Kristen Rozell skate skis in Valdez in January 2023. (Photo by Ned Rozell)

Kristen Rozell skate skis in Valdez in January 2023. (Photo by Ned Rozell)

Alaska Science Forum: Surfing in winter on cross-country skis

With mild temperatures and ample snow, much of Alaska is now primed for cross-country skiing. It’s a sport for all ages, made possible by friction.

According to Samuel Colbeck, a retired geophysicist with the Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire, gliding on skis is like surfing on a microscopic layer of water. The rubbing of ski on snow makes it possible.

Though friction is one of the major forces interfering with glide, it also allows a skier to move efficiently because it creates heat. As a skier slides over snow, weight and friction combine to melt the surface of the ski trail, a process that’s easier to understand close up.

ADVERTISEMENT
0 seconds of 0 secondsVolume 0%
Press shift question mark to access a list of keyboard shortcuts
00:00
00:00
00:00
 

The waxed bottom of a ski and a well-packed trail both look flat, but on a microscopic level they both feature tiny peaks and valleys.

Skate skiers glide along a hilltop in Anchorage’s Kincaid Park in February 2023. (Photo by Ned Rozell)

Skate skiers glide along a hilltop in Anchorage’s Kincaid Park in February 2023. (Photo by Ned Rozell)

When a wax-coated polyethylene ski base rubs the tops of snow crystals, a tiny portion at the tip of each snow crystal melts. The ski base glides on a film of water about one micron (one-millionth of a meter) thick.

Just a small percentage of a ski base is in contact with the snow at any time. In dry snow at 15 degrees F, for example, researchers found that only one percent of the ski-base area was in contact with the snow surface.

Fresh snow also has a finer grain structure, which makes for more friction-producing contact points. In older snow, the crystals fuse together over time, forming a course-grained snowpack that causes less friction and allows skiers to go faster.

Colbeck said an average skier generates about 200 watts of heat on each ski while gliding. He likened that to the heat given off by two old-school 100-watt light bulbs, spread out over the area where the ski base touches the snow.

An experienced ski racer on a college team has even more melting power, generating about 300 watts per ski. Evidence of a skier’s work is often seen as shiny ski tracks, the collective reflection of polished snow crystals.

Skiing in really frigid temperatures reduces the release of heat, and any chance for decent glide.

Extreme cold reduces the production of meltwater because of the heat lost to a cold ski base, as well as snow crystals and the air. As the temperature drops, a skier works harder, paying a higher energy price for the same glide that seemed effortless near the freezing point.

Though a water film still forms at an air temperature of 10 below zero F, that film is too thin to be an effective lubricant. Tests performed on ski glide on snow at 10 below zero confirmed that skiing on sand would be just as fast.

• Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell is a science writer for the Geophysical Institute. A version of this column appeared in 1994.

More in Sports

The 2024-25 Juneau-Douglas High School: Yadaa.at Kalé Crimson Bears softball team pose for a photo. They begin play next weekend at the Sitka Varsity Tournament. (Photo courtesy JDHS softball)
JDHS softball returns to the circle, baseball to the mound

Crimson Bears girls in new conference, boys on new field.

Basketball official Fred Angerman Jr speaks in a Region V Tournament pregame captains meeting in 2008. (Klas Stolpe / Juneau Empire)
Pure Sole: Fast Freddy

There are two sounds I can never seem to forget. One is… Continue reading

Juneau-Douglas High School: Yadaa.at Kalé girls soccer seniors pose for a photo during Wednesday practice at Thunder Mountain Middle School. Front row left to right are Alyssa Lawhorne, Adelyn Buss, Milina Mazon, Priscilla Lam and Cerys Hudson. Back row left to right are Alison Tingey, Dori Germain, Parker Boman, Daniela Lamas, Natalie Travis and Ella Orsborn. Not pictured are Mary Canapary, Lena Field and Lola Hines. (Klas Stolpe / Juneau Empire)
Soccer teams open with DI Eagle River

New season, new conference as Crimson Bears rise up.

A pseudoscorpion contemplates a red mite for lunch. (Photo by Bob Armstrong)
On The Trails: Pseudoscorpions

Just before the spring equinox, a friend and I went out on… Continue reading

Sitka’s Syd Eubanks (13) scores between Klukwan’s Andrew Friske (12) and Dave Buss (22) during the Masters Bracket Championship Saturday at the 76th Annual Juneau Lions Club Gold Medal Basketball Tournament in Juneau-Douglas High School: Yadaa.at Kalé’s George Houston Gymnasium. (Klas Stolpe / Juneau Empire)
Masterful win by Sitka earns Gold Medal Championship

Sitka tops Klukwan 73-59 for tournament title.

Hydaburg’s Darren Edenshaw is pressured by Metlakatla’s Bryan Hayward and Chris Bryant during the C Bracket Championship on Saturday at the 76th Annual Juneau Lions Club Gold Medal Basketball Tournament in Juneau-Douglas High School: Yadaa.at Kalé’s George Houston Gymnasium. (Klas Stolpe / Juneau Empire)
Hydaburg tops Metlakatla 85-70 for C Bracket title

MVP Darren Edenshaw scores 31 in Gold Medal Championship

Angoon’s Dominic Brinson (21) scores over Haines’ Kyle Rush (13) and James Hart during the B Bracket Championship on Saturday at the 76th Annual Juneau Lions Club Gold Medal Basketball Tournament in Juneau-Douglas High School: Yadaa.at Kalé’s George Houston Gymnasium. (Klas Stolpe / Juneau Empire)
Angoon defends B bracket Gold Medal championship

Repeat champions ball out in 79-66 win over Haines

Craig’s Nani Weimer (10) hits a shot past the arc during the Women’s Bracket Championship on Saturday at the 76th Annual Juneau Lions Club Gold Medal Basketball Tournament in Juneau-Douglas High School: Yadaa.at Kalé’s George Houston Gymnasium. (Klas Stolpe / Juneau Empire)
MVP Weimer leads Craig women to Gold Medal title

Craig runs past Hooper Bay for Womens Bracket Championship

Juneau-AML’s Mahina Toutaiolepo (24) scores over Mt. Edgcumbe’s Jaylin Prince (42) during the Open Bracket Championship on Saturday at the 76th Annual Juneau Lions Club Gold Medal Basketball Tournament in Juneau-Douglas High School: Yadaa.at Kalé’s George Houston Gymnasium. (Klas Stolpe / Juneau Empire)
MVP Tompkins leads Juneau to Gold Medal title

Juneau-AML tops Mt. Edgecumbe 90-84 in Open Bracket

Most Read