Wave-generated fractures in river ice covers
Wave-generated fractures in river ice covers
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DOI：
10.1016/j.coldregions.2004.07.002
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发表时间：
2004-12
影响因子：
4.1
通讯作者：
S. Beltaos
中科院分区：
文献类型：
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作者：
S. Beltaos
北部河流冰盖的破裂是许多水生物种生命周期中短暂但至关重要的事件，可能引发极端冰塞事件，造成重大社会经济影响和重大气候变化影响。一个重要但模糊理解的破裂过程是低幅度水波导致冬季冰盖破裂。之前关于这个主题的工作是基于无限长的波在无限长且“无边”的冰盖下传播的假设。这种配置没有考虑到冰边缘或横向裂缝附近所施加的结构约束。因此，它仅提供弯曲应力的近似值，并且很少说明前进波可能产生的裂纹间距，而这是可以在现场识别相关断裂机制的唯一视觉证据。在此，通过对冰响应方程进行合理的简化并使用有限范围的波形来考虑边缘邻近度。结果表明，这种条件通常比无限波/无边盖配置产生更高的弯曲应力。峰值弯曲应力与边缘的距离（定义裂缝的间距）随波长变化，并且小于 100 个冰厚度左右。这与冰塞释放引起的高振幅单波（或浪涌）相当，但比蜿蜒的河流平面形式引起的水平面弯曲产生的裂缝要少得多。目前的结果与有限的现有证据的比较表明，波浪产生的裂缝是在冰塞释放浪涌通过期间发生的。
The breakup of the ice cover in northern rivers is a brief but crucial event in the life cycle of many aquatic species and can trigger extreme ice jam events with major socio-economic impacts and significant climate change implications. An important, but vaguely understood, breakup process is the fracture of the winter ice cover by low-amplitude water waves. Previous work on this subject has been based on the assumption of an infinitely long wave propagating under an infinitely long and “edgeless” ice cover. This configuration does not account for structural constraints imposed by the proximity of an ice edge or a transverse crack. Consequently, it only furnishes approximate values of bending stresses, and tells little about the spacing of cracks that may be generated by an advancing wave, which is the only visual evidence that can identify the relevant fracture mechanism in the field. Herein, edge proximity is taken into account by making plausible simplifications to the ice response equation, and using wave forms of limited extent. It is shown that such conditions generally produce higher bending stresses than does the infinite wave/edgeless cover configuration. The distance of the peak bending stress from the edge, which defines the spacing of cracks, varies with wavelength and is less than 100 ice thicknesses or so. This is comparable to that of high-amplitude, single waves (or surges) that result from ice jam releases, but much less than fractures generated by bending on horizontal planes, caused by the meandering river plan form. Comparison of the present results with the limited available evidence indicates that wave-generated fractures occur during the passage of ice jam release surges.