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October 7, 2009

It’s a tremendous amount of fun to go out on the ice, take data, and drink in the Antarctic sites. Eventually, however, the question must arise: what is it all for? Do we have anything to show for it?

The answer, in this case, is yes. Rich has spent a couple of days diligently analyzing our albedo data, and we’ve found that, just as we expected, colder sea ice has a higher albedo, probably due to the crystallization of salts in the brine pockets. Here’s a graph of the albedo at a wide range of wavelengths of light. The graph shows three measurements at cold temperatures below the crystallization point (-23 degrees Celsius.) As you can see, the albedos get steadily higher as the temperatures drop and salt crystallizes in more brine pockets.



Rich's analysis of our albedo measurements. Click for larger image.

Rich also spent a day in our cold room, while the helpful freezer technicians changed the temperature from above -23 to below -23 and back. Here are his Highly Magnified brine pockets (as mentioned previously) in the process of going from liquid brine to crystallized hydrohalite:





The hydrohalite is behaving just as we want it to. This is an unusual thing in science.

It may not look like much, but the minute changes visible in those photos are really quite tremendously exciting. Rich’s long hours in the cold, drafty, noisy freezer have not been spent in vain.

The Ridiculous and the Slime

October 2, 2009

I don’t think I’ve talked much yet about my own personal corner of our project. This is actually a bit of science I tacked on at the last minute—it wasn’t in the original grant—and I’m hard pressed now to recall quite how I even came up with it.

You may recall that the effect we’re looking for in the sea ice depends on the formation of hydrohalite crystals inside brine pockets. Rich has actually got a nifty microscope setup in our cold room to look at the brine pockets now (pictures of which will be posted here as soon as I can pilfer them from his collection.)



Rich's tablet displays a highly magnified (and perhaps thoroughly educated) view of some brine pockets.

The brine pockets, as I explained earlier, are there because seawater got trapped in the ice when it was in the process of freezing. However, as you are well aware, seawater isn’t just a collection of water and salts. It is also home to a staggering number of microorganisms, some of which are inevitably trapped in the ice with the seawater as it freezes.



(From an essay by J. Deming and C. Krembs on NOAA’s website.)

Some diatoms (diatoms are a type of algae) living inside a brine pocket.

The brine pockets don’t provide a particularly hospitable environment for things to live. As the ice gets colder, the brine pockets also get colder, as well as smaller and saltier. Sharp pointy ice crystals may form. Some of the creatures that get caught up in these brine pockets try to protect themselves from freezing by secreting things that reduce the melting point of water, keeping it liquid at lower temperatures. One of these is a slimey substance called EPS (which stands for “expolymeric substance” or “exopolysaccharide”, but I usually just think of it as “slime.”)

Now, this substance obviously has the potential to mess up our nice simple salt-water physics. Changing the behavior of the water and salt in the brine pocket is exactly what the diatom wants it to do, after all. When our colleague Bonnie Light observed natural sea ice in the lab, she found that not all hydrohalite precipitated at the expected temperature—some brine pockets developed hydrohalite crystals earlier than others (Light, Maykut and Grenfell, 2003.) The difference could, perhaps, be due to EPS content of some brine pockets. So while Steve and Rich are investigated albedos, I’m collecting ice to see how much EPS it might contain.

The process starts when I take an ice core:



You remember this bit.

We strap it to the top of the pisten bully and take it back to the cold lab, where Steve and I cut it into manageable bits.



Even with a couple of layers of gloves, my hands get awfully cold doing this. Presumably my squid hat is also getting pretty chilly, but it remains stoic.



Manageable bits.

If there are any organisms in the sample—algae or bacteria—I don’t want to shock them too much by exposing them to very different temperatures or salinities. If I shock them, they might explode (or ‘lyse’ in biologist-speak.) When I’m starting out the critters are in brine pockets that started out between -15C and -30C, depending on what day we took the core and what depth they were at. The brine pockets they’re in are very salty at that temperature, so I mix up some very salty artificial brine and dump the samples into that to melt.





Lots of Instant Ocean and some distilled water.

Once the samples are melted, I filter them.



The filters are rather delicate and finicky.




This is very similar to a setup that Steve carted around Siberia for two months for snow research. Note handpowered vacuum pump.

There are a couple of common ways to look at EPS. One of them uses the filters plain; for the other, you dye them with something called Alcian blue that binds to the EPS:



Blue. Like a glacier! Well, sort of.

Eventually, you end up with something like this, which I’ll put back in the freezer until it can make it onto a cargo flight back to the States.



All that work for something that fits in a 1.5mL tube with room to spare.

Another Day of Science and Mystery

September 27, 2009

Friday night was another overnight at the hut. We had dinner on station, which saved us the time we would otherwise have spent cooking and washing dishes at camp, and then headed out onto the ice. (A side note and brief glimpse into the mind of a couple of working scientists: Steve and Rich both profess to greatly enjoy doing dishes. Dishes, you see, unlike science, have a straightforward methodology and a well-defined endpoint. When you’re done doing a science experiment, it has already raised ten more questions which you must rush off to address; but when you’re done doing dishes, you can bask in a sense of closure and accomplishment.)

We got up around six A.M. the next day (my cot was next to the door, so as people went in and out I got several bracing facefuls of -28C air to drag me into alertness.) The sunlight is getting longer by about 20 minutes every day, so every time we go out we have to get up earlier in order to take measurements while the sites are still in shadow. Somehow, we managed to get the light dusting of snow swept off three sites and measure them all before the sun caught up with us–we made it with just a couple of minutes to spare:

From Pupsicles and Traverse Gear

The sun catches the edge of the site just moments after we complete our measurements.

It was all very dramatic, really. Rich tells me the measurements are excellent, and are showing exactly what we predicted they would show, which is gratifying. I’ll post graphs when Rich gets them all processed.

Having completed our Science and packed our gear, we went investigate a peculiar phenomenon which Steve had discovered earlier that morning:

From Pupsicles and Traverse Gear

Rich and Steve search the snow for tracks that might suggest how this happened.

That, if it’s not obvious, is a very frozen Weddell seal pup stuck in the ice like a flagpole. We investigated the area pretty thoroughly, and found evidence of the birth (blood, the afterbirth and umbilical cord, the outline left on the ice where the mother seal had been lying) but no identifiable footprints other than our own. The seal clearly froze while lying flat on the ice, as you can see from another angle:

From Pupsicles and Traverse Gear

'Flat-bottomed Seals': the less-successful predecessor to Queen's famous hit song

We thought someone from the seal research group might have set it up somehow, but those we’ve talked to deny it, and as I’ve said, there were no visible tracks. The other possibility is that the body was simply levered up by the action of the moving sea ice; if you look at the tail, you can see where some slabs of ice have been tilted upward.

Antarctica is a mysterious place.

As a bonus, we found what we think must be new-frozen frost flowers on the ice nearby:

From Pupsicles and Traverse Gear

Today's theme: things that are charming, fuzzy, and frozen.

Audited by Emperors

September 23, 2009

I made a comment in a previous post about gangs of ne’er-do-well Adelie penguins vandalizing our site. That was, of course, a joke; there are no roving gangs of Adelie penguins out here. There are roving gangs of Emperor penguins.

From Penguin Day

The Emperors are here to inspect our work.

Backing up a bit: yesterday dawned cold and cloudy, perfect for taking measurements, so we headed out to the study site and got there around 1:00pm. The ice surface has been changing a lot in the past week or so. The snow crust is becoming thinner, probably eroded by high winds. Wandering away from our camp a ways, we found that the bare blue ice we’ve been hoping to find ever since we got here had finally begun to emerge from beneath its snowy blanket. As we explored we noticed a number of distinctive black-and-white forms in the distance.

From Penguin Day

Bare blue ice has never been so exciting. That's my boot for scale.

We selected a good site and set up our instrument, and soon acquired company in the form of fifteen Emperor penguins who sauntered up to watch. Apparently this phenomenon is fairly common: small groups of non-breeding individuals will break off from the main colony and wander aimlessly for large distances, stopping to inspect anything that catches their interest. (This is also exactly what the penguins say about scientists.)

From Penguin Day

An attentive audience of Emperor penguins watches Rich take albedo measurements.

Evidently the penguins decided our scientific endeavours were worthy of closer investigation, because when we set up the instrument at our original, carefully-groomed site for comparison measurements, we had a devil of a time keeping the entire group from marching directly across it.

From Penguin Day

Rich tries to convince the penguins to move slightly further away.

By keeping myself between the penguins and the study site, I managed to avert their repeated efforts to get penguin prints (and penguin excreta) all over our nice clean ice. Fortunately they tend to follow each other, so by discouraging the foremost penguin I could get the others to bypass the site as well. The penguins took it all with good humor and hung around for a while after we were done taking measurements.

From Penguin Day

Rich and Steve take measurements; meanwhile, the penguins stop their advance on our site to pose for a group photo.

Around six o’clock we retired to our hut to make dinner and bed down for the night. I don’t think I have told you about the ice hut we recently acquired (I’ve been shockingly lax about updating this week, for which I apologize.) The hut sleeps five in reasonable comfort and makes a good staging area for equipment during the day:

From Penguin Day

Our home away from home.

It’s also heated and equipped with solar panels for electricity. Evidently the penguins thought it was pretty nifty too, because shortly after dinner we heard their distinctive trumpeting just outside the door. We thought they might come in for cocoa, but they just wanted to get out of the wind. For obvious reasons, the side of the hut that’s out of the wind is also the side of the hut where we set up our pee bucket toilet facilities, so for most of the night any of us who went out to answer a call of nature found ourselves doing so in front of fifteen interested penguins.

Meghan, the wilderness safety person who came out to the hut to ensure we didn’t do ourselves an injury somehow, says that she heard the penguins near the hut until the wee hours of the morning; then they marched around it, perhaps to see if any of us were interested in joining them, and struck off into the night.

More photos at my Picasa album; this time I added the link under the pictures. I haven’t included the link to the album on previous posts, but a lot of them have additional photos on Picasa as well.

Frost Flowers Revisited

September 17, 2009

Somebody asked about frost flowers (thanks, MeghanC!) This gives me an excuse to pontificate upon them a bit. Here’s a great picture of frost flowers from a New Scientist gallery:



Those of you who haven’t spent a lot of time hanging out in the polar regions may not be familiar with the sequence of events involved in the formation of sea ice (apologies if I’ve explained this one before…) As the winter begins and the ocean cools down, little bits of ice begin to form at the surface of the water; these are called frazil or grease ice. Eventually they stick together into a flat sheet, called nilas ice. Pockets of seawater (brine) get trapped between the crystals as they freeze.

As the ice gets colder, water freezes onto the walls of the brine pockets. When water freezes, it tends to exclude any non-water substances, so the brine within the pockets gets saltier. Water also expands as it freezes, so some of the salty brine is pushed out of the ice. Part of it goes downward, and the sinking of this cold, dense, salty water has interesting effects on ocean currents. Part of it goes upward through whatever channels it can find:



Experimenting with hand-drawn diagrams this time, as you can see.

The ice continues to freeze, and the brine being pushed out of the pockets forms a thin layer across the ice. This layer is very salty, so it stays liquid even at very low temperatures:


Frost flowers form at temperatures below -15C (or lower, depending on who you ask.) Seawater, of course, can never get colder than -1.8C. This means that under frost-flower-forming conditions, the ocean is quite a lot warmer than the air. The brine layer on the surface of the newly-formed ice is also comparatively warm, and it gives off water vapor. The vapor re-condenses and forms crystals on top of the briny “bumps” we saw earlier:


The flowers continue to grow, and some of the brine travels up them via capillary action, making them very salty compared to most sea ice:


That, anyway, is the short version of how frost flowers form. They may have some effects on the atmosphere because salts from the ocean are caught in their delicate fronds where the salts can easily be picked up by wind. They may also, as we are now seeing, have some effect on ice albedo both by themselves and by capturing snow that blows across the ice.

MYSTERY

September 13, 2009

Another beautifully sunny day, entirely worthless for albedo measurements. We stopped by our Tent Island study site anyway, just to say hello to the seals and make sure the local street gangs (groups of young, disaffected Adelies, mostly, looking to rumble tourists for pebbles) hadn’t vandalized it.

You may recall that we spent quite a while last week, on the 4th, doing janitorial duty on the ice, clearing off the crust of salty snow that was clinging tenuously to the surface. We came back a few days later on the 7th and the surface was still perfectly clean.



Our beautiful clean ice.

We came back today to find this:



VANDALS





The top photo shows the old crust, which we originally assumed had been there for months. The bottom photo shows the new crust--the bumps are slightly smaller and it's softer, but otherwise strikingly similar.

This is intriguing, because, as I mentioned before, we originally figured that the peculiar snowy crust on the ice must be composed of old frost flowers. However, frost flowers only form on new sea ice. This sea ice is several feet thick and months old. And this new snow crust isn’t just composed of snow fallen from the sky, because that would be fresh; this is salty.

There have been a couple of warm days since the 7th, and a minor storm (seen here out the front of the pisten bully as I attempt to drive home through it):



Fortunately there is nothing to actually run into out here.

But, frankly, we’re pretty stumped as to what could have regenerated the snow crust like this.

After visiting the study site and scratching our heads over unusual snow phenomena, we headed up to Cape Evans to visit Cape Evans Hut, used by both Scott and Shackleton during various Antarctic expeditions.



Cryogenically preserved ketchup



More picturesque than our lab, if rather smaller.

Oh, and here’s our second mystery of the day: we discovered, on examining the high-resolution pictures, that a century-old British paper from the hut has a front-page story about an injury that occurred in the small town of Saranac Lake, New York. Saranac Lake, New York also happens to be the town that Rich calls home. Bizarre coincidence, or prophetic attempt to communicate across a vast span of time and space?

Our Heroes

September 7, 2009

As I mentioned in a previous post, the little band of which I am a part includes two other members:

Steve Warren is the Principal Investigator of the project, a professor at University of Washington, and my advisor (my advisor for astrobiology-related projects, that is; my advisor for glaciology projects is Ed Waddington.) He’s been down to the Ice more times than I can keep track of, he knows an immense amount about light and radiation and how it relates to climate, and he keeps his eyes open for interesting problems to solve.

Rich Brandt is a research scientist at University of Washington, though he telecommutes in from upstate New York. He is an expert on ice, snow and the reflection of light therefrom. He too has lots of on-Ice experience. He uses his excellent camera skills and vast collection of equipment to record Antarctic vistas and small stuffed penguins alike.

These are the individuals with whom I am privileged to work, who have developed most of the research protocols we’re following as we do science on this trip. They will show up in my pictures a lot.

Curse You, Frost Flowers

September 5, 2009

Another sea ice day on Friday. We admired some Fata Morgana mirages on the way out:




Some nice sastrugi (snow dunes) with a band of mirage in the background



A mysterious cyclopean edifice in the distance

We returned to our previous sample spot and attempted to get better measurements by removing the snow:



Janitorial duty on the sea ice

The crust of snow was pretty well stuck on to the ice, requiring us to shovel, sweep, and then kneel down and scrape with spatulas and ice axes until the ice was more or less clear. We tasted the snow and found it was salty, which means that a lot of it actually started out as frost flowers. Frost flowers are fluffy, rather ethereal-looking crystals that form on new sea ice; they are pretty fascinating, scientifically. If anyone requests it in the comments I’ll write up a post about how they form.

Nifty as frost flowers are, they are making our life difficult. As you may recall from my previous post Salt, Sea Ice and Science we are looking at the way the albedo of sea ice changes when the salt in brine pockets forms crystals. Unfortunately, it’s very hard to see anything useful through a layer of frost flower remains. Hence our janitorial activities.

I am reminded that I promised equipment pictures in that post I just linked. You’ve seen the field equipment, of course, but I shall have to do a post about lab technique and some pictures of my impressive array of beakers.

Some Science Occurs

September 3, 2009

On Tuesday we managed to get a slightly earlier start heading out to the sea ice. It was still later than we’d planned; starting up a new project always seems to mean discovering several dozen things you forgot to bring.

The ride out was as bumpy as before, except this time we had the Analytic Spectral Device (for measuring albedos) along and thus had to be extra careful about excessive vibration.

We were looking for first-year sea ice that was bare of snow. We ended up near Tent Island, where our Kiwi friends had told us we might be able to find something sufficiently wind-scoured. No bare ice was immediately apparent, but we did find this iceberg trapped in the sea ice:


Click for larger version.



Say 'freeze'!

We investigated it, being careful to stay well clear of any possible falling ice. Icebergs are not to be trifled with; you can see the size of this one, and imagine how even a smallish piece of it might feel if it were to detach while you were underneath it.

Having found no bare ice even in the most wind-scoured of spots, and with the sun gradually sinking towards the horizon, we retraced our steps to an area which at least didn’t have very much snow and broke out our gear.



Rich uses the ASD to measure light levels. An overcast day is best for this, because the light comes in more evenly from all directions.



Me and the ice-coring device. Wrestling one of these down into the ice warms you up rather nicely, even at temperatures in the -30 range.



The snow was not very deep at all, but unfortunately even not-very-deep snow has quite a significant effect on albedo.

We got our albedo measurements, and we got our ice core, and we got very cold indeed.

On the way back we stopped in the sea ice hut the Kiwis have been using all winter, where they graciously fed us tea and cake. They also showed us their conductivity/temperature/depth sensor and the nifty hole in the sea ice–conveniently located within the warm confines of the hut–through which they lower it to get profiles of the ocean water below. Afterwards they kindly directed us to their own road back towards base, which felt orders of magnitude smoother than the route we’d been using and allowed us to get home in one hour instead of three despite being technically longer. An excellent day all round.

Escaping the Snowball

August 22, 2009

So, how does a planet get itself out of a Snowball state? The short answer, as I mentioned in my last post, is “carbon dioxide.” When the Earth was frozen over, volcanic activity didn’t stop–volcanos kept pumping gases, including greenhouse gases such as CO2, into the atmosphere.

Now we get into the geochemical aspects, which are a bit outside my field, so please take my explanation with a grain of salt. Normally, CO2 that enters the atmosphere reacts with rocks on the Earth’s surface, creating carbonate minerals. This process gradually removes CO2 from the atmosphere. When the amount of CO2 in the atmosphere increases, the Earth warms, which speeds up the weathering process and removes CO2 more quickly. This CO2 feedback helps keep the Earth at a comparatively stable temperature over the long term (CO2 weathering is slow, so it can take thousands of years for CO2 to leave the atmosphere even at warmer temperatures.) Here’s a paper on the CO2 weathering feedback (link goes to PDF file) for those who are interested in a more in-depth treatment.

Much of this CO2 weathering process occurs when CO2 combines with minerals to form carbonates, such as calcium carbonate (the principal component of limestone, among other things.) This process is helped along when CO2 mixes with water in rain, rivers, and the ocean. However, on a Snowball Earth, little rain or snow would fall, and few, if any, rivers would flow. No CO2 could dissolve into the oceans, because they would be cut off from the atmosphere by a thick layer of ice. Instead of weathering out of the atmosphere, the CO2 would simply build up over time. As carbon dioxide levels increased, so would the greenhouse effect. Eventually, the CO2 would reach such high concentrations–hundreds of times modern levels, by some estimates (for example, Hoffman and others, 1998)–that the warming greenhouse effect would overcome the cooling effect of the light-reflecting ice.

When the greenhouse finally overcame the ice, it melted quickly, suddenly transforming most of the world’s surface from brilliantly reflective ice to dark, absorbent sea. Without the reflective effect of the ice, the greenhouse effect took over and the temperatures soared. At the same time, the massive amount of CO2 in the atmosphere began to dissolve into the ocean, where it precipitated out to form thick layers of carbonates. These “cap carbonates” are still visible today and form one piece of evidence for the Snowball Earth theory.

This is, of course, just one of several ideas about how the Snowball Earth scenario might have played out. It’s possible that, instead of Snowball Earth, there was a “Slushball” Earth, with open water at the equator. A Slushball Earth would have much less trouble supporting life, which would thrive in the areas of open ocean. On the other hand, that open ocean would act as a sink for CO2, and the Slushball might not be able to accumulate enough CO2 to overcome the albedo of the ice on the rest of the globe. Snowball Earth researchers continue to search for a model that will balance these various factors–account for sea-level glaciers at the tropics, provide a refuge for life, and permit enough CO2 buildup to initiate the return to a normal climate.

But you don’t have to take my word for it, as Levar Burton would say. Much more information on all these topics is available at SnowballEarth.org, which gives a good comprehensive overview of the whole business.

<A diagram from SnowballEarth.org, which gives a good graphical overview of the Snowball event.

A diagram from SnowballEarth.org, which gives a good graphical overview of the Snowball event.


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