Nansen Ice Shelf, Antarctica 2015: Scouting Our Field Sites by HelicopterNovember 17th, 2015 by Maria-Jose Viñas
By Ryan Walker
On our first full day at Jang Bogo, we weren’t expecting very much to happen. The majority of our equipment wouldn’t be arriving for another three days, so we thought we would settle in and learn about the basic amenities of the station — food, showers, laundry, wifi, espresso machine. (I’m not joking, there really is an espresso machine. You can learn all sorts of unexpected skills living in Antarctica.) But then the day turned out to be sunny and clear, perfect for flying, and one of our collaborators, Dr. Hyeon Jae Yoo, came and told us that he had reserved a helicopter for that afternoon to scout out our field sites.
Choosing field sites can be rather tricky. We had spent quite a while looking at satellite images and computer model output in order to estimate where the processes we wanted to study would likely be strongest. For GPS measurements of ocean tides causing ice motion, we wanted to be more in the middle of the ice shelf, away from the islands and rocky outcrops that pin its margins in place. For tilt meter measurements of ice shelf flexure, we would need to be near the landward edge of the shelf — most of an ice shelf floats freely up and down on the tides, and the bending happens in a narrow strip (maybe a few kilometers wide) between the floating ice and the ice resting on the land. Field site selection is then a balance between finding the ideal place to collect data and finding places where you actually can collect data. Crevasses (large cracks in the ice), very uneven ground, and ponds formed by melting of the ice surface can all prevent setting up instruments. In the end, it’s essential to get an in person look at your sites, preferably before you’ve dragged all your equipment there.
This was my first helicopter flight, and since it was my birthday (what a celebration!) Hyeon Jae and Christine insisted I should sit up front. Taking off is sort of like riding in a glass elevator. Flying in a helicopter is very different from flying in an airplane. Being able to go low and slow (or hover) gives great views. We were able to circle our GPS sites at about 10 feet off the ground, and touch down briefly (with the rotors going) at our tilt meter sites to test the firmness of the snow. Our GPS sites are all on blue ice, with no snow cover, and look favorable for installing the instruments. We’ll just have to shift a few of them a short distance so they’re on ridges rather than hollows — although the ice is pretty flat, this matters when the ice surface starts to melt later in the summer and the water flows downhill. Our tilt meter sites are on a snow-covered area, so we will have to dig down to ice (or at least very firm snow) to get a solid base so we can install the instruments level. This is really important because the ice only bends a little, so the tilt meters measure angles less than half a degree. (That’s a little less than 1 foot up per 100 feet across.)
Overall, we were very happy with the results of this flight. Our field areas look good, and we got truly spectacular views of the ice shelf and the rocky hills surrounding it. I shot video with a NASA-provided GoPro, and it came out great, even though all I had to do was point the camera at the windscreen and try to hold it still. The files are too large to post from Antarctica, but the best scenes should be part of the final video that Goddard will produce when we’re back home. Thanks to our pilot, Dominic of Helicopters New Zealand, for a smooth and safe flight.