The Slick Science of Making Olympic Snow and Ice

No one thought Brian Shimer had a chance. At two months shy of 40, the American bobsledder arrived at the 2002 Salt Lake City Olympics with four winter games under his belt, but no Olympic medals. So when his team zipped through the winding track and earned that long-awaited bronze, everyone was astonished—not least of all Shimer. ''I don't know what brought us down the hill so fast,'' he told The New York Times. ''The electricity in the air, the crowd waving and yelling.''

Certainly the crowd’s support—along with the team’s intense training and Shimer’s precise turns—were crucial. But one unsung hero of winter sports also played  starring role in the team's triumph: the ice.

In a sport when just hundredths of a second separate the winners and losers, every friction-inducing bump or groove matters. And ice wears down overtime, so Shimer and his team’s 17th start position could have easily been a disadvantage. Yet the sled finished in fifth, setting them up for the bronze. "You can't do that if the ice is not consistent," says Tracy Seitz, managing director of the Canadian ice track known as the Whistler Sliding Centre, which touts the “fastest ice track in the world.” Seitz would know: He was also one of Salt Lake City’s so-called “Ice Masters,” the experts tasked with the challenge of creating the ideal ice tracks for world-class athletes.

There’s a lot more to making ice than meets the eye. On a molecular level, the snow and ice of Olympic courses is exactly the same stuff that makes snowmen, blocks off your doorway and sends unsuspecting bystanders careening down driveways. All frozen water consists of molecules arranged in a hexagonal structure similar to a honeycomb. But the ice coating the sinuous sliding tracks for bobsled, luge and skeleton, or the firm, flattened snow of a ski course are precisely shaped and conditioned over the months leading up to the games, optimizing the properties of these frosty forms of water.

"It's not just a hunk of ice like you'd normally think of, like ice cubes sitting in your freezer," says Kenneth Golden, a mathematician at the University of Utah who studies the structures of ice. "It's a much more fascinating and complex substance than people would normally think."

Ice, Ice, Maybe

The first step for building any ice rink or track is to purify the water to remove dissolved solids like salts and minerals. Such impurities don’t fit in the regular hexagonal structure of ice that forms as water freezes. The same property can be seen in sea ice, Golden explains, which excludes the salt of the ocean water as it freezes, creating a plume of extra salty liquid below the ice. But in a rink or track, impurities collect between crystals or are shoved to the surface, creating slight weaknesses in the ice. As Seitz says, "the more pure the water is, the more dense the ice slab would be," which translates to a more consistent surface.

The quality and purity of ice is so important that a special position—the Ice Master—has been created to ensure its viability. Forget sculptors who make intricate ice sculptures; Ice Masters shape ice into some of the most impressive structures on earth. At least a year in advance of the Games themselves, they spray hundreds of paper-thin coats of this ultrapure water on a concrete course or rink, which is chilled by an embedded refrigeration system for rapid freezing. It takes around five days of non-stop work to lay the frozen track for a bobsled run, says Seitz.

This process prevents the formation of frost layers, which form when humid air freezes over the icy surface. Frost layers can trap air bubbles in the ice, which can work their way out as tiny pockmarks. "We don't think of it [ice] as fluid, but it is very much so fluid, and it's moving all the time," says Seitz. "Those layers of air in the ice will create weaknesses that can break out and create inconsistencies in the ice surface." For a bobsled, one tiny pockmark can cause a sled to bounce, perpetuating the problem. "One bump creates two bumps creates three bumps, and on and on and on," he says.

Other ice-based sports like hockey, ice skating and curling use similarly meticulous layering. But for each sport, the ideal ice temperature and thickness is different. Ice skating, for example, touts the thickest and warmest ice: The roughly two-inch surface is held around a balmy 25 degrees Fahrenheit, which allows skaters to hook their skates in the ice as is necessary to perform their gravity-defying jumps and spins.

Some of the magic isn’t just in the engineering—it’s in the nature of ice itself. At its edges, the water molecules in ice aren't as strongly locked into the honeycomb as in its center, creating a liquid-like layer known as pre-melt that lubricates the surface and is thought to give ice its unique slippery quality. The intense pressure of a skate or blade applied to a tiny sliver of ice can slightly depress its melting point, which likely contributes to that slick layer of water. Slight melting from the friction of a sliding blade on the surface is also thought to add liquid to the mix.

Some Ice Masters try creative measures to achieve the perfect surface. Among ice aficionados, there’s a longstanding myth that music can help ice crystallize. For the 2014 Sochi Olympics, Ice Master Dimitri Grigoriev played classical music—Vivaldi’s “Four Seasons,” to be exact—while laying the icy track. “We had classical playing here, so that the ice crystalizes in the proper hard manner, not rock music, not silence,” he told NPR, adding: “I am serious about it, look it up!” (NPR looked it up, and there is no reputable science to back this claim.)

Seitz isn’t impressed by such superstitions. "If we're going to do anything we're probably blasting heavy metal music," he says—for the crew, not the ice. It keeps his crew "awake and going hard" during the grueling hours of work laying the track, he says.

The More You Snow

As a PhD glaciologist, Sarah Konrad has spent her fair share of time thinking about snow. But her connection with the white stuff is also more personal: She competed in both biathlon and cross-country skiing events in the 2006 winter Olympics in Torino, Italy at age 38—the first U.S. female to qualify in two sports at the winter games.

Surprisingly, the slowest conditions for snowy sports are the ones recreational skiers seek most: freshly fallen powder.

Unlike ice, which forms from freezing water, snow forms from the crystallization of moisture or water vapors in the atmosphere when it is "supercool," or chilled just below its freezing point. In order to actually form a crystal, the water vapor must encounter something, like a fleck of dust, to trigger its crystallization. Exactly why these particles are needed and how they assist in snow formation is still under debate, but without them it has to be astonishingly cold—well below -20 degrees Fahrenheit—for the ice crystals to form on their own.

Once it begins, the crystal attracts other supercooled water vapors to pile in intricate patterns. The common six "winged" snowflakes, as Konrad calls them, echoes the hexagonal arrangement of frozen water molecules themselves. Though gorgeous, those intricate flakes are not optimal for sport. The edges and angles that make the snowflakes so visually appealing also mean roughness for a ski riding overtop, and slow going for the Olympians. "It's an uneven surface, even at the microscopic level," says Konrad, who is currently the associate project director at the University of Wyoming.

But once the snow touches the ground, the snowflake shape begins to change. Aside from the effects of wind and other physical forces, the snowflake itself slowly morphs over time, becoming more compact and rounded. "You go from this feathered, intricate crystal to something that's more like a ball bearing," says Konrad. "That's a lot faster, because it's got less rough edges."

Some expert course builders even prefer artificial snow—which, they say, has a “old snow” feel without the effort of aging—to the natural flakes. This snow is created by spraying a fine mist of water and compressed air over the course. The expansion of the air chills the moisture and keeps it aloft, ensuring adequate freezing time. The crystals lack the necessary conditions and time to form intricate six-winged flakes, says Konrad so the resulting shape is predictable, making it easy to work with for course building. "But that takes some of the fun out of it," Konrad adds.

For alpine courses, however, a lot of work goes into ensuring the track is fast and durable. The engineers will often wet the surface and then allow it to refreeze, creating a tightly packed, fast course. But if the snow is too wet, or the air too warm, the course will quickly become rutted and fall apart. The people responsible for snow courses spend months tending to the runs leading up to the games—constantly shaping and reshaping every corner and pitch to achieve a perfect balance between a firm, fast course and a sheet of ice.

Of course, sometimes the whims of weather are impossible to correct for. This was an issue at the 2014 games in Sochi, where unusually warm conditions led to bumpy courses and granular, or “sugary,” snow. For the half-pipe, more than half of the competitors fell during the qualifying rounds. Two-time Olympic medalist Hannah Teter called the pipe "dangerous" and "crappy."

For cross country skiing, says Konrad, "Warmer conditions are where your waxes and your structure become extraordinarily important." Various combinations of waxes are applied to the bottoms of skis—often by literal ironing—to help them glide easily atop the snow. And if you use the wrong wax, Konrad explains, "you can really blow it." Teams spend exorbitant amounts of money and time on the wax techs who handle these decisions, the techs head out to the courses in the two years leading up to the event to learn about the range of conditions they may encounter and what works best in each.

…

The Winter Sports all rely on—and exist thanks to—the unique properties of frozen water. After all, Golden points out, ice skating began because of the simple fact that ice floats atop a liquid pond. In a broader sense, the diversity of life that exists at the North and South Poles is due to the fact that the ice forms a shelf that supports life above, and protects the liquid realm below. As Golden marvels: "It's all because of this one little thing: because the solid form of water is less dense than the liquid form.”

Yet as the climate warms and snowfall becomes increasingly scarce in some locales, outdoor winter sports have come under threat. In Sochi, the organizers created enough snow to cover 1,000 football fields, covering the voluminous piles with insulated yoga-mat like blankets. Along with tech to create artificial snow and preserve snow from year to year, these types of fixes may become increasingly important for the Olympics in the years ahead.

Fortunately, that isn't the worry in PyeongChang, where February wind chill commonly hovers in the single digits. In fact, temperatures might even drop below optimum conditions for some sports: For bobsled, Seitz says, in temperatures well below 23 degrees Farenheit, the ice is extra brittle. For cross-country skiing, says Konrad, the "happy temperature" is around 25 degrees Fahrenheit; any colder and snow becomes dry and slow.

Konrad takes all the conditions in stride. "From a skier perspective, there really isn't a 'best' snow, as long as it's there and comparable for all the competitors, we're usually pretty happy," she says.

But as long as there are winter games, there will be no shortage of the factors and conditions that meticulous Ice Masters take into account when making their medium. After 45 minutes of talking ice, I asked Seitz for any parting thoughts on frozen water. "I probably could go on and on forever," he says.

Maya Wei-Haas | | READ MORE

Maya Wei-Haas is a freelance science writer who specializes in geology of Earth and beyond. Her work has been featured in National Geographic, News from Science, and AGU’s EOS.