| Abstract | This report documents the procedure that was used to develop an ice strength algorithm for forecasting ice strength during summer, when shipping in ice-covered waters is most active. The Canadian Ice Service used that algorithm to generate preliminary Ice Strength Charts. The algorithm was based upon the measured borehole strength and calculated flexural strength of level first year ice in the high Arctic. As such, it is most appropriate Arctic first year ice. Measurements showed that the strength of first-year ice decreased steadily from its maximum winter strength, in March, until measurements were terminated in August, at which time the ice strength was only about 13% of its maximum. The Ice Strength Algorithm related the seasonal decrease in strength to the accumulated degree-days, which were algebraically summed using mean daily air temperatures and a baseline temperature of -30°C. The mean daily air temperatures were obtained for specific regions of the high Arctic using output from a GEM (Global Environmental Multi-scale) forecast model, courtesy of Canadian Ice Service. Results showed very good agreement between the ice strengths forecasted using the suggested Strength Algorithm and those measured during three seasons of ice decay work. |
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