2011 Issue

38 of ice to finish off our field training. Our last task was setting up a survival tent in the wind on sheer ice. It was a bit tricky. Besides not falling down, there is nothing to nail tent stakes into. To hold a tent to sheer ice, you first drill V-shaped holes in the ice by hand with an ice crew. Next you have to thread a cord into and back out of the V-shaped hole you made. Then you tie it off, and weight down the edges with whatever you can find, such as our emergency packs. What was it like at camp K131? Success! Our tent is up! Electricity was supplied by a large diesel-powered generator. It was used to heat the lab and sleeping wanagins, running our coring drill, recharging the batteries of all of the other equipment, cooking, etc. Food boxes were delivered from Scott Base periodically during our stay, mostly dehydrated foods, with a little frozen meat and veggies, chocolate, canned or dried fruit, pasta/rice/couscous. Cooking for one would have been pretty simple, but cooking for 13 was a little peculiar, as we mixed and matched various combinations of foods to try to come up with ‘what’s for dinner.’ Strange as the combinations might have been, it all tasted good, no doubt because hunger is the best sauce for any food. Water for cooking or dish washing was slightly salty and came from melted snow. Water to drink was hauled from Scott Base. There was no other water (no showers or wash water). We kept pseudo-clean using wet wipes and dry shampoo. The toilet was a bucket in a small o u t h o u s e a n d ho l es d r ill ed i n the sea ice. When you walked just a hundred yards or so from camp, it produced the most beautiful silence, per- haps even an eerie silence, except for the wind. I am used to backpacking in Utah, where frankly, it is rarely silent as the multitude of birds, bugs, and animals keep your ear drums vibrating. So in these respects, this camp was remote. In other respects, our camp was not so remote. It was right on the ‘main drag’, so we often looked up to see some fantastical Antarctic vehicle buzzing along in the distance. A collection of treaded vehicles (Pisten Bully’s and Hagglunds, for example) as well as big-wheeled conveyances are shown on our photo blog. We were about an hour’s drive from Scott Base, and in direct line of the airport. We watched the daily C17 flights whose flight path was within easy sight of our camp. In addition, we were in constant radio contact with Scott Base, providing an emergency lifeline for everyone’s safety. What were we measuring? One of the pri - ma r y e l ec t r i c a l p r o p e r t i e s w e were measuring is electrical con- duc tivit y (whose units are 1/ohm- meter or Siemens/ meter (S/m)). Con- ductivity tells us how much current (units: Amps) the ice can carry. We know that metal wires carry current very well. Conductivity tells us how well the ice will carry current. The higher the conductivity, the more current it will carry. The lower the conductivity, the less current it can carry. Metals and wet soil generally have high conductivity. Plastics and dry soil generally have low conductivity. This is why people who work on electricity are careful to wear rubber soled shoes and stand on dry ground! Sea ice has relatively high conductivity, because of the salt water stored in it. Resistivity = 1 / [ Conductivity x Area] . We can measure re- sistivity as shown in the picture below. Put two metal plates (with Area = Width x Height as shown. Units: square meters) on either end of a block of sea ice. Attach wires to each of these plates. Measure the resistance (units: ohms) between these two wires. Resistance (ohms) = Resistivity (ohms/meter) x Length (meters). The trouble is, it is not so easy to just put two plates on a block of ice and measure the resistance. The plates do not make very good contact, particularly in field work where hand tools and blowing snow are the norm. Timing is every- thing. As soon as we would bring out the ice to test, it would immediately start to heat up or cool down, thus changing the electrical properties of the ice. We had to test quickly and ef- ficiently in order to get usable data. We wanted to measure resistivity at different depths, and our ice was 2.5 meters deep. Figure3: Antartica begins to unfold below us... Figure 4: The Utah team arrives at Scott Base Figure 5: Scott Base, Antartica Figure7: Artic Camp K131 Figure 6: Scott Base Figure8: The opposite of conductivity is resistivity (units: ohm/meter)