Subglacial conditions play a key role in the most dynamic parts of the ice sheet: ice streams, outlet glaciers and tidewater glaciers. These fast glaciers drain large quantities (90%) of the ice sheet in to the ocean. Seismic data provides the subglacial boundary condition of these dynamic parts of ice sheets. We also successfully use seismics to map and characterize conditions below ice shelves. This is an area where marine seismic data and land seismic data connect. The seismic acquisitions set-up developed by AWI fills this important niche in seismic data.
The terrain and target depth pretty much dictates the use of the seismic equipment. Since 2009 we have been experimenting and constantly improving our equipment. For larger surveys at the ice sheet or shelf where the ice is thick and surface conditions flat we use the larger 1500m streamer and a larger vibrator towed by a tracked vehicle, a Pisten-Bully. Like this we collected more than 400km of seismic data on the sheet-shelf transition of Antarctica. In more difficult terrain like the ablation zone of the Greenland Ice Sheet equipment often has to be transported by a helicopter or plane. We used the 300m snowstreamer and mini-vibrator or explosives for deeper targets. We pulled the streamer by skidoo or ourselves depending on the difficulty of the terrain. Using the mini-vibrator and spiked geophones we occasionally work on Alpine Glaciers, the most spectacular being a 4500m high Alpine saddle, Colle Gnifetti.