Posts Tagged ‘ice’

A good week for defense

January 19, 2015

I successfully defended my dissertation last Thursday! Defense title: “Measured and modeled albedos of sea-ice surfaces on the oceans of Snowball Earth.”

Here’s how I summed up my talk:

A planet orbits round a yellow sun
Light years away or megayears ago
Its seas are dark, its continent is dun
But brilliant sea ice sets its pole aglow

Its CO2 drops dangerously low
Tendrils of ice reach from the polar caps
That sparks a feedback: oceans turn to snow,
Glaciers push in to close off any gaps

The oceans roiled with countless living cells
Who learned to take their energy from light
Now locked beneath the cold of Dante’s hells
They starve; how long must they endure this night?

Why has this happened, and by what device?
To know, we must investigate the ice.

As sea ice freezes, tiny drops of brine
Are trapped between the quickly forming plates
When cold enough, their molecules align
Into sodium chloride dihydrates

The solid crystals catch and scatter light
Reflect it back, refuse its energy
And I myself have quantified how bright
The surface of the sub-eutectic sea

And in our lab we’ve watched salt ice sublime
With instruments ingeniously designed
The secrets of another space and time
Unfold beneath my models and my mind

This is my work; I hope you will agree
That it is worthy of a Ph.D.

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Ice Needles (not to be confused with Space Needles)

December 2, 2014

Yesterday on my way to the office I noticed that the ground looked weird. Inspecting it more closely I discovered that the apparent “surface” was actually composed of lots of dirt clods and small rocks on top of two-inch-tall pillars of ice.

All of these rocks and bits of dirt are on 2-inch-tall ice columns

All of these rocks and bits of dirt are on 2-inch-tall ice columns

I had never seen anything quite like it before, at least not in person. The physics involved is actually quite complicated and I don’t fully understand it myself, but it boils down to something like this: if ice is freezing at some particular spot, it “pulls” water toward itself. You mostly see this effect in porous materials that water can flow through by capillary action, like soil.

Sketch111775

So the water gets pulled toward the ice and freezes on to it, pulling yet more water along behind it, and gradually more and more ice forms. In this case you end up with columns that lift pebbles off the ground, a.k.a. needle ice. In other cases, where the freezing is happening underground, you can get frost heaves or weird permafrost landforms (this is called ice segregation.

You can see the ground through the hole.

You can see the ground through the hole.

An ice column I plucked out to examine.

An ice column I plucked out to examine.

Under the bushes the columns got surreally twisted.

Under the bushes the columns got surreally twisted.

Side view of the ice columns lifting some pebbles and a small ice sheet

Side view of the ice columns lifting some pebbles and a small ice sheet

You can see there was a change in the freezing process; the short, whiter columns seem to have been lifted by the taller, darker columns underneath.

You can see there was a change in the freezing process; the short, whiter columns seem to have been lifted by the taller, darker columns underneath. The bottoms of the small columns have frost on them.

Side view.

Side view.

More images here.

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’.]

Complex Scientific Equipment

March 29, 2011

Original audio post. Thanks to Lori for the transcription!

Hey! Well, this morning’s weather was pretty unpleasant, although we weren’t sure why it seemed quite so bad. It goes to show how much your points of reference have changed when you find yourself saying “It’s only -15 Celsius with 10-knot winds. Why does it seem so cold?”

So, anyway, we stuck close to camp. Martin and I put together a very sophisticated scientific instrument, which might appear to the uninitiated to be a cardboard box with a hole cut in the bottom.

I transport the device to the field as Ruschle looks on. Photo by Martin.

This allowed us to take photographs of the cracks in the blue ice without the picture being washed out by bright sunlight. Upending the box box on the ice and taking pictures through the hole gave us images in deep translucent blue with a delicate tracery of dark cracks. We’ll use these pictures to try and quantify the effects of cracks on the amount of reflective light.

The cracks as seen under the box.

The weather improved in the afternoon, enough for us to go out and identify sites to measure. I don’t think I mentioned yesterday exactly what we’re looking for. As the ice flows, it moves into the region where wind can scour away the upper layers. So as you walk along the line of flow, you start in an area where the surface is still snow. Then you reach an area where the surface snow has been scoured away by the wind to expose dense old snow from years past (which, as you may recall, is called firn.) Walking further, you reach bubbly ice, and finally dense old blue ice. We are trying to measure along that same line of flow to get measurements from each type of snow and ice.

So, we marked the lines with the bamboo flags that are ubiquitous around McMurdo, and perhaps we’ll get to go back tomorrow and actually measure.

I’ve been concentrating a lot on the science we’re doing here because it’s pretty exciting. But I haven’t talked much about day to day life in camp. The Scott tents alone are worth a whole post, so I’ll try to talk more about that in coming days.

Oh, and we saw a skua!

A different skua, circling over Icestock hoping someone will drop their sandwich.

Skuas are the local scavenger birds. They look like a big brown seagull and like to dive-bomb people carrying food. This one was probably a bit lost. There’s not much to eat out here. But, it was the first living thing besides ourselves we’ve seen in days, so it was pretty interesting. Anyway, until tomorrow, cheers.

Disruptions

February 26, 2011

I am far behind on transcribing posts; I’ve been traveling around New Zealand, so Web access has been difficult to get.

Most of you have probably heard about the major quake that struck Christchurch on Tuesday. I was well away from it at the time, but since Christchurch is the “gateway to the Antarctic”, quite a few people from the US Antarctic Program were there when the quake struck. Most of them have been accounted for and are alive and well, although many of them have been left with nothing but the clothes on their backs, and several have hair-raising escape stories, including one person who apparently had to dig himself out of the wreckage of his hotel room and another who rappelled down the side of a building on bedsheets. The USAP personnel in Christchurch have been exceptionally helpful, starting up a makeshift refugee camp in the Clothing Distribution Center and adjoining flight terminal.

Meanwhile, down at McMurdo, the sea ice has broken out of the sound for the first time in a decade and a half (not because of the quake, it’s just coincidental.) Probably as a result, pieces of the ice shelf are breaking off. This may prove problematic, as the ice shelf is where the planes land to take people to and from the station. Right now the station staff are hurrying to move the road so that they’ll still be able to access the runway, in hopes that the summer crew still on station won’t be obligated to winter over.

So it’s exciting times at the USAP. Everyone’s thoughts are with the quake victims, of course, and with Christchurch as it struggles to rebuild.

I’m about to leave for a four-day hike, but I’ll be back in touch when I return.

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.

Cheers!”

Repost: Blue Ice Reconnaissance

February 3, 2011

Original post, called in on January 12, 2011. Click on the links beneath the photos for their accompanying Picasa albums. Thanks again to Jonathan Beall for the transcription!

“Hey folks. It’s been another beautiful, sunny day here in the Allan Hills. We mostly don’t seem to have any other sorts, although we did have a little cloud this evening. We also had some rain, a type of precipitation I did not expect to find out here. You see, melting snow for drinking water, cooking, and in fact just hanging around and breathing in our kitchen tent creates a lot of moisture which condenses on the ceiling and freezes. When the wind dies down, the sun warms up the tent and there’s a minor deluge.

From In the Endurance

Pouring melted snow into a thermos to keep it warm/liquid during the night. These thermoses are pretty excellent, actually--water poured in at 90C (the boiling point at this altitude) will still be hot the next morning. The orange color is not a filter or special effect, it's just what things look like inside the orange Endurance tent. Pictures look a little more natural in black and white, but I thought I should give you the full experience of being there and having your color sense altered.

Aside from that, it’s been a pretty exceptional day. We headed out on snowmobiles this morning to survey our field site. We covered about 30 kilometers all told, visiting several fields of blue ice and some rocky moraines sticking up above the ice field. (A moraine, for the non-glaciologists among you, is a pile of debris that a glacier plows up as it moves, pushing rock to its front and sides.)

It’s neat to be out here. You get the experience of being on the ice sheet, with snow and ice stretching out for miles, yet there’s still enough mountains and hills to make for interesting topography. The mountains are beautiful—in that stark, lifeless sort of way that Antarctic mountains are beautiful. The ice fields are mottled blue and white with patches of snow. Driving across them in the sunlight is kind of like driving across the cloud-flecked sky, except when you’re driving into the sun, when the whole thing turns to liquid silver stretching out to the horizon, with ripples like the ocean.

From First Day Out – Allan Hills

A little liquid silver on a small ice promontory. Also a good illustration of an Antarctic photographer's dilemma: how to tell your subjects apart? Fortunately Big Red comes with a nametag, so I can tell you (using the hi-res version of this photo) that Ruschle is on the left and Martin on the right.

I even stepped into a crevasse today. Too small to fall into, but large enough to be a good object lesson about the importance of watching where you step. So, that’s your moral for today.

From First Day Out – Allan Hills

The hole I made in the snow bridge over the crevasse.

Until tomorrow, signing off…”

Repost: First Days in the Field

January 31, 2011

Original post, Jan 11 2011. (Many thanks to Jonathan Beall for the transcription!)

“Hi, I’m calling WordPress on our satellite phone. So, if I cut out suddenly, or sound a little weird, that’s why.

Sorry to let you go so long without a post. Packing was a little bit of a scramble, and I found out at the last minute that the shuttle to our plane was rather earlier than I thought it would be. I never quite expected to make it out here on schedule, not after seeing friends get caught in the endless holding pattern of weather delay after weather delay. But yes, we arrived yesterday, right on time.

The Twin Otter that took us out to the Allan Hills.



Icefields near our camp.

The camp was already set up when we arrived. Mel, Ruschle, Steve, and Peter spent four days in forty-knot winds putting it together on their first trip out. The wind is a constant here. On the last trip the rest of the team only got one or two days of calm weather. Fifteen or twenty knots is more typical. The winds steal heat quickly, bare hands go numb within a minute, or at least mine do. None of the tents are heated, although the kitchen tent does have a heater that can be used in a pinch, so we do most of our living just below freezing. Fortunately, the constant wind makes indoors seem practically tropical. We keep warm with hot tea and lots of high calorie food.

My first glimpse of the camp.

Today it was a bit too windy to go out and do science, so we set up our equipment and went for a short hike to look at the blue ice near camp. This place is amazing and alien and desolate and beautiful, and I’m really looking forward to spending the next three weeks here.”

More photos of the flight and of camp.