16 November, 1996

Journal November 16, 1996

Another interesting day. Bill wanted to learn how the intensity of ultraviolet radiation in the water under the sea ice compared with levels in the open ocean. He is trying to determine if a chemical produced by a pteropod, a type of shell-less snail, is functioning as a natural sun screen. His hypothesis is if UV concentrations are higher at the ice edge than under the ice, the concentration of the chemical should be higher in the pteropods collected in the open water. Two years ago, Pat determined that the pteropod is chemically defended from predators by the compound. There is speculation that the chemical may have a dual role in the animal since its concentration is five times greater than needed to deter predation, and it is a known UV absorber. Collecting data to test the hypothesis will require my being on the ice for about a month and one half longer than I originally expected.

The plan for today was to set a series of dosimeters at various depths at the ice edge. The dosimeter has a chemical in it which will change if exposed to UV. By measuring the amount of change and the exposure time, the intensity of the incident UV can be determined. Our major concern was getting to the ice edge without going through. We would have to go twenty five miles by skidoo and hike the last two miles to the end of Cape Royds. Although we carried survival gear in the skidoo, we didn't feel we could lug it all the way to the ice edge. It wouldn't be a good place to end up in the ocean.

Tom, a member of the Search and Rescue Team, agreed to accompanied us. He was an excellent mountaineer who could also read the ice conditions. Having him belay me while I searched for a suitable spot for the experiment was comforting. Part of the equipment he carried was a portable GPS. This allowed us to accurately determine the location of our experiment or our position in the event of an emergency. The GPS receives signals from satellites whose positions are know. By measuring the difference in time it takes for signals from different satellites to reach the receiver, it is able to calculate location to within a few feet. The key to safely working in this environment is training, vigilance, and anticipating problems before they develop. We got the experiment deployed and were back to the station by 8:00 PM. Both Pat and I had our faces sunburned, we hadn't activated the compound which would protect us from the UV we set out to measure.

Dom Tedeschi

http:/www.neca.com/antarctica/

tedeschi@csec.mcmurdo.gov