Decay of first year sea ice : A second season of field measurements

This report describes a second season of field measurements undertaken to characterize the seasonal ice decay of landfast first year sea ice. The project was conducted from 14 May to 28 June 2001. The depth of the snow cover and the thickness, temperature and salinity of the ice were measured on a near-daily basis during that time. The ice thickness between mid-May and early June ranged from 1.30 to 1.45 m. A borehole jack assembly was used to measure the in situ confined compressive strength (borehole strength) of the ice from 14 May to 11 June. More than one hundred borehole jack tests were conducted at ice depths 0.3, 0.6, 0.9 and 1.2 m. No significant ice ablation occurred during the time that the borehole jack tests were conducted. Strength measurements from the two, sequential years of testing indicated that the ice underwent four well-defined stages of strength reduction. Stage I extended from 14 May to 20 May during which the ice lost from 25 to 30% of its strength. Stage II occurred from 20 May to 3 June and was characterized by two weeks of stable ice strength measurements. Stage III occurred from 3 June to 2 July, during which the ice further lost 65 to 80% of its strength. The final stage, Stage IV, extended from early to late July (at which point measurements terminated). During Stage IV, strength throughout the full ice thickness reached a stable value of 2 to 3 MPa. Strength measurements showed that ice characterized by Stage IV had only 80 to 90% of its full winter strength.NRC publication: Ye