We organized our field activities into two seasons of intensive work preceded by an initial reconnaissance trip and a final visit to remove as much equipment as possible. Plans often must be changed, however, as weather, logistics and funding can conspire individually or in combination. Specific tasks, described below, were scheduled for the various field seasons, but actual progress did not always unfold along the same path.
Can we land safely on the PIG ice shelf? That’s the primary question to be answered in this reconnaissance field season. Next we will take care to define the size of a safe working area for subsequent field teams. Due to possible difficulties, we will carry a minimum of equipment and stay about 7-10 days. We will set up an automatic weather station, two web cams and two GPS units that will phone data back to us, hopefully for a full year, including through the dark, frigid winter. Other measurements will be made of the ice thickness, the water thickness, the snow conditions and its temperature. These data are crucial to determine the size of the drilling system, the amount of fuel needed to drill the next season’s holes and the length of cable for the oceanographic instrument package. We also will try to use a special type of radar to directly measure the rate of ice melting on the underside of the ice shelf.
What actually happened is that the first landing in a Twin Otter was successful, so a crevasse-free area large enough to accomplish our modest field objectives this season was found. Unfortunately, the surface was so hard that the small bumps scattered across the surface made landings by a ski-equipped Twin Otter so treacherous that subsequent landings were deemed unsafe. In place of the planned measurements on the ice shelf, the GPS units were deployed on nearby tributary flows that fed the ice shelf and the automatic weather station was set up on a local high spot adjacent to the ice shelf. This field experience did answer the primary question, but not quite in the desired manner: more extensive helicopter support would be needed to move ahead with the surface measurements on the ice shelf.
Helicopter (transported to ASE by LC-130) supporting field work near PIG in 1977. Photo courtesy of W. McIntosh.
[Original plan] The field work begins by drilling the first hole through the ice shelf. The initial hole will be used for exploration of the ocean cavity using the video camera. A second hole will be drilled nearby and the sub-shelf profiler deployed and monitored throughout the occupation to ensure proper operation. Winter-over AWS and GPS instruments will be serviced, data downloaded (if necessary), and prepared to survive through the next winter. Three additional GPS will be deployed and rigged for wintering over. The total surface time for the drilling, exploration, and instrument deployment phase is estimated at 6 weeks.
Helicopters are required to deploy the shelf-survey team to approximately 30 sites distributed across the ice shelf for mapping of cavity depth, ice thickness, elevation, and gravity. We estimate completing five sites per day with an equal number of flying and non-flying weather days for a total helicopter support requirement of ten days.
In reality, Antarctic logistics were stretched so thin supporting other field projects of the widespread International Polar Year, that virtually no progress was made on the PIG ice shelf project. In its place, discussion with logistics planners focused on the requirements of providing helicopter support at a coastal location so far from McMurdo Station and with a reputation for persistent cloudy and/or windy weather.
[Original plan] The drilling team returns to drill three additional holes for new ocean profiling instruments Additional video exploration may occur depending on results from the previous season. The AWS and the GPSs will be serviced, data downloaded, and readied again for the following winter. On-site work is estimated to require five weeks.
Actually, the planning of a helicopter base continues. The large amount of material (camp shelters, fuel, helo maintenance equipment, fuel, landing pads, fuel, and did I mention fuel?) and the probability of frequent bad weather, led logistics planners to favor an overland traverse as the most feasible means of establishing this camp. A traverse route was determined using satellite imagery and other satellite data so regions likely to contain crevasses could be avoided. The AWS equipment was visited and quickly maintained so that it could continue its valuable record of weather conditions near PIG.
Meanwhile, the scientists used this year to test all their equipment and procedures in Windless Bight, an ice shelf thinner than PIG, but only a few kilometers from McMurdo Station. This experience was very useful. More details of this field trip can be found by clicking the blog link at the top of this page.
[Original plan] AWS and GPSs will be maintained annually. Profiler data will be retrieved if problems occurred with Iridium communication system. We would like to keep the surface instruments working for the two-year lifetime of the profilers and would remove surface instrumentation if sub-shelf instrumentation fails.
Well, we are sliding a little further behind, but progress is steady. The surface traverse makes it to the revised helo camp location and carpenters set up the first buildings. The AWS station, now partially buried by two years snow accumulation, is dug up and moved to the helo camp location. Two other AWS sites are established nearby to provide a broader regional picture of the weather conditions. This information will become extremely useful for knowing how to interpret local weather when the helos (and we) arrive.
The only failure at Windless Bight last year was the ocean profiler, but it is a key piece of equipment. It received further testing at another site, also near McMurdo. It passes; it is ready to go.
So we are ready, logistics is ready, and the equipment is ready. Everything is being shipped from various institutions. Some will be flown to Byrd Station and added to another overland traverse that should reach the PIG helo base in early December. Soon thereafter, the helos will be partially dismantled and flown to the helo camp. The scientists will also be flown out (without being partially dismantled) in anticipation of being transported onto the ice shelf in mid-December. Work will continue until late January, when scientists and helos will return to McMurdo and the helo camp disassembled for the winter. The following season, 2012-13, will be our opportunity to finish the work and deploy at least three profilers.