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Lucia Hosekova

Visiting Scientist






2000-present and while at APL-UW

Spurious rollover of wave attenuation rates in sea ice caused by noise in field measurements

Thomson, J., Hošeková, L., M.H. Meylan, A.L. Kohout, and N. Kumar, "Spurious rollover of wave attenuation rates in sea ice caused by noise in field measurements," J. Geophys. Res., EOR, doi:10.1029/2020JC016606, 2021.

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10 Feb 2021

The effects of instrument noise on estimating the spectral attenuation rates of ocean waves in sea ice are explored using synthetic observations in which the true attenuation rates are known explicitly. The spectral shape of the energy added by noise, relative to the spectral shape of the true wave energy, is the critical aspect of the investigation. A negative bias in attenuation that grows in frequency is found across a range of realistic parameters. This negative bias decreases the observed attenuation rates at high frequencies, such that it can explain the rollover effect commonly reported in field studies of wave attenuation in sea ice. The published results from five field experiments are evaluated in terms of the noise bias, and a spurious rollover (or flattening) of attenuation is found in all cases. Remarkably, the wave heights are unaffected by the noise bias, because the noise bias occurs at frequencies that contain only a small fraction of the total energy.

Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea

Hošeková, L., M.P. Malila, W.E. Rogers, L.A. Roach, E. Eidam, L. Rainville, N. Kumar, and J. Thomson, "Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea," J. Geophys. Res., 125, doi:10.1029/2020JC016746, 2020.

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1 Dec 2020

Alaskan Arctic coastlines are protected seasonally from ocean waves by the presence of coastal and shorefast sea ice. This study presents field observations collected during the autumn 2019 freeze up near Icy Cape, a coastal headland in the Chukchi Sea of the Western Arctic. The evolution of the coupled air‐ice‐ocean‐wave system during a four‐day wave event was monitored using drifting wave buoys, a cross‐shore mooring array, and ship‐based measurements. The incident wave field with peak period of 2.5 s was attenuated by coastal pancake and frazil sea ice, reducing significant wave height by 40% over less than 5 km of cross‐shelf distance spanning water depths from 13 to 30 m. Spectral attenuation coefficients are evaluated with respect to wave and ice conditions and the proximity to the ice edge. Attenuation rates are found to be three times higher within 500 m of the ice edge, relative to values farther in the ice cover. Attenuation coefficients are in the range of <2.3,2.7> m-1, and follow a power‐law dependence on frequency.

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