| Résumé | The threat of compression of ice covers to shipping has been the subject of several recent studies. Research projects in Europe and Canada have examined factors that trigger ice convergence and approaches for predicting the risk of besetting of vessels, among other aspects of the problem. This paper examines incidents of vessel besetting due to ice compression which took place over the eastern Gulf of St. Lawrence and the Strait of Belle Isle. The paper lists reported besetting incidents over these locations during the ice season of 2013-2014. The information includes the date, time, location, prevailing wind, and observations of ambient ice conditions. The distance to the nearest shoreline was also given. Analysis of certain incidents was done by hindcasting ice drift and deformation. The results give estimates of ice pressures (ice compression) and ridge ice thickness at besetting. For incidents that were apparently triggered by onshore wind and took place over the eastern Gulf of St. Lawrence, ice pressures ranged from 24.0 kN/m to 25.7 kN/m and the ridge thickness values were from 8.2 m to 10.5 m. These values are in agreement with previous estimates obtained for besetting incidents over other parts of the Gulf of St. Lawrence and Frobisher Bay. An analysis of incidents that corresponded to wind acting nearly parallel to the shoreline in the Strait of Belle Isle produced lower values of ice pressures and ridge thickness. However, the strain rates were particularly high, which evidently caused convergence of the ice cover and prompted the besetting incidents. |
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