISEC sites.

A fourier-based method for the distribution of breaking crests from video observations

Thomson, J., and A.T. Jessup, "A fourier-based method for the distribution of breaking crests from video observations," J. Atmos. Ocean. Technol., 26, 1663-1671, doi:10.1175/2009JTECHO622.1, 2009.

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1 Aug 2009

A Fourier-based method is presented to process video observations of water waves and calculate the speed distribution of breaking crest lengths. The method has increased efficiency and robust statistics compared with conventional algorithms that assemble distributions from tracking individual crests in the time domain. The method is tested using field observations (video images of whitecaps) of fetch-limited breaking waves during case studies with low (6.7 m s-1), moderate (8.5 m s-1), and high (12.6 m s-1) wind speeds. The method gives distributions consistent with conventional algorithms, including breaking rates that are consistent with direct observations. Results are applied to obtain remote estimates of the energy dissipation associated with wave breaking.

Energy dissipation and the spectral distribution of whitecaps

Thomson, J., J.R. Gemmrich, and A.T. Jessup, "Energy dissipation and the spectral distribution of whitecaps," Geophys. Res. Lett, 36, doi:10.1029/2009GL038201, 2009.

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3 Jun 2009

Energy dissipation by breaking water waves is quantified indirectly using remote observations (digital video recordings) and directly using in situ observations (acoustic Doppler velocity profiles). The analysis is the first validation using field data to test the Duncan-Phillips formulation relating energy dissipation to the spectral distribution of whitecap speeds and lengths. Energy dissipation estimates are in agreement over two orders of magnitude, and demonstrate a promising method for routine observation of wave breaking dynamics. Breaking statistics are partitioned into contributions from waves at the peak of the wave-height spectrum and waves at higher frequencies in the spectrum. Peak waves are found to be only 10% of the total breaking rate, however peak waves contribute up to 75% of the total dissipation rate. In addition, breaking statistics are found to depend on the peak wave steepness and the energy input by the wind.

Refraction and reflection of infragravity waves near submarine canyons

Thomson, J., S. Elgar, T.H.C. Herbers, B. Raubenheimer, and R.T. Guza, "Refraction and reflection of infragravity waves near submarine canyons," J. Geophys. Res., 112, doi:10.1029/2007JC004227, 2007.

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10 Oct 2007

The propagation of infragravity waves (ocean surface waves with periods from 20 to 200 s) over complex inner shelf (water depths from about 3 to 50 m) bathymetry is investigated with field observations from the southern California coast. A wave-ray-path-based model is used to describe radiation from adjacent beaches, refraction over slopes (smooth changes in bathymetry), and partial reflection from submarine canyons (sharp changes in bathymetry). In both the field observations and the model simulations the importance of the canyons depends on the directional spectrum of the infragravity wave field radiating from the shoreline and on the distance from the canyons. Averaged over the wide range of conditions observed, a refraction-only model has reduced skill near the abrupt bathymetry, whereas a combined refraction and reflection model accurately describes the distribution of infragravity wave energy on the inner shelf, including the localized effects of steep-walled submarine canyons.

In The News

With new tech, scientists probe what lies beneath the Sound

The Herald (Everett), Chris Winters

The Adaptable Monitoring Package (AMP) undergoes tests near Sequin, WA. Instrumented with two kinds of sonar, a current profiler, three visual cameras, and four hydrophones, it can bes used for basic research on the health of the Puget Sound ecosystem or other projects requiring undersea monitoring for long periods of time.

17 Jan 2016

Wish you were here: Arctic explorer


Jim Thomson shows what it's like to measure waves in the Arctic Ocean.

3 Dec 2014

Coupeville ferry gets high-tech addition to help scientists

Everette Herald

Both ferries on the Coupeville to Port Townsend route will now pull double-duty thanks to sensors installed on their hulls. The ferries are helping to monitor water quality in Puget Sound for the Department of Ecology and APL-UW.

14 Nov 2014

More News Items

U.S. Navy awards $8 million to develop wave, tidal energy technology

UW News and Information, Hannah Hickey

The U.S. Navy has committed to get half of its energy from renewable sources by the year 2020. The University of Washington is helping to reach that goal with an $8 million, four-year contract from the Naval Facilities Engineering Command, or NAVFAC, to develop marine renewable energy for use at the Navy's facilities worldwide.

24 Oct 2014

Surf's up in the Arctic: Record-high waves seen in 2012

Fox News, Becky Oskin

Record-high waves hit Alaska's Beaufort Sea in September 2012, when Arctic sea ice shrank to an extreme summer low, a new study reports.

4 Aug 2014

Huge waves in the Arctic demonstrate ice loss — and aggravate it

Slate, Eric Holthaus

The house-sized waves measured by oceanographer Jim Thomson and his research team during a Beaufort Sea storm in 2012 are bigger than any seen before in that part of the Arctic, where it's warmer now than at any point since humans began living there 44,000 or so years ago. Previously, there was just too much ice for waves to form.

1 Aug 2014

16-foot waves in the Arctic: A harbinger of ice-free summers?

Christian Science Monitor, Pete Spotts

Until recently, the Arctic Ocean's central Beaufort Sea was ice-covered throughout the summer. But with a greater expanse of open water, scientists are tracking how waves and well-traveled swells could accelerate the loss of summer ice.

30 Jul 2014

Giant waves found in Arctic Ocean could be accelerating sea ice loss

The Washington Post — Capital Weather Gang, Angela Fritz

Huge areas of ice-free water are leading to massive waves in the Arctic Ocean, according to a study published in Geophysical Research Letters.

30 Jul 2014

Sixteen-foot swells reported in once-frozen region of Arctic Ocean

The Washington Post, Fred Barbash

The fact that researchers have now measured swells of more than 16 feet in the Arctic's Beaufort Sea, just north of Alaska, is a bit of a stunner. Swells of that size, researchers say, have the potential to break up Arctic ice even faster than the melt underway there for decades thanks to rapid global warming.

30 Jul 2014

Huges waves measured for first time in Arctic Ocean

UW News and Information, Hannah Hickey

Arctic ice used to retreat less than 100 miles from the shore. In 2012, it retreated more than 1,000 miles. Wind blowing across an expanse of water for a long time creates whitecaps, then small waves, which then slowly consolidate into big swells that carry huge amounts of energy in a single punch.

29 Jul 2014

Sensor-equipped ferry to monitor Admiralty Inlet, gateway to Puget Sound

Environmental Monitor, Daniel Kelly

Newly installed acoustic sensors on two Washington ferries will help monitor water circulation in Puget Sound. Scientists with the Applied Physics Laboratory at the University of Washington will manage the monitoring effort that relies on acoustic doppler current profilers to measure a host of environmental parameters.

30 Jun 2014

Puget Sound monitoring

The Impact @ TVW (video), Jennifer Huntley

The state ferry system is working with scientists to learn more about the water in Puget Sound. Find out about a new high-tech water monitoring device aboard the ferries.

18 Jun 2014

Ferries for science: Instrument will monitor flow in Puget Sound

UW News and Information, Hannah Hickey

It%u2019s not just vacationers who will be traveling on the ferries between Port Townsend and Coupeville this summer. A new partnership among the Washington Department of Ecology, the University of Washington and other groups is riding on Washington State Ferries to improve understanding of water circulation in Puget Sound.

16 Jun 2014

Feds approve Puget Sound tidal energy project

KUOW Radio, Courtney Flatt

A proposal for the world%u2019s first grid-connected tidal energy project received a federal license. The project has been almost eight years in the making.

20 Mar 2014

Beyond the forecast: Power play

KING5 News, Seattle

Washington State is on the forefront of green energy production, including harnessing winds, tides, and sunlight to produce electricity.

23 Nov 2013

A tide of local influences

The New York Times – Scientist at Work Blog, Jim Thomson

Principal Oceanographer Jim Thomson blogs from the Canal de Chacao in Chile. His research team is measuring the tidal turbulence in the channel to determine if the area is suitable for power generating turbine installation.

27 Feb 2013

Noisy ships, ferries create racket below Puget Sound

The Seattle Times, Craig Welch

Recent work by University of Washington researchers shows noise in some Puget Sound shipping channels regularly meets or exceeds levels the federal government suggests may be harmful to marine life.

3 Jan 2013

Heading home, and hanging ten

The New York Times, Jim Thomson

Principal Oceanographer Jim Thomson and his research team set out in the North Pacific in hopes of finding big storms and big waves. His NY Times "Scientist at Work" blog chronicles their search for the big waves and what the instruments they deploy into them tell us about the turbulence created by breaking waves in the open ocean.

17 Oct 2012

Ocean energy is a vast, unproven resource

The Kitsap Sun

Jim Thomson, a University of Washington researcher, is studying the potential energy that can be produced at Admiralty Inlet and the potential environmental effects. When the project started three years ago, almost nothing was known about that area of Puget Sound, he said.

9 Nov 2011

IBM sees energy, money in motion of the ocean

MSNBC, John Roach

APL-UW's Jim Thomson is helping characterize the noise environment in Admiralty Inlet in Washington's northern Puget Sound for a pilot project with a local utility that will install underwater turbines to capture energy from the tides.

1 Nov 2011

Renewable tidal energy's reality check

CNN Money

Jim Thomson and his research team have been collecting data for nearly three years at a potential undersea tidal energy site in Admiralty Inlet. The data will inform the best practices for harnessing tidal energy at the site when the turbines are lowered to the bottom and connected to the power grid.

20 Oct 2011

Harnessing tides in the northwest

KUOW Radio

The sun is setting as the Jack Robertson, a 65-foot research vessel, leaves the harbor. Two spidery-looking orange pieces of machinery, each one weighing about 1,000 pounds, crouch on the back deck. These sea spiders, as they're called, are for measuring tidal currents and more.

24 Aug 2011

Will oceans' tides supply endless electricity?

Bellingham Herald, Rob Hotakainen, McClatchy Newspapers

Two large hydro turbines will be installed 200 feet deep in the harsh waters of Admiralty Inlet by late summer 2013, marking the first project of its kind in Washington state. But before then, scientists want to figure out how rockfish, diving birds, whales and other marine life will respond to the intruding turbines.

6 Aug 2011

Admiralty Inlet ocean life studied to accommodate potential undersea turbine generators

Peninsula Daily News, Charlie Bermant

Four submerged data collection devices were retrieved in Admiralty Inlet off the shore of Whidbey Island on Wednesday as scientists prepare to monitor ocean life around turbine electrical generators.

9 Jun 2011

Data from Puget Sound's depths tell of marine life at proposed turbine site

Kitsap Sun, John Stang

Engineers aboard the University of Washington research vessel Jack Robertson hauled up a rig that looks like a squat three-legged spider that stores numerous gigabytes of raw data. Researchers will now take the data and study it to learn about sea life in the area where turbines for tidal energy are planned.

8 Jun 2011

Is tidal energy affecting sea life?

KING 5 News, Gary Chittim

Revolutionary efforts to harness the power of Puget Sound tides took a big step forward today. Sophisticated imaging devices have been hard at work studying the possible effects of large scale underwater energy production. They are looking at how a grid of generators might harm sensitive sea life including endangered salmon and orcas.

8 Jun 2011

Researchers Study Potential Impact Of Tidal Power Turbines

OPB News, Ashley Ahearn

Powerful tides of the Strait of Juan de Fuca suggest this is a perfect place to harness energy. Jim Thomson, oceanographer at the Applied Physics Laboratory, University of Washington is leading the feasibility research.

24 May 2011

Admiralty Inlet an ideal spot for tidal power


Nearly two years of monitoring show the Admiralty Inlet is an ideal place to harness tidal energy, University of Washington researchers say.

14 Dec 2010

Assessing the environmental effects of tidal turbines

UW News and Information, Hannah Hickey

Harnessing the power of ocean tides has long been imagined. A demonstration project planned for Puget Sound will be the first tidal energy project on the west coast of the United States, and the first array of large-scale turbines to feed power from ocean tides into an electrical grid.

13 Dec 2010

Camera paints colorful orca portrait

King 5 News, Gary Chittim

UW researchers detect resident Orca whale images at night using infrared camera technology. This tool will help ensure that whale pods are not harmed as tidal energy projects are developed in the Puget Sound.

26 Aug 2010

Currents of Change

Seattle Business Magazine, Amelia Apfel

Local experts rely on teamwork and patience to bring tidal power to the Northwest.

1 Jul 2010

What exactly is the 'Vashon Hum'?

The Seattle Post-Intelligencer, AMELIA HEAGERTY

The "Vashon Hum" is a very low pure tone that people have heard all across the Island in Puget Sound. APL-UW engineers and oceanographers weigh in on likely and unlikely sources.

15 Apr 2010

UW scientists discover mud flats produce fresh water

KING 5 News, Gary Chittim

Jim Thomson and his team made a discovery on the mud flats of Willapa Bay. Buried within the insulating mud of the flats is a reservoir of warm, fresh water that is constantly flowing into streams and the ocean.

5 Apr 2010

Post-Enron, Snohomish County utility cultivates own energy

The Daily News Online, Phuong Le, The Associated Press

This year, the utility received nearly $1 million from the federal government for a pilot project to install tidal turbines in Puget Sound and to test-drill for geothermal hot spots in the region.

4 Jul 2009

Tidal-energy project stays on course after UW's tests on Puget Sound

The Seattle Times, Michelle Ma

Researchers from the University of Washington spent four days last week on board a vessel collecting data, capturing underwater video and measuring velocity in Admiralty Inlet between Port Townsend and Whidbey Island. The channel likely will host one of the nation's largest tidal-energy projects.

15 Apr 2009

Concerns emerge about environmental effects of wave-energy technology

The Seattle Times, Michelle Ma

Energy generated from the ocean's waves and tides might be the next source of "green" power in our region, but the technology demands more study. A new marine renewable-energy research center has been launched, giving the University of Washington the lead for tidal-power research.

17 Nov 2008


SWIFT: Surface Wave Instrument Float with Tracking

Record of Invention Number: 46566

Jim Thomson, Alex De Klerk, Joe Talbert


24 Jun 2013

Heave Place Mooring for Wave Energy Conversion (WEC) via Tension Changes

Record of Invention Number: 46558

Jim Thomson, Alex De Klerk, Joe Talbert


19 Jun 2013

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center