Laboratory calibration of upward looking sonars for measuring suspended frazil ice concentration

Laboratory measurements of acoustic backscattering from polystyrene pseudo-ice particles as a basis for quantitative characterization of frazil ice

“…disk radii ≈ 0.2 mm) for the cross sections to have been either derivable from or equivalent to (see Appendix, Paper II) classic Rayleigh Theory. Such a conclusion contradicted earlier inferences and frequency dependences derived from the underlying laboratory study (Ghobrial et al, 2012). In sum, there is little evidence that single frequency methods offer useful alternatives to the multifrequency ABS techniques which have been used previously in both frazil studies (Marko and Jasek, 2010c) and, much more frequently, in sediment-profiling work (Hay and Sheng, 1992;Thorne et al, 1993).…”

“…Recent river ice research efforts have included several studies (Jasek et al, 2005;Morse and Richard, 2009;Marko and Jasek, 2010a,b,c;Richard et al, 2011and Ghobrial et al, 2012, 2013 directed at quantifying frazil suspensions from acoustic backscattering (ABS) data. Although the reported results offered previously unavailable insights into frazil dynamics and properties, underlying simplifications and approximations left considerable interpretative uncertainties.…”

“…(1) and its connection with the Sonar Equation.} The noted exception to this approach (Ghobrial et al, 2012) involved the development of empirical relationships between water column-averaged S v (ν) and fractional volume (the ratio of ice-to total fluid + ice volume) as discussed below.…”

“…It has been applied to St. Lawrence River frazil data (Richard et al, 2011) gathered at a single acoustic frequency (1.229 MHz) to identify possible compatible combinations of particle size and concentration. North Saskatchewan River frazil data (Ghobrial et al, 2013) were also interpreted using a different single frequency method based upon laboratory-derived regression relationships between S v and fractional volume (F) (Ghobrial et al, 2012). Given the strong dependences of cross sections on particle size and shape, applications of the latter relationships were limited to situations in which particle size and shape distributions could be assumed to be very similar to those associated with the laboratory measurements.…”

Modeling frazil ice growth in the St. Lawrence River

“…Detection and measurement of frazil ice in rivers and lakes is difficult because frazil ice is very sensitive to handling (it cannot be sampled easily) and it evolves and transforms rapidly. Recent studies have shown that underwater acoustic sonars might offer advantages over other methods to detect and to potentially estimate the sizes and concentration of suspended frazil ice particles (Ghobrial 2012;Ghobrial et al 2012aGhobrial et al , 2012bJasek 2010a, 2010b;Richard 2009, 2010). Underwater acoustics methods have been successfully applied to other kinds of suspended particles such as sediment particles (e.g., Gartner 2004;Tessier et al 2007) and biomass (e.g., Greenlaw 1979;Medwin 2005;Brierley et al 2006).…”