STUDY ON DEFORMATION AND FRACTURE OF ICE SHEET BY OCEAN WAVES

1)波致冰盖破裂波浪在冰盖上产生的裂隙跨度约为冰盖下波长的1/4~1/2。这种裂缝跨度对波长的依赖导致了在实际冰海中观察到的冰破裂的规律。冰盖破裂的临界波高取决于冰盖下的波长以及冰盖的厚度、弹性模数和抗弯强度。本文提出的临界条件公式很好地解释了实验结果。2)随机波与冰盖的相互作用随机波在冰盖边缘的波高变化特征和频率分量在冰盖下的衰减率都取决于冰层厚度和频率，与相同频率的规则波相似。研究结果表明，随机海浪的变形可以归结为各频率分量变形的线性求和。3)半开阔水域全冰形成预报模型提出了一个预报模型，用于预测港湾等半开阔水域的全冰形成。在该模式中，冰盖的形成和增长是基于热量平衡方程和冰盖对风应力和波动的稳定性进行计算的。

1) Fracture of Ice Sheet by WavesThe crack span on the ice sheet induced by waves is between 1/4 and 1/2 of the wave length under the ice sheet. This dependency of the crack span on the wave length brings the regular pattern of ice fracture observed in the actual ice sea. The critical wave height for ice sheet fracture depend on the wave length under the sheet and the thickness, elastic modulus and bending strength of the ice sheet. The formula for critical condition proposed herein gives a very good explanation for experimental results.2) Interaction between Random Wave and Ice SheetThe characteristics of both the wave height change at the ice sheet edge and the attenuation rate under the sheet of the frequency components of random waves depend on the ice thickness and the frequency, and almost similar to that of regular wave with the same frequency. The results of this study shows that deformation of random waves can be analyzed as a linear summation of deformation of each frequency component.3) Prediction Model for Complete Ice Cover formation in Partly Open WalterA prediction model was proposedto predict the complete ice cover formation in a partly open water like a harbor or bay. In this model, the initiation and growth of ice sheet is calculated based on a heat budget equation and the stability of the ice sheet against wind stress and the wave motion.