Detection of subsurface permafrost features with ground-penetrating radar,Barrow, Alaska

A ground-penetrating radar (GPR) survey was conducted in May 1999 on the 1 km(2) Circumpolar Active Layer Monitoring (CALM) grid 5km east of Barrow, A laska. Spatially continuous measurements were collected along established t ransects while the active layer remained frozen. The primary objectives wer e to determine the 'long-term' position of the permafrost table, to recogni ze ice wedges and ice lenses, and to locate the organic-mineral soil interf ace. GPR signal and core collection were performed in tandem to verify sign al interpretation, to calibrate the instrument, and to determine optimal GP R data-collection parameters. Two-way travel times from the antenna to subs urface reflectors were compared with measured depths obtained from soil cor es to estimate an average pulse propagation velocity of 0.13 m/ns through t he frozen soil. The most conspicuous subsurface reflectors were ice wedges, which gave high-amplitude hyperbolic reflections. Owing to its higher ice content, the approximate long-term position of the permafrost table could b e traced laterally across the profile. Radar interpretations were obscured by the effects of cryoturbation, and because some horizons lack sufficient contrast in electrical properties. Highly detailed information can be obtai ned by collecting radar data at relatively slow speeds of advance, by using faster scanning rates (> 32 scans/s), and by employing high-frequency ante nnas (> 400 MHz). Copyright (C) 2001 John Wiley & Sons, Ltd.