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Fracture of warm ice

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If you have a question about this talk, please contact Michael Thorne.

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Understanding how ice fractures has fundamental importance in arctic marine technology, geophysics, and climate studies. The fracture processes of interest include fragmentation of sea ice against polar ships and offshore wind turbines, failure of sea ice by ocean waves, formation of large leads in sea ice, and formation of crevasses in glaciers. The importance of ice fracture research is enhanced by global warming, which is not only melting the ice, but is both increasing the fragmentation and changing the mechanical properties of ice. Warm ice is different than cold ice.

The talk will introduce recent large scale laboratory experiments on the deformation and fracture of warm (-0.5C) columnar freshwater ice. The largest test plate had dimensions of 19.5m x 36m and a scale range of 1:39 was covered. Loading times from 2 seconds to 1000 seconds resulted in both elastic and viscous behaviour. It was observed that the rate and scale effects of fracture were interrelated and that the viscoelastic component of ice deformation was negligible. The results obtained include apparent fracture toughness, fracture energy, and size of the fracture process zone at the crack tip. The results are useful in future modelling of ice fracture.

The talk will also discuss the effects of the warming ice on polar navigation. It appears that the forces on a ship hull, when breaking warm and weak ice, may be just as high as the ice loads caused by cold and strong ice. While the strengths of cold and warm ice are different, the resulting forces on a ship hull may be similar. This observation underlines the importance of fracture processes over strength in ice research.

This talk is part of the British Antarctic Survey series.

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