| Résumé | A field program was carried out to measure the properties of multi-year ice in the high Arctic. Thicknesses are reported for multi-year ice floes in Nares Strait (9 floes), Norwegian Bay (1 floe) and Lady Anne Strait (1 floe). The diameter of the 11 floes ranged from 175 m to 7.5 km. Multi-year ice in mainstream Nares Strait drifted south at 1.38 to 2.04 km/hr in a near-straight trajectory. The trajectories of two floes were mapped using satellite tracking beacons. Floe N06, which had an average thickness of more than 9.5 m but was only about 500 m in diameter, drifted south from Nares Strait until it disintegrated along the eastern coast of Baffin Island almost two months later. Floe N08 was a 2.8 km diameter floe that had an average thickness of more than 8.7 m. The beacon on Floe N08 continues to transmit at the time of writing this report, six months later, off the eastern coast of Baffin Island. More than 1500 m of ice was drilled during the program. Five of the floes had an average thickness of more than 7.7 m, whereas the average thickness of the other six floes ranged from 3.6 to 5.9 m. Standard deviations in thickness on the 11 floes ranged from 0.7 to 3.7 m. The temperature and salinity of the multi-year ice was measured on 4.80 to 5.50 m long cores. The top ice surface was the warmest (-0.9°C) and the interior of the ice was the coldest (-6.9°C). The average temperature of the ice cores ranged from -2.6°C to -4.7°C. Salinities in the uppermost 60 to 100 cm of ice were negligible (0 to 0.2 ‰) and increased to a maximum of 3.6 ‰ towards the interior of the ice. Most of the floes had an average salinity that was quite uniform (1.0 to 1.7 ‰). Borehole strengths were conducted on five floes. The strength was lowest in the uppermost 60 cm of ice (4.0 to 11.5 MPa) and generally increased with increasing depth to 21.5 to 30.6 MPa. The average borehole strength was remarkably consistent on four of the floes (15.9 to 17.5 MP). One floe had an average borehole strength of 23.1 MPa. Comparison of the strength and temperature profiles for the different floes illustrate the inverse relation between temperature and strength. ScanSAR and Standard imagery from RADARSAT-1 were examined to determine whether individual floes were recognizable. Standard imagery was preferred over ScanSAR imagery because of its higher resolution (25 m vs. 150 m). ScanSAR images adequately captured multiyear ice floes upwards of 4.0 km in diameter, but they were not useful for identifying floes less than several kilometers across. In comparison, floes from 400 to 500 m across were detectable in the Standard images, except for when they were masked by the high concentrations of pack ice. |
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