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Madison Smith

Research Assistant

Email

mmsmith@apl.uw.edu

Publications

2000-present and while at APL-UW

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.

Ocean surface turbulence in newly formed marginal ice zones

Smith, M., and J. Thomson, "Ocean surface turbulence in newly formed marginal ice zones," J. Geophys. Res., EOR, doi:10.1029/2018JC014405, 2019.

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1 Feb 2019

Near‐surface turbulent kinetic energy dissipation rates are altered by the presence of sea ice in the marginal ice zone, with significant implications for exchanges at the air‐ice‐ocean interface. Observations spanning a range of conditions are used to parameterize dissipation rates in marginal ice zones with relatively thin, newly formed ice, and two regimes are identified. In both regimes, the turbulent dissipation rates are matched to the turbulent input rate, which is formulated as the surface stress acting on roughness elements moving at an effective transfer velocity. In marginal ice zones with waves, the short waves are the roughness elements, and the phase speed of these waves is the effective transfer velocity. The wave amplitudes are attenuated by the ice, and thus, the size of the roughness elements is reduced; this is parameterized as a reduction in the effective transfer velocity. When waves are sufficiently small, the ice floes are the roughness elements, and the relative velocity between the sea ice and the ocean is the effective transfer velocity. A scaling is introduced to determine the appropriate transfer velocity in a marginal ice zone based on wave height, ice thickness and concentration, and ice‐ocean shear. The results suggest that turbulence underneath new sea ice is mostly related to the wind forcing and that marginal ice zones generally have less turbulence than the open ocean under similar wind forcing.

Overview of the Arctic Sea State and Boundary Layer Physics Program

Thomson, J., and 32 others, including L. Rainville, and M. Smith, "Overview of the Arctic Sea State and Boundary Layer Physics Program," J. Geophys. Res., 123, 8674-8687, doi:10.1002/2018JC013766, 2018.

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1 Dec 2018

A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.

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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