Flexural waves in a floating ice sheet: Modeling and comparison with data

Abstract

Ice vibrations caused by a vertical impulse force are calculated in this paper using fluid-loaded thin elastic plate theory. The plate response is calculated in the frequency domain, multiplied with the source spectrum and inverse Fourier transformed to obtain the time domain solution. The time domain solution is compared with the vertical-axis geophone array data collected in the Arctic on a smooth ice floe using a vertical hammer strike as the source. The model, assuming a linear frequency dependence in ice attenuation, provides a reasonably good fit to the spectral densities as a function of distance for three bands of frequencies. The modeled waveforms along the array of receivers matches reasonably well with the data. Frequency-wave number analysis is applied to the modeled time series as was done for the data. Overall good agreement was found between the modeled and measured frequency dispersion curves but the model could not account for the splitting of the frequency dispersion seen in the data. The forced and free-wave components excited by a point versus a line force are examined and comments are made on the experimental implications for ice attenuation measurement and inverse source determination.