Multi-year pressure ridges in the Canadian Beaufort Sea

Abstract

Pressure ridges and hummocks are the largest of the sea ice relief features seen in the ice cover which characterizes the Canadian Beaufort Sea. Due to their massiveness and structural integrity, multi-year pressure ridges are generally considered to be the most formidable formations in this area and represent not only a significant impediment to shipping but also a major problem in the design of offshore structures. Here, the findings of a field study designed to generate fundamental data on multi-year pressure ridges in the near shore zone of the Canadian Beaufort Sea are presented. The study investigated the geometry of eleven floating multi-year ridges or ridge fragments and the sail height and keel depth of four additional multi-year ridge fragments. The cross-sections of multi-year ridges with total thicknesses varying between 9.6 and 41.8 m were examined and the results suggest that they can be adequately represented by one ridge model with a constant sail to keel ratio and geometry. It is also shown that the ice comprising multi-year ridges is solid with the interblock voids existing at the time of their formation being completely filled with ice. The data obtained from this study is being used in the engineering design of exploration and production systems for the Beaufort Sea. In the shallow waters of this area, exploratory drilling from artificial islands has been carried out since 1973 and, since 1976, the exploration effort has extended into the deeper waters of the Beaufort Sea using drillships.