Step into the freezer...

Basal ice from the GISP-2 core. This ice was the second to last meter before hitting bedrock, where sediment has been pulled up into the ice by the flow of the ice

      I spent most of my hours for the latter half of the summer at the National Ice Core Lab, where the current project was processing a 3.3 km long ice core that comes from Antarctica. That was about all that I knew going into the job. Later on, mostly through talking with the PI's and graduate students, I learned that there is much more to this than meets the eye. There have been more than 20 years worth of planning and work that went into this particular ice core.  The concept for a core from Antarctica was first conceived in 1989, when scientists were working on processing GISP-2, an ice core drilled from Greenland. Their work inspired curiosity to see if ice from the other side of the world would show them the same things that they had seen in GISP-2.

Ice Cores drilled over twenty years ago reside here at NICL in a -46 C deep freeze

As the cores are brought out of their tubes, they are measured and aligned according to how they were marked
in the field.

     These scientists, such as Kendrick Taylor and Mark Twickler, spent years obtaining radar profiles, mapping the bedrock below the ice, and looking at the rates of flow in the ice. When influenced by gravity, ice behaves fluidly, and actually flows. The motion is described in introductory geology texts as being similar to dropping pancake batter onto a hot skillet, where it pools and gains elevation where locally applied, but quickly flows outward. The data that the scientists are seeking would best be obtained from an undisturbed section, where they can be confident that mixing or motion of the ice is relatively low. After several years of research, they found a spot in the West Antarctic Ice Sheet, along a divide where the elevation was highest. The ice was thick there, and the bedrock profile showed that there was a large valley surrounded by two distinct and sharply rising mountains on either side. The hope is that in a dome or a divide, the motion of the ice will be low in the center of the feature. As they began test drilling to measure accumulation rates, the site took on its acronym, WAIS Divide.

The Horizontal Saw, also known as the H-saw, cuts two slabs of thicknesses 1.3 cm and 3 cm

     It is important to note here that the science of drilling deep ice cores was relatively untested, if not new,  at the point of conception. During the twenty years of planning to drill this ice core, they had to design and drill their own new drill, invent new instruments to measure the ice, and figure out schematics of living in the harsh ice covered land. They even went to such lengths as to figure out whether or not they could leave their human waste on-site (as it turns out they did, and they have figured that the waste pits will be stretched into a 1cm layer and pulled out to sea). Labs like NICL were constructed to store and process the ice cores that were being drilled from Greenland and Antarctica. The only other time that the U.S. had drilled for ice in Antarctica was at Byrd, a site that was selected because the numbers of its latitude and longitude sounded "nice", and without any consideration to radar profiles or disturbance of the ice. What they came to conclude after drilling and analyzing a core from that site is that folding and mixing near the bottom of the ice had stripped the core of its ability to represent correctly the ancient stratrigraphy, and thus held little scientific value.

   After they had worked out every detail of the drilling, they set out to antarctica for their first field season in 2006. They were only allowed one snow-cat to work with to construct all of their drill shelters and work areas. Drillers who were on the job for all season had quarters, visiting scientists resided in a field of tents specifically designed for the Antarctic. For five seasons of work in the field, they have 3,334 meters of ice core to show for their hard work. That's a hole that descends 3.334 km into the ice sheet. The amazing thing is that the drill only takes 3m of core at a time, and they have to pull up and lower the drill head into the hole each time. The wait times to winch the drill in and out while nearing the bottom of the hole were nearing 12 hours if I recall correctly. They stopped their drilling for fear of what is at the bottom, and for concern for the environment. There is a strong belief that at the bottom, near the contact with bedrock, the ice begins to melt, and sits upon a large body of water. If the drill penetrates the body of water, the drill fluid ( some nasty chemical) will be released into the otherwise untouched body. To keep the borehole open while drilling, they had to pour in some 200 barrels of drill fluid.

     The drilling teams only work during the North American winter, when it is warmest in Antarctica. Weather permits them a relatively short working season, because an ice breaker ship must be able to reach Mc Murdo, which acts a supply point for this camp and others on Antarctica.

The "ECM" or Electrical Conductivity Meter Sends an A/C
and D/C shock through the ice and measures the result

The resulting readout from the ECM

And so, after all of this effort, someone has to be able to use the ice to do some science. Every week at NICL, we would have a scientist give a talk. Usually it was a PI who came to visit, but scientists who were staying the whole summer also gave their talks. There are over nine PI's, or primary investagators that collect samples and run them to receive the data, which is in some cases then handed to another scientist for analysis. Scientists use machines that often times they have built, with complex functions and names like mass spectrometer and accelerated particle spectrometers. They look at a wide variety of things in the ice, including gases, chemistry, isotopes, physical properties, its electrical conductivity, and there is even someone who counts each and every visible layer within the ice. The level of analysis on the core is amazing, we heard from Kees Welton who looks at Beryllium-10 isotopes within the ice as indicating the amount of incoming solar radiation per year of accumulation. His data is correlating quite nicely with known sunspot counts that were visually confirmed and marked in history over the last few thousand years. Scientists used data from Greenland ice cores, other sites in Antarctica, and other outside data, and have proved the existence of several correlations. Most of the data that they analyze comes in the form of squiggly little lines that represent annual or event-based changes, much like the data from the ECM.


   The ice at the bottom of the core was estimated to be around 40,000 years old. This estimation is made from a proposed depth-age scale and from the actual count of the annual layers. One day, we took "snow" from the planer, a machine used to flatten one half of the ice core, and made some snow cones with grenadine and strawberry syrup. We chose the planer because it cuts from mostly the interior of the core where the exposure to the nasty drill fluid is least. I could never have imagined that a 40k year old snow cone could taste so good on a hot day.

The first cut of the chemistry slab is made on an ice core from over 3 km below the surface


The work that I did involved taking a 3 cm thick slab of ice, roughly a meter long and about 12 cm wide, and cutting out of this a 3 cm tall by 3 cm wide stick of ice. This stick of ice roughly a meter long would be shipped to Nevada to be processed with what is called a "continuous melter". This produces a constant flow of meltwater that can be tested as it is melted. By running this melt through several machines that measure different molecules, a large amount of information is obtained from these samples. During cutting, the bandsaws produce "snow" as if they would produce sawdust if cutting wood. This snow must be removed from the samples using a paint brush. This stick then had to be bagged, labeled, and its card correctly stapled onto it in order to be put into a box, which was put onto a pallet to be shipped to the PI. The remaining pieces also had to be bagged and sent to the pack-up station, which returned the remaining pieces of the ice core to the tube in which it came and stores them in the deep-freeze, for the possibility of future research. During the whole process, plastic gloves must be worn to prevent contamination of the core.