Modified Discrete Element Model For Sea Ice Dynamics In The Bohai Sea

In recent years, sea ice, as a kind of common natural phenomena, has been concerned widely with the acceleration development of the Marine resources and the global warming trend. In order to avoid ice disaster, a lot of numerical simulations of sea ice dynamics and monitoring methods have been investigated for more than several decades.Breakup, rafting and ridging of ice cover appears widely in the polar and sub-polar regions, and affects the growth and drifting of sea ice obviously. According to the discrete distribution of sea ice on various scales, the discrete element model (DEM) should be developed to improve the sea ice numerical model and perfect the computational precision. Thus, a modified discrete element model (MDEM) is established to simulate the sea ice dynamics in this study. Different with the transitional DEM, the ice cover is divided into a series disks with their own thickness, velocity, size and concentration adopting the concept of smoothed particle hydrodynamics (SPH) of sea ice dynamics. The size, concentration and thickness of each sea ice element, which is looked as an assembly of ice floes, can be adjusted with the law of mass conservation during the inter-element collisions. According to the non-continuous distribution and rheology characteristics of ice cover, the viscous-elastic constitutive model is adopted considering the Mohr-Coulomb friction law to determine the plastic deformation and tangential friction. To validate the reliability of this MDEM for sea ice dynamics, the drifting, ridging and diverging of ice cover in a various-width channel is simulated, and the simulated distribution of ice thickness is compared well with the analytical solution. Moreover, the drifting of sea ice in a vortex wind field is also simulated efficiently with high precision.To analyze the size distribution of ice floes in the Bohai Sea, the digital process and analysis system is developed for sea ice satellite remote images. With the techniques of denoising, binarization algorithms in the image processing, the parameters of ice floes are extracted in the Bohai Sea on January15,2001, January22,2010. February15,2013. The probability distribution of ice floe size is determined. This image processing system can be combined with the discrete element method of sea ice to simulate the dynamic and thermodynamic process of sea ice.Finally, This paper using MDEM and the initial ice field on January22,2010in Bohai Sea simulate sea ice dynamic in48hrs. The simulated results match well with the satellite remote images and field observed data. In the near future study, the MDEM will be improved with coupling dynamics and thermodynamics of sea ice. The growth and drifting of sea ice will be simulated more accurately with considering the refrozen effect and breakage feature of ice cover.