Geophysics Entry
Now we’re talking, lets get some phun physics action going in Antarctica. We did 3 geophysics experiments. The stake field, the pit and Maswar Seismograph data. These should be familiar if you read the Cass Field Station entries….
The stake field was a preexisting experiment set up by a scientist, Wolfgang, from Gateway Antarctica at Canterbury University. Earlier in the season he had set up a square with long bamboo posts every couple hundred meters. He had taken several measurements to monitor the characteristics of the Ross Ice Shelf. To complete one of the observations for him we had to do several things. First was to measure the GPS location of the 4 corners of the square. Then we had to go around and measure the height of each individual pole. (It took one grad student close to 36 hours to do this by himself with only man power and a sled, it took us approximately 5 hours with a ski doo) We reported this data back to Wolfgang, and now he can use it when compiling all his data. The results should be able to tell us how much the ice shelf is moving and how much snow is accumulated every year. This is also going to accompanied by a satellite flying over Antarctica. This was some very real and cutting edge science we were involved with!
Lorna setting up the GPS device
The third part of the stake field was to measure the depth of the ice. We did this by sending a pulse down through the ice. Knowing that the angle of incidence is the same as the angle of reflection, we were able to pick up the pulse when it returned to the surface. This was repeated for 2.5 meters one centimeter at a time. That’s 250 readings as we moved the detectors from a central location! By compiling the different readings we will be able to determine the density of the ice in this region.
Annette with the radar detectors
The snow pit is exactly what it sounds like. There was a lot of physical labor as we dug a 4.68 meter
hole over the course of 7 days. The idea here was to monitor the ice properties as we descended. Measurements of the temperature, ice crystal size and shape, and density were measured every 10 or 20 centimeters. I found it so exciting to be doing some in field work. It was neat how things worked on paper and then seeing them in action. It was tricky hanging on the the small metal cord ladder while holding a spade and shovel. We had to take horizontal measurements of the ice density because we couldn’t get the right angles for vertical measurements. As you might have guessed we found the ice was colder and more dense as we got deeper. The crystal size and structure also changed through different layers. Oh man is science fun!
Caution: Sarah the scientist at work
The third and final experiment involved the expensive computer, hammer and metal plate. This had easy set up as we placed the 20 meter cord along the surface of the ice and pressed in the seismic wave detectors. Then we got to take out all our frustration as we slammed the hammer down on the disk. The vibrations traveled through the ice and the waves were picked up by the sensors. This information was then feed back to the computer which created some really pretty pictures for us. By noting the qualities of the waves the density and structure of the ice can be determined.
Martina getting ready for a swing