Session: 07-01-01 Operations in ice

Submission Number: 157728

Theoretical Analysis of Nonlinear Flexural-Gravity Waves Interacting With Shear Currents in Polar Seas 

In polar seas, the impact of large waves on ice sheets is particularly evident. Especially during strong storms or extreme weather, waves can erode the edges of ice sheets, accelerating the collapse of ice shelves. This process makes it easier for the sea ice to break into several smaller pieces, further accelerating the melting of the ice sheet. According to recent field studies, the role of waves in breaking up and melting sea ice is much more pronounced than predicted by previous models (Julienne Stroeve, 2007; A. L. Kohout, 2014; Shinsuke Iwasaki, 2023). As sea ice breaks into smaller pieces, the ratio of length to thickness of each piece changes. In this situation, the influence of mass on the movement behavior of sea ice becomes very important, and considering the mass of the ice sheet is a factor that has not been deeply explored in past studies.

This study uses perturbation methods to derive the interaction between flexural-gravity waves and shear flows under compressive forces, while deeply considering the impact of the mass of floating ice. The main innovation of this study is our discovery of the importance of the mass properties of ice sheets in flexural-gravity waves. When the mass properties of ice sheets are taken into account, the group velocity curves for different vortices show significant branching at the endpoints due to the inclusion of the mass term, this phenomenon has not been previously explored in the literature. This finding allows us to predict ice cracking more accurately. In the detailed analysis of the group velocity curve, we found that as wave height increases, the wave number at which wave blocking occurs is significantly higher than for smaller waves. This key finding highlights the importance of nonlinear waves, as linear wave theory cannot address the problems of large waves. This allows our results to discuss wave blocking under extreme wave conditions. Most importantly, we have also analyzed the effect of the presence or absence of compressive forces and the values of the compressive forces under ice cracking conditions on particle trajectories. Our results show that the vertical displacement of particle trajectories is significantly affected by compressive forces, particularly in large wave conditions where the vertical displacement of particles is significantly less than in smaller wave conditions. The article also found that in the presence of opposing environmental currents, the compressive forces that cause the ice sheet to break are lower than in situations without shear currents.

In summary, our research presents two important innovative findings: 1. After the change in vorticity, the consideration of ice sheet mass significantly alters the results of the group velocity curve. Such results illustrate that we still need to consider the effects of ice sheet mass characteristics. 2. We found that the trajectories of water particles show significant differences due to wave steepness and compressive forces, providing a new theoretical basis for assessing the risk of ice sheet damage in polar regions.

Presenting Author: 徐洪 珠 國立中山大學

Presenting Author Biography: Professor at Sun Yat-sen University