Numerical Simulation Of Sea Ice Dynamics And Wave-ice Interaction

Better forcasting sea ice conditions is the most concern for studying the interactions between sea ice and globle climate system, and for solving the sea ice problems encountered in offshore applications such as navigation and expoitation of natural sources. This thesis focuses on the numerical method for sea ice dynamics and wave-ice interactions.In the Bohai Sea or the marginal ice zone, various dynamical characteristics such as breakup, rafting and ridging are ofter observed. In this thesis, a hybrid Lagrangian-Eulerian (HLE) method is developed to simulate the sea ice dynamics accurately and efficiently. With the HLE model, the ice ridging process in a rectangular basin and the sea ice dynamical process in a vortex wind field are simulated. The simulated results show that the HLE model can simulate the sea ice dynamics accurately and efficiently. The HLE model is also applied to model the sea ice dynamics in the Bohai Sea. The simulated ice thickness, ice concentration and ice velocity match the saterllite images and the field observed data well.Wave-ice interactions, which have been ignored or crudely parameterized in all present sea ice models, need to be included into the sea ice model to further improve the accuracy of the sea ice modeling. Wave characteristics play a key role in sea ice dynamical and thermodynamical processes. To investigate the ice effect on wave propagation, the dispersion relation for waves propagating into different types of ice cover is studied systematically. A laboratory experiment was carried out to study the wave propagating through ice covers consisting of a grease and pancake ice mixture. The comparision between experimental results and the two-layer viscous model shows that modeling the tested ice layer as a viscous fluid is not sufficient to describe the observed dispersion relation and amplitude attenuation. Based on the ice morphology in marginal ice zone, a visco-elastic model is proposed to describe the propagation of gravity waves into various types of ice cover. The visco-elastic model bridges the gap among the existing models and provides a unified tool for wave-ice modelers to parameterize the Polar Regions populated with various types of ice cover. The dispersion relation, however, contains several propagating wave modes. The eigenfunction expansion-matching method is used to solve the transimision coefficients of each wave mode. Apparent wave number and attenuation rate are calculated for different conditions. The visco-elastic model is applied to the laboratory experiment to inversely determine the viscosity and elasticity of the tested ice covers. The further validation process using the laboratory experiment is discussed. To estimate the wave enhanced ice production rate, the ice production rates under wave condtions are calculated from two experiments conducted in HSVA. The results show that the total ice production is enhanced under wave conditions, and the ice production rates under wave conditions could be twice as large as the calm water one.