Flexural Strength Study of Laboratory-Produced Freshwater and Saline Ice and Beaufort Sea Ice with Granular Layer, 2023-2024

A granular layer can form on top of sea ice due to processes like snowfall, wind-blown snow accumulation, or freeze-thaw cycles, which create a distinct, less consolidated ice layer that affects the overall mechanical properties of the ice. Understanding the mechanical properties of ice with a thin granular layer is essential for predicting and mitigating the impacts of climate change on polar environments, global sea levels, and the safety of human activities in these regions. A series of flexural experiments were performed on columnar-grained ice of three kinds atop which a layer of freshwater granular ice had been bonded: first-year sea ice harvested from the winter cover on the Beaufort Sea, saline ice produced in the laboratory, and freshwater ice also produced in the laboratory. These new experiments have revealed that a thin layer of granular ice bonded to salty and to salt-free columnar-grained ice increases flexural strength when the material is rapidly bent to the point of brittle fracture. When bent slowly, the layer has no detectable effect. Strengthening is attributed to the suppression of cracking; its absence, to dislocation creep. This study was conducted at Dartmouth College's Ice Research Laboratory.

海冰表面可因降雪、风吹积雪或冻融循环等过程形成颗粒层，该层为结构松散的独特冰层，会影响海冰整体的力学性能。了解带有薄颗粒层的冰层的力学性能，对于预测和缓解气候变化对极地环境、全球海平面及该区域人类活动安全的影响至关重要。研究人员对三种表面结合了淡水颗粒冰层的柱状晶粒冰开展了一系列弯曲试验：三种冰分别为从波弗特海冬季冰盖采集的一年期海冰、实验室制备的盐冰及实验室制备的淡水冰。这些新试验揭示，当材料被快速弯曲至脆性断裂时，结合在含盐或无盐柱状晶粒冰表面的薄颗粒冰层会提高其弯曲强度；而缓慢弯曲时，该颗粒层则无明显影响。强度提升归因于裂纹扩展的抑制；而无强化效果则与位错蠕变有关。本研究在达特茅斯学院冰研究实验室开展。