Seasonal Decay of First-year Sea Ice: Field Measurements

• Main Authors: Johnston, Michelle, Frederking, Robert
• Format: Report
• Language: unknown
• Published: National Research Council Canada 2000
• Subjects: Sea ice
• Online Access: https://dx.doi.org/10.4224/12340899; https://nrc-publications.canada.ca/eng/view/object/?id=bb6f1319-ea75-4d06-9367-043874217e90

This report describes the field program undertaken from 21 May to 19 July 2000 to measure the parameters that best characterize the ice decay process. During the field program, thickness of the first-year sea ice decreased from 1.55 m to 0.80 m, at which point the ice was virtually isothermal. The ice freeboard decreased from 60 mm in late May to a negative freeboard (melt ponding) in late July. Desalination was first observed in the surface layer of ice and eventually occurred in the bulk layer of ice, as indicated by the bulk salinity of 5 � in late May and 0.5 � in late July. More than one hundred borehole jack tests were conducted over the sampling period at depths 0.3, 0.6, 0.9 and 1.2 m. The average decrease in ice strength for the four depths was 8.7 MPa over the sampling period, most of which occurred between 4 June and 1 July. The surface layer of ice showed the largest decrease in strength over the sampling period (14.1 MPa to 2.1 MPa). Ice at a depth of 0.90 m had the least amount of change in strength (10.5 MPa to 3.7 MPa). In late July the bulk strength of the ice was only about 27% of what it was in late May.