The consolidation and strength of rafted sea ice
PublisherUniversity College London (University of London)
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The research presented in this thesis is an investigation into the consolidation and strength of rafted sea ice. A model for the consolidation of rafted sea ice has been developed that predicts how long it will take for the layers in a rafted section of sea ice to bond effectively into a coherent ice sheet. The rafted ice is assumed to be composed of layers of sea ice of equal thickness, separated by thin layers of ocean water. Heat transport within the sea ice is described using the mushy layer equations and the rate of freezing is given by the Stefan condition. Concurrent laboratory experiments were conducted in the Rock and Ice Physics Laboratory at UCL. To simulate a section of rafted sea ice, layers of laboratory grown saline ice were stacked on top of one another with spacers between adjacent ice sheets allowing water from the tank below to flood in. The rate of consolidation was then monitored using a combination of temperature readings recorded in the ice and liquid layer, salinity measurements of the liquid layer, and cores taken using a manual core auger. Once consolidated, cores were taken and sheared using the four-point asymmetrical bending method to measure the strength of the bond between two-rafted ice sheets. These were then compared to the shear strength of level ice. Results showed that the rafted ice had consolidated in less than a day, however it took many more days (6 to 30 depending on the conditions) for the blocks to reach maximum strength. Increasing the thickness of the ice, the salinity of the solution and the gap size all increased the consolidation time. The shear strength of the bond between rafted ice sheets was found to be ~30% weaker than that of level ice.