Geophysical surveys designed to delineate the altitudinal limit of mountain permafrost: an example from Jotunheimen, Norway

Three geophysical methods have been applied to delineate the altitudinal limit of permafrost at Juvvasshoe/Jotunheimen in southern Norway. By using each method in a complementary way according to its applicability, the permafrost distribution could be analysed on both large and small scales. In addition, temperature-based methods such as the BTS method (bottom temperature of snow cover) were used to validate the results. On a large scale, electromagnetic induction profiling with the EM-31 was used to detect the location of the transition area between frozen and unfrozen ground. Within this area direct-current (DC) resistivity and refraction seismic tomography were also applied to further characterize and visualize the permafrost transition. The large scale surveys revealed a sharp increase in conductivity, indicating an increase in unfrozen water content, near 1400 m a.s.l., with a possible transition zone between 1500 m a.s.l. and 1380 m a.s.l. The small scale investigation delineated the altitudinal limit of permafrost between 1470 m a.s.l. and 1410 m a.s.l., with sporadic ground ice occurrences and temperatures near the freezing point. Copyright © 2004 John Wiley & Sons, Ltd.