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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


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

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

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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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

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.

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

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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

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.

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, 2013.

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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.

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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," in 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," in 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

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

More News Items

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