Healing of cracks in freshwater, saline and sea ice, 2020-2022

The combination of a decrease of the ice coverage on the Arctic Ocean, an increase of the amplitude of ocean waves, and damage due to the daily increases and decreases in temperature may lead to the breakup of ice cover. Of interest, therefore, is the strength of ice that was thermally damaged during diurnal temperature cycles. To understand the behavior of ice under these conditions, we conducted new systematic experiments on freshwater and sea ice in the present study, where the ice was cracked by thermal shocking. The cracks initially weakened the ice but within a short period of time, the ice strength returned to its original value. This observation of crack healing is attributed to the formation of a thin liquid water layer on opposing crack surfaces which aid to its freezing as contact is made during warming. The effect of crack healing may help to avoid ice breakup. Sea ice was collected in the Beaufort Sea during winter 2020, while saline ice and freshwater ice were produced in the laboratory.北冰洋海冰覆盖范围缩减、海浪振幅增大，叠加昼夜温度波动引发的热损伤，均可能导致海冰崩解。因此，研究昼夜温度循环中受热损伤海冰的强度具有重要学术价值。为探明此类条件下冰体的力学行为，本研究针对淡水冰与海冰开展了全新的系统性实验，实验中通过热冲击方式使冰体产生裂纹。初始阶段，裂纹会削弱冰体强度，但在极短时间内，冰体强度即可恢复至初始水平。上述裂纹自愈现象，可归因于相对而立的裂纹表面形成的薄液水层：当升温过程中裂纹表面发生接触时，该液层会加速冻结。裂纹自愈效应可有效规避海冰崩解风险。本实验所用海冰采集自2020年冬季的波弗特海（Beaufort Sea），而盐冰与淡水冰均在实验室环境中制备得到。