An Upward-Looking Sonar System to Profile Ice Keels for One Year

A seabed mounted, upward-looking sonar device was deployed in the shear zone of the Southern Beaufort Sea for the winter 1978/79. Keel drafts were recorded every 6 seconds, providing the first time section of this ice regime. The ice growth rate is about half that measured in landfast ice and predicted by the thermodynamic models of Maykut et al (1975). The most likely cause is the substantial ice movement within the zone resulting in dense ridging and open leads, coupled with increased fog and snow cover. Keel drafts show grounding in 30m of water, while the probability function fits a negative exponential. Based on this equation and other laser photographic data statistics, a keel-to-sail ratio of 4.0 is derived.