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Canadian technology marks future of snow studies

Researchers studying how sound waves travel through snow to produce snow property profiles



Do you want to push the button?"

The button is red, flat and a bit larger than a poker chip.

Unremarkable visually, it's what the button does that makes me feel honoured by the invitation.

The button engages a switch connected by two wires to a 20-by 30-centimetre circuit board encased in a metal box with a glass cover. The box is secured like an android infant in a cross-country skiing child carrier. A hole in the bottom of the buggy provides an unobstructed 15-centimetre space between the box and the snowpack.

Walking in snowshoes, Nicholas Kinar tows the buggy across a snowy meadow south of Bow Summit on the Icefields Parkway in Banff National Park. Every 10 paces he stops to depress the button. A saucer-sized speaker on the bottom of the unit emits a blast of crackly static, sending a sound wave to penetrate the snowpack. Two-dozen tiny microphones, each the diameter of an aspirin, are mounted on the bottom of the box 10 centimetres from the speaker.

"It sounds like static, but really it's a carefully produced and designed noise," Kinar explained. "The goal of the SAS2 [acronym for System for the Acoustic Sensing of Snow] is to determine snow water equivalent, snow depth and density, as well as snow structural and thermal properties, and to recompose images of snowpack layers."

Similar to a sonar device sending sound waves to the ocean bottom, the loudspeaker sends the noise into the snowpack. The microphones detect the reflections from the snow layers.

"The time of arrival and frequency response of the reflections are then used as inputs to a mathematical model," Kinar continued with rapid-fire enthusiasm. "This mathematical model is a collection of equations that describe propagation of sound waves through snow. By evaluating these equations, I obtain measurements of the physical properties of snow without having to dig into the snowpack."

While Kinar operates the cutting-edge technology, research technician May Guan follows. Inserting a hollow Plexiglas snow tube at the spot where Kinar took his reading (the SAS2 records centimetre-accurate GPS coordinates with each reading), she withdraws a sample from the 80-centimetre-deep snowpack, then weighs it on a hand-held scale to calculate its weight and water equivalency. Daniel Guenther, an undergrad hydrology student visiting from Germany, digs a snow study pit in the same spot. Later in the lab, they will compare the manual measurements with Kinar's SAS2.

For a century, glaciologists, snow hydrologists, climatologists and avalanche professionals have measured snow depth and density the same way — by digging a snow pit and manually examining snowpack layers. Using a snow saw, thermometer, weigh scale, scoop, magnifying glass and ruler, they study snowpack structure, density and temperature, as well as the shapes, sizes and types of snow crystals. While avalanche forecasters and backcountry skiers focus on how the snowpack layers have bonded to determine the likelihood of avalanches, snow hydrologists determine how much freshwater the snowpack will supply to creeks and rivers once it melts.