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Descripción
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| Austfonna (79.5°N, 25°E) at 8120 km2 is by far the largest ice cap in Svalbard and one of the largest in the Arctic. Within the framework of the IPY project GLACIODYN and CryoSat calibration and validation activities, annual field visits to Austfonna started in April 2004. Ice thickness and bedrock maps inferred by airborne radio-echo sounding are available for the entire ice cap, but date back in time to the mid 1980s. Here we present additional new bedrock information acquired using a ground-based 20 MHz system. The low-frequency radar data were acquired using a ground-penetrating radar VIRL-6, with centre frequency of 20 MHz. The transmitter generates pulses of 25 ns duration at a pulse repetition frequency of 20 kHz, and the receiver uses a variable-gain linear amplifier. The antennae were resistively loaded half-wave dipoles of 5.8 m in length, which were arranged collinearly, following the profiling direction. The digital recording system (DRS) counts on a high stacking capability (user-selectable, from 256 to 16384 traces summed in real time) aimed at suppressing external electromagnetic noise. The DRS records 4000 samples for each trace, with a 2.5 ns sampling interval. Navigation information from a GPS Garmin II Plus receiver was recorded simultaneously with radar data. Data was collected along several profiles across the ice cap, and along/across the flow lines of two fast flowing outlets with the aim to complement the existing airborne data and to provide an improved input geometry for numerical studies of the flow dynamics of Austfonna. Furthermore, data was collected along some parts of the old flightlines from 1983/1986 in order to validate the quality of the airborne data. Total length of VIRL-6 profiles made at Austfonna was close to 800 km. Bed return could be seen in all profiles and also internal reflection horizons could be followed and will be interpreted and compared with higher frequency radar data. For time to depth conversion, a radio-wave velocity of 168 m/¿s, typical of cold ice, was used. Maximum ice thickness of 590 m was found at the central part of the ice cap. | |
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Internacional
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Comentarios Mérito
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Contribución a Congreso Internacional (IASC-NAG Meeting, Kananaskis Country, Alberta, Canada: 16-19 February 2009) cuyo libro de Abstracts carece de ISBN/ISSN. |