First-year Ice Conditions for Operations of the Canadian Coast Guard Polar Icebreaker

摘要

This paper describes a study of first-year ice conditions that the new Canadian Coast Guard Polar Icebreaker is likely to encounter. About 50 years of ice thickness, snow depth and air temperatures at 10 stations in the Arctic were analyzed for average and extreme values. The maximum annual ice thickness at 8 of the 10 stations was less than 2.5 m. At two stations, Eureka and Hall Beach, maximum annual thickness greater than 2.5 m was measured but only occurred about once every 10 years. Overall an ice thickness of 2.5 m is a reasonable representation of maximum first-year ice thickness. Long term trends in maximum ice thickness and decadal comparisons were assessed and showed a trend of 1 to 3 cm decrease per decade. The flexural strength of sea ice depends directly on salinity and temperature of the ice cover, which are indirectly related to ice thickness and air temperature. The flexural strength, determined from these indirect factors, was seen to decrease from March onwards, decreasing rapidly in May and June. The flexural strength in March averaged 0.7 MPa. While flexural strength decreased from March onwards, ice thickness continues to increase through to June. Ship resistance in first-year ice at slow speeds relates to ice thickness and flexural strength. Examining the two factors indicated the maximum low speed resistance would be expected in April.