Pack ice stress and convergence measurements by satellite-tracked ice beacons

Relationships between pack ice stress, ice convergence and atmospheric conditions are investigated with data collected by satellite-tracked ice beacons deployed on the pack ice off the Canadian east coast in March 1996. Ice beacons containing Global Positioning System (GPS) sensors monitored pack ice convergence and divergence. Stationary tests showed that on average the beacons provided hourly data 93% of the time with an absolute positional accuracy of 37m. The mean relative distance accuracy was 17m with a 87% data return when positions from all satellite constellations were used. When only positions from similar satellite constellation were used the relative distance accuracy was 1.7m with a 55% data return. Ice stress data were collected by a 3-directional ice stress sensor deployed on a floe that was the centre of a pack ice triangle monitoring ice convergence/divergence with GPS ice beacons. The pressure sensor facing the thick offshore pack ice recorded pressures between 20 and 40 kPa when ice temperatures at the sensor were between -3.5°C and -2.5°C. Multi-variate regression analysis showed that the response of the major principal stress was 0.36 kPa for each 1 m/s of wind forcing and that the wind and the ice temperature effects explained 85% of the variance in the major principal ice stress. Since at these warm ice temperatures both the ice volume and ice strength decrease when ice warms, the thermal response of the major principal stress was a decrease of 24.9 kPa for each 1°C of ice warming