STUDY ON DEFORMATION AND FRACTURE OF ICE SHEET BY OCEAN WAVES

1)波浪对冰盖的破坏波浪在冰盖上引起的裂缝跨度为冰盖下波长的1/4 ~ 1/2。这种裂缝宽度与波长的关系，使实际海冰中观测到的冰断裂具有规律性。冰盖断裂的临界波高取决于冰盖下的波长和冰盖的厚度、弹性模量和弯曲强度。文中提出的临界条件公式能很好地解释实验结果。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冰盖下频率分量的衰减速率都与冰盖厚度和频率有关，与同频率的规则波基本相似。研究结果表明，随机波的变形可以分析为各频率分量变形的线性求和。3)部分开放水域完全冰盖形成预测模型提出了港口、海湾等部分开放水域完全冰盖形成的预测模型。在该模式中，根据热收支方程和冰盖对风应力和波浪运动的稳定性计算冰盖的开始和增长。

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.