BAS Research - Launching a weather balloon
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Surveying Pine Island Glacier Inserting explosive charges into pre-drilled holes Explosives are laid out in a line Seismic survey in action! DELORES radar behind skidoo Ground penetrating radar (GPR) behind skidoo GPS station < 1 2 3 4 5 6 >During the first summer campaign glacial geophysicists Andy Smith and Julian Scott together with field assistants Rob Smith and Roger Stilwell measured ice flow using Global Positioning Systems (GPS) and drilled into the upper ice layers to determine accumulation and density. Some of the most dramatic fieldwork involved setting off high explosives near the ice surface to measure the time it takes for the resultant acoustic waves to echo from the ice bed 2 km below. This method was particularly effective for detecting water and ‘soft’ sediments that reduce friction between bedrock and ice and enables faster ice flow.
At 95 days on the ice the second summer field season was longer and much more extensive than the first. Julian Scott, glacial geophysicist Robert Bingham, with field assistants Feargal Buckley and Chris Griffiths, increased the area of the first year’s survey and used a range of over-snow radars to investigate subsurface conditions. They also added ‘passive seismics’ to the array of surveying techniques. Where active seismics use artificial signals created by explosives, passive seismics rely on natural ‘icequake’ activity. Icequakes have been observed on many glaciers around the world. Monitoring their frequency and magnitude with high-resolution sensors, reveals how ice flow in a major ice stream such as Pine Island Glacier is controlled by slippage over the bed.
"It was a fantastic experience to skidoo 90 km in order to be the first people to visit the site of the largest known subglacial volcanic eruption in Antarctica. Returning in the cold hours of early morning with a low sun lighting up the glacier." Dr. Julian ScottSurveying techniques involved Rob and Feargal driving skidoos, towing a radar transmitter and receiver that stretched over half a kilometre. BAS’s high resolution DEep-LOoking Radar Echo Sounder (DELORES) can not only ‘see’ through the 2 km of ice to the bed, but also pick out ‘internal reflectors’ - layers of equal age which represent one or more discrete snowfall events. These internal layers act as crucial input and control for ice-flow modelling. They collected 1500 km of data during the season crossing the glacier several times.
Using over-snow radar Julian and Chris were able to create an image of the Hudson Mountains subglacial volcano discovered by Hugh Corr and David Vaughan while analysing the 2004-05 airborne data. They also detected a highly reflective internal layer that may contain high amounts of volcanic ash from an eruption about 2000 years ago .
Pine Island Glacier Fact File© NERC-BAS 2007
