Aerial observations of sea ice breakup by ship waves

Abstract

We provide high-resolution in situ observations of wave-induced sea ice breakup in the natural environment. In order to obtain such data, a drone was deployed from the Canadian Coast Guard ship Amundsen as it sailed in the vicinity of large ice floes in Baffin Bay and in the St. Lawrence Estuary, Canada. The footage recorded during these experiments was used to obtain the floe size distribution (FSD) and the temporal evolution of the breakup. Floe-area-weighted FSDs exhibit a modal shape, indicating that a preferential size is generated by wave-induced breakup. Furthermore, the increase of the mode of the distribution with greater thickness indicates that ice thickness plays a defined role in determining the preferential size. Comparison with relevant theory suggests that the maximum floe size is dictated not only by the ice rigidity but also by the incident wavelength. It was also observed that the in-ice wavelength is smaller than the estimated incident wavelength, suggesting that waves responsible for the breakup obey mass loading dispersion. The fact that the breakup advances almost as fast as the wave energy suggests that fatigue might not have been an important physical component during the experiments. Moreover, the observed breakup extents show that thicker ice can attenuate waves less than thinner ice. Overall, this dataset provides key information on wave-induced sea ice breakup and highlights the potential for better understanding the physics of natural sea ice in response to waves.