Field measurements of suspended frazil ice. Part II: Observations and analyses of frazil ice properties during the principal and residual supercooling phases

Abstract

The FrazilCam system, developed to photograph suspended frazil ice crystals in field environments, was deployed in the Kananaskis, North Saskatchewan, and Peace Rivers in Alberta. Images captured during each deployment were processed and analysed using a support vector machine (SVM) learning algorithm to separate fine suspended sediment particles that were visible in the images from the suspended frazil crystals. The size distribution of the frazil ice crystals was then produced and found to be well described by a lognormal distribution in almost all cases where the flow rate remained constant. The mean particle diameter ranged from 0.32 to 1.32 mm and volume concentrations ranging from 1.0 to 15 × 10−6 m3/m3 were calculated by assuming a constant diameter to thickness ratio of 37 for the frazil ice discs. Additionally, a unique supercooling event that reached the extremely low temperature of −0.15 °C was observed in the North Saskatchewan River and resulted in the growth of long, shard-like anchor ice crystals on all objects submerged in the flow.