Laboratory study of wave-induced flexural motion of ice floes

Abstract

Wave-ice interactions involve complex physical processes. Well-designed laboratory investigations are indispensable for studying these processes. In the present study, laboratory experimental data on saline ice obtained during the HYDRALAB+ project: Loads on Structure and Waves in Ice (LS-WICE) are analyzed. Here, we devise a cross-validation method that reduces the uncertainty in estimating the wavelength of surface gravity waves from wave elevation measurements made by closely located and equidistant sensors. Both experimental and numerical case studies show that the new method produces accurate results (normalized error smaller than 5%). Furthermore, experimental case studies show that the elasticity of ice lengthens the waves within the ice cover compared with the open-water wavelength, and predictions of the wavelength from the elastic-plate model are concordant with the experimental values for waves beneath intact ice sheets. In addition, we apply multivariate analysis methods to identify flexural modes of ice floes under wave actions. The analysis results suggest that multiple flexural modes exist in the motion. The results produced by using the Morlet wavelet and Prony's method confirm the presence of second-order harmonics in the motion. Part of the nonlinearity likely originates from ice-ice interactions in addition to some contributions from nonlinearity in the waves.