ANALYSIS OF BESETTING INCIDENTS IN FROBISHER BAY DURING 2012 SHIPPING SEASON

摘要

This paper examines the build up of ice pressure in Frobisher Bay. Ice conditions during the summer of 2012 were particularly severe and resulted in a relatively large number of besetting events. Observations were collected from four vessels and describe the conditions, which correspond to 10 besetting events. The salient factors that influenced the besetting events are examined. A summary of the observations is given, including estimates of ice cover coverage and thickness, ridge sail heights, wind conditions and level of pressure severity. For all events there was full ice coverage (95 to 100%). Reported ridge sail heights were consistently 1.2 m, with widespread rafting. A hindcast of ice stresses and deformation examined in detail a besetting incident of the Umiavut on 10 July 2012. The distributions of ice thickness, concentration, pressures and ridge thickness are presented. Critical values of the pressure and ridge thickness, which correspond to the besetting, are also given. The present work additionally addresses some of the environmental forcing patterns that give rise to ice pressure and pose risk for vessels in Frobisher Bay.