Ice thickness surveys of the Southern Patagonian Ice Field using a low frequency ice penetrating radar system

An airborne low frequency radar system used to survey the ice thickness of the northern part of the Southern Patagonian Ice Field (SPI) is presented. The radar is an impulse system operating at a central frequency of 20 MHz. The system is controlled and operated from a helicopter cabin connected with an optical fibre cable to the antennas that are fixed to an aluminium structure weighting 350 kg that is hanging 40-50 m below the helicopter. At the antenna, there is a high-power transmitter working at a 5 kHz PRF, and a radar receiver. Also, there is a dual frequency GPS for the real-time positioning of the measurements. The survey took place in August 2015 and October 2016 while flying more than 400 kilometres of Glaciares Jorge Montt, OHiggins and the high plateau of the SPI. The system performance was adequate to survey most of the ice thicknesses, including the steep slopes and inaccessible crevassed areas. The maximum ice thickness penetration yielded 581 m of temperate ice. Several bottom reflections were obscure by englacial water and/or surface crevasses.