Archive for July, 2011

Ice roads and igloos

July 11, 2011

Ice melt to close off Arctic’s interior riches: study

One of the things I find interesting about ice is its use in engineering. Ice and snow are actually fantastic building materials for certain purposes–mostly due to their cheapness and ubiquity, but sometimes also because they have useful physical properties. You may have heard of Pykrete, the mixture of ice and wood pulp that was proposed as a potential material for aircraft carriers. The wood pulp increased the strength of the brittle ice; it also reduced its thermal conductivity, slowing down melt. But apparently the fact that ice flows under its own weight, combined with the fact that such a carrier could only be used in cold weather or with massive refrigerating apparatus, doomed the project.

In cold climates, however, ice is a natural material for all kinds of things. For instance, the ice roads made famous by the show Ice Road Truckers and whose impending loss is bemoaned in the article at the top of this post. Or the ice pier at McMurdo, mentioned in this post and shown below being trimmed to size by several explosive charges:

BOOM

Ice structures needn’t be solely functional. For one thing, it’s a popular sculptural medium. You’ve also probably heard of ice hotels like this one in Sweden or this one in Québec. Despite its beauty, though, ice isn’t the most functional material for living quarters; it conducts heat too well. For dwellings, you want something with good insulative properties: snow!

The most famous snow dwellings are those made by the Inuit people of the high Arctic: igloos. (“Iglu” can actually refer to any type of dwelling, but for my current purposes I’m most interested in the temporary, dome-shaped, snow-and-ice structures.) This webpage discusses igloo technique, including the use of lamps to melt the interior so that it will refreeze as structurally stronger ice. (It is worth noting that traditional cut-block igloos work best with a certain type of wind-packed dry snow that is, I think, much easier to find in the Arctic and Antarctic than in temperate regions.)

But snow shelters are useful for anyone camping in snowy conditions. This chapter of the US Antarctic Program Field Manual (PDF link) describes the basics of several different types of snow shelter. The quinzhee, for instance, used to be a major feature of McMurdo Happy Camper school. The US Antarctic Program approach is to build up the quinzhee by shoveling snow on top of a pile of equipment which is then removed to create a cavity; more traditional quinzhees may involve creating a pile of snow and later hollowing it out.

When I did Happy Camper they emphasized the snow trench as a shelter that could more easily be built by one person, if necessary:

Snug and warm(ish.)

The one disadvantage of a snow dwelling this small is that one is forever knocking snow off the walls and down the back of one’s neck. Igloos and quinzhees are far preferable if you have the time and manpower, not to mention being more visually impressive.

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Transcript: The Snow Wall

July 6, 2011

Hey, back to transcripts! I’m pleased that this one was next in the sequence, because it actually ties in nicely with a post I’ve been wanting to do about engineering with ice and snow.

Original audio post.

“The wind came back today. It started out calm enough, and we almost went out to make measurements. But when we called the forecasters at McMurdo, they told us that the wind was due to pick up soon, and would get to thirty knots–gusting to fifty–sometime tomorrow.

On hearing this, Mel pointed out that we were going to need to prepare the camp for the onslaught of wind and drifting snow. This meant building another snow wall.

A snow wall is both made of snow and designed to control snow. It’s simply a low structure made of snow blocks that serves to slow down the wind and make it drop its snow upwind of camp, instead of on top of us. The wind carries truly impressive amounts of drifting snow across the landscape, and it dumps it every time it gets slowed down by passing over irregularities, such as our tents. We already have two snow walls, but in the six weeks the camp has been here, the space behind them has already entirely filled with drifted snow.


A snow wall with the space behind it filled in with snow.

Most of the snow around here is extraordinarily hard-packed, and our resident snow scientists are astonished by its strength-to-weight ration. In many places, you need a chainsaw to really make much of a dent in it in any sort of efficient way. So, Mel got out the chainsaw, and cut enough blocks to make our walls.


Sorry, no chainsaw pics--this is after it gave out and Mel and Martin were cutting out the last few blocks by hand.

We had them assembled in fairly short order, so we got a little creative. Mel built an arch, I built a turret, and Martin and Ruschle spent most of the afternoon digging a snow pit and being astonished at it.


Blocks en route to their place in the wall.


Mel's arch and flowerpot (or rooster, depending who you ask.)

Martin says the snow here consists mostly of depth hoar, a sort of re-crystallized snow that’s ordinarily [that is, in more temperate regions] light and crumbly, but here is very hard—“like cement”, he says. Ordinary snow shovels would break on the first try. We use sturdy metal gardening shovels (the labels say they’re “contractor grade”) and they still have trouble. The depth hoar snow is also full of little crystalline cups and ??, quite delicate-looking for all its strength.

So, we have a new snow wall, and hopefully we’re well prepared for the coming storm. I’ll let you know how it goes. Cheers!”


Part of the complete wall.


Detail.