Seussian Snowballs

November 27, 2012

I wrote this poem about Snowball Earth for the Pacific Science Center’s Polar Science Weekend. Usually I take considerable enjoyment in putting as many obscure and multi-syllabic words into my poems as possible, but in this case I was trying for a younger audience.


I. THE FREEZE, or, Ice-Albedo Feedback

A long time ago, in a place not so far
On the third planet out from a middle-sized star
A watery world, all flecked blue and white
Where conditions would shortly be perfectly right:

The gases that made up the atmosphere changed
As the continents gradually got rearranged
Reflecting more sunlight back out into space
And allowing heat out at a speedier pace.
As the planet cooled down, ice crept toward the equator
And the sunlight reflected grew greater and greater
And the planet cooled more and the ice grew still faster
And the ice sheets and glaciers were vaster and vaster.
When the tropical seas fell beneath the ice pack
It was clear from that point there was no turning back.

The planet was wrapped in a blanket of ice
So thick it could swallow the Space Needle—twice.
It looked like a snowball, so shiny and white
And therefore it reflected most of the sun’s light.
With no light to absorb, it stayed snowy and cold
Till this super-Ice-Age was millions of years old.

II. THE THAW, or, CO2 to the Rescue

But—volcanoes! Undaunted by ice, they don’t care
They just keep spewing lava and gas in the air
With the oceans iced up, gas had no place to go
And so, though the progress was terribly slow
Greenhouse gases built up for a very long time.
Very slowly, the temperature started to climb.
We don’t know all the details (we’re still finding out!)
We do know the ice melted—of that there’s little doubt.

For the planet was Earth, as you no doubt have guessed.
Ice now sticks to the poles (perhaps taking a rest.)
Though the Sun’s now too warm to let Earth freeze again
Earth-like worlds around other stars might well have been
Sealed up under the ice, like we were long ago.
Perhaps some worlds still lie under miles of snow.
There could even be life, waiting for things to warm
Or well-suited to cold with a strange alien form.

But this story I’ve told of seas dark and snow pale
Is just a small part of a more complex tale
For water and ice come in other shades too
From near black to snow white to umpteen kinds of blue.

So the thing I’ve been working to find out so far
Is: what makes ice and snow be the colors they are?

III. LIGHT AND ICE, or, Why Things Work This Way

Two ways that light works are the main things that matter:
We science types call them absorption and scatter.

All things absorb light, but some don’t absorb much–
things like air and Saran Wrap and windows and such.
The more “stuff” light goes through, the less light is left
So you’ll get more absorption from things with more heft.
And some things allow only certain shades through
Like ice, which absorbs red but still lets through blue.
That’s why glaciers are blue, and not red or green
(Or some times they’re a nice sort of aquamarine.)

So that’s why ice looks blue, but then why is snow white?
Snowflakes are just miniature ice crystals, right?
Indeed, snow is just ice in the form of small flakes
But what makes it unique is the shape that it takes.
See, when light hits a surface, it changes direction.
(You can see this yourself with a moment’s inspection:
Put a pencil in water—it looks bent, right where
It comes out of the water and into the air.
It’s not really bent, but the light you see is.
That’s what we call refraction in this science biz.)

So every time light hits a snowflake, it bends
And with lots of snowflakes, that beam of light ends
Up bouncing around and around ‘till it goes
Back out into the air and away from the snows.
That’s why snow looks so bright—any light that goes in
Will quickly be scattered right back out again.
This works much the same for light red, blue or green
Which is why snow looks white. (But, as you may have seen
Light that goes through enough snow will look a bit blue
Because snow’s made of ice, and it can absorb too.)

There are many more ways to change ice’s color
Ice is brighter with bubbles, while dust makes it duller.
And there’s probably ways that we haven’t found yet
So we’re out there looking for new ones, you bet!


Graupeling with Seattle Snow, or, Rime and Reason

January 17, 2012

Seattle is enjoying one of its all-too-rare episodes of snow—well, I’m enjoying it, at least. Upon leaving the house this morning to walk to work, I found the sidewalks lightly dusted with an interesting type of snow we in the biz call graupel.

Most snowflakes, the six-sided ones you probably think of when you think of “snowflake”, grow by the condensation of water vapor. The individual water molecules attach to the snowflake in an orderly fashion, like building a structure out of Legos, and you end up with a regular crystalline shape.

Sometimes, though, the snowflake will pass through a cloud of water droplets as it falls down to the ground. As it hits the snowflake, the whole water droplet will freeze almost instantly, retaining its rounded shape. The snowflake bounces around in the cloud of water droplets, accumulating more and more, and your orderly Lego structure starts to look like someone has been pelting it with spitballs. These frozen water droplets are called rime. When so much rime has accumulated that the underlying shape is no longer visible, the snowflake has become a pellet of graupel.

In the picture below (sorry for the questionable quality, it’s a cell phone camera) you can see quite a few snowflakes; I’ve circled one on the left that retains the crystalline snowflake shape, and one on the right that’s still clearly six-sided, but so covered in rime it looks like it’s wearing a fur coat. (My advisor called this a “textbook” rimed snowflake.) Elsewhere in the picture you can see a few pellets of shapeless graupel.

Rimed and unrimed snowflakes

Circled on the left: a classic snowflake. Circled on the right: a snowflake covered with rime (frozen water droplets.)

Incidentally, this also goes to show that you don’t need a microscope to appreciate snowflakes; your eyes will do just fine. I’ve found that a good method is to go out when the snow is falling and catch snowflakes on a fuzzy hat, either faux fur or knitted with especially fuzzy yarn; the snowflakes will be caught on the fibers, where they can be more easily examined without melting.

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:


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.

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.


Oh, and speaking of timelapse…

June 25, 2011

Speaking of timelapse videos, here are a couple of others that I quite like:

Sea ice near an Adelie Penguin colony. Shows the evolution of sea ice over a period of time (perhaps late spring and summer?) Partly I just like this because the motion of the tides makes it look like the ice is breathing.

Sea stars, urchins, Nemertean worms, and other denizens of the under-ice seafloor consume a seal carcass. Narrated by Sir David Attenborough! Not for the easily grossed out or those who are unsettled by crawly things.

Other people talk about ice!

June 25, 2011

I’ve been trying to do more with this blog than just write text and post it—WordPress offers a wide variety of features, and blogging is at its best when it’s part of a larger ecosystem rather than just one person talking in isolation. So I’ve been adding links to the blogroll. Allow me to present a few here:

From a Glacier’s Perspective offers detailed descriptions of glacier retreat around the world, with each post focusing on a different glacier. This post describes how a glacial feature called ogives can be used to help measure glacier velocity. (Ogives are “ripples” in the glacier that form due to the influence of icefalls: the area of ice that happens to be going over the icefall during the summer melt season melts faster than the ice around it, leaving a trough that then moves down the glacier.)

The IceBridge Blog recounts news from NASA’s IceBridge Campaign. The aerial surveys of IceBridge use a variety of instruments–lasers, radar, even a gravimeter–to survey the Earth’s ice. The information gathered from IceBridge will “bridge” the gap between IceSAT-1, which stopped taking data in 2009, and IceSAT-2, which is scheduled for launch in 2016. The blog includes both pretty pictures of icy landscapes and discussions of the science behind the work, such as this post on how airborne gravimetry can tell us about the shape of the land below water and ice.

For those of you wanting to see more of Antarctica (one of my favorite continents!) there’s the “Landsat Image Mosaic of Antarctica (LIMA)” which allows you to pan and zoom all over the continent. Anthony Powell’s photography shows the place on a slightly more intimate scale, mostly around McMurdo and including some justly famed timelapse films. Or Maria Coryell-Martin’s Expeditionary Art captures both the Antarctic and the Arctic, capturing the feel of the icy realms in a way photographs sometimes can’t.

I’ll be adding more as time goes along! In particular, I want to find some good resources on ice elsewhere in the solar system, which is a fascinating subject I haven’t even gone into yet.

One glacier, two glacier, fast glacier, blue glacier

June 20, 2011

Oneof the tricky bits about glaciology is distinguishing between different ice features. There’s the question of terminology, such as figuring out when an icefield (a large mass of glacial ice, often with many glaciers flowing out of it) becomes an ice cap (same thing, but larger and tending to be dome-shaped) becomes an ice sheet (like an ice cap, but over 50,000 square kilometers.) Today my dad (happy Father’s Day!) alerted me to an article in the Anchorage Daily News discussing the difficulties of counting glaciers.

Glaciers, like rivers and streams, often flow into each other or split apart. Exactly when one glacier becomes two glaciers can be a tricky thing to determine, and now that so many glaciers are retreating, these points of merging or splitting may disappear altogether. So what was one glacier with three branches might become three glaciers. For instance, in the photo below you can see how several tributaries merge into a single calving front at Columbia Glacier.

Columbia Glacier in 2004

Columbia Glacier in 2004. Photo by W. Tad Pfeffer.

(I got this photo from Wikimedia Commons.)

And here’s an amazing timelapse video from the Extreme Ice Survey (I’ve seen it shown at a lot of glaciologist meetings and conferences) that shows how the front of Columbia Glacier retreats back until the several “tributaries” start to look like separate glaciers again. It goes so far and so fast they have to move their camera several times so that the front of the glacier stays in the frame.

Of course, for many purposes, the important thing is not how many glaciers there are, but how much ice there is in the glaciers. Although there’s not very much water stored in mountain glaciers like these compared to the water stored in the great ice sheets of Antarctica and Greenland, the mountain glaciers are melting extremely quickly (well, quickly by glacial standards) so a major percentage of current sea level rise is due to meltwater from glaciers like the Columbia. You can’t tell how thick a glacier is just by looking, so determining the volume of the world’s glaciers—and just how fast that volume is changing—is one of the important ongoing problems in glaciology.

Feeding life, feeding back

June 16, 2011
A scanning electron microscope image of cells of Chaetoceros dichaeta, from Cefarelli et al. 2011.

A scanning electron microscope image of cells of Chaetoceros dichaeta, a type of diatom, from Cefarelli et al. 2011.

One of the most interesting aspects of climate dynamics is the role of feedbacks. There are two kinds of feedbacks, positive and negative. This earlier post about Snowball Earth describes a positive feedback, in which Effect One (the freezing of seawater) leads to Effect Two (the reflection of light back into space, which cools the planet) which in turn intensifies Effect One (more seawater freezes.) You can see a positive feedback effect at work in a more familiar environment when there’s a run on a bank: Effect One (the bank looks like it might fail) leads to Effect Two (depositors rush to get their money out of the bank) which strengthens Effect One (the bank, bleeding cash, now looks like it’s in even more trouble.) Positive feedbacks tend to make a system unstable. So they’re not really all that positive in the conversational sense of the word; in most systems, you want to avoid them.

This post, on the other hand, describes the carbonate weathering cycle–a negative feedback effect. In negative feedback, Effect One (warming of the planet from CO2) leads to Effect Two (weathering speeds up, removing CO2 from the air more quickly) which damps down Effect One (with less CO2, the planet cools down again.) Negative feedbacks make systems more stable.

Climate is an incredibly complicated system, with many feedbacks both positive and negative. This article at Science News, Melting icebergs fertilize ocean, describes the discovery of yet another one.

Living things in the ocean are limited by available nutrients, including iron. Some people think we should deliberately dump iron in the ocean to spur the growth of plankton that will suck CO2 from the atmosphere as they grow and then seal it away on the ocean floor when they die and sink to the bottom. Of course, many other people think that this is likely to have a lot of unintended consequences if we do enough of it to make a dent in atmospheric CO2.

But it turns out that icebergs in the Weddell Sea are already doing this, on a smaller scale. Glacier ice has a lot of iron in it compared to seawater, probably due to a combination of dust collected from the atmosphere and sediment from underneath the glacier. When icebergs break off the glacier and melt in the ocean, that iron is released, and thriving communities of algae and plankton spring up around the bergs. The more the planet warms, the faster glaciers flow and the more icebergs end up in the sea; the more icebergs there are, the more carbon gets soaked up by sea life, slowing down warming a little bit.

This effect is probably small compared to other feedbacks that are part of climate change, and it’s not very helpful from a human perspective, since each melting iceberg contributes to rising sea levels. But it’s always interesting to discover a new cog in the great machine of the Earth.


Cefarelli, A.O., Vernet, M. & Ferrario, M.E., 2011. Phytoplankton composition and abundance in relation to free-floating Antarctic icebergs. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1436-1450.
Lin, H. et al., 2011. Free-drifting icebergs as sources of iron to the Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1392-1406.
Raiswell, R., 2011. Iceberg-hosted nanoparticulate Fe in the Southern Ocean: Mineralogy, origin, dissolution kinetics and source of bioavailable Fe.Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1364-1375.
Shaw, T.J. et al., 2011. Input, composition, and potential impact of terrigenous material from free-drifting icebergs in the Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1376-1383.
Smith Jr., K.L. et al., 2011. Carbon export associated with free-drifting icebergs in the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 58(11-12), pp.1485-1496.

The Voyage of the Endurance

June 11, 2011

Hey guys! I wrote you a song! It’s about the epic tale of survival that resulted from Shackleton’s attempted Trans-Antarctic Expedition; I used this website as a reference for some of the events, or you could read Shackleton’s own book on the experience, South. Be sure to check out the pictures, which are widely and deservedly regarded as the best part of the book.

Sung to the tune of (The Bonnie Ship) The Diamond.

The Voyage of the Endurance

‘Twas early in the century
The world prepared for war
But Shackleton intended the Antarctic to explore.
Some men sail for profit
Some sail for renown
But this one sailed for Science and the glory of the Crown.

Through the icebergs that clash, through the great waves that roll,
The mighty ship Endurance went a-sailing for the Pole.

The whalermen had warned them
That the ice would be severe
They were still above the Circle when the first floes did appear
Still bravely they sailed southward
But soon they were beset
Imprisoned in the heaving ice, but not defeated yet

Through the icebergs…

They whiled away the winter
Drifting ‘cross the Weddell Sea
When finally the sun arose, they thought they’d soon be free
But the mounting pressure of the ice
Was more than she could bear
In just days the stout Endurance was crushed beyond repair

Through the icebergs…

They loaded up the lifeboats
With provisions piled high
They watched her sink beneath the ice as, helpless, they stood by
The men camped on an icefloe
Let it take them where it would
It brought them near an island before breaking up for good.

Through the icebergs…

The isle was cold and barren
Inhospitable to man
So Shackleton devised another daring rescue plan.
He’d sail eight hundred miles
‘Cross the world’s most stormy sea
To the whalers on South Georgia he would make his earnest plea.

Through the icebergs…

A thousand times the pounding waves
Near sank the tiny boat
They lost most of their gear and food, yet somehow stayed afloat
When the party reached South Georgia
Thirst-tormented and sore
They realized the whaler-camp was on the further shore.

Through the icebergs…

They scaled the craggy mountains
And crossed crevasses deep
They stumbled into whaler-camp half-crazed from lack of sleep
The whalers were astonished
When these strange men came in view
Soon Shackleton secured a ship to rescue all his crew

Through the icebergs…

Let Shackleton’s Antarctic fame
For centuries survive
For with all their trials and troubles, every man came back alive!

Ice Sectional Preview

May 2, 2011

Not much time–heading to the airport soon to wing my way home to Seattle–but here are some nice pictures of ice sections, the things I spent long long hours in the cold lab working on. I’ll talk more about the process, and their scientific importance, soon.

Vertical section, from around 10 cm below the surface.

Same section between crossed polarizers to show some of the crystal structure.

Larger, more clearly defined crystals in a horizontal cross section of the core.

Also, because everyone likes charismatic megafauna, here is a Svalbardian reindeer! (“Reindeer” in English means a domesticated caribou, but the Svalbard ones are wild.)

This reindeer is foraging just a short ways from our lodgings.