Posts Tagged ‘snow’

Notes from a Defense (cross-posted from S.A.G.A.N.)

July 28, 2013

I wrote this while my friend and colleague Marcela Ewert presented her work at her Ph.D. defense. She’s been doing a lot of really cool work about how Arctic microbes make their living despite the temperature and salinity extremes found in the sea ice and in the snow that rests on it. Here’s a link to some of the work included in her dissertation.

Jargon note: exopolysaccharides, also known as extracellular polysaccharides or EPS, are substances secreted by microbes (bacteria, algae, etc.) You may be familiar with extracellular polysaccharides like xanthan gum, which is produced by a soil bacterium and used as a thickener by the food industry. The exopolysaccharide produced by the Arctic microbes Marcela studies seems to be especially good at sticking to ice.

Colwellia and Psychrobacter are both species of sea-ice-dwelling bacteria.

Bacteria in Arctic Sea Ice and Salty Snow

Our universe is full of water ice
Whose particles in stellar-forming clouds
Are substrates on which molecules can splice
To veil the ice in thin organic shrouds.
On Earth, the ice on mountains and near poles
Plus snow and sea ice makes the cryosphere
In cold ecologies it plays its roles;
Sea ice and salty snow concern us here.

As sea ice forms, its icy fingers reach
Encapsulating nets of salty brine
And with the salty water, many creat-
ures will be trapped–by chance, or by design?
Bacteria and algae both secrete
Ice-loving exopolysaccharide
Which grips the icy matrix to defeat
The brine flow that would carry them outside
But in snow, changing temperatures and salt
To microbes like Colwellia spell doom
While Psychrobacter lives through this assault
And finds home where Colwellia finds a tomb.

But with the proper solutes all can thrive
And Arctic ice and snow can come alive.

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.

A Field Scientist’s Work is Never Done

April 7, 2011

Original audio post.

Today’s science fell a bit flat, at least on my end. Ruschle and I went out to re-take some albedo measurements, but were frustrated by rapidly-changing cloud conditions that confused the instrument.

Ruschle covers the Sun so I can photograph the clouds around it, in an effort to compensate for their effects; eventually we just gave up.

Mel and Martin had better luck making snow measurements and taking samples. Right now, Martin is sitting behind me with his makeshift lab, pouring diethyl phthalate into snow samples to preserve them. We’ve been having a little trouble getting the stuff cold enough to set, but that’s another post, I think.

Anyway, I figured I’d talk a little more about the rhythms of life in camp. Life in any camp seems to be defined by its chores, so I’ll start with those. Thinking about chores, actually, I was surprised at how few I could come up with. Perhaps that’s because a lot of chores at normal camps involve cleaning things, and we happen to be living in a place with essentially zero dirt.

Responsibilities begin in the morning, when whoever slept with the satellite phone (it has to be kept warm, so it’ll work when it’s needed) calls McMurdo to let them know we’re still OK. Every field camp does this check-in. It’s a sort of failsafe, in case something disastrous happens and we aren’t able to contact anyone to call for help.

Whoever’s cooking breakfast–or sometimes whoever’s in the kitchen tent first–collects a bucket of snow from outside to melt for water. Melting snow is probably the most constant and time-consuming chore. All the water for cooking, drinking, dishwashing, and other miscellaneous uses must be melted in the big pot on the propane stove. Notably, bathing is not really on the list of uses. Living in unheated tents means that getting wet is more or less courting hypothermia, so we mostly do without. I’m sure there are ways to manage it [bathing], but for three weeks, in a place without dirt, we think we can get away with it.

The water-melting pot, which was in near-constant use when we were in the tent.

We hold an informal meeting after breakfast to decide, mostly based on the weather, what to do with the day. If we’re going out, we need to take the covers off the snow machines and inspect them before heading out to the field to do science. Coming back, we re-fuel and re-cover the snow machines. Without the covers, the engine compartments fill with drifted snow.

Snowmachines, neatly put away.

The cook for the day (tomorrow, that’s me) starts dinner while everyone else puts away the scientific instruments. (I’m thinking I might make some kind of Malaysian-style curry.) More snow is melted–again, usually by the Cook for the Day. Someone might sweep the kitchen, if it’s filled up with drifted snow again. Snow is kind of our equivalent of dirt, but it’s much less bothersome, since it generally evaporates if you leave it long enough. Still, when it accumulates in the kitchen, it becomes somewhat irritating.

Supplementary audio post.

Hey, sorry–I think my last post got cut off when the satellite phone went out. Somewhere around where I was talking about how it’s irritating when the kitchen fills up with drifted snow. I’m actually rather surprised that the satphone hasn’t cut out mid-post before now. Unfortunately the WordPress voice-post function is a bit primitive; the only option is to call, leave a post, and hang up. You can’t really edit it afterwards. So, I won’t try to re-record the whole post this time, since I was mostly finished anyway. After dinner, pretty much all that’s left to be done is to wash the dishes and decide who’s going to sleep with the satphone. So, uh, it’s about time for bed here, so I will bid you all goodnight and talk to you soon. ‘Bye.

Cruising Down the Ice Line

March 31, 2011

Original audio post.

Hi! It’s been an excellent and extremely productive couple of days. Yesterday the wind was much lower, so we went out to take cores from our various measurement sites. By the end of the day it was dead calm, and the subjective temperature had jumped by about forty degrees Fahrenheit. I don’t what the actual temperature was, but it felt like summer had suddenly arrived. We took 16 cores, dragged our chairs outside to have dinner in the sun, and went for a walk to enjoy the weather–hence the lack of blog post.

I feel like I talk about the weather a lot, but it really does have a huge effect on both our ability to do science and our general experience of this place. Without wind, there’s nothing to make noise except us and the ice. Last night we could hear the cracking beneath us very clearly. Actually, it doesn’t exactly go “crack”–it makes two different noises that Martin described today as “voomf” and “bloop.” I’m not sure quite what causes these different noises, but perhaps I’ll find out.

The calm also makes it easier to overheat in one’s cold-weather gear, especially when drilling ice cores, which is a labor-intensive job. I wrote a couple of limericks about the day’s activities.

Limerick One:
A day spent in the Allan Hills coring
Could never be useless or boring
The reward for our troubles
Is a bounty of bubbles
Tiny worlds we’ll spend hours exploring

Limerick two:
The Antarctic’s mercurial mood
Demands a relaxed attitude.
Though the morning’s harsh storm
Needs three coats to keep warm
By six, you’ll be more comfortable nude.

So. Today the weather was very similar to yesterday, light wind in the morning falling off to nothing in the afternoon. We retraced our footsteps from yesterday, taking albedo measurements at each site. Sunny weather isn’t ideal for that, but you can correct for the direction of the light, and we didn’t want to risk waiting for a cloudy, calm day that never came.

Snowmobiles and science equipment.

We managed to get all the measurements done by five, so now we’re hanging around camp waiting for dinner (we take turns being Cook for a Day) and sunning ourselves. Sunning yourself must be done with care in the Antarctic, of course, since the ozone hole is just above us, and the sun would be exceedingly bright even without it.

Ah, I forgot to mention–while Ruschle and I were making [albedo] measurements, Mel and Martin were making maps of the cracks in the ice, using the box-and-camera method I described the other day. [It’s] now christened the Ice Fracture Observatory, or IFO. They randomized the location of their measurements by the again exceedingly scientific method of turning around three times, taking fives steps, then throwing a glove in the air and taking a picture wherever it landed.

Our randomization procedure.

I am excited to see what tomorrow will bring. We might hike over the hill and do reconaissance on the glacier on the other side. We might make measurements of snow microstructure. We might spend some time investigating the weird, inexplicable features we’ve take to calling “crevasse blisters.” For that matter, we might spend all day in sleeping bags again, hiding from the howling winds.

By the way, I’m not much for self-promotion, but I do think it’s really cool that, thanks to the wonders of modern satellite phone technology, I can give you day-by-day updates of what we’re doing. If you happen to know of anyone else who would also find it cool, I encourage you to tell them about it. Anyway, thanks for listening! ‘Till next time, as my Swiss-German-speaking colleagues would say, [word I cannot spell but which I am assured is the German version of ‘ciao’.]

Repost: The Snow Device

February 8, 2011

Original post, called in on January 14, 2011. Transcription thanks to Jonathan Beall.

(Sorry it’s taking me so long to put these up, by the way. Believe it or not, adding photos is the most time-consuming part of the process. Maybe I need to work on my methods.)

“Well, the wind is blowing just about as hard today as it did yesterday, but a helpful meteorologist at McMurdo told us that things are only going to get worse over the weekend, so we figured we had better make the most of it. We headed out on snowmobiles into the ice field to choose a new place to take measurements. We can’t actually make albedo measurements when the wind is this strong because blowing snow interferes with them. But we can select good sites to measure, which saves us time later on. Once we get a calm enough day, we’ll jump on our snow machines and spend it running around to different sites with our albedo measuring device. (I made a post about this instrument, the ASD, some time last year. If I had internet access, I’d link to it, but since I don’t perhaps some helpful person will do so in the comments. [A couple mentions, but I don’t see a post all about it.–Jonathan] [He’s right, I misremembered. Sorry! I’ll have to make one. — me]) We marked a site and took an ice core or three, and then went home for lunch.

In the afternoon, we tested out Martin’s device for measuring snow surface areas, which he made himself. It’s a sort of framework meant to be inserted into the snow. Then you dig the snow out of it to make a pit and take a picture of the wall of the pit using near-infrared light.

Ruschle, Mel and Martin working on the pit.

Snow grains of different sizes reflect different amounts of near-infrared light. They reflect different amounts of other light too, but the differences are easier to see in the near infrared. It’s a little bit of a simplification to say that the amount of reflected light tells you the grain size. It really tells you the surface area, because it tells you how many surfaces the light has bounced off before it reaches the camera. Once you’ve taken that picture, you dig a second one, leaving just a thin wall of snow, and shine a light through that wall to see how much gets through. This lets you calculate the density of the snow.

Snow structures.

It also happens to be beautiful. The different layers in the snow make delicate strips, shading from light to dark, depending on the time of year they were deposited, the weather when the snow fell, and various other things.

So, that’s what we were trying to do. However, things didn’t go quite as planned. We soon discovered that the snow here is much harder than the snow in the Alps, and we couldn’t insert the frame without damaging the snow we wanted to measure. Finally, we figured out that we could drill holes in the snow with our auger, which allowed us to set up the device with relative ease, although it still took a lot of hard shoveling to dig out the pit. And then, at some point, as we tried to get everything set up, we made the unwelcome discovery that Martin’s supplier for frame connectors had been somewhat mistaken about their tolerance for cold, and the frame snapped in half.

A broken fitting.

And of course, remember, that we’re doing all this in twenty-knot winds. But we finally managed to get everything set up, we took our measurements, and we went home feeling like scientific heroes. We got to take an item off the list of tasks that Ruschle wrote up for us, so we’re all feeling pretty good about ourselves.

The wind meant that we had to put a tarp over the site to prevent everything from being covered with fine drifted snow.

It’s supposed to snow tonight. It should be an interesting weekend. Until then, ciao.”

Repost: Cracks and Bubbles

February 8, 2011

Original post, called in on January 13, 2011. Thanks once again to Jonathan Beall for the transcription!

“Hi. Today was a quiet day. Well, in terms of activity. It was a quiet day in terms of activity because it was a noisy day in terms of wind. We had a good day of spirited scientific discussions in the tent instead. We were mostly discussing bubbles and their contribution to the amount of light reflected from ice, or its albedo.

Bubbles are awesome.

Ice is very transparent. Light can travel a long way before it gets absorbed. If there are no bubbles in the ice, most light will just travel straight through, and the albedo will be low. If there are bubbles, though, light can hit the bubbles and bounce away in a different direction. A lot of the light that goes into the ice will end up bouncing right back out, which is why bubbly ice has a higher albedo than clear ice. Ice in glaciers and on ice sheets, like where we are, has lots of bubbles because it’s formed from compressed snow. The spaces between snowflakes at the surface will turn into bubbles as the snow is squeezed into ice and a small amount of the air remains behind as bubbles form.

Complex bubble shapes are partly a result of the complex shapes in the snow crystals that formed them.

We also talked about cracks in the ice, which can increase the albedo just like bubbles do. The blue ice here has lots of cracks in it, mostly quite thin. We think they form partly because the ice is cracking as it moves, and partly because, as the top of the ice erodes away from the constant wind, the ice lower down is no longer under as much pressure, and it expands creating more cracks.

Cracks in the ice (picture taken using the Crack Box, an invention I'll explain in a later post)

We actually put on our parkas and went out to look at the ice near camp to see how the cracks behaved and to figure how we might account for them in our measurements. We probably looked a little silly lying face down on the ice and wriggling along the ice like seals, but then science is frequently a little silly; that’s one of the reasons I like it.

Another incident of science being silly.


Camping Happily

January 6, 2011

Since my mother wrote some awesome limericks for my previous posts, I thought I should add a couple of my own.

From Happy Camper

Patient Field Safety personnel strive
To keep each Happy Camper alive
With rigorous training
And lots of explaining
Hoping when crisis strikes, we’ll survive

From Happy Camper

For my happily camping cohort
No mere tent of the usual sort
With so much snow around
Each of us can be found
In a fabulous personal fort

From Happy Camper

A note: I realize this post-a-day experiment has been going on for a very short time, but I’m already realizing some significant problems with it. Firstly, it makes it difficult to get a good, solid science post done–there’s too much background to do in a day. And secondly, it’s distracting me from doing actual science, not to mention enjoying Antarctica while I’m here. So, while post-a-day would be a laudable goal, I am going to scale back a bit and aim for maybe twice or thrice weekly.