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Snow scientist explores cool secrets of our winter landscape

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Posted: Saturday, March 10, 2012 11:43 pm | Updated: 1:44 pm, Wed Jan 16, 2013.

FAIRBANKS — For most of the year, snow is one of my favorite forms of precipitation.

While summer rain soaks into the ground and hail never lasts, snow tends to stick like paint, at least during the winter, leaving us ample time to appreciate it.

I’ve been meaning to write about the scientific work Matthew Sturm has done to explain the wonders of snow to school children. But the interview I did with him in October about the hidden world of snow never crystallized in a column.

I had visions of a regular series on snow throughout the winter, but other topics drifted in and occupied my attention.

The recent snowfall reminded me it’s not too late, however, to tell you about Sturm’s book, “Apun: The Arctic Snow.”

While “Apun: The Arctic Snow,” is suitable for third-and fourth-graders, the teacher’s guide that goes with it is for everyone.

The teacher’s guide, published along with the children’s book by the University of Alaska Press, is a 68-page guide, sold separately, that contains what every Alaskan should know about snow.

For people who live with snow for months on end, most of us know surprisingly little about it.

We drive by it, look at it, slip on it, ski on it, ride snowmachines on it and shovel it. But mostly we take it for granted.

We think if you’ve seen one snowflake you’ve seen them all, paying no attention to the unending white blanket that covers our part of the world from October to April, broken only by snowplows and occasional dripping brought on by warm spells.

Sturm is a geologist who came to Fairbanks 30 years ago to study under Carl Benson, a prominent local scientist who specialized in snow and ice research.

Benson, who did pioneering research on the Greenland ice cap, as well as on the glaciers of Mount Wrangell, says that today Sturm is among the outstanding figures in the world of snow research.

Sturm earned a master’s degree and a doctorate at UAF and continues to be fascinated by snow, not just in a technical sense, but in trying to interest a general audience in its properties.

We may regard it as a uniform and unchanging mass in which billions of particles remain static, much as particles of sand on a beach are the same on one day as the next. But out of our sight there are complicated processes at work.

It was about this time years ago that Sturm surprised me by informing me that the snowflakes that had fallen earlier in the winter were long gone.

I figured the snowflakes would become packed together, but I didn’t realize that they underwent a complicated metamorphosis.

Here is how he explains this particular phenomenon in the teacher’s guide:

“Once the snowflakes have piled up on the ground, changes start to take place, driven by weather conditions, solar heating and gravity. Three basic forces alter the snow: wind, temperature gradients and heat. The three forces are known as metamorphic forces and they can produce large changed in the characteristics of the apun,” he writes, using the Inupiaq word for the arctic snow cover.

The temperature gradient is at work every day in Fairbanks, invisibly changing the snowpack, while the wind and the heat of the sun remake the snowscape when conditions are right.

Snow on the ground is such a good insulator that the temperature on the bottom may be 30 degrees warmer than on the top. Powered by this difference, an invisible flow of water molecules takes place all around us.

“These gradients drive sublimation and condensation of water vapor, producing rapid changes in the size and shape of snow grains,” he writes. “The resulting grains, while different than snowflakes, can be equally beautiful, with elegant features and sharp geometric angles.”

Water molecules move from the bottom of the snowpack up towards the surface in a process known as “dry snow metamorphism.” One Japanese scientist compared this to a hand-to-hand bucket brigade moving pails of water to a fire.

The snow at the bottom loses moisture content and the crystals become more rounded, while the snow higher up gains moisture and the crystals grow larger and sharper.

The surface of the ground, through the course of a winter, will lose most of its moisture to the snow above it, freeze-drying the top few inches of soil.

Despite dozens of winters in Fairbanks, I never had a clue that was happening.

Before breakup I intend to mention a few more things about ice and snow that I should have known, but didn’t, before reading Sturm’s book.

•••

WEIGHING THE ODDS: The snow is weighing heavily on our minds this week, but it’s not enough to create problems for well-designed roofs.

Measurements taken at the airport and on top of City Hall show the snowload in the flatlands is about 20 pounds per square foot.

City design standards in effect since the early 1990s require roof designs capable of handling 50 pounds per square foot. The standard was raised from 40 pounds per square foot after a particularly heavy snow year when several local buildings collapsed.

The City Building Department found the roof of City Hall has about 23.5 inches of snow and it weighs 20.5 pounds per square foot.

The snow is measured with a cylinder that is pushed down through the snow to retrieve a fair sample. The contents of the cylinder are then weighed.

A cubic foot of water weighs about 62.4 pounds. A cubic foot of the snow this year weighs 10.5 pounds.

Dermot Cole can be reached at cole@newsminer.com or

459-7530.

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