Wave-Ice Interaction in Polar Oceans

• Main Author: Cheng, Sukun
• Format: Thesis
• Language: English
• Published: Clarkson University 2018
• Subjects: Geophysics|Civil engineering|Ocean engineering; Arctic; Arctic Ocean; Pancake; Sea ice; ice covered waters
• Online Access: http://pqdtopen.proquest.com/#viewpdf?dispub=10785835

As the Arctic sea ice extent shrinks, it becomes feasible to navigate through the Arctic Ocean. The Arctic routes shorten the marine transport between the American and Asian-European continents. To enable navigation planning, reliable wave forecasts in the ice covered area is highly demanded. However, as one component of the ocean wave models, the wave-ice interaction modelling is still under development. To obtain good wave forecasts, the effect of all ice types on wave propagation must be modeled correctly. This dissertation contributes to the wave-ice interaction modelling for general sea ice-covered waters. For this purpose, the research questions addressed include investigating a theoretical model that assumes ice covers as a continuous layer of viscoelastic material. The derived dispersion relation contains two parameters associated with the equivalent viscoelastic properties of different ice types. Implementation of this model in an operational ocean wave model is a numerical problem to solve. Parameters in this viscoelastic model require data calibration. Inverse methods are developed using measurements from a recent field campaign to establish a relation among ice types and these theoretical parameters. Three main questions of this study are answered as the following. 1) To understand the physical nature of ice-water layered system in the viscoelastic model. The wave characteristics are compared with those from developed theories of wave propagation in other layered systems. It concludes that the roots of the dispersion relation are identified as the flexural gravity, pressure, shear, evanescent and Rayleigh-Lamb waves. A wave mode swap phenomenon is also discussed. 2) To solve the numerical issues in applying the model in a global ocean wave model WAVEWATCH III®. Strategies of determining the dominant wave mode and expediency of the numerical procedure are proposed. The updated ice source module for WAVEWATCH III ® performs better in accuracy, efficiency and robustness than its predecessor. 3) Inverse methods are applied to calibrate the model using data collected in the western Arctic Ocean, populated predominantly with pancake ice. The calibrated parameters can be used for wave forecasts in fields of the same ice type in the future. Furthermore, a combined laboratory and numerical study is conducted for wave propagating through an array of uniformed floes. The effective rigidity of the cover is explained by the change of elastic strain energy due to the free edges of each floe. An empirical relation is obtained for the effect rigidity in terms of the floe size and other length scales. This relation may be used to estimate the effective rigidity of an ice cover by in situ or remote sensing images. By answering the above questions, this dissertation contributes to the application of a viscoelastic model for wave hindcasts/forecasts in the whole ice-covered waters.