Characteristics of pack ice stress in the Alaskan Beaufort Sea

Ice stresses in a multiyear flee were continuously monitored over 6 months in the fall-winter-spring of 1993-1994. Stresses sensors were installed at sites near the edge and at the center of the flee, which was located in the pack ice of the Alaskan Beaufort Sea. Compressive stresses in the major principal stress component varied significantly among the measurement sites, being of greater magnitude and exhibiting more high-frequency variations at the edge than at the center of the flee. Maximum compressive stresses, measured at a site 400 m from the edge of the flee, ranged from 100 to 300 kPa. Tensile stresses (maximum of 50 kPa) and the minor principal stress component (+/-50 kPa) were relatively constant at all measurement sites. A cross-correlation analysis indicates that the minor principal stress is strongly correlated to changes in the ice temperature. This result suggests that the minor principal stress component provides a good first-order approximation of thermally induced stresses. Correlation between the major principal stress component and the ice temperature at the center site was also high, but weakened near the edges of the flee where the ice-motion-induced stresses became more significant. Attempts to filter the major principal stress signal to separate the thermal and ice-motion-induced stresses were unsuccessful. This result implies that the ice-motion-induced stresses, distinguished by variations in magnitude of the order of hours, also have a significant low-frequency content similar to the thermal stresses;These low-frequency changes occur over a period of days. Seasonal variations in the characteristics of the stress were also evident and are likely to reflect the developing continuity of the pack as the winter season progresses.