Permafrost mapping by transient electromagnetic method

Abstract

A transient electromagnetic (TEM) survey was performed for permafrost mapping in Central Alaska, where permafrost is discontinuously distributed. The most stable data were obtained from the measurement of an outside loop with a single‐turn loop of 60×60 m. Electrical sounding was also conducted to evaluate the potential of TEM for permafrost mapping. In permafrost areas, the one‐dimensional inversion results typically show three‐layer geoelectrical sections of resistive subsurface and basement layers separated by a thin conductive layer. The resistive layers of subsurface and basement correspond to permafrost and the top of bedrock, respectively. The second conductive layer indicates an unfrozen state. The ground temperature profiles support these postulated resistivity structures. In permafrost‐free areas, two layers are resolved. The projected thickness of permafrost from the electrical sounding is thinner than the estimates derived from the TEM method. In permafrost‐free areas, results obtained by two methods coincide with each other. We conducted a numerical experiment using synthetic data calculated from a four‐layer permafrost model with appropriate noise for two methods. The inversion procedures show that TEM is better used more precisely for determining the permafrost thickness. Copyright © 2000 John Wiley & Sons, Ltd.

Internal Structure of Open System Pingos, Adventdalen, Svalbard: The Use of Resistivity Tomography to Assess Ground-Ice Conditions

“…However, this is not the case in many areas of lowland permafrost, where permafrost is developed within thick sequences of unconsolidated, fine-grained superficial sediments, or in areas of sedimentary or volcanic bedrock. Permafrost resistivities in these settings are normally much lower (1-10 kV m) (e.g., Hoekstra et al, 1975;Allard et al, 1988;Sellmann et al, 1988;Gahe et al, 1988;Delaney et al, 1988;Harada et al, 2000Harada et al, , 2006Farbrot et al, 2005;Etzelmü ller et al, 2006), although values remain much greater than the unfrozen equivalents. This paper describes electrical resistivity tomography surveys of open system pingos in Adventdalen, Svalbard.…”

Resistivity structures in alas areas in Central Yakutia, Siberia, and the interpretation of permafrost history

“…Sinha and Stephens, 1983;Todd and Dallimore, 1998). The surface TEM method has been used for the detection of permafrost, and for defining its spatial distribution and vertical distribution (Rozenberg et al, 1985;Harada et al, 2000;Wada et al, 2000;Hauck et al, 2001). Siberia possesses some of the thickest permafrost in the world.…”

“…We applied the TEM method to investigate the resistivity structure from the ground surface to the permafrost base near Yakutsk, Siberia, in order to obtain basic information for the interpretation of permafrost history. In August 1999, preliminary TEM surveys were carried out in order to obtain basic information about resistivity structures of the alas and taiga forest in Neleger (Wada et al, 2000). In August 2000, a TEM survey was also carried out at Magan in order to compare the observed resistivity structure with the temperature profiles.…”

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

“…Electromagnetic (EM) induction methods have been widely used in studies of lowland permafrost, mostly in the arctic regions (e.g. Hoekstra and McNeill, 1973;Harada et al, 2000). It is only recently that these methods have been applied in mountainous regions and especially in the European Alps Cannone et al, 2003).…”