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Madison Smith

Postdoctoral Scholar

Email

mmsmith@apl.uw.edu

Phone

206-616-5736

Department Affiliation

Polar Science Center

Publications

2000-present and while at APL-UW

Pancake sea ice kinematics and dynamics using shipboard stereo video

Smith, M., and J. Thomson, "Pancake sea ice kinematics and dynamics using shipboard stereo video," Ann. Glaciol., EOR, doi:10.1017/aog.2019.35, 2019.

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18 Nov 2019

In the marginal ice zone, surface waves drive motion of sea ice floes. The motion of floes relative to each other can cause periodic collisions, and drives the formation of pancake sea ice. Additionally, the motion of floes relative to the water results in turbulence generation at the interface between the ice and ocean below. These are important processes for the formation and growth of pancakes, and likely contribute to wave energy loss. Models and laboratory studies have been used to describe these motions, but there have been no in situ observations of relative ice velocities in a natural wave field. Here, we use shipboard stereo video to measure wave motion and relative motion of pancake floes simultaneously. The relative velocities of pancake floes are typically small compared to wave orbital motion (i.e. floes mostly follow the wave orbits). We find that relative velocities are well-captured by existing phase-resolved models, and are only somewhat over-estimated by using bulk wave parameters. Under the conditions observed, estimates of wave energy loss from ice–ocean turbulence are much larger than from pancake collisions. Increased relative pancake floe velocities in steeper wave fields may then result in more wave attenuation by increasing ice–ocean shear.

Wave attenuation by sea ice turbulence

Voermans, J.J., A.V. Babanin, J. Thomson, M.M. Smith, and H.H. Shen, "Wave attenuation by sea ice turbulence," Geophys. Res. Lett., 46, 6796-6803, doi:10.1029/2019GL082945, 2019.

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28 Jun 2019

The dissipation of wave energy in the marginal ice zone is often attributed to wave scattering and the dissipative mechanisms associated with the ice layer. In this study we present observations indicating that turbulence generated by the differential velocity between the sea ice cover and the orbital wave motion may be an important dissipative mechanism of wave energy. Through field measurements of under‐ice turbulence dissipation rates in pancake and frazil ice, it is shown that turbulence‐induced wave attenuation coefficients are in agreement with observed wave attenuation in the marginal ice zone. The results suggest that the turbulence‐induced attenuation rates can be parameterized by the characteristic wave properties and a coefficient. The coefficient is determined by the ice layer properties.

A new version of the SWIFT platform for waves, currents, and turbulence in the ocean surface layer

Thomson, J., M. Moulton, A. de Klerk, J. Talbert, M. Guerra, S. Kastner, M. Smith, M. Schwendeman, S. Zippel, and S. Nylund, "A new version of the SWIFT platform for waves, currents, and turbulence in the ocean surface layer," Proc., IEEE/OES 12th Currents, Waves, Turbulence Measurement and Applications Workshop, 10-13 March, San Diego, CA (IEEE, 2019).

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10 Mar 2019

The Surface Wave Instrument Float with Tracking (SWIFT) is a freely drifting platform for measurements of waves, currents, and turbulence in the ocean surface layer. This platform
has been used globally to study wave breaking, wave-current interactions, and waves in ice. A new version (v4) of the buoy has recently been developed and demonstrated in the Office of
Naval Research “Langmuir Circulations” field campaign along the California coast (2017). The new version is built around a 5-beam Acoustic Doppler Current Profiler (Nortek Signature 1000) with a multi-pulse coherent mode for high-resolution turbulence measurements. The new Doppler profiler enables estimates of the turbulent dissipation rate down to 3.5 m below waves, compared with 0.5 m in the previous version, and can measure a much larger range of turbulence levels than the previous version. The new version also uses a broadband Doppler mode to profile the mean currents down to 20 m. Mean Eulerian velocity profiles are estimated from the wave-averaged profiler velocities by applying a wave-following bias correction that scales with the Stokes drift and has twice the vertical decay scale. Finally, the new version supports real-time telemetry of raw sea surface elevations for reconstruction of individual waves by processing a coherent array of multiple SWIFTs, with applications for short-range wave-by-wave forecasting. These combined improvements to the platform are intended to advance understanding of wave processes and applications in the ocean surface layer.

More Publications

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
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